JP7163093B2 - Broker device, communication system, communication method, and program - Google Patents

Description

The embodiments of the present invention relate to a broker device , a communication system, a communication method, and a program applied to communication based on a publish/subscribe model.

2. Description of the Related Art In recent years, a communication method called a publish/subscribe model has been known as a communication method capable of asynchronously exchanging published data in a distributed application.

According to the publication/subscription model, as disclosed in Patent Document 1, information subscribers can efficiently receive only desired information.

According to the technology disclosed in Patent Document 1, in communication based on the publication/subscription model, reliability can be ensured by redundancy of broker devices, and security can be ensured by controlling access to content. can also be realized.

JP 2007-287148 A

However, in the technology disclosed in Patent Literature 1, the roles of broker devices are subdivided, and each broker device must be made redundant in the case of redundancy. Furthermore, when a failure occurs in a broker device that plays a specific role, availability cannot be guaranteed even if other broker devices are normal.

SUMMARY OF THE INVENTION Problems to be solved by the present invention are a broker device capable of ensuring availability without implementing new redundancy, a communication system including a broker device and a client device, and a communication method applied in the communication system. , as well as providing programs.

A broker device according to an embodiment is a broker device that transmits publication data received from a first client device to a second client device and other broker devices, and comprises a self-subscribed information receiving unit and a self-published data receiving unit. , a self-published data transmitting unit, a non-published data transmitting unit, a non-published data receiving unit, a latest published data holding unit, a non-subscribed information management unit, and a self-subscribed information management unit.
The own subscription information receiving unit receives a subscription request for a topic subscribed by the second client device from the second client device.
The self-published data receiver receives topic-related publication data from the first client device.
The self-published data transmission unit transmits the published data received by the self-published data reception unit to the second client device.
The other publication data transmission unit transmits the publication data received by the own publication data reception unit to the other broker device.
The other publication data receiving unit receives publication data related to the topic from other broker devices.
The latest publication data holding unit extracts and holds the latest publication data for each topic from the publication data received by the own publication data reception unit and the other publication data reception unit.
The other subscription information management unit receives subscription requests for topics subscribed by other broker devices from other broker devices.
The own subscription information management unit manages the topic subscribed by the broker device, and transmits this topic to other broker devices when there is a change in the managed topic.
The self-published data transmission unit further acquires the latest published data of the topic related to the subscription request received from the second client device from the latest published data holding unit and transmits the data to the second client device.
The other publication data transmission unit further acquires the latest publication data related to the topic related to the subscription request received by the other subscription information management unit from the latest publication data holding unit and transmits it to the other broker device.
When a subscription request for a certain topic is received from the second client device, the subscription information management unit further determines whether the topic is a new topic. Determine if the device is present.
The self- subscription information management unit outputs a subscription request for new subscription registration when there is no client device that subscribes to the managed topic .
If there is no client device subscribing to the topic managed by the self-subscription information management unit among the topics subscribed to by two or more broker devices, the other subscription information management unit issues a subscription cancellation request. is output to the subscription information management unit .

1 is a conceptual diagram showing a configuration example of a communication system according to a first embodiment; FIG. FIG. 11 is a diagram showing an example of another broker device subscription information management table; 2 is a block diagram showing a configuration example of a broker device applied to the communication system of the first embodiment; FIG. FIG. 10 is a diagram showing an example of a self-broker apparatus subscription information management table; FIG. FIG. 10 is a flow chart showing an example of a processing procedure by a local broker device when receiving a subscription request from a client device; FIG. It is a figure which shows an example of a subscription information subscription number management table. FIG. 10 is a diagram showing an example of a broker device subscription number management table; FIG. 10 is a flow chart showing an example of a processing procedure by the own broker device when receiving a subscription request from another broker device; FIG. FIG. 10 is a flow chart showing an example of a processing procedure by a local broker device when a client device issues a publication data publication request; FIG. 10 is a flow chart showing an example of a processing procedure by the own broker device when publishing data is transmitted from another broker device; FIG. 10 is a flow chart showing an example of a processing procedure when another broker device terminates and an abnormality is detected; FIG. It is a conceptual diagram which shows the modification of the communication system of 1st Embodiment. FIG. 4 is a block diagram showing a configuration example of a broker device and a sub-broker device applied to a modification of the communication system of the first embodiment; FIG. 9 is a block diagram showing a configuration example of a broker device applied to the communication system of the second embodiment; It is a figure which shows an example of another subscription information management table. It is a figure which shows an example of a self-subscription information management table. FIG. 10 is a flow chart showing an example of a processing procedure by a local broker device when receiving a subscription request from a client device; FIG. FIG. 10 is a flow chart showing an example of a processing procedure by the own broker device when receiving a subscription request from another broker device; FIG. FIG. 12 is a block diagram showing a configuration example of a broker device applied to the communication system of the third embodiment; FIG. FIG. 10 is a diagram showing an example of a transmission waiting list; FIG. It is a figure which shows an example of a maximum waiting time list|wrist and time conditions. FIG. 4 is a data structure diagram illustrating a packet format of compressed and aggregated publication data; FIG. 10 is a flow chart showing an example of a processing procedure when receiving a publication request for publication data from a client device; FIG. 10 is a flow chart showing an example of a processing procedure when transmitting publication data in response to a publication request; FIG. 10 is a flowchart showing an example of a processing procedure when publishing data is transmitted from another broker device; FIG. FIG. 11 is a conceptual diagram showing a configuration example of a client device applied to a modification of the communication system of the third embodiment; It is a figure which shows an example of a maximum waiting time list. FIG. 10 is a diagram showing an example of a transmission waiting list; FIG. FIG. 4 is a data structure diagram illustrating a packet format of compressed and aggregated data; FIG. 10 is a flow chart showing an example of a processing procedure when receiving a publication request for publication data from a client device; FIG. FIG. 10 is a flowchart showing an example of a processing procedure when packet aggregation/compression and transmission processing are performed for each subscription information (topic); FIG. 4 is a flow chart showing an example of a processing procedure when publishing data is transmitted from a broker device;

A communication system according to each embodiment of the present invention will be described below with reference to the drawings.

In the description of each embodiment below, the same parts are denoted by the same reference numerals to avoid repeated description.

(First embodiment)
FIG. 1 is a conceptual diagram showing a configuration example of a communication system according to the first embodiment.

The communication system 1 includes a plurality of broker devices 10 communicatively connected to each other via a network 20, and an arbitrary number of clients communicatively connected to one of the plurality of broker devices 10 via the network 20. device 30;

In the example shown in FIG. 1, four broker devices 10 (#0 to #3) are communicably connected to each other via the network 20, and one of these broker devices 10 (#0 to #3) Client devices 30 (#1 to #6) communicably connected via network 20 are shown.

In the example shown in FIG. 1, the client devices 30 (#1), (#2), and (#3) are communicably connected to the broker device 10 (#1), and the broker device 10 (#2): The client devices 30 (#4) and (#5) are communicably connected, and the client device 30 (#6) is communicably connected to the broker device 10 (#3).

The network 20 may be, for example, a local line such as LAN, a wide area wired communication line such as the Internet or a dedicated line, or a wide area wireless communication line such as 3G.

A group of information exchanged between the broker device 10 and the client device 30 is classified by "topic". The client device 30 registers a topic to be received in the connected broker device 10 . Hereinafter, this registration operation will be referred to as "subscription".

Also, the client device 30 can transmit topic-related publication data to the connected broker device 10 . Hereinafter, this transmission operation will be referred to as "publishing".

When the publication data is published together with the topic from the client device 30, the broker device 10 transmits the publication data to the client devices 30 subscribing to this topic. For example, in FIG. 1, when the client device 30 (#1) subscribes to the topic of information group A, the broker device 10 (#1) receives information related to the topic of information group A from the client device 30 (#2). When the publication data to be published is published, the publication data is transferred only to the client device 30 (#1). In this way, the client device 30 (#1) can receive only publication data to which it has subscribed.

When there are a plurality of broker devices 10, each broker device 10 holds, for example, another broker device subscription information management table 200 as shown in FIG. share.

FIG. 2 is a diagram showing an example of an other broker device subscription information management table.

Other broker device subscription information management table 200 (hereinafter simply referred to as “management table 200”) is, for example, a subscribing broker device m1 indicating a subscribed broker device 10 and a broker device 10 designated by the subscribing broker device m1. This is a data table in which records composed of two items, namely subscription information (topic) m2 indicating topics subscribed to in , are piled up. The management table 200 is stored in a storage (not shown) within the broker device 10 and can be referenced by each component within the broker device 10 .

In the management table 200 illustrated in FIG. 2, topics of information group A, information group B, and information group C are subscribed to in the broker device 10 (#1), and information group A and information group C are subscribed to in the broker device 10 (#2). is subscribed to, and the broker device 10 (#3) is subscribed to a topic of information group B.

By referring to the management table 200, when publication data is published from the client device 30, the broker device 10 transfers it to which other broker device 10 based on which topic the publication data is related to. determine what to do.

For example, when the client device 30 (#3) publishes publication data related to the topic of information group B to the broker device 10 (#1), the broker device 10 (#1) reads from the management table 200 the broker device 10(#3) determines that this publication data is required and transfers it to the broker device 10(#3).

In this way, the communication system 1 transfers only the minimum necessary publication data, so that the network bandwidth is efficiently used.

Further, in protocols adopting a publication/subscription model such as MQTT (Message Queue Telemetry Transport), each broker device 10 has a function to hold the latest publication data for each topic (hereinafter referred to as a "retain function"). ).

According to the retain function, the client device 30 can always acquire the latest publication data related to the subscribed topic even when the subscription is started after the publication data is published.

Also, for example, if the client device 30 is of a battery-powered type, it cannot always hold a communication session. However, according to the retain function, not only the battery-powered type client device 30 but also the client device 30 that is activated intermittently establishes a communication session with the broker device 10 each time to make a subscription request. It is also possible to obtain the latest publication data, perform predetermined processing, and then disconnect the communication session and shift to the power saving state.

According to the retain function, even if the client device 30 terminates abnormally, it is possible to acquire the latest publication data after restarting.

By the way, if all the broker devices 10 are to hold the latest publication data, it is necessary to transfer all the publication data to all the broker devices 10 at the time of publication. However, not all broker devices 10 necessarily need all publication data. Therefore, transferring all published publication data to all broker devices 10 wastes communication resources and is inefficient. Therefore, in order to improve communication efficiency, the communication system 1 transfers the publication data only to the broker device 10 to which the client device 30 that is a subscriber of the topic related to the publication data is connected.

For example, when the relationship between the subscription broker device and subscription information (topic) is illustrated in the management table 200, publication data related to the topic of information group B is published to the broker device 10 (#1). Then, the broker device 10(#1) transfers this publication data only to the broker device 10(#3). Broker device 10 (#3) holds the transferred publication data.

On the other hand, when the topic of information group B is subscribed to by a plurality of broker devices 10 other than broker device 10 (#1), publication data related to the topic of information group B is sent to broker device 10 (#1). When published, the broker device 10 (#1) transfers this publication data to all broker devices 10 to which the information group B is subscribed. Each broker device 10 to which the publication data is transferred retains the publication data.

By the way, if the latest publication data is held in only one broker device 10, and an abnormality occurs in this broker device 10, the latest publication data may be lost. This is not preferable from the viewpoint of reliability. Therefore, as described below, the communication system 1 has a function of ensuring the redundancy of publication data according to the holding state of publication data while maintaining communication efficiency and improving reliability. A broker device 10 is employed.

FIG. 3 is a block diagram showing a configuration example of a broker device applied to the communication system of this embodiment.

The broker device 10 includes a communication unit 102, a communication unit 104, a subscription information receiving unit 106, a subscription information management unit 108, a self-published data receiving unit 110, a self-published data transmitting unit 112, a latest published data holding unit 114, and other publications. A data transmission unit 116 , another publication data reception unit 118 , another subscription information management unit 120 , and an end detection unit 122 are provided.

The communication unit 102 communicates with other broker devices 10 other than its own broker device 10 via the network 20, and transmits information from each part in its own broker device 10 to the other broker devices 10 via the network 20. Conversely, it receives information transmitted from another broker device 10 via the network 20 and outputs it to each part within its own broker device 10 .

The communication unit 104 communicates with the client device 30 via the network 20, and transmits information from each part in its own broker device 10 to the client device 30 via the network 20, or conversely, transmits information to the client device 30 via the network 20. receives the information transmitted from via the network 20 and outputs it to each part in the own broker device 10 .

In the following description, as an example, the own broker device 10 is assumed to be the broker device 10 (#0), and the other broker devices 10 are assumed to be the broker devices 10 (#1), (#2), and (#3). Furthermore, for ease of explanation, the other broker devices 10 (#1), (#2), and (#3) are simply referred to as other broker devices 10. FIG.

The own subscription information receiving unit 106 transmits a subscription request KR for a topic, which is a group of information subscribed by the client device 30, to the client device 30 (for example, the client device 30 (#2)) that is the source of the subscription request via the communication unit 104. ).

When the subscription request KR is a subscription registration request, the subscription information receiving unit 106 notifies the subscription information management unit 108 of the topic specified by the subscription request KR and the client device 30 that is the source of the subscription request. , for example, using the self-broker device subscription information management table 205 illustrated in FIG.

FIG. 4 is a diagram showing an example of a self-broker device subscription information management table.

Own broker device subscription information management table 205 (hereinafter simply referred to as "management table 205") includes own broker device subscription information m3 indicating subscription information (topic) subscribed to by own broker device 10 (#0), It is a data table in which records composed of two items, namely, a subscribing client device m4 indicating a client device 30 subscribing to the subscription information specified by the broker device subscription information m3, are stacked. The management table 205 is stored in a storage (not shown) within the broker device 10 and can be referenced by each component within the broker device 10 .

The management table 205 illustrated in FIG. 4 indicates that the client device 30 (#1) subscribes to the topic of information group A in the own broker device 10 (#0).

The self-published data receiving unit 110 receives the topic and its publication data SD from the client device 30 of the publisher (for example, the client device 30 (#1)) via the communication unit 104 .

Further, when the subscription request KR received by the own subscription information receiving unit 106 is a request to cancel the subscription, the own subscription information managing unit 108 determines from the management table 205 that the client device 30 that is the source of the subscription request is the subscribing client device m4. Delete records written to . Thus, the management table 205 is used to manage the subscription information (topics) of the client device 30 connected to its own broker device 10 (#0).

If the subscription request KR received by the own subscription information receiving unit 106 is a request to cancel the subscription, the own subscription information management unit 108 further considers the subscription status of the other broker device 10 and sends the request to the other broker device 10. Decide whether to notify unsubscribe. When making this decision, the subscription information management unit 108, for example, uses the management table 200 to determine the number of other broker devices 10 (subscribing broker devices) subscribing to the topic to be unsubscribed. , apply an algorithm that unsubscribes only if the determined number is greater than or equal to 2. As a result, when the number of subscription broker devices 10 is 1, even if the subscription is canceled, the subscription is not canceled, so the redundancy of the publication data SD can be continuously ensured.

Also, in this algorithm, if the own broker device 10 (#0) subscribes to a large number of topics, there is a high possibility that traffic will be uneven. On the other hand, if the broker device 10 that subscribes to the least topic subscribes to the topic, the traffic can be distributed efficiently. Therefore, if the number of subscribing broker devices 10 is not two or more, the own subscription information management unit 108 compares the number of subscriptions of the other broker devices 10 and the own broker device 10 (#0), and determines that the own broker device 10 (# 0) has the lowest number of subscriptions, the subscription may continue.

Self-published data transmission unit 112 transmits publication data SD received by self-published data receiving unit 110 to client device 30 (for example, client device 30 (#2)) that requested subscription via communication unit 104. do. The client device 30, which is the destination of the publication data SD, is determined by referring to the management table 205, for example. According to the management table 205, when the topic specified as the self-broker device subscription information m3 is the information group A, the destination is determined to be the client device 30 (#1).

The other publication data transmission unit 116 transmits the publication data SD received by the own publication data reception unit 110 to the other broker device 10 via the communication unit 102 . For example, the management table 200 is used to determine the broker device 10 of the transmission source. By grasping the subscription information (topic) m2 related to the publication data SD from the management table 200 and reading the corresponding subscription broker device m1, the destination broker device 10 is determined.

The other publication data receiving unit 118 receives the topic and its publication data SD from the other broker device 10 via the communication unit 102 .

The other subscription information management unit 120 receives topics required by the other broker devices 10 (topics subscribed by the client devices 30 connected to the other broker devices 10), and manages them using the management table 200, for example.

The latest publication data holding unit 114 extracts the latest publication data SD for each topic from the publication data SD received by the own publication data reception unit 110 and the other publication data reception unit 118 in order to realize the above-described retain function. and hold.

Further, when receiving a new subscription request KR from another broker device 10, the other subscription information management unit 120 registers it in the management table 200 if it is a subscription registration request, and the latest publication data holding unit 114 When the latest publication data SD is held, the other publication data transmission unit 116 is caused to acquire the latest publication data SD from the latest publication data holding unit 114, and the acquired publication data SD is sent to this The publication data SD is transmitted to another broker device 10 that has started subscribing.

In addition, in order to avoid transmission of the latest publication data SD from a plurality of other broker devices 10, the other subscription information management unit 120 assigns a broker number to each broker device 10 as a mere serial number so that the latest publication data SD Among the broker devices 10 holding the publication data SD, only one broker device 10 transmits the latest publication data SD, for example, only the broker device 10 assigned the smallest broker number is permitted to transmit the publication data SD. system may be adopted.

Further, the other subscription information management unit 120 may assign the broker number according to the capability of the broker device 10 instead of simply assigning the broker number as the reference number. For example, if a smaller broker number is assigned to a broker number 10 with a higher capability, only the broker device 10 with the highest capability among the broker devices 10 holding the latest publication data SD can transmit the publication data SD. be allowed.

Furthermore, in order to avoid continuing to receive the publication data SD even though the subscribing client device 30 does not exist, the other subscription information management unit 120 determines that the number of subscriptions to the topic to which the other broker device 10 has started subscribing is 2 (self When the broker device 10 (#0) is not included), if the own broker device 10 (#0) subscribes to the topic and the subscribing client device 30 does not exist, the subscription information is deleted. Then, a subscription request KR, which is a subscription cancellation request, may be transmitted.

Furthermore, when the subscription request KR from the other broker device 10 is a subscription cancellation request, the other subscription information management unit 120 prevents the number of subscription broker devices 10 from becoming two or less. When the number of 10 is 1, if the own broker device 10 (#0) has the smallest number of subscriptions and has the smallest broker number among the broker devices 10 with the smallest number of subscriptions, the topic is selected. It is also possible to subscribe and transmit a subscription request KR to the other broker device 10 .

The self-published data transmission unit 112 acquires the latest published data SD of the topic specified by the subscription request KR from the latest published data holding unit 114, and sends it to the client device 30 (for example, the client device 30 (#2 )). The client device 30 to which the publication data SD is transferred is determined by referring to the management table 205, for example, as described above.

If the latest publication data SD is not held in the latest publication data holding unit 114, that is, if none of the client devices 30 has published the publication data SD, the own publication data transmission unit 112 performs the above-described transmission processing. do not

The other subscription information management unit 120 receives a subscription request KR for a topic, which is a group of information subscribed by the other broker device 10 , from the other broker device 10 via the communication unit 102 . Then, the content of the management table 200 is updated according to the received subscription request KR. For example, the broker device 10 that is the source of the subscription request is written as the subscription broker device m1, and the topic specified by the subscription request KR is written as the subscription information (topic) m2.

If the subscription request KR received by the other subscription information management unit 120 is a subscription registration request, the other publication data transmission unit 116 sends the latest publication data SD related to the topic specified by the subscription request KR to the latest publication. It acquires from the data holding unit 114 and transmits the acquired publication data SD to the other broker device 10 that is the source of the subscription request. The other broker device 10 that is the source of the subscription request is determined using the management table 200, for example.

The self-subscribed information management unit 108 manages a topic, which is a group of information subscribed by the self-broker device 10 (#0). 102 to another broker device 10 .

If there is no client device 30 that subscribes to the managed topic, the own subscription information management unit 108 outputs a subscription request KR that is a new subscription registration request.

Other subscription information management unit 120 divides topics specified by received subscription requests KR into topics subscribed to by two or more broker devices 10 and topics managed by own subscription information management unit 108. If there is no client device 30 that subscribes to , a subscription request KR, which is a subscription cancellation request, is output to the own subscription information management unit 108 .

Other subscription information management unit 120 calculates the number of topics subscribed to for each broker device 10, and only when the minimum value exceeds the total number of topics managed by own subscription information management unit 108, A subscription request KR, which is a new subscription registration request, is output to own subscription information management unit 108 .

The self-subscription information management unit 108 transmits the subscription request KR, which is a new subscription registration request, and the subscription request KR, which is a subscription cancellation request, output from the other publication data receiving unit 118 to other broker devices via the communication unit 102. 10. The own subscription information management unit 108 may perform this transfer to all broker devices 10, or may perform this transfer only to a specific broker device 10 in consideration of the network topology. If it is transferred only to a specific broker device 10, only that broker device 10 returns the publication data SD related to the topic specified by the subscription request KR.

The termination detection unit 122 detects at least one of termination and abnormality of the other broker device 10 . For this detection, the end detection unit 122, for example, periodically transmits a heartbeat to the other broker device 10 via the communication unit 102, and when the other broker device 10 can no longer receive the heartbeat, , an abnormality in the other broker device 10 is detected. Also, the termination of the other broker device 10 is detected at the stage of detecting the termination notification spontaneously transmitted at the time of termination of the other broker device 10 . When the termination or abnormality is detected by the termination detection unit 122, the record in which the broker device 10 whose termination or abnormality was detected is written as the subscribing broker device m1 is deleted from the management table 200. FIG.

As a result, the other subscription information management unit 120 does not receive the subscription request KR from the other broker device 10 whose termination or abnormality has been detected by the termination detection unit 122 .

Next, an operation example of the communication system of the first embodiment configured as above will be described.

FIG. 5 is a flow chart showing an example of a processing procedure by the own broker device when receiving a subscription request from a client device.

In own broker device 10 (#0), when subscription request KR transmitted from client device 30 is received by own subscription information receiving unit 106 via communication unit 104 (S1), subscription request KR is transmitted as a subscription request. It is determined whether it is a registration request or a subscription cancellation request (S2). If it is a subscription registration request (S2: subscription registration), the subscription information management unit 108 refers to the management table 205, and the subscription information requested for subscription registration (for example, information group A) is stored in the subscription information m3 of the own broker device. , and the requesting client device 30 is written as the subscribing client device m4, thereby registering the subscription information (S3).

Further, the own subscription information management unit 108 determines whether or not the registered subscription information is a topic to be newly subscribed to within the own broker device 10 (#0) (S4). If it is determined to be a topic to be newly subscribed to (S4: Yes), the other publication data transmission unit 116 sends the publication related to the topic to which the new subscription is started to the other broker device 10 via the communication unit 102. Data SD is transmitted (S5).

After that, when the latest publication data SD of the topic is transmitted from the other broker device 10 and received by the other publication data receiving unit 118 via the communication unit 102 (S6: Yes), this publication data SD is The data is output from the publication data receiving section 118 to the latest publication data holding section 114 and held in the latest publication data holding section 114 (S7). Further, the publication data SD held in the latest publication data holding unit 114 is output to the own publication data transmission unit 112, and the subscription to the topic is started from the self publication data transmission unit 112 via the communication unit 104. is sent to the client device 30 (S8), and the process ends.

On the other hand, in step S6, if the latest publication data SD of the topic has not been transmitted from the other broker device 10 (S6: No), that is, if the publication data SD of the topic has never been published, the process exit.

On the other hand, in step S4, if the newly requested topic has already been subscribed to by another client device 30 (S4: No), is the latest publication data SD held in the latest publication data holding unit 114? Other publication data receiving unit 118 confirms whether or not (S9), and if it is held (S9: Yes), self-publishing data transmission unit 112 transmits the latest publication to client device 30 via communication unit 104. Data is transmitted (S10). On the other hand, if the latest publication data is not held (S9: No), the process is terminated.

On the other hand, in step S2, if the subscription request KR is a subscription cancellation request (S2: subscription cancellation), the subscription information management unit 108 selects the topic (for example, information The record in which the group A) is written as the own broker device subscription information m3 is deleted (S11).

After that, if there remains a record in the management table 205 in which the subscribing client device 30 is associated with the topic (for example, information group A) (S12: Yes), the process ends.

On the other hand, if there is no record in the management table 205 in which the subscribing client device 30 is associated with the topic (S12: No), the subscription information management unit 108, based on the management table 200, is created, and based on the management tables 200 and 205, a broker apparatus subscription number management table 215 is created as shown in FIG. is grasped (S13).

FIG. 6 is a diagram showing an example of a subscription information subscription number management table.

FIG. 7 is a diagram showing an example of a broker device subscription count management table.

Subscription information subscription number management table 210 (hereinafter simply referred to as "management table 210") includes subscription information (topic) m5 indicating topics to be subscribed to and topics specified by subscription information (topic) m5 are subscribed to. It is a data table in which records composed of two items, namely, the number of subscriptions m6 indicating the number of other broker devices 10 are stacked. According to the management table 200, there are two subscribing broker devices for the topic information group A: the broker device 10 (#1) and the broker device 10 (#2). Accordingly, in the management table 210, the number of subscriptions corresponding to the topic of information group A is indicated as two. Similarly, in the management table 200, there are two subscribing broker devices for the topic of information group B, and there are two subscribing broker devices for the topic of information group C. The number of subscriptions is indicated as 2, and the number of subscriptions corresponding to the information group C is indicated as 2. The management table 210 is stored in a storage (not shown) within the broker device 10 and can be referenced by each component within the broker device 10 .

The broker device subscription count management table 215 (hereinafter simply referred to as the “management table 215”) contains two numbers: a broker device m7 in which broker devices are described and a subscription count m8 indicating the number of topics subscribed to in each broker device. It is a data table in which records consisting of one item are stacked. The management table 205 indicates that the own broker device 10 (#0) subscribes to one topic, information group A. FIG. Accordingly, the management table 215 indicates that the number of subscriptions of the local broker device 10 (#0) is one. Further, the management table 200 indicates that the broker device 10 (#1) subscribes to three topics: information group A, information group B, and information group C. FIG. Therefore, the management table 215 indicates that the number of subscriptions for the broker device 10 (#1) is three. Similarly, based on the information in the management table 200, the management table 215 indicates two subscriptions for the broker device 10(#2) and one subscription for the broker device 10(#3). The management table 215 is stored in a storage (not shown) within the broker device 10 and can be referenced by each component within the broker device 10 .

When the contents of the management tables 200 and 205 are updated, the subscription information management section 108 also updates the management tables 210 and 215 according to the updated contents.

In step S13, if the number of other broker devices 10 subscribing to the topic (for example, information group A) is two or more (S13: Yes), self-subscription information management unit 108 automatically The record in which the topic (for example, information group A) is written as the broker device subscription information m3 is deleted (S16), and the unsubscribe request for the topic is transmitted to the other broker device 10 via the communication unit 102. (S17).

On the other hand, in step S13, if the number of broker devices 10 subscribing to the topic is less than 2 (S13: No), based on the management table 215, other subscription information management unit 120 The number of subscriptions is grasped, and furthermore, it is determined whether or not the number of subscriptions of own broker device 10 (#0) is the minimum (S14).

For example, in the management table 215, the number of subscriptions for each broker device 10 is 1 for the own broker device 10 (#0), 3 for the broker device 10 (#1), 2 for the broker device 10 (#2), and 2 for the broker device 10 (#2). 10 (#3) is shown to be 1. In this case, the own broker device 10 (#0) has the smallest number of subscriptions together with the broker device 11 (#3) (S14: Yes).

If the number of subscriptions is not the minimum (S14: No), the process proceeds to step S16 described above.

On the other hand, if the number of subscriptions is the smallest in step S14 (S14: Yes), other subscription information management unit 120 determines whether the own broker device 10 has the smallest broker number among the broker devices 10 with the smallest number of subscriptions. (S15).

As shown in the management table 215, the broker devices 10 with the smallest number of subscriptions are the own broker device 10 (#0) and the broker device 10 (#3) with the number of subscriptions of 1. #0) is 0, which is the smallest broker number (S15: Yes), so the process is terminated.

On the other hand, in step S15, when it is not the minimum (S15: No), it progresses to step S16 mentioned above.

FIG. 8 is a flow chart showing an example of a processing procedure by the own broker device when receiving a subscription request from another broker device.

When the subscription request KR is transmitted from the other broker device 10, this subscription request KR is received by the other subscription information management unit 120 via the communication unit 102 (S21).

If the subscription request KR is a subscription registration request (S22: subscription registration), the other subscription information management unit 120 writes the subscription requesting broker device 10 as the subscription broker device m1 in the management table 200, and the subscription information ( Registration is performed by writing the subscription information (topic) specified in the subscription request KR as topic) m2 (S23).

The topic specified by the subscription request KR is subscribed to by its own broker device 10 (#0) (S24: Yes), and the latest publication data SD of the topic is held in the latest publication data holding unit 114. (S25: Yes), if the own broker device 10 (#0) has the smallest broker number among the subscribing broker devices 10 (S26: Yes), the latest publication data SD is sent to the other publication data transmission unit 116 to the requesting broker device 10 via the communication unit 102 (S27).

In step S25, if the latest publication data SD of the topic is not held in the latest publication data holding unit 114 (S25: No), or in step S26, if the broker number of the subscription broker device 10 is the smallest broker number If not (S26: No) or after step 27, the process proceeds to step S28.

In step S28, the own subscription information management unit 108 refers to the management table 205 to determine whether or not there is a client device 30 subscribing to the topic within the own broker device 10 (#0). If it is determined that it exists (S28: Yes), the process ends.

On the other hand, if it is determined not to exist (S28: No), the other subscription information management unit 120 retrieves from the management table 210 the number of other subscribing broker devices 10 subscribing to the topic (for example, information group A) (subscription number ) is determined, and if the number is 2 or more (S29: Yes), the record in which the topic (for example, information group A) is written as own broker device subscription information m3 is deleted from the management table 205 ( S30), a subscription cancellation request for the topic is transmitted from the own subscription information management unit 108 to the other broker device 10 via the communication unit 102 (S31).

On the other hand, in step S29, if the number of subscribing broker devices 10 is not two or more (S29: No), although there is no client device 30 subscribing to the topic within its own broker device 10 (#0), publication data SD In order to continue the subscription at the own broker device 10 (#0) for redundancy, the processing ends without performing any processing.

In step S24, the topic is not subscribed to by its own broker device 10 (#0) (S24: No), the number of other subscribing broker devices 10 is 1 (S33: Yes), and its own broker device 10 ( #0) is the broker device with the smallest number of topic subscriptions (S34: Yes), and if the broker number of its own broker device 10 (#0) is the smallest among the broker devices 10 with the smallest number of subscriptions (S35: Yes ), in order to subscribe to the topic for redundancy of the publication data SD, the subscription information of the topic (for example, information group A) is stored as the subscription information m3 of the own broker device in the management table 205 by the own subscription information management unit 108. It is written (S36), and thereafter, a subscription request KR designating the topic is transmitted to another broker device 10 via the communication unit 102 (S37).

Furthermore, when the latest publication data SD output from the other broker device 10 is received by the other publication data receiving unit 118 via the communication unit 102 (S38: Yes), the received latest publication data SD is output to the latest publication data holding unit 114 and held (S39), and the process ends.

If the number of subscriptions of the other broker device 10 is not 1 in step S33 (S33: No), and if the number of subscriptions of the own broker device 10 (#0) is not the minimum in step S34 (S34: No), If the broker number of its own broker device 10 (#0) is not the smallest broker number in step S35 (S35: No), and if the latest publication data SD is not transmitted in step S38 (S38: No), No processing is performed and the processing ends.

In step S22, if the subscription request KR transmitted from the other broker device 10 is a subscription cancellation request (S22: subscription cancellation), the other subscription information management unit 120 reads the subscription request KR from the management table 200. is written as subscription information (topic) m2 (S32), and then the process proceeds to step S33.

Incidentally, in this embodiment, whether or not the broker number is the smallest is used as the judgment criterion used for the judgments in steps S15, S26, and S35. However, the criterion is not limited to this and may instead use whether or not it is the highest broker number. Alternatively, an algorithm such as continuing the subscription of the broker device 10 with the least recent traffic volume regardless of the broker number may be used.

FIG. 9 is a flow chart showing an example of a processing procedure by the own broker device when a publication data publication request is made from a client device.

When the topic and its publication data SD are transmitted from the client device 30 (for example, the client device 30 (#1)) in the own broker device 10 (#0), the publication data SD is transmitted via the communication unit 104 as follows: It is received by self-published data receiving section 110 and further output to self-published data transmitting section 112 (S41). The self-published data transmission unit 112 refers to the management table 205 to determine whether or not there is a client device (subscribing client device) 30 subscribing to a topic related to the published data SD (S42).

If it is determined that there is a subscribing client device 30 (S42: Yes), the client device 30 (for example, client device 30 (#2)) that has been determined to have a , the publication data SD is transmitted (S43), and the process proceeds to step S44.

On the other hand, if there is no subscribing client device 30 (S42: No), the process proceeds directly to step S44.

In step S44, the other subscription information management unit 120 determines whether or not there is another broker device 10 subscribing to the topic related to the publication data SD by referring to, for example, the management table 200 (S44). .

If it is determined to exist (S44: Yes), the publication data SD is transmitted from the other publication data transmission unit 116 to the determined broker device 10 via the communication unit 102 (S45), The publication data SD is held in the latest publication data holding unit 114 (S46).

On the other hand, if it is determined in step S44 that it does not exist (S44: No), the process proceeds to step S46, and the publication data SD is held in the latest publication data holding unit 114 (S46).

Although not shown in FIG. 9, if there is publication data SD related to a topic that is not subscribed to by both the own broker device 10 (#0) and the other broker device 10 (both determinations in S42 and S44 are No). If there is), a subscription registration request for that topic is sent to the other broker device 10 .

FIG. 10 is a flow chart showing an example of a processing procedure by the own broker device when publishing data is transmitted from another broker device.

The publication data SD transmitted from the other broker device 10 is received by the other publication data receiving section 118 via the communication section 102 (S51).

In response, the own subscription information management unit 108 refers to the management table 205 to determine whether the client device (subscribing client device) 30 that subscribes to the topic related to the publication data SD is connected to the own broker device 10. is determined (S52).

If it is determined to be connected (S52: Yes), self-published data transmission unit 112 transmits data to the determined client device 30 (for example, client device 30 (#2)) via communication unit 104. , and the publication data SD are transmitted (S53). Also, this publication data SD is held in the latest publication data holding unit 114 (S54), and then the process ends.

On the other hand, if it is determined that there is no connection (S52: No), the process proceeds to step S54, and the publication data SD is held in the latest publication data holding unit 114 (S54).

FIG. 11 is a flow chart showing an example of a processing procedure when another broker device terminates and when an abnormality is detected.

When a voluntary termination notification arrives from the other broker device 10 to the termination detection unit 122 of the own broker device 10 (#0) (S61: Yes), or when the termination detection unit of the own broker device 10 (#0) 122 detects an abnormality in the other broker device 10 (S62: Yes), the other subscription information management unit 120 adds the topic subscribed by the broker device 10 that has terminated or caused the abnormality to the subscription list in the management table 200. Whether or not it is written as information (topic) m2 is confirmed (S63).

If the voluntary end notification does not arrive (S61: No), and if no abnormality of the other broker device 10 is detected (S62: No), the process returns to step S61. Also, if it is determined in step S63 that no writing has been done, that is, if there is no topic subscribed to by the broker device 10 that has terminated or caused an error (S63: No), the processing of step S61 is also performed. back to

On the other hand, if it is determined in step S63 that writing has been done, that is, if there is a topic subscribed to by the broker device 10 that has terminated or caused an error (S63: Yes), the other subscription information management unit 120 deletes from the management table 200 the record in which the topic subscribed to by the broker device 10 that has terminated or caused an error is written as the subscription information (topic) m2 (S64).

Further, the topic is not subscribed to by its own broker device 10 (#0) (S65: No), the number of other subscribing broker devices 10 is 1 (S66: Yes), and its own broker device 10 (#0) ) has the smallest number of subscriptions (S67: Yes), and the own broker device 10 (#0) has the smallest broker number among the broker devices 10 with the smallest number of subscriptions (S68: Yes), the topic A subscription is registered for redundancy in the broker device 10 (S69), and this topic is transmitted from the own subscription information management unit 108 to the other broker device 10 via the communication unit 102 (S70).

Otherwise (S65: Yes, S66: No, S67: No, S68: No), the process returns to step S63.

After step S70, when the own broker device 10 (#0) receives the latest publication data SD (S71: Yes), the latest publication data SD is held in the latest publication data holding unit 114 (S72 ), and then returns to step S63.

On the other hand, after step S70, if the own broker device 10 (#0) does not receive the latest publication data SD (S71: No), the process returns to step S63.

With the above configuration, the own broker device 10 (# 0 ) can ensure the redundancy of the publication data SD, so that the publication data SD will not be lost even when an abnormality occurs in another broker device 10 . As a result, reliability can be improved in a system that employs a publication/subscription model communication protocol. Moreover, since the transmission destination of the publication data SD for redundancy can be changed according to the data amount of the publication data SD subscribed by the broker device 10, appropriate load distribution can be realized.

(Modification)
A modification of the communication system of the first embodiment will be described.

The broker device 10 illustrated in FIG. 3 has a function of determining whether or not to subscribe to a topic in order to make publication data SD redundant. In this modification, such a function is provided as a sub-broker device outside the broker device.

FIG. 12 is a conceptual diagram showing a modification of the communication system of the first embodiment.

That is, in the communication system 2 of this modified example, as shown in FIG. 12, the sub-broker device 40 is connected to the outside of the broker device 11 via the network 21 . In the example shown in FIG. 12, a sub-broker device 40 is provided for each broker device 11 on a one-to-one basis, but the configuration is not limited to this, and a sub-broker device 40 may be provided only for a specific broker device 11. good too. Also, one sub-broker device 40 may be connected to a plurality of broker devices 11 so that one sub-broker device 40 functions in common for the plurality of broker devices 11 .

As with the network 20, the network 21 may be, for example, a local line such as a LAN, a wide area wired communication line such as the Internet or a dedicated line, or a wide area wireless communication line such as 3G. can.

FIG. 13 is a block diagram showing a configuration example of a broker device and a sub-broker device applied to the modification of the communication system of the first embodiment.

The broker device 11 has a configuration obtained by removing the end detection unit 122 from the broker device 10 .

The sub-broker device 40 includes a termination detection unit 402 and a subscription decision unit 404 .

The end detector 402 has the same function as the end detector 122 .

The subscription determination unit 404 receives a subscription change request for the subscription request KR from the own subscription information management unit 108 and the other subscription information management unit 120 of the broker device 11 . Instead of receiving subscription change requests from both the own subscription information management unit 108 and the other subscription information management unit 120, the subscription determination unit 404 recognizes the subscription change requests by monitoring communications or the like. may

Further, when the subscription change request is received, the subscription determination unit 404 determines whether the broker device 11 that is the source of the subscription change request is a new subscription request, a cancellation request, or a subscription continuation request for the topic associated with the subscription request KR. , to determine whether it is a continued unsubscribe request.

As a criterion for this determination, for example, if there remains a record in which the subscribing client device 30 is associated with the topic (for example, information group A) as subscribing information (topic) m2 in the management table 205, the subscribing is performed. If it continues and there is no remaining topic, it is possible to determine whether or not to continue subscribing to this topic according to the number of subscriptions of other broker devices 11 and the number of subscriptions of the own broker device 11 (#0).

The subscription determination unit 404 further outputs a subscription request KR to the own subscription information management unit 108 of the broker device 11 for a new subscription request or unsubscribe request.

As described above, according to the modified example, by providing the sub-broker device 40, it is possible to realize a high redundancy function even when using the broker device 11 which is not provided with a new redundancy function. A possible communication system 2 can be realized.

(Second embodiment)
Some protocols that employ a publish-subscribe model, such as MQTT, have QoS capabilities. By using the QoS function, the publication data SD can be labeled in order to distinguish publication data SD whose arrival must always be guaranteed, publication data SD whose arrival need not be guaranteed, and the like.

In the first embodiment, it is assumed that redundancy is ensured for all publication data SD, but it is not always necessary to ensure redundancy depending on the QoS value. Focusing on this, in the present embodiment, in order to reduce the amount of communication and the load on the broker device 10, redundancy is not secured for the publication data SD whose arrival does not need to be guaranteed.

FIG. 14 is a block diagram showing a configuration example of a broker device applied to the communication system of the second embodiment.

The configuration of the broker device 12 is similar to the configuration of the broker device 10, but the broker device 12 includes a QoS management unit 124, which is not provided in the broker device 10, in addition to the other subscription information management unit 120 and the own subscription information management unit 108. It is different in that it is prepared between Therefore, the points different from the broker device 10 will be described below.

In addition to the functions described in the first embodiment, the other subscription information management unit 120 receives a subscription request KR, which is a subscription cancellation request, from the other broker device 10, based on the received subscription cancellation request. update the content of the other subscription information management table 220 illustrated in .

FIG. 15 is a diagram showing an example of the other subscription information management table.

Other subscription information management table 220 (hereinafter simply referred to as "management table 220") is a modified example of management table 200, and includes three types of subscription broker device m1, subscription information (topic) m2, and QoSm9. A data table in which records consisting of items are stacked. The management table 220 is stored in a storage (not shown) within the broker device 12 and can be referenced by each component within the broker device 12 .

The QoS management unit 124 manages the QoS value for each subscription information (topic) by calculating a QoS value, which is an index value of reliability required for transmission/reception of the publication data SD, and writing it as QoSm9 in the management table 220. . Also, using the management table 220, it is determined whether or not duplication of the publication data SD is necessary.

Other subscription information management unit 120 outputs subscription request KR, which is a subscription registration request, to own subscription information management unit 108 only when QoS management unit 124 determines that duplication of publication data SD is necessary.

In response, the own subscription information management unit 108 determines whether or not the own broker device 12 (#0) subscribes to the publication data SD according to the algorithm described in the first embodiment. .

The subscription information management unit 108 manages a subscription information management table 225 as illustrated in FIG. 16 in addition to the functions described in the first embodiment.

FIG. 16 is a diagram showing an example of a subscription information management table.

Own subscription information management table 225 (hereinafter simply referred to as "management table 225") is a modified example of management table 205, and is composed of own broker device subscription information m3 and subscribed client device m4, with QoSm9 newly added. A data table in which records consisting of items are stacked. The management table 225 is stored in a storage (not shown) within the broker device 12 and can be referenced by each component within the broker device 12 .

When the QoS management unit 124 determines that duplication of the publication data SD is necessary, the own subscription information management unit 108 determines whether or not to continue the subscription according to the algorithm described in the first embodiment. Further, when transmitting the changed contents of the management table 225 to the other broker device 10, the corresponding QoS information can also be transmitted together.

The QoS management unit 124 is called when a topic is output from the other subscription information management unit 120 or the own subscription information management unit 108, and determines whether the publication data SD related to the topic is information whose redundancy should be guaranteed. determine whether or not

For example, QoS takes a binary value of 0 or 1, 0 means publication data SD whose arrival need not be guaranteed, and 1 means publication data SD whose arrival should be guaranteed. In this case, the QoS management unit 124 refers to the management tables 220 and 225 and calculates the maximum QoS value of the topic.

For example, according to the management table 220, when the subscription information (topic) is information group A, the broker device 10 (#1) has QoS=0 and the broker device 10 (#2) has QoS=1. , when the subscription information of the own broker device 12 (#0) is information group A, QoS=1, and the maximum value of QoS is 1;

On the other hand, in the case of the information group C, according to the management table 220, the broker device 10 (#1) has QoS=0, the broker device 10 (#2) also has QoS=0, and the maximum value is 0.

When the maximum value is 1, the QoS management unit 124 determines that the publication data SD should be redundant, and when the maximum value is 0, the publication data SD does not need to be redundant. I judge.

Even when QoS takes values other than the two values described above, for example, if the maximum value is 1 or more, it is determined that the publication data SD should be made redundant. Judgment can be made.

For example, in the example shown in management table 220, information group B is subscribed to by broker device 10(#1) and broker device 10(#3). The maximum QoS value of the information group B is 1, and the publication data SD should be made redundant. has been made

Here, it is assumed that the broker device 10 (#1) issues a subscription cancellation request. Then, the information group B is subscribed only by the broker device 10 (#3). In this case, in the first embodiment, the own broker device 12 (#0) with the smallest number of subscriptions and the smallest broker number is the broker device 10 (#0) even though there is no client device 30 that subscribes to the information group B. #1) subscribing to information group B instead.

However, in the second embodiment, the maximum QoS value is 0, and the publication data SD does not require redundancy. In this case, only the broker device 10 (#3) continues the subscription and the self-broker device 12 (#0) does not subscribe. #0) to reduce the processing load.

Next, an operation example of the communication system of the second embodiment configured as above will be described.

FIG. 17 is a flow chart showing an example of a processing procedure by the own broker device when receiving a subscription request from a client device.

The flowchart shown in FIG. 17 is obtained by adding step S12a between step S12 and step S13 of the flowchart shown in FIG.

Therefore, the processing related to step S12a will be described below, and duplicate description will be avoided.

In step S12, if the subscribing client device 30 does not exist and the subscribing client device 30 is subscribed by another broker device 10 at the time of canceling the subscription (S12: No), in step S12a, it is determined whether or not redundancy of the publication data SD is necessary. Therefore, the QoS management unit 124 determines whether or not the QoS maximum value is zero (S12a).

If the QoS maximum value is determined to be zero (S12a: Yes), the process proceeds to step S16, and if not determined to be zero (S12a: No), the process proceeds to step S13.

FIG. 18 is a flow chart showing an example of a processing procedure by the own broker device when receiving a subscription request from another broker device.

The flowchart shown in FIG. 18 is obtained by adding step S28a between steps S28 and S29 of the flowchart shown in FIG. 8, and adding step S32a between steps S32 and S33. .

Therefore, below, the processing related to step S28a and step S32a will be described to avoid redundant description.

If it is determined in step S28 that there is no client device 30 subscribing to the topic at the time of subscription registration (S28: No), the QoS management unit 124 determines whether the maximum QoS value is zero, as in step S12a. It is determined whether or not (S28a).

If the QoS maximum value is determined to be zero (S28a: Yes), the process proceeds to step S30, and if not determined to be zero (S28a: No), the process proceeds to step S29.

Also after step S32, the QoS management unit 124 determines whether or not the maximum QoS value is zero (S32a), as in step S12a.

If it is determined that the QoS maximum value is zero (S32a: Yes), the process ends, and if it is not determined to be zero (S32a: No), the process proceeds to step S33.

An example of the processing procedure when a client device 30 connected to its own broker device 12 (#0) issues a publication request for publication data SD is as shown in the flow chart of FIG. , an example of the processing procedure when the publication data SD is transmitted is as shown in the flow chart of FIG.

As described above, according to the communication system of the second embodiment, it is not necessary to ensure redundancy for all publication data SD in order to determine whether or not redundancy is necessary according to the QoS value. Therefore, it is possible to reduce the amount of communication and the load on the broker device.

(Third embodiment)
In the first and second embodiments, when publishing the publication data SD, the individual publication data SD are transmitted as individual packets. When MQTT is used for IoT (Internet of things), when packets are transmitted, a large amount of published data such as sensor published data is generated and a large amount of communication packets are transmitted and received. In general, the performance limit of network equipment such as routers is determined by the number of packets and the total amount of published data. Therefore, reducing the number of packets and the total amount of communication publication data is essential to enable more publication data to be sent and received. The third embodiment provides a technique for reducing the total amount of MQTT packets and the amount of transmitted published data while maintaining communication reliability.

FIG. 19 is a block diagram showing a configuration example of a broker device applied to the communication system of the third embodiment.

The configuration of the broker device 13 is similar to that of the broker device 10, but the broker device 13 includes an aggregation/compression unit 126, a real-time determination unit 128, and a division/development unit 130, which are not provided in the broker device 10. and Therefore, the points different from the broker device 10 will be described below.

The real-time determination unit 128 is connected to the other publication data transmission unit 116 in order to determine the publication data SD to be periodically transmitted. Publishing data SD exceeding the maximum waiting time determined for each is determined to be subject to aggregation by the aggregation/compression unit 126 .

Therefore, in the present embodiment, the self-published data receiving unit 110 also records the reception time of the published data SD received from the client device 30 (for example, the client device 30 (#1)).

FIG. 20 is a diagram showing an example of a transmission waiting list.

In the transmission waiting list 230, as an example, data in which records composed of items such as publication data destination m10, subscription information (topic) m11, publication data m12, reception date and time m13, and processed flag m14 are piled up. is a table. The transmission waiting list 230 is stored in a storage (not shown) within the broker device 13 and can be referred to by each component within the broker device 13 .

When the client device 30 requests the publication data SD, the real-time determination unit 128 updates the record contents of the transmission waiting list 230 .

FIG. 21 is a diagram showing an example of a maximum waiting time list and time conditions.

The maximum waiting time list 235 is a data table in which records composed of two items of subscription information (topic) m15 and maximum waiting time m16 are piled up. The maximum waiting time list 235 and the time conditions 240 are stored in storage (not shown) within the broker device 13 and can be referenced by each component within the broker device 13 .

The time condition 240 indicates, as an example, packet transmission period T=10 ms (milliseconds) and current time=2017/12/01 00:00:01.090.

Since the real-time property required for transmission/reception differs for each publication data SD, the real-time property determination unit 128 further uses the maximum waiting time list 235 to write the maximum waiting time m16 for each subscription information (topic) m15. manages the maximum time to wait before sending a message.

For example, as shown in the time condition 240, when packet transmission is performed every T=10 milliseconds, the real-time determination unit 128 is called every 10 milliseconds, and the real-time determination unit 128 is called at the next call time. 128 retrieves packets exceeding the maximum wait time m16 shown in the maximum wait time list 235 .

For example, as shown in the time condition 240, if the "current time" is "2017/12/01 00:00:01.090", the next packet transmission time will be the current time with the packet transmission period T=10. It becomes "2017/12/01 00:00:01.100" with milliseconds added. Then, in the transmission waiting list 230, the packets exceeding the maximum waiting time written as the maximum waiting time m16 at the next packet transmission time are the 1st, 2nd, and 4th records from the top in the transmission waiting list 230 illustrated in FIG. A packet corresponding to

In the transmission waiting list 230, the subscription information (topic) m11 of the packet corresponding to the first record is the information group A, so the maximum waiting time m16 of the information group A shown in the maximum waiting time list 235 is displayed in the reception date and time m13. Even if 100 milliseconds is added, the result is only "00:00:01.095", and the next packet transmission time "2017/12/01 00:00:01.100" is not reached. The time exceeds the maximum waiting time m16. Similarly, since the subscription information (topic) m11 of the packet corresponding to the second record is information group B, even if 15 milliseconds, which is the maximum waiting time m16 of information group B, is added to the reception date and time m13, " 00:00:01.097" and does not reach the next packet transmission time of "2017/12/01 00:00:01.100", so the waiting time also exceeds the maximum waiting time m16. do. Similarly, since the subscription information (topic) m11 of the packet corresponding to the fourth record is information group C, even if 50 milliseconds, which is the maximum waiting time m16 of information group C, is added to the reception date and time m13, Since it is only "00:00:01.095" and does not reach the next packet transmission time "2017/12/01 00:00:01.100", the waiting time exceeds the maximum waiting time m16. .

On the other hand, the waiting time for other packets does not exceed the maximum waiting time m16 at the next packet transmission time, so the transmission is postponed.

The aggregation/compression unit 126 is connected to the other publication data transmission unit 116 and aggregates the publication data SD transmitted to the other broker device 10 into one aggregated publication data for each other broker device 10 at regular time intervals. Aggregation/compression unit 126 further compresses the aggregated publication data according to a predetermined algorithm.

Specifically, the aggregating/compressing unit 126 collects a plurality of publication data SD to be transmitted to other broker devices 10 extracted by the real-time determination unit 128 for each broker device 10 specified by the destination m10 in the transmission waiting list 230. into one packet and compress it.

For example, in the example described with reference to FIGS. 20 and 21, the 1st, 2nd, and 4th from the top in the transmission waiting list 230 at the “current time” of “2017/12/01 00:00:01.090”. The packets corresponding to the records are transmitted. For the destination m10 in the transmission waiting list 230, the packets corresponding to the first and second records are the broker device 10 (#1), and the packet corresponding to the fourth record is the broker apparatus 10 (#1). It is the broker device 10 (#2). Therefore, the aggregation/compression unit 126 aggregates the packets corresponding to the first and second records into one packet and compresses it. Also, the packet corresponding to the fourth record is compressed as one packet. An example of a compressed packet format is shown in FIG.

FIG. 22 is a data structure diagram illustrating a packet format of compressed and aggregated publication data.

The compressed/aggregated publication data 245 is obtained by further compressing the aggregated multiple publication data SD by the aggregation/compression unit 126 .

In the example shown in FIG. 22, the compressed/aggregated publication data 245 has a structure in which the publication data SD1 and the publication data SD2 are arranged, aggregated as one publication data, and then compressed. Publication data SD1 includes subscription information (topic) j1, data header (publication data size, etc.) h1, and data body b1. Publication data SD2 includes subscription information (topic) j2, data header (publication data size, etc.) h2. , and a data body b2. Note that the number of publication data SD aggregated in the compressed and aggregated publication data 245 is not limited to two, and may be any number.

The division/expansion unit 130 is connected to the other publication data reception unit 118, expands the compressed and aggregated publication data 245 transmitted from the other broker device 10, restores the aggregated publication data, and divides the aggregated publication data. Then, the restored publication data SD1 and SD2 are restored to the publication data SD1 and SD2, and the restored publication data SD1 and SD2 are output to the other publication data reception unit 118. FIG.

Further, the division/development unit 130 restores the aggregated publication data from the compressed and aggregated publication data by expanding the compressed and aggregated publication data output from the other broker device 10 according to a predetermined algorithm. Further, by dividing the aggregated publication data, multiple pieces of publication data are restored from the aggregated publication data.

Next, an operation example of the communication system of the third embodiment configured as above will be described.

First, processing when receiving a publication request for publication data SD from the client device 30 will be described.

FIG. 23 is a flow chart showing an example of a processing procedure when receiving a publication data publication request from a client device.

When the publication request transmitted from the client device 30 is received (S81), the own subscription information management unit 108 refers to the management table 205 and sets the topic for which the publication request is made to the own broker device subscription information m3. 30 is confirmed whether or not there is a record in which it is written as the subscribing client device m4 (S82).

If the subscribing client device 30 determines that there is a record written as the subscribing client device m4 (S82: Yes), the publication data SD is transmitted to the client device 30 (S83), and the process proceeds to step S84.

If it is determined in step S82 that it does not exist (S82: No), the process proceeds directly to step S84.

In step S84, the management table 200 is referred to, and it is determined whether or not there is a record in which the other broker device 30 that subscribes to the subscription information (topic) for which the publication request is written as the subscribing broker device m1 exists (S84 ).

If it is determined to exist (S84: Yes), registration is made by writing information corresponding to each item in the transmission waiting list 230 as shown in FIG. 20 (S85), and the final publication data SD is It is held in the latest publication data holding unit 114, and the process ends (S86). Note that when a plurality of broker devices 10 subscribe to the topic of a single publication data SD, the transmission standby list 230 holds the publication data SD for each destination broker device 10 .

On the other hand, if it is determined in step S84 that it does not exist (S84: No), only the latest publication data SD is held in the latest publication data holding unit 114, and then the process ends.

Next, the processing for transmitting publication data in response to a publication request will be described.

FIG. 24 is a flow chart showing an example of a processing procedure when publishing data is transmitted in response to a publication request.

First, in order to generate a packet to be transmitted to each broker device 10 other than its own broker device 13 (#0), it is checked whether or not there is an unprocessed destination (S91).

If there is no unprocessed destination (S92: No), after waiting for a certain period of time (for example, T=10 milliseconds) (S99), the flag written in the corresponding processed flag m14 in the transmission waiting list 230 is It is cleared (S100) and returns to step S91.

On the other hand, if there is an unprocessed destination in step S91 (S91: Yes), that destination is acquired (S92).

Subsequently, the transmission waiting list 230 shown in FIG. 20 is referred to, and it is determined whether or not there is unprocessed publication data SD with the acquired destination designated as the destination m10, that is, without the processed flag m14. (S93).

If it is determined that the publication data SD exists (S93: Yes), the publication data SD is extracted and a flag is added to the processed flag m14 of the corresponding record in the transmission waiting list 230 (S94).

Furthermore, the maximum waiting time (for example, maximum waiting time M) of the subscription information (topic) is acquired from the maximum waiting time list 235 (S95). Note that the maximum waiting time list 235 may be prepared in advance or dynamically generated upon request from the client device 30 or the like.

Further, it is determined whether or not the execution date and time will be after the maximum waiting time M has elapsed from the registration date and time, that is, whether (current time + T) > (registration date and time + M) (S96).

When it is determined that the execution date and time will be after the maximum waiting time M has passed from the registration date and time (S96: Yes), in order to send the current publication data SD, the publication data SD is the same as the transmission waiting list 230. It is registered in the configured transmission list (S97), correspondingly, the publication data SD is deleted from the transmission standby list 230 (S98), and the process returns to step S93. Note that the transmission list has the same configuration as the transmission standby list 230, so illustration thereof is omitted.

On the other hand, if it is determined in step S96 that the execution date and time will not be after the maximum waiting time M has elapsed from the registration date and time (S96: No), the process also returns to step S93.

On the other hand, in step S93, if it is determined that there is no publication data SD (S93: No), the held publication data SD is combined with the transmission list (S101), compressed (S102), and sent to the destination broker device 30. The packet is transmitted (S103), the transmission list is cleared (S104), and the process returns to step S91.

Next, processing when publication data is transmitted from another broker device 10 will be described.

FIG. 25 is a flow chart showing an example of a processing procedure when publication data is transmitted from another broker device.

When the publication data SD transmitted from the other broker device 10 is received by its own broker device 13 (#0) (S111), the compressed packet is decompressed by the division/decompression unit 130, and the decompressed packet contains a plurality of publication data SD, the expanded packet is further divided and each publication data SD is restored (S112).

If it is determined that the unprocessed publication data SD does not exist in the divided packets (step S113: No), the process ends.

On the other hand, if it is determined that there is unprocessed publication data SD in the divided packet (step S113: Yes), one piece of unprocessed publication data SD is taken out (S114), and subscription to management table 205 is performed. It is determined whether or not the subscribing client device 30 of the topic exists in the broker device m1 (S115).

If it is determined that the subscribing client device 30 exists (S115: Yes), the publication data SD is transmitted to the client device 30 (S116), and the latest publication data SD is held in the latest publication data holding unit 114 ( S117) and returns to step S113.

On the other hand, if it is determined in step S115 that the subscribing client device 30 does not exist (S115: No), the process proceeds to step S117.

The processing procedure when own broker device 13 (#0) receives a subscription request from client device 30 is as described with reference to the flowchart of FIG. The processing procedure when a subscription request is received from the device 10 is as described using the flowchart of FIG. As explained.

Thus, according to the third embodiment, it is possible to reduce the total amount of packets and the amount of transmitted published data while maintaining the reliability of communication.

(Modification)
A modification of the communication system of the third embodiment will be described.

In the third embodiment, as shown in FIG. 19, aggregation/compression and segmentation/decompression of packets are executed by the broker device 13 having an aggregation/compression unit 126 and a segmentation/decompression unit 130. In a variant, it is executed by the client device instead of the broker device 13 .

FIG. 26 is a conceptual diagram showing a configuration example of a client device applied to the modification of the communication system of the third embodiment.

The client device 31 of the modified example is connected to the broker device 10 via the network 20 . Since the configuration of the broker device 10 is as shown in FIG. 3, redundant description will be avoided.

The client device 31 includes a communication unit 302 , a division/development unit 304 , a subscription/publication request unit 306 , an aggregation/compression unit 308 , an abnormality detection unit 310 , and a load detection unit 312 .

The aggregation/compression unit 308 aggregates a plurality of publication data SD related to the same topic to generate one piece of aggregated publication data, compresses the generated aggregated publication data, and generates aggregated compressed publication data. do. However, since the aggregating/compressing unit 308 does not know the topic to which each broker device 10 subscribes, it cannot compress packets for each destination broker device 10 . Therefore, the publication data SD are aggregated and compressed for each topic.

FIG. 27 is a diagram showing an example of a maximum waiting time list.

FIG. 28 is a diagram showing an example of a transmission waiting list.

The maximum waiting time list 250 and time conditions 255 shown in FIG. 27 are the same as the maximum waiting time list 235 and time conditions 240 shown in FIG. The maximum waiting time list 250 and the time conditions 255 are stored in a storage (not shown) within the client device 31 and can be referred to by each component within the client device 31 .

The transmission standby list 260 shown in FIG. 28 has a configuration in which the destination m10 is deleted from the transmission standby list 230 shown in FIG. The transmission waiting list 260 is also stored in a storage (not shown) within the client device 31 and can be referred to by each section within the client device 31 .

For example, if the maximum waiting time m16 for each subscription information (topic) m15 is as shown in FIG. The subscription information (topic) m1 for which the maximum waiting time has passed at some time becomes information group A, information group B, information group B, and information group C corresponding to the first to fourth records from the top. Therefore, the aggregation/compression unit 308 aggregates and compresses the information group A packets, the information group B packets, and the information group C packets. Since the data of the information group A is only the first record and the data of the information group C is only the fourth record, they are compressed as they are. On the other hand, since the packet of the information group B has data corresponding to the second and third records, the two data are aggregated and then compressed.

FIG. 29 is a data structure diagram illustrating a packet format of compressed aggregated data.

The compressed aggregated publication data 265 is obtained by further compressing the aggregated multiple publication data SD by the aggregation/compression unit 308 .

In the example shown in FIG. 29, the compressed and aggregated publication data 265 has a structure in which the publication data SD1 and the publication data SD2 are aggregated as one publication data and then compressed. Here, since the publication data SD1 and the publication data SD2 are the same subscription information (topic), the subscription information (topic) j is provided at the beginning as information common to the publication data SD1 and the publication data SD2. The data header h1 and data body b1 of SD1 may follow, followed by the data header h2 and data body b2 of publication data SD2. Note that the number of publication data SD aggregated in the compressed and aggregated publication data 265 is not limited to two, and may be any number. On the broker device 10 side, the client device 31 and the broker device 10 to be transferred are determined by referring to the topic information of the received packet. When transferring to another broker device 10, the publication data SD may be aggregated for each destination broker device 10 and then transmitted in combination with the configuration of FIG.

On the other hand, when the publication data SD transmitted from the broker device 10 is received by the client device 31, the publication data SD is aggregated and compressed for each topic. It has a function of dividing aggregated and compressed publication data in which publication data SD is aggregated and compressed into individual publication data.

That is, the division/development unit 304 expands the aggregated compressed publication data, restores the aggregated publication data before compression, divides the restored aggregated publication data, and restores a plurality of publication data SD. .

When detecting an abnormality in the connected broker device 10, the abnormality detection unit 310 changes the connection destination from the abnormal broker device 10 to another broker device 10 (for example, the broker device 10 (#1)).

When the load detection unit 312 detects an increase in the load on the broker device 10, the load detection unit 312 changes the connection destination from the broker device 10 whose load increase has been detected to another broker device 10 (for example, the broker device 10 (#1)).

The communication unit 302 transmits the aggregated compressed publication data to the broker device 10 (for example, the broker device 10 (#1)) changed as the connection destination by the abnormality detection unit 310 and the load detection unit 312, and outputs the aggregated and compressed publication data transmitted from , to the dividing/expanding unit 304 .

In this modification, the broker device 10 has a function of managing subscription information (topics) of aggregated/compressed packets in addition to the functions described in the first embodiment.

FIG. 30 is a flow chart showing an example of a processing procedure when receiving a publication request for publication data from a client device.

When the client device 31 makes a publication request (S121), the subscription information (topic) m11, the data m12, and the registration date and time m13 of the publication data SD are held in the transmission waiting list 260 shown in FIG. (S122).

On the other hand, the client device 31 periodically transmits the publication data SD to the broker device 10, and therefore aggregates, compresses, and transmits packets for each subscription information (topic).

FIG. 31 is a flow chart showing an example of a processing procedure when aggregation/compression and transmission processing of packets are performed for each subscription information (topic).

Since the flowchart shown in FIG. 31 is similar to the flowchart shown in FIG. 24, redundant description will be avoided and differences will be described.

That is, in FIG. 24, packet aggregation/compression processing is performed for each destination broker device 10, but in FIG. 31, packet aggregation/compression processing is performed for each topic. Therefore, in FIG. 31, in step S131, it is determined whether or not unprocessed subscription information (topic) exists. is acquired, and in step S133 it is determined whether or not there is transmission waiting data that matches the acquired subscription information (topic), and if it is determined that there is, in step S134 the acquired subscription information Data awaiting transmission that matches is retrieved.

If it is determined not to exist in step S131 (S131: No), the processing from step S99 onward in FIG. 24 is performed. 24 are performed, and after step S134, the processes after step S95 in FIG. 24 are performed.

FIG. 32 is a flow chart showing an example of a processing procedure when publishing data is transmitted from a broker device.

In the client device 31, when the publication data SD transmitted from the broker device 10 is received by the communication unit 302 (S141), the publication data SD is developed by the dividing/developing unit 304 and then divided (S142). ). Furthermore, since processing is performed for each individual publication data SD, it is determined whether or not unprocessed publication data SD exists in the divided publication data SD (S143).

If there is no unprocessed publication data SD (S143: No), the process is terminated, and if there is unprocessed publication data SD (S143: Yes), one publication data SD is extracted and processed. is executed, the process returns to S144.

It should be noted that the processing procedure for the subscription request is omitted here because it only transmits the subscription request to the broker device 10 . Also, since the processing procedure on the broker device 10 side has already been explained in the first embodiment, redundant explanation is avoided.

This modification also makes it possible to reduce the total amount of packets and the amount of published data to be transmitted while maintaining the reliability of communication.

While several embodiments of the invention have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, as well as the scope of the invention described in the claims and equivalents thereof.

1 communication system, 2 communication system, 10 broker device, 11 broker device, 12 broker device, 13 broker device, 20 network, 21 network, 30 client device, 31 client device, 40 sub-broker device, 102 communication unit, 104 communication unit, 106 Own subscription information reception unit 108 Own subscription information management unit 110 Own publication data reception unit 112 Own publication data transmission unit 114 Latest publication data storage unit 116 Other publication data transmission unit 118 Other publication data reception unit 120 Other subscription information management unit 122 End detection unit 124 QoS management unit 126 Aggregation/compression unit 128 Real-time determination unit 130 Division/expansion unit 200 Other broker device subscription information management table 205 Own broker device subscription information management Table 210 subscription information subscription number management table 215 broker device subscription number management table 220 other subscription information management table 225 own subscription information management table 230 transmission waiting list 235 maximum waiting time list 240 time conditions 245 compression aggregation Completed publication data, 250 Maximum waiting time list, 255 Time condition, 260 Transmission waiting list, 265 Compressed and aggregated publication data, 302 Communication unit, 304 Division/development unit, 306 Subscription/publication request unit, 308 Aggregation/compression unit, 310 Abnormality detection unit 312 Load detection unit 402 End detection unit 404 Subscription determination unit.

Claims (9)

A broker device that transmits publication data received from a first client device to a second client device and another broker device,
a subscription information receiving unit that receives a subscription request for a topic subscribed by the second client device from the second client device;
a self-published data receiving unit that receives published data related to the topic from the first client device;
a self-published data transmission unit that transmits the published data received by the self-published data receiving unit to the second client device;
an other publication data transmission unit that transmits the publication data received by the own publication data reception unit to the other broker device;
a other publication data receiving unit that receives publication data related to the topic from the other broker device;
a latest publication data holding unit for extracting and holding the latest publication data for each topic from the publication data received by the own publication data reception unit and the other publication data reception unit;
a other subscription information management unit that receives a subscription request for a topic subscribed by the other broker device from the other broker device;
a self-subscription information management unit that manages topics subscribed by the broker device and transmits the topic to the other broker device when there is a change in the managed topic;
The self-published data transmission unit obtains from the latest published data holding unit the latest published data of a topic related to the subscription request received from the second client device, and transmits the data to the second client device;
The other publication data transmission unit obtains the latest publication data related to the topic related to the subscription request received by the other subscription information management unit from the latest publication data holding unit, and transmits the latest publication data to the other broker device. ,
When a subscription request for a certain topic is received from the second client device, the self-subscription information management unit subscribes to the managed topic in order to determine whether the topic is a new topic. determining whether a client device is present;
The self-subscription information management unit outputs a subscription request for new subscription registration when there is no client device that subscribes to the managed topic,
If there is no client device subscribing to the topic managed by the self-subscription information management unit among the topics subscribed to by two or more broker devices, the other subscription information management unit cancels the subscription. to the own subscription information management unit . A broker device that transmits publication data received from a first client device to a second client device and another broker device,
a subscription information receiving unit that receives a subscription request for a topic subscribed by the second client device from the second client device;
a self-published data receiving unit that receives published data related to the topic from the first client device;
a self-published data transmission unit that transmits the published data received by the self-published data receiving unit to the second client device;
an other publication data transmission unit that transmits the publication data received by the own publication data reception unit to the other broker device;
a other publication data receiving unit that receives publication data related to the topic from the other broker device;
a latest publication data holding unit for extracting and holding the latest publication data for each topic from the publication data received by the own publication data reception unit and the other publication data reception unit;
a other subscription information management unit that receives a subscription request for a topic subscribed by the other broker device from the other broker device;
a self-subscription information management unit that manages topics subscribed by the broker device and transmits the topic to the other broker device when there is a change in the managed topic;
The self-published data transmission unit obtains from the latest published data holding unit the latest published data of a topic related to the subscription request received from the second client device, and transmits the data to the second client device;
The other publication data transmission unit obtains the latest publication data related to the topic related to the subscription request received by the other subscription information management unit from the latest publication data holding unit, and transmits the latest publication data to the other broker device. ,
When a subscription request for a certain topic is received from the second client device, the self-subscription information management unit subscribes to the managed topic in order to determine whether the topic is a new topic. determining whether a client device is present;
The self-subscription information management unit outputs a subscription request for new subscription registration when there is no client device that subscribes to the managed topic,
The other subscription information management unit calculates the number of topics subscribed to for each broker device, and the minimum number of topics subscribed to each broker device is managed by the own subscription information management unit. A broker device that outputs a subscription request for new subscription registration to the own subscription information management unit when the total number of topics exceeds the total value. A broker device that transmits publication data received from a first client device to a second client device and another broker device,
a subscription information receiving unit that receives a subscription request for a topic subscribed by the second client device from the second client device;
a self-published data receiving unit that receives published data related to the topic from the first client device;
a self-published data transmission unit that transmits the published data received by the self-published data receiving unit to the second client device;
an other publication data transmission unit that transmits the publication data received by the own publication data reception unit to the other broker device;
a other publication data receiving unit that receives publication data related to the topic from the other broker device;
a latest publication data holding unit for extracting and holding the latest publication data for each topic from the publication data received by the own publication data reception unit and the other publication data reception unit;
a other subscription information management unit that receives a subscription request for a topic subscribed by the other broker device from the other broker device;
a subscription information management unit that manages the topic subscribed by the broker device and transmits the topic to the other broker device when there is a change in the managed topic;
an index value management unit that manages an index value of reliability required for transmission and reception of the publication data for each topic and determines whether or not duplication of the publication data is necessary ;
The self-published data transmission unit obtains from the latest published data holding unit the latest published data of a topic related to the subscription request received from the second client device, and transmits the data to the second client device;
The other publication data transmission unit obtains the latest publication data related to the topic related to the subscription request received by the other subscription information management unit from the latest publication data holding unit, and transmits the latest publication data to the other broker device. ,
When a subscription request for a certain topic is received from the second client device, the self-subscription information management unit subscribes to the managed topic in order to determine whether the topic is a new topic. determining whether a client device is present;
The self-subscription information management unit outputs a subscription request for new subscription registration when there is no client device that subscribes to the managed topic,
When the index value management unit determines that duplication of the publication data is necessary for the topic for which a subscription cancellation request has been received from the other broker device, the other subscription information management unit A broker device that outputs a subscription request for registration to the own subscription information management unit. an aggregating unit for aggregating the publication data transmitted from the other publication data transmission unit to a plurality of the other broker devices into one aggregated publication data at regular time intervals for each of the other broker devices;
4. The broker device according to any one of claims 1 to 3 , further comprising a compression unit for compressing said aggregated publication data aggregated by said aggregation unit according to a predetermined first algorithm. The self-published data receiving unit records the reception time of the published data received from the first client device,
Further, the aggregating unit determines that the publication data in which the difference between the time when the predetermined time has passed from the current time and the reception time exceeds a predetermined maximum waiting time for each topic is to be aggregated by the aggregating unit. 5. The broker device according to claim 4 , comprising a real-time determining unit that By developing aggregated publication data, which is obtained by aggregating and compressing a plurality of publication data transmitted from the other broker device and received by the other publication data receiving unit, according to a predetermined second algorithm, a decompression unit that restores the aggregated publication data before compression from the compressed aggregated publication data;
and a dividing unit that divides the uncompressed aggregated publication data restored by the expansion unit, and restores a plurality of unaggregated publication data from the uncompressed aggregated publication data. 6. The broker device according to any one of 1 to 5. A communication method implemented by a broker device for transmitting publication data received from a first client device to a second client device and other broker devices, comprising:
The broker device
a first step of receiving from said second client device a subscription request for a topic subscribed to by said second client device;
a second step of receiving publication data related to the topic from the first client device;
a third step of transmitting said received publication data to said second client device;
a fourth step of transmitting the received publication data to the other broker device;
a fifth step of receiving publication data related to the topic from the other broker device;
a sixth step of extracting and holding the latest publication data for each topic from the publication data received in the second step and the fifth step;
a seventh step of receiving a subscription request for a topic subscribed by the other broker device from the other broker device;
an eighth step of managing topics subscribed to by said broker device and transmitting this topic to said other broker device when there is a change in said managed topic;
a ninth step of retrieving and transmitting to the second client device the latest publication data for topics related to the subscription request received from the second client device;
a tenth step of sending the latest publication data related to the topic related to the subscription request received in the seventh step to the other broker device;
If there is a subscription request for a certain topic from the second client device, whether or not there is a client device that subscribes to the managed topic in order to determine whether the topic is a new topic an eleventh step of determining
a twelfth step of outputting a subscription request for a new subscription if no client device subscribes to the managed topic ;
a thirteenth step of outputting a subscription request for unsubscribing when there is no client device subscribing to the managed topic among the topics subscribed to by two or more broker devices. . A program for transmitting publication data received from a first client device to a second client device and another broker device,
a first function for receiving from said second client device a subscription request for a topic subscribed to by said second client device;
a second function for receiving publication data related to the topic from the first client device;
a third function of transmitting said received publication data to said second client device;
a fourth function of transmitting the received publication data to the other broker device;
a fifth function of receiving publication data related to the topic from the other broker device;
A sixth function for extracting and holding the latest publication data for each topic from the publication data received by the second function and the fifth function;
a seventh function of receiving, from the other broker device, a subscription request for a topic subscribed by the other broker device;
an eighth function of managing topics subscribed to by a broker device and transmitting this topic to the other broker device when there is a change in the managed topic;
a ninth function of retrieving and transmitting to the second client device the latest publication data for topics related to the subscription request received from the second client device;
A tenth function of sending the latest publication data related to the topic related to the subscription request received by the seventh function to the other broker device;
If there is a subscription request for a certain topic from the second client device, whether or not there is a client device that subscribes to the managed topic in order to determine whether the topic is a new topic An eleventh function that determines
A twelfth function that outputs a subscription request for new subscription registration when there is no client device that subscribes to the managed topic;
a thirteenth function of outputting a subscription request for unsubscribing when there is no client device subscribing to the managed topic among the topics subscribed to by two or more broker devices;
A program for realizing on a computer. A communication system comprising a plurality of client devices and a plurality of broker devices,
At least one broker device among the plurality of broker devices,
a subscription information receiving unit that receives, from the second client device, a subscription request for a topic subscribed by the second client device among the plurality of client devices;
a self-published data receiving unit that receives published data related to the topic from a first client device among the plurality of client devices;
a self-published data transmission unit that transmits the published data received by the self-published data receiving unit to the second client device;
an other publication data transmission unit that transmits the publication data received by the own publication data reception unit to another broker device among the plurality of broker devices;
a other publication data receiving unit that receives publication data related to the topic from the other broker device;
a latest publication data holding unit for extracting and holding the latest publication data for each topic from the publication data received by the own publication data reception unit and the other publication data reception unit;
a other subscription information management unit that receives a subscription request for a topic subscribed by the other broker device from the other broker device;
a self-subscription information management unit that manages topics subscribed by the broker device and transmits the topic to the other broker device when there is a change in the managed topic;
The self-published data transmission unit obtains from the latest published data storage unit the latest published data of a topic related to the subscription request received from the second client device, and transmits the data to the second client device;
The other publication data transmission unit obtains the latest publication data related to the topic related to the subscription request received by the other subscription information management unit from the latest publication data holding unit, and transmits the latest publication data to the other broker device. ,
When a subscription request for a certain topic is received from the second client device, the self-subscription information management unit subscribes to the managed topic in order to determine whether the topic is a new topic. determining whether a client device is present;
The self-subscription information management unit outputs a subscription request for new subscription registration when there is no client device that subscribes to the managed topic,
If there is no client device subscribing to the topic managed by the self-subscription information management unit among the topics subscribed to by two or more broker devices, the other subscription information management unit cancels the subscription. to the subscription information management unit,
At least one client device among the plurality of client devices,
developing aggregated publication data, which is obtained by aggregating and compressing a plurality of publication data, transmitted from a connection destination broker device among the plurality of broker devices, and restoring the aggregated publication data before compression; a division expansion unit that divides the restored aggregated publication data and restores publication data before aggregation;
an aggregation compression unit that aggregates a plurality of publication data to be transmitted to the connection destination broker device for each related topic to generate aggregated publication data, and compresses the generated aggregated publication data;
transmitting the aggregated publication data compressed by the aggregation compression unit to the connection destination broker device, receiving the aggregated publication data transmitted from the connection destination broker device, and dividing and decompressing unit a communication unit for providing to.

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