JP2020017118A - Broker device, client device, communication system, communication method, and program - Google Patents

Abstract

To provide a broker device that can secure availability without providing new redundancy.SOLUTION: According to an embodiment, the broker device includes: a self-subscription information receiving unit that receives a subscription request for a topic subscribed by a second client device, from the second client device; a self-publishing data receiving unit that receives publishing data concerning the topic from a first client device; a self-publishing data transmission unit that transmits the publishing data received by the self-publishing data receiving unit to the second client device; and another publishing data transmission unit that transmits the publishing data received by the self-publishing data receiving unit to another broker device.SELECTED DRAWING: Figure 1

Description

  An embodiment of the present invention relates to a broker device, a client device, a communication system, a communication method, and a program applied to communication based on a publish / subscribe type (publish / subscribe) model.

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

  According to the publish / subscribe model, as disclosed in Patent Literature 1, a subscriber of information can efficiently receive only desired information.

  According to the technology disclosed in Patent Literature 1, in communication based on the publish / subscribe model, reliability can be ensured by making a broker device redundant, and security is ensured by controlling access to content. Can also be realized.

JP 2007-287148 A

  However, in the technique disclosed in Patent Literature 1, the role of the broker device is subdivided, and in the case of performing redundancy, it is necessary to make each broker device redundant. Further, when a failure occurs in a broker device that plays a specific role, it becomes impossible to ensure availability even if another broker device is normal.

  The problem to be solved by the present invention is to provide a broker device capable of ensuring availability without taking new redundancy, a client device performing communication with the broker device based on a publish / subscribe model, a broker device and a client device And a communication method and a program applied to the communication system.

  A broker device according to an embodiment is a broker device that transmits publishing data received from a first client device to a second client device and another broker device, and a subscription request for a topic subscribed by the second client device. From the second client device, a self-publishing data receiving unit receiving publishing data related to the topic from the first client device, and a publishing received by the self-publishing data receiving unit. It includes a self-published data transmitting unit for transmitting data to the second client device, and another published data transmitting unit for transmitting the published data received by the self-published data receiving unit to another broker device.

FIG. 1 is a conceptual diagram illustrating a configuration example of a communication system according to a first exemplary embodiment. FIG. 14 is a diagram illustrating an example of another broker device subscription information management table. FIG. 2 is a block diagram illustrating a configuration example of a broker device applied to the communication system according to the first embodiment. FIG. 11 is a diagram illustrating an example of a management information table of the own broker device. 9 is a flowchart illustrating an example of a processing procedure performed by a local broker device when a subscription request is received from a client device. It is a figure showing an example of a subscription information subscription number management table. It is a figure showing an example of a broker device subscription number management table. It is a flowchart which shows an example of the processing procedure by the own broker apparatus at the time of receiving the subscription request from another broker apparatus. 9 is a flowchart illustrating an example of a processing procedure performed by the own broker device when a publication data publication request is issued from the client device. 11 is a flowchart illustrating an example of a processing procedure performed by the own broker device when transmitting publication data from another broker device. It is a flowchart which shows an example of the processing procedure at the time of termination of another broker apparatus, and the time of abnormality detection. FIG. 3 is a conceptual diagram illustrating a modification of the communication system according to the first embodiment. It is a block diagram showing the example of composition of the broker device and the sub-broker device applied to the modification of the communication system of a 1st embodiment. FIG. 9 is a block diagram illustrating a configuration example of a broker device applied to a communication system according to a second embodiment. It is a figure showing an example of other subscription information management tables. It is a figure showing an example of a self-subscription information management table. 9 is a flowchart illustrating an example of a processing procedure performed by a local broker device when a subscription request is received from a client device. It is a flowchart which shows an example of the processing procedure by the own broker apparatus at the time of receiving the subscription request from another broker apparatus. FIG. 14 is a block diagram illustrating a configuration example of a broker device applied to a communication system according to a third embodiment. It is a figure showing an example of a transmission waiting list. It is a figure showing an example of a maximum waiting time list and time conditions. FIG. 4 is a data structure diagram illustrating a packet format of compressed and aggregated publication data. 9 is a flowchart illustrating an example of a processing procedure at the time of receiving a publication request for publication data from a client device. 9 is a flowchart illustrating an example of a processing procedure when transmitting publication data in response to a publication request. 9 is a flowchart illustrating an example of a processing procedure when publishing data is transmitted from another broker device. It is a conceptual diagram showing the example of composition of the client device applied to the modification of the communication system of a 3rd embodiment. It is a figure showing an example of a maximum waiting time list. It is a figure showing an example of a transmission waiting list. FIG. 4 is a data structure diagram illustrating a packet format of compressed and aggregated data. 9 is a flowchart illustrating an example of a processing procedure at the time of receiving a publication request for publication data from a client device. It is a flowchart which shows an example of the processing procedure at the time of performing aggregation / compression and transmission processing of a packet for every subscription information (topic). 9 is a flowchart illustrating an example of a processing procedure when transmitting publication data from a broker device.

  Hereinafter, a communication system according to each embodiment of the present invention will be described with reference to the drawings.

  In the following description of each embodiment, the same portions are denoted by the same reference numerals, and redundant description will be avoided.

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

  The communication system 1 includes a plurality of broker devices 10 communicably connected to each other via a network 20, and an arbitrary number of clients communicably connected to any 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) communicably connected to each other via a network 20 and one of these broker devices 10 (# 0 to # 3) The client devices 30 (# 1 to # 6) communicably connected via the network 20 are illustrated.

  In the example illustrated in FIG. 1, the client devices 30 (# 1), (# 2), and (# 3) are communicably connected to the broker device 10 (# 1), and are connected to 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 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.

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

  In addition, the client device 30 can transmit publishing data related to the topic to the connected broker device 10. Hereinafter, this transmission operation is referred to as “publishing”.

  When publication data is published together with a topic from the client device 30, the broker device 10 transmits the publication data to the client device 30 subscribed to the topic. For example, in FIG. 1, when the client device 30 (# 1) has subscribed to the topic of the information group A, the broker device 10 (# 1) transmits the information related to the topic of the information group A from the client device 30 (# 2). When the publishing data is published, the publishing data is transferred only to the client device 30 (# 1). Thus, the client device 30 (# 1) can receive only the subscribed publication data.

  When a plurality of broker devices 10 exist, each broker device 10 stores information on topics subscribed to by each broker device 10 by holding, for example, another broker device subscription information management table 200 as shown in FIG. To share.

  FIG. 2 is a diagram illustrating an example of another broker device subscription information management table.

  The other broker device subscription information management table 200 (hereinafter, simply referred to as “management table 200”) includes, for example, a subscription broker device m1 indicating the broker device 10 to be subscribed, and a broker device 10 designated by the subscription broker device m1. 3 is a data table in which records composed of two items of subscription information (topic) m2 indicating a topic to be subscribed are stacked. The management table 200 is stored in a storage (not shown) in the broker device 10 and can be referred to by each unit in the broker device 10.

  In the management table 200 illustrated in FIG. 2, topics such as the information group A, the information group B, and the information group C are subscribed in the broker apparatus 10 (# 1), and the information group A and the information group C are subscribed in the broker apparatus 10 (# 2). This indicates that the topic “information group B” is subscribed to in the broker device 10 (# 3).

  By referring to the management table 200, when the publication data is published from the client device 30, the broker device 10 transfers the publication data to any other broker device 10 based on which topic the publication data relates to. Determine if you should.

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

  As described above, the communication system 1 transfers only the minimum necessary publication data, and thus uses the network bandwidth efficiently.

  Also, among protocols adopting a publish / subscribe model such as MQTT (Message Queue Telemetry Transport), each broker device 10 has a function of holding 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 topic to be subscribed even if the subscription is started after the publication data is published.

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

  According to the retain function, even if the client device 30 ends abnormally, the latest publication data can be acquired after the restart.

  By the way, in order to make all the broker devices 10 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 need all publishing data. For this reason, transferring all published data to be published to all the broker devices 10 wastes communication resources and is inefficient. Therefore, 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 in order to improve communication efficiency.

  For example, when the relationship between the subscription broker device and the subscription information (topic) is exemplified in the management table 200, the publication data related to the 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). The broker device 10 (# 3) holds the transferred publication data.

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

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

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

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

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

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

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

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

  When the subscription request KR is a subscription registration request, the self-subscription information receiving unit 106 sends the topic specified by the subscription request KR and the client device 30 of the subscription request source to the self-subscription information management unit 108. For example, the management is performed using the own broker apparatus subscription information management table 205 illustrated in FIG.

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

  The own broker apparatus subscription information management table 205 (hereinafter, simply referred to as “management table 205”) includes own broker apparatus subscription information m3 indicating subscription information (topic) subscribed in the own broker apparatus 10 (# 0), This is a data table in which records composed of two items, a subscription client device m4 indicating the client device 30 that subscribes 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) in the broker device 10 and can be referred to by each unit in the broker device 10.

  The management table 205 illustrated in FIG. 4 indicates that the topic called the information group A is subscribed by the client device 30 (# 1) in the own broker device 10 (# 0).

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

  If the subscription request KR received by the self-subscription information receiving unit 106 is a subscription cancellation request, the self-subscription information management unit 108 determines from the management table 205 that the client device 30 that has issued the subscription request has the subscription client device m4 Delete the record written in. As described above, the management table 205 is used to manage the subscription information (topic) of the client device 30 connected to the own broker device 10 (# 0).

  If the subscription request KR received by the self-subscribe information receiving unit 106 is a subscription release request, the self-subscribe 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 you of unsubscription. At the time of this determination, the self-subscription information management unit 108 determines, for example, using the management table 200, the number of other broker devices 10 (subscriber broker devices) that have subscribed to the topic subject to unsubscription. Apply an algorithm for unsubscribing only when the determined number is 2 or more. Accordingly, when the number of the subscription broker apparatuses 10 is 1, the subscription is not released even if the subscription is released, so that the redundancy of the publication data SD can be continuously maintained.

  Further, in this algorithm, when the own broker apparatus 10 (# 0) has subscribed to a large number of topics, there is a high possibility that a traffic bias will occur. On the other hand, when the broker device 10 that has the least subscribed topics subscribes to the topic, traffic can be efficiently distributed. Therefore, when the number of the subscribed broker apparatuses 10 is not two or more, the own subscription information management unit 108 compares the number of subscriptions between the other broker apparatus 10 and the own broker apparatus 10 (# 0), and checks the own broker apparatus 10 (# Subscription may be continued only when the number of subscriptions in 0) is the smallest.

  The self-published data transmitting unit 112 transmits the published data SD received by the self-published data receiving unit 110 to the client device 30 (for example, the client device 30 (# 2)) that has issued the subscription request via the communication unit 104. I do. The client device 30 to which the publication data SD is transmitted is determined with reference to, for example, the management table 205. According to the management table 205, when the topic specified as the own broker apparatus subscription information m3 is the information group A, it is determined that the transmission destination is the client apparatus 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. When the broker device 10 of the transmission source is determined, for example, the management table 200 is used. By grasping the subscription information (topic) m2 related to the publishing 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 a topic required by the other broker device 10 (a topic to which the client device 30 connected to the other broker device 10 is subscribed) and manages the received topic using the management table 200, for example.

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

  When the new subscription request KR is received from the other broker device 10 and is a subscription registration request, the other subscription information management unit 120 further registers the new subscription request KR in the management table 200, and the latest publication data holding unit 114 When the latest publication data SD is held, the other publication data transmission unit 116 is made to acquire the latest publication data SD from the latest publication data holding unit 114, and the acquired publication data SD is The subscription to the publishing data SD is transmitted to the other broker device 10 which has started the subscription.

  In order to prevent the latest publication data SD from being transmitted from a plurality of other broker devices 10, the other subscription information management unit 120 assigns a broker number as a simple reference number to each broker device 10 and updates the latest broker data. Only one broker device 10 transmits the latest publication data SD, such as permitting transmission of the publication data SD only to the broker device 10 with the smallest broker number among the broker devices 10 holding the publication data SD. A mechanism may be adopted.

  Further, the other subscription information management unit 120 is not limited to simply assigning the broker number as the serial number, but may assign the number according to the capability of the broker device 10. For example, if a smaller broker number is assigned to a broker number 10 having a higher capability, transmission of the publication data SD only from the broker device 10 having the highest capability among the broker devices 10 holding the latest publication data SD is performed. You will be able to authorize.

  Further, in order to avoid continuing to receive the publication data SD even though the subscription client device 30 does not exist, the other subscription information management unit 120 determines that the number of subscriptions of the topic started by the other broker device 10 is 2 (automatically). When the broker device 10 (# 0) does not include), the own broker device 10 (# 0) has subscribed to the topic, and if there is no subscription client device 30, the subscription information is deleted. Then, a subscription request KR which is a subscription cancellation request may be transmitted.

  Furthermore, in order to prevent the number of the subscribed broker apparatuses 10 from becoming two or less when the subscribe request KR from the other broker apparatus 10 is the unsubscribe request, the subscribe broker apparatus 10 If 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 changed. A subscription may be made, and the subscription request KR may be transmitted to the other broker device 10.

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

  If the latest publication data SD is not stored in the latest publication data holding unit 114, that is, if no client device 30 publishes the publication data SD, the own publication data transmission unit 112 performs the above-described transmission processing. Do not do.

  The other subscription information management unit 120 receives a subscription request KR for a topic, which is a group of information to be 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 of the subscription request source 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 updates the latest publication data SD related to the topic designated by the subscription request KR with the latest publication. The publishing data SD acquired from the data holding unit 114 and transmitted is transmitted to the other broker device 10 that has issued the subscription request. The other broker device 10 that has issued the subscription request is determined using, for example, the management table 200.

  The self-subscribed information management unit 108 manages a topic that is a group of information subscribed by the self-broker device 10 (# 0), and when there is a change in the managed topic, transmits this topic to the communication unit. The data is transmitted to the other broker device 10 via 102.

  If there is no client device 30 that subscribes to the topic managed by the self-subscription information management unit 108, the other publication data reception unit 118 transmits a subscription request KR that is a new subscription registration request to the self-subscription information management unit. Output to 108.

  The other-published-data receiving unit 118 includes, among the topics specified by the subscription request KR received by the other-subscribed information managing unit 120, the topics subscribed to by two or more broker apparatuses 10, and the self-subscribed information managing unit 108. If there is no client device 30 that subscribes to the topic managed by the client, the client device 30 outputs a subscription request KR, which is a subscription cancellation request, to the self-subscription information management unit 108.

  The other-published-data receiving unit 118 calculates the number of topics subscribed for each broker device 10, and only when the minimum value exceeds the total value of the number of topics managed by the self-subscribed information management unit 108, a new topic is calculated. A subscription request KR, which is a subscription registration request, is output to the own subscription information management unit 108.

  The self-subscription information management unit 108 transmits the new subscription registration request KR or the new subscription request KR output from the other publication data receiving unit 118 to the other broker device via the communication unit 102. Transfer to 10. The self-subscription information management unit 108 may perform this transfer to all the broker devices 10 or only to a specific broker device 10 in consideration of the network topology. When the transfer is performed only to a specific broker device 10, the publication data SD related to the topic specified by the subscription request KR is returned from only the broker device 10.

  The end detection unit 122 detects at least one of the end of the other broker device 10 and an abnormality. For this detection, the end detection unit 122 periodically transmits a heartbeat to the other broker device 10 via the communication unit 102, for example, and the stage in which the other broker device 10 cannot receive the heartbeat. To detect an abnormality of the other broker device 10. Further, the end of the other broker device 10 is detected at the stage when the end notification transmitted voluntarily at the time of the end of the other broker device 10 is detected. When the end detection unit 122 detects the end or the abnormality, the record in which the broker device 10 in which the end or the abnormality is detected is written as the subscription broker device m1 is deleted from the management table 200.

  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 according to the first embodiment configured as described above will be described.

  FIG. 5 is a flowchart illustrating an example of a processing procedure performed by the own broker device when a subscription request is received from a client device.

  In the own broker device 10 (# 0), when the subscription request KR transmitted from the client device 30 is received by the own subscription information receiving unit 106 via the communication unit 104 (S1), the subscription request KR is subscribed. It is determined whether the request is a registration request or a subscription release request (S2). If it is a subscription registration request (S2: subscription registration), the self-subscribe information management unit 108 refers to the management table 205, and the subscription information (for example, information group A) for which the subscription registration request has been made becomes the own broker device subscription information m3. The subscription information is registered by writing the requesting client device 30 as the subscription client device m4 (S3).

  Further, the own subscription information management unit 108 determines whether the registered subscription information is a topic to be newly subscribed in the own broker apparatus 10 (# 0) (S4). If it is determined that the topic is a topic to be newly subscribed (S4: Yes), the publishing related to the topic for which the new subscription is started is transmitted to the other broker device 10 via the communication unit 102 by the other publication data transmitting unit 116. The data SD is transmitted (S5).

  Thereafter, 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), the publication data SD is It is output from the publication data receiving unit 118 to the latest publication data holding unit 114, and is held in the latest publication data holding unit 114 (S7). Further, the publication data SD held in the latest publication data holding unit 114 is output to the self-published data transmission unit 112, and the self-published data transmission unit 112 starts to subscribe to the topic via the communication unit 104. Is transmitted to the client device 30 (S8), and the process ends.

  On the other hand, in step S6, when the latest publication data SD of the topic is not transmitted from the other broker device 10 (S6: No), that is, when the publication data SD of the topic has not been published yet, the processing is performed. To end.

  On the other hand, in step S4, if the topic for which registration is newly requested is already subscribed by another client device 30 (S4: No), whether the latest publication data SD is held in the latest publication data holding unit 114? It is confirmed by the other publication data receiving unit 118 (S9), and if it is held (S9: Yes), the latest publication is transmitted from the own publication data transmission unit 112 to the client device 30 via the communication unit 104. The data is transmitted (S10). On the other hand, if the latest publication data is not held (S9: No), the process ends.

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

  Thereafter, if there is a record in the management table 205 in which the subscribed client device 30 is associated with the topic (for example, the 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 subscription client device 30 is associated with the topic (S12: No), the self-subscription information management unit 108 uses the management table 200 based on the management table 200 as shown in FIG. The subscription information subscription number management table 210 shown in FIG. 7 is created, and the broker device subscription number management table 215 shown in FIG. 7 is created based on the management tables 200 and 205. (S13).

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

  FIG. 7 is a diagram illustrating an example of a broker device subscription number management table.

  The subscription information subscription number management table 210 (hereinafter, simply referred to as “management table 210”) includes subscription information (topic) m5 indicating a topic to be subscribed, and a topic specified by the subscription information (topic) m5. This is a data table in which records composed of two items of the number of subscriptions m6 indicating the number of other broker devices 10 are stacked. According to the management table 200, the two subscribed broker devices for the topic of the information group A are the broker device 10 (# 1) and the broker device 10 (# 2). Accordingly, the management table 210 indicates that the number of subscriptions corresponding to the topic of the information group A is 2. Similarly, in the management table 200, there are two subscription broker devices for the topic of the information group B, and there are two subscription broker devices for the topic of the information group C. Therefore, the management table 210 corresponds to the information group B. 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) in the broker device 10 and can be referred to by each unit in the broker device 10.

  The broker device subscription number management table 215 (hereinafter, simply referred to as a “management table 215”) includes a broker device m7 in which a broker device is described and a subscription number m8 indicating the number of topics subscribed in each broker device. It is a data table in which records composed of two items are stacked. The management table 205 indicates that the own broker device 10 (# 0) subscribes to one topic called the information group A. Accordingly, the management table 215 indicates that the number of subscriptions of the own broker apparatus 10 (# 0) is 1. Further, the management table 200 indicates that the broker device 10 (# 1) subscribes to three topics of the information group A, the information group B, and the information group C. Therefore, the management table 215 indicates that the number of subscriptions of the broker apparatus 10 (# 1) is 3. Similarly, based on the information in the management table 200, the management table 215 indicates that the number of subscriptions of the broker device 10 (# 2) is 2 and the number of subscriptions of the broker device 10 (# 3) is 1. The management table 215 is stored in a storage (not shown) in the broker device 10 and can be referred to by each part in the broker device 10.

  When the contents of the management tables 200 and 205 are updated, the management tables 210 and 215 are also updated by the self-subscription information management unit 108 in accordance with 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), the self-subscription information management unit 108 reads the self-subscription information from the management table 205 from the management table 205. The record in which the topic (for example, the 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. Is performed (S17).

  On the other hand, in step S13, when the number of broker apparatuses 10 subscribed to the topic is less than 2 (S13: No), the other subscription information management unit 120 performs the management of each broker apparatus 10 based on the management table 215. The number of subscriptions is grasped, and it is determined whether the number of subscriptions of the own broker apparatus 10 (# 0) is the minimum (S14).

  For example, in the management table 215, the number of subscriptions of 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 (# 3) is indicated as 1. In this case, the own broker apparatus 10 (# 0) has the minimum number of subscriptions together with the broker apparatus 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), the other subscription information management unit 120 determines whether or not the broker number of the own broker device 10 is the smallest among the broker devices 10 with the smallest number of subscriptions. Is determined (S15).

  As shown in the management table 215, the broker devices 10 with the minimum number of subscriptions are the own broker device 10 (# 0) and the broker device 10 (# 3) with the number of subscriptions being one, and among them, the own broker device 10 (# 3). Since the broker number of # 0) is 0 and the minimum (S15: Yes), the process ends.

  On the other hand, if it is not the minimum in step S15 (S15: No), the process proceeds to step S16 described above.

  FIG. 8 is a flowchart illustrating an example of a processing procedure performed by the own broker device when a subscription request is received from another broker device.

  When the subscription request KR is transmitted from the other broker device 10, the 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), in the other subscription information management unit 120, the broker device 10 of the subscription request source is written as the subscription broker device m1 of the management table 200, and the subscription information ( Registration is performed by writing the subscription information (topic) specified in the subscription request KR as the topic) m2 (S23).

  The topic specified by the subscription request KR is subscribed to the 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), when the own broker apparatus 10 (# 0) has the smallest broker number among the subscribed broker apparatuses 10 (S26: Yes), the latest publication data SD is transmitted to the other publication data transmission unit. The data is transmitted to the requesting broker device 10 via the communication unit 102 by the communication unit 116 (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, the broker number of the subscribed 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 self-subscription information management unit 108 refers to the management table 205 to determine whether or not there is a client device 30 that subscribes to the topic in the own broker device 10 (# 0). If it is determined that the file exists (S28: Yes), the process ends.

  On the other hand, when it is not determined that the topic exists (S28: No), the number of other subscribed broker apparatuses 10 subscribing to the topic (for example, information group A) from the management table 210 by the other subscription information management unit 120 (the number of subscriptions) ) Is determined, and if the number is 2 or more (S29: Yes), the record in which the topic (for example, the information group A) is written as the own broker apparatus subscription information m3 is deleted from the management table 205 (S29: Yes). S30), the self-subscription information management unit 108 transmits a subscription release request for the topic 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 that subscribes to the topic in the own broker device 10 (# 0), the publication data SD In order to continue the subscription in the own broker apparatus 10 (# 0) for the redundancy of, the processing ends without any processing.

  In step S24, the topic is not subscribed to the own broker device 10 (# 0) (S24: No), the number of other subscribed broker devices 10 is 1 (S33: Yes), and (# 0) is the broker device with the smallest number of topic subscriptions (S34: Yes), and if the broker number of the 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 a topic for redundancy of the publication data SD, the self-subscription information management unit 108 sets the topic subscription information (for example, information group A) as the own broker apparatus subscription information m3 in the management table 205. Written (S36), and then a subscription request KR specifying the topic is transmitted to another broker device 10 via the communication unit 102 (S37).

  Further, 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 received. 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), if the number of subscriptions of the own broker device 10 (# 0) is not minimum (S34: No) in step S34, In step S35, if the broker number of the own broker apparatus 10 (# 0) is not the smallest broker number (S35: No), 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, when the subscription request KR transmitted from the other broker device 10 is a subscription release request (S22: subscription release), the subscription request KR is transmitted from the management table 200 by the other subscription information management unit 120 from the management table 200. The record in which the topic specified in is written as the subscription information (topic) m2 is deleted (S32), and thereafter, the process proceeds to step S33.

  In the present embodiment, whether or not the number is the minimum broker number is used as a criterion used for the determination in steps S15, S26, and S35. However, the criterion is not limited to this, and whether or not it is the largest broker number may be used instead. Alternatively, an algorithm such as continuing to subscribe to the broker device 10 having the least recent communication amount may be used regardless of the broker number.

  FIG. 9 is a flowchart illustrating an example of a processing procedure by the own broker device when a publication data publication request is issued from the client device.

  In the own broker device 10 (# 0), when the topic and its publication data SD are transmitted from the client device 30 (for example, the client device 30 (# 1)), the publication data SD is transmitted via the communication unit 104. The self-published data is received by the self-published data receiving unit 110, and further output to the self-published data transmitting unit 112 (S41). The self-published data transmission unit 112 refers to the management table 205 and determines whether or not there is a client device (subscribed client device) 30 that has subscribed to a topic related to the published data SD (S42).

  If it is determined that the subscription client device 30 exists (S42: Yes), the self-published data transmission unit 112 sends the determined client device 30 (for example, the client device 30 (# 2)) via the communication unit 104. The publishing data SD is transmitted (S43), and the process proceeds to step S44.

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

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

  If it is determined that it exists (S44: Yes), the publication data SD is transmitted from the other publication data transmission unit 116 via the communication unit 102 to the determined broker device 10 (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, when there is publishing data SD related to a topic that is not subscribed to both the own broker apparatus 10 (# 0) and the other broker apparatus 10 (both determinations in S42 and S44 are No). In some cases), a subscription registration request for the topic is transmitted to the other broker device 10.

  FIG. 10 is a flowchart illustrating an example of a processing procedure by the own broker device when transmitting the publication data from another broker device.

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

  In response, the self-subscription information management unit 108 refers to the management table 205, and determines whether the client device (subscriber 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).

  When it is determined that the connection is established (S52: Yes), the self-published data transmission unit 112 sends the determined client device 30 (for example, the client device 30 (# 2)) via the communication unit 104. Then, the publication data SD is transmitted (S53). Further, the publication data SD is held in the latest publication data holding unit 114 (S54), and thereafter, the processing is terminated.

  On the other hand, when it is determined that the connection is not established (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 flowchart illustrating an example of a processing procedure at the time of termination of another broker device and detection of an abnormality.

  When a spontaneous end notification arrives from another broker apparatus 10 to the end detection unit 122 of the own broker apparatus 10 (# 0) (S61: Yes), or the end detection unit of the own broker apparatus 10 (# 0) When the abnormality of the other broker device 10 is detected by the 122 (S62: Yes), the topic subscribed by the broker device 10 that has ended or caused the abnormality by the other subscription information management unit 120 is subscribed to the management table 200. It is confirmed whether or not the information (topic) m2 has been written (S63).

  If no spontaneous end notification has arrived (S61: No) and no abnormality of the other broker device 10 is detected thereafter (S62: No), the process returns to step S61. Further, when it is determined in step S63 that the topic has not been written, that is, when there is no topic subscribed to by the broker device 10 that has ended or has an error (S63: No), the process of step S61 is also performed. Return to

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

  Further, the topic is not subscribed even to the own broker apparatus 10 (# 0) (S65: No), the number of other subscribed broker apparatuses 10 is 1 (S66: Yes), and the own broker apparatus 10 (# 0). )) Is the smallest (S67: Yes), and the broker number of the own broker device 10 (# 0) is the smallest among the broker devices 10 with the smallest number of subscriptions (S68: Yes). The subscription is registered for redundancy in the broker device 10 (S69), and this topic is transmitted from the self-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 return to step S63.

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

  With the above configuration, the own broker device 10 (# 0) can ensure the redundancy of the publishing data SD, so that the publishing data SD is not lost even when an abnormality occurs in the other broker device 10. This makes it possible to improve the reliability of a system that employs the communication protocol of the publish / subscribe model. Also, the destination of the publication data SD for redundancy can be changed according to the data amount of the publication data SD to which the broker device 10 subscribes, so that it is possible to realize appropriate load distribution.

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

  The broker device 10 illustrated in FIG. 3 has a function of determining whether to subscribe to a topic in order to make the 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 illustrating a modification of the communication system according to the first embodiment.

  That is, in the communication system 2 of the present modification, 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, the sub-broker device 40 is provided for each of the broker devices 11 in a one-to-one manner. However, the present invention is not limited to such a configuration, and the sub-broker device 40 is provided only for a specific broker device 11. Is also good. In addition, 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.

  Similarly to the network 20, the network 21 may be 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. it can.

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

  The broker device 11 has a configuration in which the end detection unit 122 is deleted from the broker device 10.

  The sub-broker device 40 includes an end detection unit 402 and a subscription determination unit 404.

  The end detection unit 402 has the same function as the end detection unit 122.

  The subscription determination unit 404 receives a subscription change request of the subscription request KR from the self-subscription information management unit 108 and the other subscription information management unit 120 of the broker device 11. The subscription determining unit 404 recognizes the subscription change request by monitoring communication instead of receiving the subscription change request from both the self-subscription information management unit 108 and the other subscription information management unit 120. You may.

  When receiving the subscription change request, the subscription determination unit 404 further determines whether the broker device 11 that has issued the subscription change request is a new subscription request, a subscription cancellation request, or a subscription continuation request for the topic associated with the subscription request KR. It is determined whether the request is a subscription cancellation continuation request.

  As a criterion for this, for example, if a record in which the subscription client device 30 is associated with the topic (for example, the information group A) remains as the subscription information (topic) m2 of the management table 205, the subscription is performed. If it is continued and there is no remaining one, it is possible to determine whether or not to continue the subscription for this topic according to the number of subscriptions of the other broker device 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 self-subscription information management unit 108 of the broker device 11 for a new subscription request or a subscription release request.

  As described above, according to the modified example, by providing the sub-broker device 40, a high redundancy function can be realized even when the broker device 11 having no new redundancy function is used. A possible communication system 2 can be realized.

(Second embodiment)
Some protocols, such as MQTT, that adopt a publish / subscribe model have a QoS function. By using the QoS function, it is possible to label the publication data SD in order to distinguish between the publication data SD whose arrival should be guaranteed and the publication data SD whose arrival does not need to be guaranteed.

  In the first embodiment, it is assumed that the redundancy of all the publication data SD is secured, but it is not always necessary to secure the 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 ensured for the publication data SD that does not need to be guaranteed to arrive.

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

  Although the configuration of the broker device 12 is similar to the configuration of the broker device 10, the broker device 12 replaces the QoS management unit 124 that the broker device 10 does not have with the other subscription information management unit 120 and the own subscription information management unit 108. Is different between the two. Therefore, only the differences from the broker device 10 will be described below.

  When receiving the subscription request KR, which is a subscription release request, from the other broker device 10 in addition to the functions described in the first embodiment, the other subscription information management unit 120 performs, based on the received subscription release request, FIG. Is updated in the other subscription information management table 220 illustrated in FIG.

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

  The other subscription information management table 220 (hereinafter, simply referred to as “management table 220”) is a modified example of the management table 200, and includes three types of newly added QoSm9 to the subscription broker device m1 and the subscription information (topic) m2. This is a data table in which records composed of items are stacked. The management table 220 is stored in a storage (not shown) in the broker device 12, and can be referred to by each unit in the broker device 12.

  The QoS management unit 124 manages the QoS value for each subscription information (topic) by calculating a QoS value that is an index value of reliability required for transmitting and receiving the publication data SD and writing the QoS value as the QoSm9 in the management table 220. . Further, it is determined whether or not the publication data SD needs to be copied using the management table 220.

  The other subscription information management unit 120 outputs the subscription request KR, which is a subscription registration request, to the own subscription information management unit 108 only when the QoS management unit 124 determines that the publication data SD needs to be copied.

  In response, the own subscription information management unit 108 determines whether to subscribe to the publication data SD in the own broker device 12 (# 0) according to the algorithm described in the first embodiment. .

  The self-subscription information management unit 108 manages a self-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 illustrating an example of the self-subscription information management table.

  The self-subscription information management table 225 (hereinafter, simply referred to as “management table 225”) is a modified example of the management table 205, and includes three new QoS m9 added to the own broker apparatus subscription information m3 and the subscription client apparatus m4. This is a data table in which records composed of items are stacked. The management table 225 is stored in a storage (not shown) in the broker device 12, and can be referred to by each part in the broker device 12.

  When the QoS management unit 124 determines that the publication data SD needs to be copied, the self-subscription information management unit 108 determines whether to continue the subscription according to the algorithm described in the first embodiment. Further, when the content of the change of the management table 225 is transmitted to the other broker device 10, the corresponding QoS information can be transmitted together.

  The QoS management unit 124 is called by outputting a topic from the other subscription information management unit 120 or the self-subscription information management unit 108, and determines whether the publication data SD related to the topic is information for which redundancy should be ensured. Determine whether or not.

  For example, suppose that the QoS takes a binary value of 0 or 1, where 0 is the publication data SD that does not have to guarantee the arrival and 1 means the publication data SD that should guarantee the arrival. In this case, the QoS management unit 124 refers to the management tables 220 and 225 and calculates the maximum value of the QoS of the topic.

  For example, from the management table 220, when the subscription information (topic) is the information group A, the broker device 10 (# 1) has QoS = 0 and the broker device 10 (# 2) has QoS = 1. When the own broker apparatus 12 (# 0) subscription information is the 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, from 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 data is the publication data SD to be subjected to redundancy, and when the maximum value is 0, it is the publication data SD that does not need to be subjected to redundancy. Is determined.

  If the QoS takes a value other than the above-described binary value, for example, if the maximum value is 1 or more, the necessity of the redundancy is determined by a similar algorithm, such as determining that the publication data SD should be subjected to the redundancy. A determination can be made.

  For example, in the example shown in the management table 220, the information group B is subscribed to the broker device 10 (# 1) and the broker device 10 (# 3). The maximum value of the QoS of the information group B is 1, which is the publication data SD to be subjected to redundancy. However, since it is originally subscribed by the broker 10 (# 1) and the broker 10 (# 3), the redundancy is already set. Has been

  Here, it is assumed that the broker device 10 (# 1) issues a subscription release 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) having the smallest number of subscriptions and the smallest broker number has the broker device 10 (# 0) despite the fact that there is no client device 30 that subscribes to the information group B. Subscribe to the information group B in place of # 1).

  However, in the second embodiment, the maximum value of the QoS is 0, and the publication data SD does not need to be redundant. In this case, only the broker device 10 (# 3) continues to subscribe, and the own broker device 12 (# 0) does not subscribe, so that the communication band can be used efficiently and the own broker device 12 (# 3) can be used. The processing load of # 0) is reduced.

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

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

  The flowchart shown in FIG. 17 is different from the flowchart shown in FIG. 5 in that step S12a is added between step S12 and step S13.

  Therefore, the process related to step S12a will be described below, and redundant description will be avoided.

  In step S12, when the subscription client device 30 does not exist and is subscribed by another broker device 10 when the subscription is canceled (S12: No), in step S12a, it is determined whether the publication data SD needs to be made redundant. Therefore, the QoS management unit 124 determines whether or not the QoS maximum value is zero (S12a).

  When it is determined that the QoS maximum value is zero (S12a: Yes), the process proceeds to step S16, and when it is not determined that the QoS maximum value is zero (S12a: No), the process proceeds to step S13.

  FIG. 18 is a flowchart illustrating an example of a processing procedure performed by the own broker device when a subscription request is received from another broker device.

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

  Therefore, in the following, processing related to step S28a and step S32a will be described, and redundant description will be avoided.

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

  When it is determined that the QoS maximum value is zero (S28a: Yes), the process proceeds to step S30, and when it is not determined that the QoS maximum value is zero (S28a: No), the process proceeds to step S29.

  After step S32, similarly to step S12a, the QoS management unit 124 determines whether or not the QoS maximum value is zero (S32a).

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

  Further, an example of a processing procedure when a publication request of the publication data SD is issued from the client apparatus 30 connected to the own broker apparatus 12 (# 0) is as shown in the flowchart of FIG. An example of the processing procedure when the publication data SD is transmitted is as shown in the flowchart of FIG.

  As described above, according to the communication system of the second embodiment, it is not necessary to ensure the redundancy for all the publication data SD in order to determine whether the 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 the publishing data SD is published, the individual publishing data SD is transmitted as individual packets. When MQTT is used for IoT (Internet of things), if packet transmission is performed, a large amount of publication data such as sensor publication data is generated, and a large amount of communication packets are transmitted and received. Generally, the performance limit of a network device such as a router is determined by the number of packets and the total amount of published data. That is, it is important to reduce the number of packets and the total amount of communication publication data so that more publication data can be transmitted and received. The third embodiment provides a technique for reducing the total amount of MQTT packets and the amount of publishing data to be transmitted while maintaining communication reliability.

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

  Although the configuration of the broker device 13 is similar to the configuration of the broker device 10, the broker device 13 includes an aggregation / compression unit 126 not provided in the broker device 10, a real-time determination unit 128, and a division / decompression unit 130. And Therefore, only the differences from the broker device 10 will be described below.

  The real-time property determination unit 128 is connected to the other publication data transmission unit 116 to determine the publication data SD to be transmitted periodically, and determines the difference between the time at which a certain time has elapsed from the current time and the reception time by using the topic. It is determined that the publication data SD that exceeds the maximum standby time set for each of the publication data SD is to be aggregated by the aggregation / compression unit 126.

  For this reason, in the present embodiment, the self-published data receiving unit 110 further 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 illustrating an example of the transmission waiting list.

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

  When there is a request for the publication data SD from the client device 30, the real-time property determination unit 128 updates the contents of the record in the transmission waiting list 230.

  FIG. 21 is a diagram illustrating an example of a maximum standby time list and time conditions.

  The maximum waiting time list 235 is a data table in which records including two items of subscription information (topic) m15 and maximum waiting time m16 are stacked. The maximum waiting time list 235 and the time condition 240 are stored in a storage (not shown) in the broker device 13 and can be referred to by each part in the broker device 13.

  The time condition 240 indicates, for example, a packet transmission cycle T = 10 ms (millisecond) and a current time = 2017/12/01 00: 00: 01.090.

  Since the real-time property required for transmission / reception differs for each piece of publication data SD, the real-time property determining unit 128 further writes, as a maximum waiting time m16, for each piece of subscription information (topic) m15 using the maximum waiting time list 235. Manages the maximum wait time before sending.

  For example, as shown in the time condition 240, when a packet is transmitted every T = 10 milliseconds, the real-time determining unit 128 is called every 10 milliseconds, and at the next calling time, the real-time determining unit 128 is called. 128 retrieves packets that exceed the maximum waiting time m16 shown in the maximum waiting time list 235.

  For example, as shown in the time condition 240, when the “current time” is “2017/12/01 00: 00: 01.090”, the next packet transmission time becomes the packet transmission cycle T = 10 The result is “2017/12/01 00: 00: 01.100” after adding the millisecond. Then, the packets exceeding the maximum standby time written as the maximum standby time m16 at the next packet transmission time in the transmission standby list 230 are the first, second, and fourth records from the top in the transmission standby list 230 illustrated in FIG. Becomes a packet corresponding to

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

  On the other hand, other packets are not sent at the next packet transmission time because the waiting time does not exceed the maximum waiting time m16.

  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. The aggregation / compression unit 126 further compresses the aggregated publication data according to a predetermined algorithm.

  Specifically, the consolidation / compression unit 126 transmits a plurality of pieces of publication data SD to be transmitted to the other broker devices 10 extracted by the real-time property determination unit 128 for each of the broker devices 10 specified by the destination m10 of the transmission standby list 230. Into one packet and compress it.

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

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

  The compressed and aggregated publication data 245 is obtained by further compressing the plurality of publication data SD aggregated by the aggregation and compression unit 126.

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

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

  The dividing / decompressing unit 130 further 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, a plurality of publication data is restored from the aggregated publication data.

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

  First, a process at the time of receiving a publication request of the publication data SD from the client device 30 will be described.

  FIG. 23 is a flowchart illustrating an example of a processing procedure when a publication request for publication data is received from a client device.

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

  If the subscription client device 30 determines that there is a record written as the subscription 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 the information does not exist (S82: No), the process directly proceeds to step S84.

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

  If it is determined that the data exists (S84: Yes), registration is performed 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 stored. The data is held in the latest publication data holding unit 114, and the process ends (S86). When a plurality of brokers 10 subscribe to a single topic of the publication data SD, the publication data SD is stored in the transmission standby list 230 for each destination broker 10.

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

  Next, a process when transmitting publication data in response to a publication request will be described.

  FIG. 24 is a flowchart illustrating an example of a processing procedure when transmitting publication data in response to a publication request.

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

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

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

  Subsequently, by referring to the transmission standby list 230 shown in FIG. 20, it is determined whether or not there is unprocessed publication data SD having the acquired destination designated as the destination m10, that is, without the processed flag m14. Is performed (S93).

  When 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 record in the transmission waiting list 230 (S94).

  Further, the maximum standby time (for example, the maximum standby time M) of the subscription information (topic) is obtained from the maximum standby time list 235 (S95). The maximum waiting time list 235 may be prepared in advance or may be dynamically generated by a request from the client device 30 or the like.

  Further, it is determined whether or not the execution date and time is after a lapse of the maximum standby time M from the registration date and time, that is, whether or not (current time + T)> (registration date and time + M) (S96).

  When it is determined that the execution date and time is after the maximum standby time M has elapsed from the registration date and time (S96: Yes), the current publication data SD is transmitted in the same manner as the transmission standby list 230 in order to transmit the current publication data SD. The publication data SD is registered in the configured transmission list (S97). In response, 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, and is not shown.

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

  On the other hand, when it is not determined in step S93 that the publication data SD exists (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, a process performed when publication data is transmitted from another broker device 10 will be described.

  FIG. 25 is a flowchart illustrating an example of a processing procedure in a case where publication data is transmitted from another broker device.

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

  When 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, when it is determined that unprocessed publication data SD is included in the divided packets (step S113: Yes), one unprocessed publication data SD is extracted (S114), and the management table 205 is subscribed. It is determined whether or not the subscribed client device 30 of the topic exists in the broker device m1 (S115).

  If it is determined that the subscription 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), returning to step S113.

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

  The processing procedure when the own broker device 13 (# 0) receives the subscription request from the client device 30 is as described with reference to the flowchart of FIG. The processing procedure when a subscription request is received from the apparatus 10 is as described with reference to the flowchart in FIG. 8, and the processing procedure when the other broker apparatus 10 terminates and when an abnormality is detected is described with reference to the flowchart in FIG. 11. As described.

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

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

  In the third embodiment, as shown in FIG. 19, aggregation / compression and division / expansion of packets are executed by the broker device 13 including the aggregation / compression unit 126 and the division / expansion unit 130. In a modified example, the process is executed by the client device, not the broker device 13.

  FIG. 26 is a conceptual diagram illustrating a configuration example of a client device applied to a modified example 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. The configuration of the broker device 10 is as shown in FIG.

  The client device 31 includes a communication unit 302, a division / decompression unit 304, a subscription / publishing 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 aggregated publication data, compresses the generated aggregated publication data, and generates aggregated compressed publication data. I do. However, since the aggregation / compression unit 308 does not know the topic to which each broker device 10 has subscribed, it cannot compress the packet for each destination broker device 10. Therefore, the publication data SD is aggregated and compressed for each topic.

  FIG. 27 is a diagram illustrating an example of the maximum standby time list.

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

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

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

  For example, when the maximum standby time m16 for each piece of subscription information (topic) m15 is as shown in FIG. 27 and packet transmission is performed every T = 10 milliseconds, the next call in the transmission standby list 260 shown in FIG. The subscription information (topic) m1 that sometimes passes the maximum standby time becomes an information group A, an information group B, an information group B, and an 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 packet, the information group B packet, and the information group C packet. 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, the data is compressed as it is. 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 the compressed and aggregated data.

  The compressed and aggregated publication data 265 is obtained by further compressing the plurality of publication data SD aggregated by the aggregation and compression unit 308.

  In the example illustrated in FIG. 29, the compressed and aggregated publication data 265 has a configuration in which the publication data SD1 and the publication data SD2 are aggregated as one publication data and then compressed. Here, the publishing data SD1 and the publishing data SD2 are the same subscription information (topic), so that the subscription information (topic) j is provided at the beginning as information common to the publishing data SD1 and the publishing data SD2, and thereafter, The format may be such that a data header h1 and a data body b1 of SD1 follow, followed by a data header h2 and a data body b2 of the publication data SD2. In addition, the number of publication data SD aggregated in the compressed aggregated publication data 265 is not limited to two, and may be an arbitrary 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 apparatus 10, the publication data SD may be further aggregated for each destination broker apparatus 10 and then transmitted in combination with the configuration of FIG.

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

  That is, the division / decompression unit 304 decompresses 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 broker device 10 in which the abnormality is detected to another broker device 10 (for example, the broker device 10 (# 1)).

  Upon detecting an increase in the load of the broker device 10, the load detection unit 312 changes the connection destination from the broker device 10 that has detected the increase in the load to another broker device 10 (for example, the broker device 10 (# 1)).

  The communication unit 302 transmits the aggregated compressed publishing data to the broker device 10 (for example, the broker device 10 (# 1)) whose connection destination has been changed by the abnormality detection unit 310 and the load detection unit 312, and also transmits the broker device 10 The aggregated compressed publishing data transmitted from is output to the division / decompression unit 304.

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

  FIG. 30 is a flowchart illustrating an example of a processing procedure when receiving a publication request for publication data from a client device.

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

  On the other hand, in order to periodically transmit the publication data SD to the broker device 10, the client device 31 performs aggregation / compression and transmission processing of the packet for each subscription information (topic).

  FIG. 31 is a flowchart illustrating an example of a processing procedure when aggregating / compressing and transmitting a packet for each piece of subscription information (topic).

  The flowchart shown in FIG. 31 is similar to the flowchart shown in FIG. 24, and therefore, a duplicate description will be avoided and only 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. For this reason, in FIG. 31, it is determined whether or not unprocessed subscription information (topic) exists in step S131. If it is determined that the subscription information does not exist, in step S132, the unprocessed subscription information (topic) is determined. Is determined, and in step S133, it is determined whether there is transmission standby data that matches the obtained subscription information (topic). If it is determined that transmission standby data is present, in step S134, the obtained subscription information is determined. Is retrieved.

  If it is not determined in step S131 that there is any data (S131: No), the processing after step S99 in FIG. 24 is performed. If it is not determined in step S133 that there is any data (S133: No), the process proceeds to step S131. The processing after step S101 in FIG. 24 is performed, and the processing after step S95 in FIG. 24 is performed after step S134.

  FIG. 32 is a flowchart illustrating an example of a processing procedure when transmitting publication data from the broker device.

  In the client device 31, when the publishing data SD transmitted from the broker device 10 is received by the communication unit 302 (S141), the publishing data SD is developed by the dividing / developing unit 304 and then divided (S142). ). Further, in order to perform processing 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. If there is any unprocessed publication data SD (S143: Yes), one piece of publication data SD is extracted and processed. Is executed, the process returns to S144.

  Note that the processing procedure at the time of the subscription request only transmits the subscription request to the broker device 10, and thus the description is omitted here. In addition, the processing procedure on the broker device 10 side has been described in the first embodiment, and thus redundant description will be avoided.

  According to such a modification, the total amount of packets and the amount of transmitted publication data can be reduced while maintaining the reliability of communication.

  Although several embodiments of the present invention have been described, these embodiments are provided by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in other various forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 Communication system, 2 communication systems, 10 broker apparatuses, 11 broker apparatuses, 12 broker apparatuses, 13 broker apparatuses, 20 networks, 21 networks, 30 client apparatuses, 31 client apparatuses, 40 sub broker apparatuses, 102 communication sections, 104 communication sections, 106 Self-subscription information receiving unit, 108 Self-subscription information management unit, 110 Self-published data receiving unit, 112 Self-published data transmitting unit, 114 Latest published data holding unit, 116 Other published data transmitting unit, 118 Other published data receiving unit, 120 Other subscription information management unit, 122 end detection unit, 124 QoS management unit, 126 aggregation / compression unit, 128 real-time property determination unit, 130 division / decompression 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 Equipment Subscription Number Management Table, 220 Other Subscription Information Management Table, 225 Own Subscription Information Management Table, 230 Transmission Wait List, 235 Maximum Waiting Time List, 240 Time Conditions, 245 Compressed Aggregated Publishing Data, 250 Maximum waiting time list, 255 time condition, 260 transmission waiting list, 265 compressed and aggregated publication data, 302 communication unit, 304 division / expansion unit, 306 subscription / publishing request unit, 308 aggregation / compression unit, 310 abnormality detection unit, 312 load detector, 402 end detector, 404 subscription determiner.

Claims (16)

A broker device for transmitting publication data received from a first client device to a second client device and another broker device,
A self-subscribe information receiving unit that receives a subscription request for a topic to be 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-publishing data transmitting unit that transmits the publication data received by the self-publishing data receiving unit to the second client device;
A broker for transmitting the publication data received by the self-published data receiver to the other broker device; From the other broker device, another publication data receiving unit that receives publication data related to the topic,
The latest publication data holding unit that extracts and holds the latest publication data for each topic from the publication data received by the self-published data reception unit and the other publication data reception unit,
2. The broker device according to claim 1, wherein the self-published data transmitting unit acquires the latest published data of a topic related to the subscription request from the latest published data holding unit and transmits the latest published data to the second client device. 3. . A subscribe request for a topic subscribed to by the other broker device, comprising a subscribe information management unit that receives from the other broker device;
The other publication data transmission unit 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 the latest publication data to the other broker device. The broker device according to claim 2. While managing the topic to be subscribed by the broker device, further includes a self-subscription information management unit that transmits this topic to the other broker device when there is a change in the managed topic,
The other publication data receiving unit outputs a subscription request for new subscription registration to the self-subscribed information management unit when there is no client device that subscribes to a topic managed by the self-subscribed information management unit. The broker device according to claim 3.   The other publication data receiving unit manages the topic related to the subscription request received by the other subscription information management unit, the topic being subscribed by two or more broker devices, and the self-subscription information management unit. The broker device according to claim 4, wherein when there is no client device that subscribes to the topic, the broker device outputs a subscription request for unsubscription to the self-subscription information management unit.   The other publication data receiving unit calculates the number of the topics subscribed for each broker device, and when the minimum value exceeds the total value of the number of the topics managed by the self-subscription information management unit, a new value is added. The broker device according to claim 4, wherein a subscription request for subscription registration is output to the self-subscription information management unit. Further comprising an end detection unit for detecting the end or abnormality of the other broker device,
The broker device according to claim 3, wherein the other subscription information management unit does not receive the subscription request from the other broker device when the termination detection unit detects the termination or abnormality of the other broker device. For each topic, manages an index value of reliability required for transmission and reception of the publication data, and further includes an index value management unit that determines whether the publication data needs to be copied,
The other subscription information management unit, when the index value management unit determines that the publication data needs to be duplicated by the index value management unit for the topic for which a subscription request for unsubscription was issued from the other broker device, The broker device according to claim 4, wherein a subscription request for registration is output to the self-subscription information management unit. An aggregation unit that aggregates the publication data transmitted to the plurality of other broker devices from the other publication information data transmission unit into one aggregated publication data at predetermined time intervals for each of the other broker devices;
The broker device according to any one of claims 1 to 8, further comprising a compression unit configured to compress the aggregated publication data aggregated by the aggregation unit in accordance with a predetermined first algorithm. The self-published data receiving unit records a reception time of the published data received from the first client device,
Further, it is determined that the publication data in which the difference between the time when the certain time has elapsed from the current time and the reception time exceeds the maximum standby time predetermined for each topic is the object of aggregation by the aggregation unit. The broker device according to claim 9, further comprising a real-time determination unit that performs the determination. By expanding the aggregated publication data, which is transmitted from the other broker device and received by the other publication data receiving unit, in which a plurality of publication data are aggregated and compressed, according to a second predetermined algorithm, From the compressed aggregated publication data that has been compressed, a decompression unit that restores the aggregated publication data before compression,
A dividing unit configured to divide the uncompressed aggregated publishing data restored by the decompression unit and restore a plurality of unpublished publishing data from the uncompressed aggregated publishing data. The broker device according to any one of 2 to 10. A client device connectable to a plurality of broker devices,
Of the plurality of broker devices, transmitted from the broker device of the connection destination, a plurality of publication data is aggregated and expand the aggregated publication data that is compressed, to restore the aggregated publication data before compression, Dividing the restored aggregated publishing data, and a split developing unit for restoring the publishing data before aggregation,
A plurality of publication data transmitted to the broker device of the connection destination, aggregating compression unit for generating aggregated publication data by aggregating each related topic, and compressing the generated aggregated publication data,
The aggregated publishing data compressed by the aggregation compression unit is transmitted to the broker device of the connection destination, and the aggregated publication data transmitted from the broker device of the connection destination is received. And a communication unit for providing to the client device. When detecting an abnormality in the broker device of the connection destination, an abnormality detection unit that changes the connection destination to another broker device,
13. The client device according to claim 12, further comprising: a load detection unit configured to change the connection destination to another broker device when the increase in the load of the connection destination broker device is detected. A communication method performed by a broker device to transmit publishing data received from a first client device to a second client device and another broker device, comprising:
The broker device,
Receiving, from the second client device, a subscription request for a topic subscribed to by the second client device;
Receiving publication data associated with the topic from the first client device;
Transmitting the received publication data to the second client device;
Transmitting the received publication data to the other broker device. A program for transmitting publishing data received from a first client device to a second client device and another broker device,
A function of receiving a subscription request for a topic subscribed by the second client device from the second client device;
A function of receiving publication data related to the topic from the first client device;
Transmitting the received publication data to the second client device;
A program for causing a computer to implement a function of transmitting the received publication data to the other broker device. 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 self-subscription information receiving unit that receives, from the second client device, a subscription request for a topic subscribed by a second client device among the plurality of client devices;
A self-published data receiving unit that receives, from a first client device of the plurality of client devices, publication data related to the topic;
A self-publishing data transmitting unit that transmits the publication data received by the self-publishing data receiving unit to the second client device;
The publication data received by the self-published data receiving unit, the other publication data transmission unit that transmits to another broker device among the plurality of broker devices,
At least one client device among the plurality of client devices,
Of the plurality of broker devices, transmitted from the broker device to which the connection is made, a plurality of publication data is aggregated and expands the aggregated publication data formed by compression, to restore the aggregated publication data before compression, Dividing the restored aggregated publishing data, a split developing unit for restoring the publishing data before aggregation,
A plurality of publication data transmitted to the broker device of the connection destination, to generate aggregated publication data by aggregating each related topic, an aggregation compression unit that compresses the generated aggregated publication data,
Transmitting the aggregated publication data compressed by the aggregation compression unit to the broker device of the connection destination; receiving the aggregated publication data transmitted from the broker device of the connection destination; A communication system comprising: