JPWO2015068381A1 - Transmitting apparatus, information processing system, master server, database system and method - Google Patents

Abstract

The present invention provides a technique that more sufficiently prevents a reduction in the congestion window size in intermittent communication. The transmission device 10 includes a data transmission unit 11 and a dummy data transmission control unit 12. The data transmission unit 11 transmits target data requested to be transmitted by the application or dummy data to the receiving device 50. The dummy data transmission control unit 12 transmits data so as to transmit dummy data having a size satisfying the predetermined condition when target data having a size satisfying the predetermined condition is not transmitted to the receiving device 50 during the predetermined period. The unit 11 is controlled. When receiving the target data, the receiving device 50 performs a predetermined process on the target data. In addition, when receiving the dummy data, the receiving device 50 discards the dummy data.

Description

  The present invention relates to a technique for transferring data between devices connected via a network.

  In an information processing system that transfers data between devices connected via a network, it is required to shorten the transfer time as much as possible while performing reliable communication. An example of such an information processing system is a memory database system. Generally, a memory database system has a copy of data held by a master server on one or more prepared slave server memories. The master server transfers the update log to the slave server along with the data update. Compared to a disk-based database system, a memory database system that stores all data in memory can access data at high speed. Accordingly, the time required for network transfer of the update log accompanying data update becomes a bottleneck in performing high-speed transactions. Thus, in the memory database system, there is a demand for a data transfer method that shortens the network transfer time.

  In general, TCP (Transmission Control Protocol) is used to realize reliable communication. In TCP, congestion control using an algorithm called slow start is performed. Slow start is described in RFC (Request for Comments) 2001 by IETF (Internet Engineering Task Force) (W. Stevens, “TCP Slow Start, Congestion Avoidance, Fast Retransmit, and Fast Recovery Algorithms”, Jan 1997). Has been. Congestion control is described in RFC2861 (M. Handley, J. Padhye, S. Floyd, “TCP Congestion Window Validation”, June 2000). Slow start is an algorithm that starts from a small amount of communication and increases the data size (congestion window size) that can be transmitted gradually in order to prevent congestion. This operation continues until the congestion window size reaches the window size announced by the receiving side or congestion occurs. When congestion occurs, the slow start starts again.

  Specifically, this algorithm increases the congestion window size when an ACK is returned from the transmission destination in response to transmission of a packet exceeding the congestion window size. If no communication occurs during a retransmission timeout time (RTO: Retransmission Time Out, generally several hundred milliseconds), the congestion window size is reduced and slow start is started. Here, in the above-described memory database system or the like, the master server transfers the update log according to the data update, and therefore the transfer is performed intermittently. Therefore, when the transfer interval becomes equal to or longer than the RTO time, the once-expanded congestion window size is reduced and slow start is started.

  However, the above-described memory database system or the like requires a response time of less than 1 millisecond, for example. In such an information processing system, when slow start is started at the time of transfer of an update log, communication takes several tens to several hundreds of times. As a result, there arises a problem that the response time required for transfer (replication) of the update log is not satisfied.

  Here, in the memory database as described above, the master server and the slave server are often installed in the same premises (in the same rack). In this case, a network is often prepared exclusively for replication in order to ensure high speed replication communication between the master server and the slave server. In such a case, it is not necessary to consider that congestion occurs due to other communication in a network dedicated to replication. For this reason, the response speed may be slower due to the slow start. As described above, the congestion control using the slow start is often unnecessary when a highly reliable dedicated network is used.

  Depending on the operating system (OS), there may be a setting for invalidating the slow start, or a setting for changing the RTO time or the delayed ACK interval to an arbitrary value. Therefore, in order to increase the response speed of replication, it may be possible to make settings such as uniformly disabling slow start in the OS, or changing the RTO time or delay ACK interval. However, for example, a server involved in data transfer may be connected to the normal Internet in addition to a replication-dedicated network. In such a server, if the above settings are uniformly set by the OS, there is a possibility that the performance of the communication on the Internet connection side is significantly deteriorated due to congestion. Therefore, it is difficult to solve the problem of a decrease in communication speed caused by the start of slow start due to intermittent communication in a specific network connection by setting the OS.

  A technique for dealing with such a problem is described in Patent Document 1. This related technique transmits RTO avoidance data through the TCP connection before the elapsed time from the most recent use time of the TCP connection becomes the elapsed time to transit to the slow start mode. As a result, this related technique avoids a slow start in intermittent data communication.

JP 2006-100919 A

  However, the related technique described in Patent Document 1 may not prevent the congestion window size from being reduced when the size of data requested to be transmitted from an application is small. This is because the congestion window size may be reduced if the data does not satisfy the congestion window even if the data has been transmitted before the elapsed time to transition to the slow start mode (see above). See RFC2861). Further, Patent Document 1 does not describe the size of RTO avoidance data. Therefore, this related technique may not sufficiently prevent the congestion window size from being reduced.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a technique that more sufficiently prevents a reduction in the congestion window size in intermittent communication.

  In order to achieve the above object, a transmitting apparatus according to the present invention includes a predetermined condition between a data transmitting unit that transmits target data to be transmitted from an application or dummy data to a receiving apparatus, and a predetermined period. Dummy data transmission control means for controlling the data transmission means to transmit the dummy data having a size satisfying the predetermined condition when the target data having a size satisfying the condition is not transmitted to the receiving device; Prepare.

  The receiving device of the present invention includes data receiving means for performing predetermined processing on the target data when receiving the target data from the transmitting device and discarding the dummy data when receiving the dummy data.

  The information processing system of the present invention includes the above-described transmission device and the above-described reception device.

  In addition, the master server of the present invention updates the master data, master data storage means for storing master data, and information indicating the difference before and after updating the master data (update Application means for requesting the data transmission means to transmit the generated update log as the target data.

  Further, the slave server of the present invention receives the update log or the dummy data as the target data from the replica data storage means for storing the replica (replicated data) of the master data and the master server described above. And the above-described receiving apparatus that executes a process of updating the replicated data using the received update log as the predetermined process.

  The database system of the present invention includes the above-described master server and the above-described slave server.

  In the data transfer method of the present invention, when there is a request for transmitting target data from an application, the target data is transmitted to a receiving device, and the target data having a size satisfying a predetermined condition is received during the predetermined period. When not transmitted to the apparatus, dummy data having a size satisfying the predetermined condition is transmitted to the receiving apparatus.

  In addition, the storage medium of the present invention provides a target data transmission step of transmitting the target data to a receiving device when a request for transmission of target data is received from an application, and the target having a size satisfying a predetermined condition between a predetermined period A computer program for causing a computer device to execute a dummy data transmission step of transmitting dummy data having a size satisfying the predetermined condition to the receiving device when data is not transmitted to the receiving device. doing.

  The present invention can provide a technique that more sufficiently prevents the reduction of the congestion window size in intermittent communication.

It is a block diagram which shows the structure of the information processing system as the 1st Embodiment of this invention. It is a functional block diagram of an information processing system as a 1st embodiment of the present invention. It is a hardware block diagram of the information processing system as a 1st embodiment of the present invention. It is a flowchart explaining operation | movement of the data transmission part in the 1st Embodiment of this invention. It is a flowchart explaining operation | movement of the dummy data transmission control part in the 1st Embodiment of this invention. It is a flowchart explaining operation | movement of the data receiver in the 1st Embodiment of this invention. It is a block diagram which shows the structure of the memory database system as the 2nd Embodiment of this invention. It is a functional block diagram of a memory database system as a 2nd embodiment of the present invention. It is a flowchart explaining operation | movement of the application part in the 2nd Embodiment of this invention. It is a flowchart explaining operation | movement of the data transmission part in the 2nd Embodiment of this invention. It is a flowchart explaining operation | movement of the dummy data transmission control part in the 2nd Embodiment of this invention. It is a flowchart explaining operation | movement of the data receiver in the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the memory database system as the 3rd Embodiment of this invention. It is a functional block diagram of the memory database system as the 3rd Embodiment of this invention. It is a flowchart explaining operation | movement of the data transmission part in the 3rd Embodiment of this invention. It is a flowchart explaining operation | movement of the predetermined period calculation part in the 3rd Embodiment of this invention. It is a flowchart explaining operation | movement of the start control part in the 3rd Embodiment of this invention. It is a flowchart explaining operation | movement of the dummy data transmission control part in the 3rd Embodiment of this invention. It is a functional block diagram of the memory database system in the other aspect of the 3rd Embodiment of this invention. It is a flowchart explaining operation | movement of the data transmission part in the other aspect of the 3rd Embodiment of this invention. It is a flowchart explaining operation | movement of the dummy data transmission control part in the other aspect of the 3rd Embodiment of this invention. It is a functional block diagram of the memory database system as the 4th Embodiment of this invention. It is a flowchart explaining operation | movement of the data transmission part in the 4th Embodiment of this invention. It is a flowchart explaining operation | movement of the data receiver in the 4th Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 shows the configuration of an information processing system 1 as a first embodiment of the present invention. In FIG. 1, the information processing system 1 includes a transmission device 10 and a reception device 50. The transmission device 10 and the reception device 50 are connected to be communicable via a network.

  Next, FIG. 2 shows functional blocks of each device constituting the information processing system 1. In FIG. 2, the transmission device 10 includes a data transmission unit 11 and a dummy data transmission control unit 12. The receiving device 50 includes a data receiving unit 51.

  Here, an example of the hardware configuration of the transmission device 10 and the reception device 50 is shown in FIG. In FIG. 3, the transmission device 10 includes a CPU (Central Processing Unit) 1001, a RAM (Random Access Memory) 1002, a ROM (Read Only Memory) 1003, a storage device 1004 such as a hard disk, and a network interface 1005. It can be configured by a computer device. The receiving device 50 can be configured by a computer device including a CPU 5001, a RAM 5002, a ROM 5003, a storage device 5004 such as a hard disk, and a network interface 5005. In this case, the data transmission unit 11 includes a network interface 1005 and a CPU 1001 that reads a computer program and various data stored in the ROM 1003 and the storage device 1004 into the RAM 1002 and executes them. The dummy data transmission control unit 12 includes a CPU 1001 that reads a computer program and various data stored in the ROM 1003 and the storage device 1004 into the RAM 1002 and executes them. The data receiving unit 51 includes a network interface 5005 and a CPU 5001 that reads a computer program and various data stored in the ROM 5003 and the storage device 5004 into the RAM 5002 and executes them. Note that the hardware configurations of the transmission device 10 and the reception device 50 and each functional block of each device are not limited to the above-described configurations.

  Next, details of functional blocks of the transmission apparatus 10 will be described.

  The data transmission unit 11 transmits the target data or dummy data to the receiving device 50. The target data is data requested from an external application or an application (not shown) on the own device to be transmitted to the receiving device 50. Specifically, when receiving the target data from the transmission request source, the data transmission unit 11 transmits the target data through a communication connection established with the receiving device 50.

  The dummy data is data discarded in the receiving device 50. For this reason, the dummy data may have any content. Specifically, the data transmission unit 11 transmits dummy data having a size satisfying a predetermined condition to the reception device 50 in response to a request from a dummy data transmission control unit 12 described later. The predetermined condition may be equal to or greater than the congestion window size at that time.

  The dummy data transmission control unit 12 performs data transmission so as to transmit dummy data having a size satisfying the predetermined condition when target data having a size satisfying the predetermined condition is not transmitted to the receiving device 50 during the predetermined period. The unit 11 is controlled. Specifically, the dummy data transmission control unit 12 transmits the target data having a size satisfying a predetermined condition to the receiving device 50 during a predetermined period in the communication connection established with the receiving device 50. Determine whether or not. The dummy data transmission control unit 12 performs the above-described dummy data transmission control through the communication connection if such target data is not transmitted in a predetermined period.

  The predetermined condition may be equal to or greater than the congestion window size at that time, as described above. That is, the dummy data transmission control unit 12 transmits the dummy data larger than the congestion window size when the target data larger than the congestion window size at that time is not transmitted during the predetermined period. May be notified.

  Further, the predetermined period may be a period based on an elapsed time that is specified to reduce the congestion window size. Here, in the communication connection for transmitting the target data, when the elapsed time from the latest communication from the transmitting device 10 to the receiving device 50 reaches the length of the specified elapsed time, the congestion window size is reduced. . Therefore, for example, the dummy data transmission control unit 12 may define a period less than ½ of the specified elapsed time as the predetermined period. Then, each time the predetermined period elapses, the dummy data transmission control unit 12 may determine whether target data having a size satisfying the predetermined condition has been transmitted in the predetermined period up to that point.

  Next, details of functional blocks of the receiving device 50 will be described.

  The data reception unit 51 receives target data or dummy data from the transmission device 10. The data receiving unit 51 performs a predetermined process on the received target data. The predetermined process may be a process of saving in the storage device 5004, for example. Further, the data receiving unit 51 discards the received dummy data.

  The operation of the information processing system 1 configured as described above will be described.

  First, the operation of the data transmission unit 11 of the transmission device 10 is shown in FIG.

  In FIG. 4, first, the data transmission unit 11 receives a data transmission request (Yes in step S1).

  Here, when the received transmission request is a transmission request for target data from the application (“target data” in step S2), the data transmission unit 11 transmits the target data to the receiving device 50 (step S3). ).

  On the other hand, when the transmission request received in step S1 is a dummy data transmission request from the dummy data transmission control unit 12 (“dummy data” in step S2), the data transmission unit 11 has a dummy size that satisfies a predetermined condition. Data is transmitted to the receiving device 50 (step S4). Then, the operation of the data transmission unit 11 returns to step S1.

  Above, description of operation | movement of the data transmission part 11 of the transmitter 10 is complete | finished.

  Next, the operation of the dummy data transmission control unit 12 of the transmission device 10 is shown in FIG.

  In FIG. 5, first, the dummy data transmission control unit 12 determines whether or not target data having a size satisfying a predetermined condition has been transmitted from the data transmission unit 11 during a predetermined period up to this point (step S11). .

  If it is determined that target data having a size satisfying the predetermined condition has been transmitted, the operation of the dummy data transmission control unit 12 proceeds to step S13.

  On the other hand, when determining that the target data having a size satisfying the predetermined condition has not been transmitted, the dummy data transmission control unit 12 requests the data transmission unit 11 to transmit dummy data having a size satisfying the predetermined condition (step S12). ).

  Next, the dummy data transmission control unit 12 waits for a time set as a predetermined period (step S13).

  Then, the operation of the dummy data transmission control unit 12 returns to step S11.

  Above, description of operation | movement of the dummy data transmission control part 12 of the transmitter 10 is complete | finished.

  Next, the operation of the receiving device 50 is shown in FIG.

  In FIG. 6, first, the data reception unit 51 receives data from the transmission device 10 (Yes in step S <b> 21).

  Here, when the received data is target data (“target data” in step S22), the data receiving unit 51 executes a predetermined process on the target data (step S23).

  On the other hand, when the received data is dummy data (“dummy data” in step S22), the data receiving unit 51 discards the dummy data (step S24).

  Then, the operation of the receiving device 50 returns to step S21.

  Above, description of operation | movement of the receiver 50 is complete | finished.

  Next, effects of the first exemplary embodiment of the present invention will be described.

  The information processing system as the first exemplary embodiment of the present invention can more sufficiently prevent the reduction of the congestion window size in intermittent communication.

  The reason is that the data transmission unit transmits the target data or dummy data requested by the application to the receiving device. The dummy data transmission control unit transmits dummy data having a size satisfying the predetermined condition to the receiving device through the data transmission unit when target data having a size satisfying the predetermined condition is not transmitted during the predetermined period. This is because control is performed. In addition, as the predetermined period, a period based on the elapsed time from the latest communication in which the congestion window size is specified to be reduced in the communication connection established for transmitting the target data is used.

  As a result, in the information processing system in which communication from the transmission device to the reception device occurs intermittently, the present embodiment is the target data having a size that satisfies the predetermined condition at intervals of less than twice the predetermined period. Or dummy data is transmitted. Therefore, this embodiment can avoid that the congestion window size does not satisfy the predetermined condition, and can keep the size that can be transmitted at a time satisfying the predetermined condition. Therefore, the present embodiment does not reduce the congestion window size so as not to satisfy the predetermined condition in the communication connection in which intermittent communication is performed. Further, for example, if the predetermined condition is that the congestion window size is equal to or larger than the current congestion window size, this embodiment does not further reduce the once-expanded congestion window size.

(Second Embodiment)
Next, a second embodiment of the present invention will be described in detail with reference to the drawings. In this embodiment, an example in which the information processing system of the present invention is applied to a memory database system will be described. Note that, in each drawing referred to in the description of the present embodiment, the same reference numerals are given to the same configuration and steps that operate in the same manner as in the first embodiment of the present invention, and the detailed description in the present embodiment. Description is omitted.

  First, FIG. 7 shows a configuration of a memory database system 2 as a second embodiment of the present invention. In FIG. 7, the memory database system 2 includes a master server 20 including the transmission device of the present invention and a slave server 60 including the reception device of the present invention. The master server 20 and the slave server 60 are communicably connected via a network.

  Next, functional blocks of each device constituting the memory database system 2 are shown in FIG. In FIG. 8, the master server 20 includes a data transmission unit 21, a dummy data transmission control unit 22, a master data storage unit 23, and an application unit 24. Here, the master server 20 can be configured by a computer device including the same hardware elements as those of the transmission device according to the first embodiment of the present invention described with reference to FIG. In this case, the master data storage unit 23 is configured by the RAM 1002. The application unit 24 includes a CPU 1001 that reads a computer program and various data stored in the ROM 1003 and the storage device 1004 into the RAM 1002 and executes them.

  The slave server 60 includes a data receiving unit 61 and a duplicate data storage unit 62. Here, the slave server 60 can be configured by a computer device including the same hardware elements as the receiving device according to the first embodiment of the present invention described with reference to FIG. In this case, the duplicate data storage unit 62 is configured by the RAM 5002.

  Next, details of each functional block of the master server 20 will be described.

  The master data storage unit 23 stores master data.

  The application unit 24 updates the master data. The master data is updated in response to, for example, an external request or a request from another functional block (not shown) in the own device. And the application part 24 produces | generates the information (update log) showing the difference before the update and the post-update according to the update of master data. In addition, the application unit 24 requests the data transmission unit 21 to transmit the generated update log to the slave server 60. For example, after issuing a commit request, the application unit 24 may generate an update log and request transmission thereof.

  The data transmission unit 21 is configured to operate in substantially the same manner as the data transmission unit 11 in the first embodiment of the present invention. However, in the present embodiment, the update log requested from the application unit 24 is applied to the target data. In the present embodiment, the transmission destination of the update log or dummy data is the slave server 60.

  Further, the data transmission unit 21 may hold a transmitted flag for determination processing by the dummy data transmission control unit 22. In this case, when the update log requested and transmitted from the application unit 24 satisfies a predetermined condition, the data transmitting unit 21 sets the transmitted flag to ON and holds it. In the present embodiment, a condition that the size is s (s is a positive number) or more is applied as the predetermined condition.

  The dummy data transmission control unit 22 performs processing according to whether an update log having a size of s or more is transmitted during a predetermined period. Here, the predetermined period is a period similar to the predetermined period described in the first embodiment of the present invention. For example, when the transmitted flag is held by the data transmission unit 21, the dummy data transmission control unit 22 is configured to operate as follows.

  Specifically, the dummy data transmission control unit 22 checks the transmitted flag every time a predetermined period elapses. Then, the dummy data transmission control unit 22 controls the data transmission unit 21 to transmit dummy data of size s or more when the transmitted flag is off. Further, the dummy data transmission control unit 22 sets the transmitted flag to OFF when the transmitted flag is ON.

  Next, details of each functional block of the slave server 60 will be described.

  The duplicate data storage unit 62 stores duplicate data. The duplicate data is a duplicate of master data stored in the master server 20.

  The data receiving unit 61 is configured to operate in substantially the same manner as the data receiving unit 51 in the first embodiment of the present invention. Specifically, the data receiving unit 61 receives an update log or dummy data as target data from the master server 20. Further, the data receiving unit 61 updates the duplicate data in the duplicate data storage unit 62 using the update log. Further, the data receiving unit 61 discards the dummy data.

  The operation of the memory database system 2 configured as described above will be described with reference to the drawings.

  First, the operation of the application unit 24 in the master server 20 is shown in FIG.

  In FIG. 9, first, the application unit 24 updates the master data in the master data storage unit 23 (step S31).

  Next, the application unit 24 generates difference information between the master data before and after the update as an update log (step S32).

  Next, the application unit 24 requests the data transmission unit 21 to transmit the update log generated in step S32 (step S33).

  Above, description of operation | movement of the application part 24 is complete | finished.

  Next, the operation of the data transmission unit 21 in the master server 20 is shown in FIG. It is assumed that the transmitted flag is set to OFF at the start of the operation.

  In FIG. 10, first, the data transmission unit 21 operates in substantially the same manner as the data transmission unit 11 in the first embodiment of the present invention from step S1 to S3. However, in the present embodiment, an update log requested to be transmitted from the application unit 24 is applied as the target data.

  In addition, after transmitting the update log to the slave server 60 in step S3, the data transmission unit 21 determines whether or not the size of the transmitted update log is greater than or equal to s (step S131).

  If the size is greater than or equal to s, the data transmission unit 21 sets the transmission completion flag to ON and holds it (step S132). Then, the operation of the data transmission unit 21 returns to step S1.

  On the other hand, when the size is less than s, the operation of the data transmission unit 21 returns to step S1.

  If the transmission request received in step S1 is a dummy data transmission request (“dummy data” in step S2), the data transmission unit 21 sends dummy data of size s or more to the slave server 60. Transmit (step S133). Then, the operation of the data transmission unit 21 returns to step S1.

  Above, description of operation | movement of the data transmission part 21 of the master server 20 is complete | finished.

  Next, the operation of the dummy data transmission control unit 22 in the master server 20 is shown in FIG.

  In FIG. 11, first, the dummy data transmission control unit 22 checks the content of the transmitted flag and determines whether or not it is on (step S141).

  Here, if the transmitted flag is on, the dummy data transmission control unit 22 sets (resets) the transmitted flag to off (step S142).

  On the other hand, when the transmitted flag is off, the dummy data transmission control unit 22 executes step S12 as in the first embodiment of the present invention, and requests the data transmission unit 21 to transmit dummy data. (Step S12). However, in this embodiment, the dummy data transmission control unit 22 requests transmission of dummy data whose size is s or more.

  Next, the dummy data transmission control unit 22 waits for a predetermined period (step S13).

  Then, the operation of the dummy data transmission control unit 22 returns to step S141.

  Above, description of operation | movement of the dummy data transmission control part 22 of the master server 20 is complete | finished.

  Next, the operation of the slave server 60 is shown in FIG.

  In FIG. 12, first, the data receiving unit 61 receives data from the master server 20 (Yes in step S41).

  If the received data is an update log (“update log” in step S42), the data receiving unit 61 updates the replicated data in the replicated data storage unit 62 using the update log (step S43). .

  On the other hand, when the received data is dummy data (“dummy data” in step S42), the data receiving unit 61 discards the dummy data (step S44).

  Then, the operation of the data receiving unit 61 returns to step S41.

  Above, description of operation | movement of the data receiver 61 is complete | finished.

  Next, the effect of the second exemplary embodiment of the present invention will be described.

  In the memory database system according to the second embodiment of the present invention, even when the update log is intermittently transferred from the master server to the slave server, the congestion window size becomes a predetermined size or less. Can be sufficiently prevented.

  The reason is that when the data transmission unit transmits an update log of a predetermined size s or more to the slave server, the transmission flag is set to ON, and the dummy data transmission control unit has been transmitted every time the predetermined period elapses. This is because the flag is checked. Then, the dummy data transmission control unit resets to OFF if the transmitted flag is ON, and transmits dummy data of size s or more to the slave server through the data transmitting unit if the transmitted flag is OFF. It is because it controls. In addition, as the predetermined period, a period based on a length determined to reduce the congestion window size is used for the elapsed time from the recent communication from the master server to the slave server in the communication connection for transmitting the update log. is there.

  As a result, the present embodiment allows the size s to be set at an interval of less than twice the time set as the predetermined period, even if communication by update log transfer does not occur between the master server and the slave server. The above dummy data is transmitted. Therefore, this embodiment can avoid a state in which the congestion window size is s or less. Therefore, this embodiment does not extremely reduce the communication speed even when the update log is transferred to the slave server after the update log is not transferred from the master server for a certain period. As a result, this embodiment can always perform high-speed replication processing in a memory database system that constitutes an online transaction system that requires high availability and high-speed response at the same time.

(Third embodiment)
Next, a third embodiment of the present invention will be described in detail with reference to the drawings. In the present embodiment, as in the second embodiment of the present invention, an example in which the information processing system of the present invention is applied to a memory database system will be described. Note that, in each drawing referred to in the description of the present embodiment, the same configurations and steps that operate in the same manner as in the first and second embodiments of the present invention are denoted by the same reference numerals, and the present embodiment. The detailed description in is omitted.

  First, FIG. 13 shows a configuration of a memory database system 3 as a third embodiment of the present invention. In FIG. 13, the memory database system 3 includes a master server 30 and n (n is an integer of 1 or more) slave servers 60 (60_1 to 60_n). The master server 30 and each slave server 60 are communicably connected via a network.

  Next, FIG. 14 shows functional blocks of each device constituting the memory database system 3. In FIG. 14, the master server 30 is different from the master server 20 according to the second embodiment of the present invention in that n data transmission units 31 (31_1 to 31_n) and dummy data are used instead of the data transmission unit 21. The difference is that n dummy data transmission control units 32 (32_1 to 32_n), a predetermined period calculation unit 35, and a start control unit 36 are provided instead of the transmission control unit 22. The predetermined period calculation unit 35 and the start control unit 36 constitute an embodiment of a part of the dummy data transmission control unit of the present invention. Here, the master server 30 can be configured by a computer device including the same hardware elements as those of the transmission device according to the first embodiment of the present invention described with reference to FIG. In this case, the predetermined period calculation unit 35 and the start control unit 36 are configured by the CPU 1001 that reads the computer program and various data stored in the ROM 1003 and the storage device 1004 into the RAM 1002 and executes them.

  Each of the n slave servers 60 is configured in the same manner as the slave server 60 in the second embodiment of the present invention.

  Next, details of each functional block of the master server 30 will be described.

  The data transmission unit 31_i (i = 1 to n) is associated with the slave server 60_i. The data transmission unit 31_i transmits the update log or the dummy data to the corresponding slave server 60_i. Specifically, the data transmission unit 31_i performs communication while holding a TCP connection with the corresponding slave server 60_i. In addition, the data transmission unit 31_i holds a transmitted flag regarding the corresponding slave server 60_i. That is, in the master server 30, n transmitted flags are held for each slave server 60_i.

  Specifically, when receiving a transmission request for an update log from the application unit 24, the data transmission unit 31_i transmits the update log to the corresponding slave server 60_i through a TCP connection. At this time, if the size of the transmitted update log is greater than or equal to s, the data transmission unit 31_i sets the transmission completion flag regarding the corresponding slave server 60_i to ON and holds it.

  Here, the size s may be a value calculated by the following equation (1).

s = 2 × MSS (1)
MSS (Maximum Segment Size) represents the maximum size of data that can be transferred in one segment in TCP, and is calculated by the following equation (2).

MSS = MTU-40 (2)
Here, the MTU (Maximum Transmission Unit) indicates the maximum size of data that can be transmitted in one transfer. The MSS is calculated as a value obtained by removing the IP (Internet Protocol) header 20 bytes and the TCP header 20 bytes from the MTU. Therefore, the data transmission unit 31_i may calculate the size s according to Equation (1) based on the MTU value that can be acquired from the system. The data transmission unit 31_i may acquire the value of s set by the user instead of calculating the value of the size s using the above-described equation (1). In this case, it is desirable that the value of s is set so as to satisfy the formula (1).

  Further, the data transmission unit 31_i transmits dummy data of size s or more to the slave server 60_i in response to a request from a dummy data transmission control unit 32_i described later.

  The predetermined period calculation unit 35 determines the predetermined period t using the following equation (3) and notifies the dummy data transmission control units 32_1 to 32_n, respectively. The notified predetermined period t is used as an interval for checking the transmitted flag by each dummy data transmission control unit 32_i.

t = RTO × α (0 <α <0.5) (3)
Here, RTO represents a retransmission timeout time in TCP communication. In TCP, if no communication has occurred for an RTO time or longer, a slow start starts in the next communication. Therefore, the predetermined period calculation unit 35 may calculate the predetermined period t according to the equation (3) based on the value of the RTO time that can be acquired from the OS (Operating System). Note that, depending on the OS, the value of the RTO time varies depending on the network load status. In such a case, the predetermined period calculation unit 35 may re-acquire the value of the RTO time at any timing and calculate the predetermined period t again. Further, the predetermined period calculation unit 35 may acquire the value of t set by the user instead of calculating the value of the predetermined period t using the above equation (3). In this case, it is desirable that the value of t is set so as to satisfy Expression (3).

  The start control unit 36 activates the dummy data transmission control units 32_1 to 32_n at different timings. Specifically, for example, the start control unit 36 may sequentially activate the dummy data transmission control units 32_1 to 32_n at each activation interval T calculated based on the following equation (4).

T = t ÷ n (4)
As a result, the n dummy data transmission control units 32_i are sequentially activated by the start control unit 36, and execute processing corresponding to the content of the transmitted flag every predetermined period t at different timings. Specifically, after being activated, the dummy data transmission control unit 32_i checks the transmitted flag regarding the corresponding slave server 60_i every predetermined period t. Then, the dummy data transmission control unit 32_i controls the data transmission unit 31_i to transmit dummy data of size s or more to the slave server 60_i when the corresponding transmitted flag is off. Further, when the corresponding transmitted flag is on, the dummy data transmission control unit 32_i sets the transmitted flag to off.

  The operation of the memory database system 3 configured as described above will be described with reference to the drawings.

  First, the operation of the application unit 24 in the master server 30 will be described. The operation of the application unit 24 is substantially the same as the operation of the application unit 24 in the second embodiment of the present invention described with reference to FIG. However, in the present embodiment, in step S33, the application unit 24 requests the data transmission units 31_1 to 31_n to transmit update logs.

  Next, an operation of the data transmission unit 31_i in the master server 30 is illustrated in FIG. Note that, at the start of the operation, it is assumed that the transmitted flag regarding each slave server 60_i is set to off. In addition, it is assumed that the data transmission unit 31_i has already calculated the value of the predetermined size s based on the above equation (1).

  In FIG. 15, first, the data transmission unit 31_i receives a data transmission request (Yes in step S51).

  Next, if the received transmission request is an update log transmission request from the application unit 24 (“update log” in step S52), the data transmission unit 31_i transmits the update log to the slave server 60_i. (Step S53).

  Next, the data transmission unit 31_i determines whether or not the size of the update log transmitted in step S53 is greater than or equal to s (step S54).

  Here, when the size is equal to or larger than s, the data transmission unit 31_i sets the transmission completion flag related to the slave server 60_i to ON and holds (step S55). Then, the operation of the data transmission unit 31_i returns to Step S51.

  On the other hand, when the size is less than s, the operation of the data transmission unit 31_i returns to Step S51.

  If the transmission request received in step S51 is a dummy data transmission request (“dummy data” in step S52), the data transmission unit 31_i sends dummy data of size s or more to the corresponding slave server 60_i. It transmits to (step S56). Then, the operation of the data transmission unit 31_i returns to Step S51.

  Above, description of operation | movement of the data transmission part 31_i is complete | finished.

  Next, the operation of the predetermined period calculation unit 35 in the master server 30 is shown in FIG. For example, the predetermined period calculation unit 35 may perform this operation when the system is started. Further, as described above, in the case of a system in which the RTO time changes according to the load state of the network, the predetermined period calculation unit 35 may repeatedly execute this operation at any timing.

  In FIG. 16, the predetermined period calculation unit 35 acquires the RTO time from the OS (step S61).

  Next, the predetermined period calculation unit 35 calculates the predetermined period t using Expression (3) (step S62).

  Next, the predetermined period calculation unit 35 notifies the value of t calculated in step S62 to each of the n dummy data transmission control units 32_i (step S63).

  Above, description of operation | movement of the predetermined period calculation part 35 is complete | finished.

  Next, the operation of the start control unit 36 in the master server 30 is shown in FIG. It is assumed that the start control unit 36 has already calculated the activation interval T using the above equation (4).

  In FIG. 17, first, the start control unit 36 initializes the slave server number i to 1 (step S71).

  Next, the start control unit 36 waits for the activation interval T (step S72).

  Next, the start control unit 36 activates the i-th dummy data transmission control unit 32_i (step S73).

  Next, if i is smaller than the number n of slave servers 60 (Yes in Step S74), the start control unit 36 adds 1 to i (Step S75), and repeats the operation from Step S72.

  On the other hand, when i becomes n or more (No in step S74), the start control unit 36 ends the operation.

  Above, description of operation | movement of the start control part 36 is complete | finished.

  Next, the operation of the dummy data transmission control unit 32_i in the master server 30 is shown in FIG. It is assumed that the dummy data transmission control unit 32_i has already been notified of the predetermined period t from the predetermined period calculation unit 35. Also, the dummy data transmission control unit 32_i starts the following operation when activated by the start control unit 36.

  In FIG. 18, first, the dummy data transmission control unit 32_i checks the content of the transmitted flag regarding the corresponding slave server 60_i (step S81).

  Here, when the transmitted flag is on, the dummy data transmission control unit 32_i sets (resets) the transmitted flag to off (step S82).

  On the other hand, when the transmitted flag is off, the dummy data transmission control unit 32_i requests the data transmission unit 31_i to transmit dummy data having a size of s or more to the slave server 60_i (step S83).

  Next, the dummy data transmission control unit 32_i waits for a predetermined period t (step S84).

  Then, the operation of the dummy data transmission control unit 32_i returns to Step S81.

  Above, description of operation | movement of the dummy data transmission control part 32_i is complete | finished.

  Note that the operation of each of the n slave servers 60_1 to 60_n is the same as the operation of the slave server 60 in the second embodiment of the present invention described with reference to FIG. The description in is omitted.

  Next, effects of the third exemplary embodiment of the present invention will be described.

  In the memory database system according to the third embodiment of the present invention, even when the update log is intermittently transferred from the master server to the slave server, the congestion window size becomes a predetermined size or less. Can be sufficiently prevented.

  The reason is that the data transmission unit sets the transmitted flag to ON when an update log of a predetermined size s or larger is transmitted to the slave server. This is also because the dummy data transmission control unit checks the transmitted flag every predetermined period t obtained by multiplying the RTO time by α (0 <α <0.5). Then, the dummy data transmission control unit resets to OFF if the transmitted flag is ON, and transmits dummy data of size s or more to the slave server through the data transmitting unit if the transmitted flag is OFF. It is because it controls.

  As a result, this embodiment can transmit dummy data of size s or more within the RTO time at the longest, even when communication by update log transfer does not occur. Therefore, in the present embodiment, the congestion window size is maintained at s or more without causing the slow start to start. As described above, the present embodiment can avoid the slow start by preventing the once enlarged congestion window size from being reduced to the predetermined size s or less. Therefore, this embodiment can eliminate the communication delay even when the update log is transferred to the slave server after the update log is not transferred for a certain period. As described above, this embodiment can always perform high-speed replication processing in a memory database system that constitutes an online transaction system in which high availability and high-speed response are required at the same time.

  Furthermore, the memory database system according to the third embodiment of the present invention does not generate a delayed ACK in the transfer of the update log from the master server to the slave server, and enables faster data transfer.

  The reason is that the data transmission unit sets the size of the dummy data to s or more, and applies twice the maximum size (MSS) of data that can be transferred in one segment in TCP to the value of s. Here, in TCP, the receiving side immediately returns ACK when it receives two segments of size MSS. Therefore, this embodiment can suppress the communication delay caused by the delayed ACK by keeping the congestion window size at least twice the MSS.

  Further, the memory database system according to the third embodiment of the present invention can avoid the compression of the bandwidth due to unnecessary transfer of dummy data during the execution of replication.

  The reason is that when the data transfer unit transmits an update log of size s or more, the transmitted flag is turned on, and when the transmitted flag is on, the dummy data transfer control unit resets it to off and sets dummy data. Is not transmitted.

  As a result, according to the present embodiment, transmission of dummy data can be omitted if an update log of size s or more has already been transferred within the RTO time from the previous communication. Therefore, this embodiment does not transfer unnecessary dummy data during replication.

  The memory database system according to the third embodiment of the present invention does not temporarily increase the load on the CPU and the network load by transferring dummy data to a plurality of slave servers.

  The reason is that the data transmission unit transmits the update log or dummy data to the plurality of slave servers via different connections, and holds the transmitted flag for each slave server. In addition, the dummy data transmission control unit executes the processing according to the value of the transmitted flag for each slave server at a predetermined time t at a different timing for each slave server. For example, the activation control unit sequentially activates the n dummy data transmission control units at each activation interval T obtained by dividing the predetermined period t by the number of slave servers n.

  As a result, the present embodiment can distribute the transmission timing of dummy data to a plurality of slave servers, and equalizes the load on the CPU and the load on the network. As a result, this embodiment can suppress the influence on the operation of the application unit or other important processes due to the transmission of dummy data.

(Other aspects of the third embodiment)
Next, another aspect of the third embodiment of the present invention will be described.

  As shown in FIG. 19, the memory database system 3 is configured such that the master server 30 has one data transmission unit 31 instead of the n data transmission units 31_i and omits the start control unit 36. Is also possible.

  In this case, the data transmission unit 31 operates as shown in FIG. 20 instead of the operation shown in FIG.

  In FIG. 20, first, the data transmission unit 31 receives a data transmission request (Yes in step S51).

  Next, if the received transmission request is an update log transmission request from the application unit 24 (“update log” in step S52), the data transmission unit 31 sends the update log to the slave servers 60_1 to 60_n. Each is transmitted (step S93).

  Next, when the size of the update log transmitted in step S93 is greater than or equal to s (Yes in step S54), the data transmission unit 31 sets each of the n transmitted flags related to the slave servers 60_1 to 60_n to on. (Step S95). Then, the operation of the data transmission unit 31 returns to step S51.

  On the other hand, when the size is less than s, the operation of the data transmission unit 31 returns to step S51.

  If the transmission request received in step S51 is a transmission request for dummy data to one of the slave servers 60 (“dummy data” in step S52), the data transmission unit 31 stores dummy data whose size is s or more. And transmitted to the target slave server 60 (step S96). Then, the operation of the data transmission unit 31 returns to step S51.

  In this case, the dummy data transmission control unit 32_i operates as illustrated in FIG. 21 instead of the operation illustrated in FIG.

  In FIG. 21, first, when notified of the predetermined period t from the predetermined period calculation unit 35, the dummy data transmission control unit 32_i waits for the start of operation for the activation standby time T1 calculated by the following equation (5) (step S101). ).

T1 = {(i−1) ÷ n} × t (5)
Here, i is a number indicating the number of dummy data transmission control unit 32. N is the number of slave servers 60. In addition, t is a predetermined period notified from the predetermined period calculation unit 35.

  Thereafter, the dummy data transmission control unit 32_i operates as described with reference to FIG. 18 from step S81 to step S84, and repeats the operation from step S81.

  Thereby, the master server 30 can distribute the transmission timing of the dummy data by each dummy data transmission control unit 32_i even in the configuration in which the start control unit 36 is omitted.

  By configuring in this way, another aspect of the third exemplary embodiment of the present invention is that when it is assumed that the data transmission unit, the dummy data transmission control unit, and the start control unit are each configured by a thread. The number and type of CPUs can be reduced, and the CPU load can be further reduced.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described in detail with reference to the drawings. In the present embodiment, as in the second and third embodiments of the present invention, an example in which the information processing system of the present invention is applied to a memory database system will be described. In each drawing referred to in the description of the present embodiment, the same reference numerals are given to the same configuration and steps that operate in the same manner as in the first to third embodiments of the present invention. The detailed description in is omitted.

  First, FIG. 22 shows the configuration of the memory database system 4 as the fourth embodiment of the present invention. In FIG. 22, the memory database system 4 is different from the memory database system 3 according to the third embodiment of the present invention in that a master server 40 is replaced with a master server 40 and n slave servers 60 are replaced with n. The difference is that the slave servers 70 (70_1 to 70_n) are provided. The master server 40 is different from the master server 30 according to the third embodiment of the present invention in that the master server 40 includes n data transmission units 41_i instead of the n data transmission units 31_i. Also, each of the slave servers 70 differs from the slave server 60 in the second and third embodiments of the present invention in that a data receiving unit 71 is provided instead of the data receiving unit 61.

  The data transmission unit 41_i of the master server 40 differs from the data transmission unit 31_i in the third embodiment of the present invention in the process when receiving an update log transmission request and dummy data transmission request substantially simultaneously. Specifically, when these transmission requests are received substantially simultaneously, if the size of the update log is not less than s, the data transmission unit 41_i transmits this update log to the slave server 70_i and omits transmission of dummy data. To do. When these transmission requests are received substantially simultaneously, if the size of the update log is less than s, the data transmission unit 41_i adds dummy data to the update log to make it larger than the size s and then the slave server 70_i. Send to.

  The update log transmission request and the dummy data transmission request are received substantially simultaneously, for example, after the data transmission unit 41_i receives the update log transmission request and before starting the update log transmission process. It may be a case where a data transmission request is received. The update log transmission request and the dummy data transmission request are received substantially simultaneously, for example, after the data transmission unit 41_i receives the dummy data transmission request and before starting the dummy data transmission process. It may be a case where a log transmission request is received.

  When the update log transmission request and the dummy data transmission request are received at different timings, the data transmission unit 41_i is configured to operate in the same manner as the data transmission unit 31_i in the third embodiment of the present invention. Is done.

  When the data receiving unit 71 of the slave server 70 receives the update log to which the dummy data is added from the master server 40, the data receiving unit 71 discards the dummy data part and obtains the remaining update log. Then, the data receiving unit 71 updates the replicated data stored in the replicated data storage unit 62 using the obtained update log.

  When an update log to which dummy data is not added is received and when only dummy data is received, the data receiving unit 71 is a data receiving unit according to the second and third embodiments of the present invention. 61 is configured to operate in the same manner as

  The operation of the memory database system 4 configured as described above will be described. The operation of the memory database system 4 is substantially the same as the operation of the memory database system 3 as the third embodiment of the present invention. However, the details of the operation of the data transmission unit 41 — i in the master server 40 and the operation of the data reception unit 71 in the slave server 70 are different.

  First, the operation of the data transmitter 41_i is shown in FIG.

  In FIG. 23, first, the data transmission unit 41_i receives a data transmission request (Yes in step S111).

  Next, the data transmission unit 41_i determines whether the transmission request received in step S111 is an update log transmission request from the application unit 24 or a dummy data transmission request (step S112).

  If it is an update log transmission request (“update log” in step S112), the data transmission unit 41_i determines whether or not dummy data transmission requests are received substantially simultaneously (step S113). For example, as described above, if the data transmission unit 41_i has received a transmission request for dummy data that has not yet started processing at this time, it has received a transmission request for dummy data substantially simultaneously. You may judge.

  On the other hand, if the transmission request is dummy data (“dummy data” in step S112), the data transmission unit 41_i determines whether or not the update log transmission request is received substantially simultaneously (step S114). For example, as described above, if the data transmission unit 41_i has already received an update log transmission request that has not yet started processing at this point, the data transmission unit 41_i has received the update log transmission request almost simultaneously. You may judge.

  If it is determined in step S113 or step S114 that the update log transmission request and the dummy data transmission request are received substantially simultaneously, the data transmission unit 41_i determines whether or not the size of the update log is greater than or equal to s. (Step S115).

  Here, when the size of the update log is less than s (No in step S115), the data transmission unit 41_i adds dummy data to the update log so that the overall size is s or more (step S116).

  On the other hand, if the size of the update log is greater than or equal to s (Yes in step S115), the operation of the data transmission unit 41_i proceeds to step S117.

  Next, the data transmission unit 41_i transmits the update log to the slave server 70_i (Step S117). The update log transmitted here is an update log to which dummy data is added in step S116 or an update log determined to have a size of s or more in step S115. As a result, when the update log transmission request and the dummy data transmission request are received substantially simultaneously, if the size of the update log is greater than or equal to s, the data transmission unit 41_i omits transmission of dummy data.

  Next, the data transmitting unit 41_i sets the transmitted flag regarding the slave server 70_i to ON and holds it (step S118).

  On the other hand, a case will be described in which it is determined in step S112 that an update log transmission request has been received, and in step S113 that it is determined that dummy data transmission requests have not been received substantially simultaneously. In this case, the data transmission unit 41_i operates in the same manner as the data transmission unit 31_i in the third embodiment of the present invention from step S53 to S55.

  A case will be described in which it is determined in step S112 that a dummy data transmission request has been received, and in step S114 that it has been determined that update log transmission requests have not been received substantially simultaneously. In this case, the data transmission unit 41_i executes step S56 in the same manner as the data transmission unit 31_i in the third embodiment of the present invention.

  Then, the operation of the data transmission unit 41_i returns to Step S111.

  Above, description of operation | movement of the data transmission part 41_i is complete | finished.

  Next, the operation of the data reception unit 71 in each of the n slave servers 70 is shown in FIG.

  In FIG. 24, first, the data receiving unit 71 receives data from the master server 40 (Yes in step S41).

  Next, when the received data is an update log (“update log” in step S42), the data receiving unit 71 determines whether dummy data is added to the update log (step S123).

  If dummy data is added, the data receiving unit 71 separates and discards the dummy data portion (step S124).

  Then, the data receiving unit 71 updates the copy data in the copy data storage unit 62 using the update log (step S43).

  On the other hand, if it is determined in step S123 that no dummy data is added, the data receiving unit 71 executes step S43 using the update log received in step S41.

  If the received data is dummy data (“dummy data” in step S42), the data receiving unit 71 discards the dummy data (step S44).

  Then, the operation of the data receiving unit 71 returns to step S41.

  Above, description of operation | movement of the data receiver 71 is complete | finished.

  Next, effects of the fourth exemplary embodiment of the present invention will be described.

  The memory database system according to the fourth embodiment of the present invention can more efficiently prevent the congestion window size from being reduced when the update log is intermittently transferred from the master server to the slave server. .

  The reason is that the data transmission unit of the master server operates as follows when the update log transmission request and the dummy data transmission request are received substantially simultaneously. That is, in this case, if the size of the update log is greater than or equal to s, the data transmission unit transmits the update log by omitting transmission of dummy data to the slave server. In addition, if the size of the update log is less than s, the data transmission unit adds dummy data to the update log so that the size is greater than or equal to s and transmits the update log to the slave server. Thereby, this embodiment can produce the same effect as the second or third embodiment of the present invention while reducing the amount of dummy data to be transmitted. Therefore, the present embodiment can reduce the CPU load and the network load, and more effectively prevent the communication speed from decreasing.

  In the above-described second to fourth embodiments of the present invention, the description has been made centering on an example in which the information processing system of the present invention is applied to a memory database system. In addition, each embodiment is applicable to other database systems that perform replication between a master server and a slave server.

  Further, in the second to fourth embodiments of the present invention described above, the example is described mainly in which the size of the dummy data or the size of the update log to which the dummy data is added is s (twice the MSS) or more. . However, in each embodiment, it is desirable that these sizes are values closer to s (and values equal to s). Thereby, each embodiment does not increase the load on the CPU and the network due to the transmission of dummy data of an unnecessarily large size.

  In the second to fourth embodiments of the present invention described above, an example in which the condition that s (twice the MSS) or more is applied as the predetermined condition has been mainly described. The predetermined condition here is a predetermined condition related to the size of the update log to be checked to turn on the transmitted flag, and a predetermined condition to be satisfied by the size of the update log to which dummy data or dummy data is added. . In addition, in each embodiment, the predetermined condition may be that the congestion window size at that time or more. In addition, in each embodiment, the predetermined condition may be a condition based on another value calculated as a data size for more sufficiently preventing the congestion window size from being reduced.

  In each embodiment of the present invention described above, an example in which each functional block of the transmission device, the reception device, the master server, and the slave server is realized by a CPU that executes a computer program stored in a storage device or ROM. It explained mainly. In addition, some, all, or a combination of each functional block of each device may be realized by dedicated hardware.

  In each of the above-described embodiments of the present invention, the functional blocks of the transmission device, the reception device, the master server, and the slave server may be distributed and realized in a plurality of devices.

  In each of the above-described embodiments of the present invention, the operations of the transmission device, the reception device, the master server, and the slave server described with reference to the flowcharts are stored in the storage device ( It may be stored in a storage medium. Then, the computer program may be read and executed by the CPU. In such a case, the present invention is constituted by the code of the computer program or a storage medium.

  Moreover, each embodiment mentioned above can be implemented in combination as appropriate.

  The present invention is not limited to the above-described embodiments, and can be implemented in various modes.

  The present invention has been described above using the above-described embodiments as exemplary examples. However, the present invention is not limited to the above-described embodiments. That is, the present invention can apply various modes that can be understood by those skilled in the art within the scope of the present invention.

  This application claims the priority on the basis of Japanese application Japanese Patent Application No. 2013-229313 for which it applied on November 5, 2013, and takes in those the indications of all here.

DESCRIPTION OF SYMBOLS 1 Information processing system 10 Transmission apparatus 50 Reception apparatus 2, 3, 4 Memory database system 20, 30, 40 Master server 60, 70 Slave server 11, 21, 31, 41 Data transmission part 12, 22, 32 Dummy data transmission control part 23 Master Data Storage Unit 24 Application Unit 35 Predetermined Period Calculation Unit 36 Start Control Unit 51, 61, 71 Data Receiving Unit 62 Replicated Data Storage Unit 1001, 5001 CPU
1002, 5002 RAM
1003, 5003 ROM
1004, 5004 Storage device 1005, 5005 Network interface

Claims (18)

Data transmission means for transmitting target data requested to be transmitted from the application or dummy data to the receiving device;
When the target data having a size satisfying a predetermined condition is not transmitted to the receiving apparatus during a predetermined period, the data transmitting unit is controlled to transmit the dummy data having a size satisfying the predetermined condition. Dummy data transmission control means;
A transmission device comprising: The data transmission means transmits the target data or the dummy data via different connections to the plurality of receiving devices,
The dummy data transmission control means performs a process according to whether or not the target data having a size satisfying the predetermined condition is transmitted to each receiving apparatus during the predetermined period, at a different timing for each receiving apparatus. The transmission apparatus according to claim 1, wherein   When the data transmission means receives the transmission request for the target data and the transmission request for the dummy data substantially simultaneously, if the size of the target data satisfies the predetermined condition, the data transmission means transmits the target data and transmits the dummy data The target data to which dummy data is added so as to satisfy the predetermined condition is transmitted if the size of the target data does not satisfy the predetermined condition. Transmitter.   The dummy data transmission control means has a length determined for the elapsed time from the latest communication from the transmission device to the reception device in the communication connection for transmitting the target data as the predetermined period, and the elapsed time 4. The transmission apparatus according to claim 1, wherein a period based on a length defined that the congestion window size is reduced when the length is reached is applied.   5. The transmission apparatus according to claim 4, wherein when the data transmission unit communicates with the reception apparatus through a TCP (Transmission Control Protocol) connection, the predetermined period is a period based on a retransmission timeout period.   6. The transmission apparatus according to claim 1, wherein the dummy data transmission control unit uses, as the predetermined condition, a size equal to or larger than a congestion window size.   The transmission according to any one of claims 1 to 5, wherein the dummy data transmission control unit uses, as the predetermined condition, a size equal to or larger than a predetermined size s (s is a positive number). apparatus.   8. The transmission apparatus according to claim 7, wherein when the data transmission unit communicates with the reception apparatus through a TCP connection, the predetermined size s is twice the maximum size of a segment.   Data receiving means for performing predetermined processing on the target data when receiving the target data from the transmission device according to any one of claims 1 to 8, and discarding the dummy data when receiving the dummy data A receiving device.   When the data receiving means receives the target data to which the dummy data is added from the transmission device according to claim 3, the data receiving means discards the dummy data portion and performs the predetermined processing on the target data. The receiving device according to claim 9. A transmission device according to any one of claims 1 to 8,
The receiving device according to claim 9 or 10,
Information processing system with A transmission device according to any one of claims 1 to 8,
Master data storage means for storing master data;
An application that updates the master data, generates information (update log) indicating the difference before and after updating the master data, and requests the data transmission means to transmit the generated update log as the target data Means,
Master server with Replicated data storage means for storing a replica of the master data (replicated data);
The update log as the target data or the dummy data is received from the master server according to claim 12, and the process of updating the replicated data using the received update log is executed as the predetermined process. The receiving device according to claim 9 or 10,
A slave server with A master server according to claim 12;
A slave server according to claim 13;
A database system with When there is a request to send target data from the application, the target data is sent to the receiving device,
Data transfer for transmitting dummy data having a size satisfying the predetermined condition to the receiving device when the target data having a size satisfying the predetermined condition is not transmitted to the receiving device during a predetermined period. Method.   16. A data receiving method, wherein when the target data transmitted using the data transfer method according to claim 15 is received, predetermined processing is performed on the target data, and when the dummy data is received, the dummy data is discarded. A target data transmission step of transmitting the target data to a receiving device when there is a target data transmission request from an application;
Dummy data transmission for transmitting dummy data having a size satisfying the predetermined condition to the receiving apparatus when the target data having a size satisfying the predetermined condition is not transmitted to the receiving apparatus during a predetermined period. Steps,
A storage medium storing a computer program that causes a computer device to execute the program. A target data receiving step for performing predetermined processing on the target data upon receiving the target data transmitted by execution of the computer program stored in the storage medium according to claim 17;
A dummy data discarding step of discarding the dummy data when the dummy data is received;
A storage medium storing a computer program that causes a computer device to execute the program.

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