JP4167089B2 - Error concealment method in server system and client server type system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a server system such as an Internet business system such as an EC server, a Web server, an authentication server, or a node system of a communication network in which service stoppage due to a failure is not permitted.
[0002]
[Prior art]
This type of server system must always provide services appropriately to clients. That is, it is necessary to conceal the “error” of the server system and prevent the occurrence of “failure”. Here, “failure” means a loss of function of the system. Specific examples of the cause of the “failure” include a hardware bug or failure, a software bug, and the like. The cause of these “failures” is called “fault”. Even if a “fault” exists in the system, it does not always cause a “failure” but may be latent. The appearance of an abnormality due to a “fault” is called “error”. When the system in which the “error” occurs deviates from the normal state, a “failure” occurs. Note that the “error” is not caused only by a narrowly defined “fault” such as a bug or a failure. For example, an intermittent failure, an operator setting error or an operation error can also cause an “error”.
[0003]
As an example of a highly reliable server system that can conceal this “error”, “an error concealment method in a server system, mediation apparatus, and client server type system” (Japanese Patent Application No. 2001-256511) has been proposed. An example of this highly reliable server system will be described with reference to FIG. Here, a system that provides a Web service to a client will be exemplified.
[0004]
As shown in FIG. 19, the high reliability server system 1010 receives a request from the client 1041 and intervenes between the high reliability server 1020 that responds to the request and the high reliability server 1020 and the client 1041. An intermediary device 1030.
[0005]
The high reliability server 1020 includes one or more servers. In the example of FIG. 19, the high reliability server 1020 includes three servers 1021, 1022, and 1023. In response to the same request transmitted from the mediation device to each server, each server returns the same response if it is operating normally.
[0006]
The intermediary device 1030 receives a request from the client 1041 via the network 1050, transfers the request to the high reliability server 1020 at an appropriate timing to be described later, checks the validity of the response from the high reliability server, and sends a correct response. A control unit 1031 to be returned to the client 1041 and a server management table 1032 for managing the states of the servers 1021, 1022, and 1023 of the high reliability server 1020 are provided. The control unit 1031 registers which server is normal or faulty in the server management table 1032, refers to the server management table 1032, and causes which server to process a request from the client 1041. Determine whether. The server management table 1032 includes a server ID for identifying a server, a server IP address, and server operation information.
[0007]
The client 1041 requests a Web page from the high reliability server 1020 via the network 1050 using a Web browser.
[0008]
Next, the operation of the mediation device 1030 will be described. The client 1041 transmits a Web page request message 1110 to the high reliability server system 1010. The control unit 1031 receives this request message 1110, looks at the server management table 1032 and forwards it to a normal server. In the example of FIG. 19, since the servers 1021, 1022, and 1023 are normal, the control unit 1031 creates copies 1111, 1112, and 1113 of the request message 1110, and transfers the copies to the servers 1021, 1022, and 1023, respectively.
[0009]
The server 1021 receives the request message 1111 and returns a response 1121 to the control unit 1031. Similarly, the server 1022 returns a response 1122 and the server 1023 returns a response 1123 to the control unit 1031. The control unit 1031 makes a majority decision with the responses 1121, 1122, and 1123, determines that the majority response is normal, and returns a response 1120 to the client 1041.
[0010]
If the results of majority decision indicate that all the responses do not match and there is a mismatched response, the control unit 1031 determines that the server that returned the response is a failure, and the operation status information in the server management table 1032 is changed from “normal”. Change to "failure". Thereafter, the control unit 1031 does not transfer the request from the client to the failed server.
[0011]
In addition to the system as described above, a dual system in which two computers perform the same processing in parallel (see, for example, Patent Document 1), between two control computers divided into an online side and a standby side, A control system that takes task synchronization (see, for example, Patent Document 2) is known as a prior art.
[0012]
[Patent Document 1]
JP 52-60540 A
[Patent Document 2]
JP-A-1-303562
[0013]
[Problems to be solved by the invention]
As described above, in the conventional highly reliable server system, a control unit that receives a request from a client transfers the request to a plurality of servers, receives responses from the server in response to the request, and executes a majority vote. Has been adopted. Therefore, even if a certain server fails and returns an incorrect response to the control unit, the error can be concealed by majority vote.
[0014]
However, when the control unit itself becomes a failure, there is a problem that the entire system goes down. In order to avoid this problem, it is possible to simply arrange a plurality of control units. In this case, a plurality of control units can be seen from the client or server. For this reason, it is necessary to change the settings manually on the client and server side every time the control unit fails, or when the manual setting is avoided, both the client and the server are modified for automation. There was a problem of need.
[0015]
The present invention has been made in view of the above circumstances, and an object thereof is to provide a server system, an intermediary device, and an error concealment method that are highly reliable, suitable for continuous operation, and can be constructed at low cost. is there.
[0016]
To achieve the above object, according to the present invention, in a server-side system in a client-server system, a request from a client is transferred to a server, and a legitimate response to the request received from the server is requested. A plurality of intermediary devices including transfer means for transferring to the client, and the intermediary device includes a packet transmission / reception unit that transmits and receives packets, and is common to each intermediary device so that it can be seen as a single server from the client. One virtual IP address and one virtual MAC address are pre-assigned to other virtual IP addresses and other virtual MAC addresses that are common to each intermediary device so that they appear to the server as a single router. ARP asking for MAC address for each virtual IP address Response means for responding to the virtual MAC address corresponding to the virtual IP address in response to the solicited packet, wherein the packet transmitting / receiving unit receives a packet whose destination MAC address is related to each virtual MAC address, and the transfer means The source address of the IP packet related to the processing request transferred from the intermediary device to the server is set as the client address, and the IP packet related to the response result whose destination address is the client address is fetched into the transfer means. Hand over In addition, each intermediary device executes the same process independently in parallel, and the server and the client discard the duplicate second and subsequent packets among a plurality of identical packets received from the intermediary device. Do A server system characterized by this is used as a solution.
[0017]
According to the present invention, even if one mediation device that transfers a request and a response between a client and a server becomes a failure, the transfer can be continued by another normal mediation device, thereby preventing the entire system from being down, A more reliable client-server system can be constructed. Also, Virtual MAC address common to each intermediary device And any mediation device This virtual MAC address It can handle requests and responses addressed to it. As a result, no change is required for the server or the client even if any intermediary device goes down due to a failure or the like. In other words, since existing servers and clients can be used without modification, a highly reliable client-server system can be constructed at low cost.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
A highly reliable server system according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram illustrating the overall configuration of a highly reliable server system according to the present embodiment. In the present embodiment, a system that provides an authentication service, that is, a system in which the server is a RADIUS server is illustrated. Further, in a personal computer or an intermediary device in which a server is operating, a system in which Linux (registered trademark) is operating as an OS is exemplified.
[0019]
As shown in FIG. 1, the high reliability server system 10 includes a high reliability server 20 that returns a response to a request from the client 70, and an intermediary device that is interposed between the high reliability server 20 and the client 70. 30. In the example of FIG. 1, the mediation device 30 includes two mediation devices 30 a and 30 b. In the following description, when each of the plurality of mediating devices 30 and their constituent elements is individually represented, the symbols “a” and “b” are added, such as the mediating device 30a and the mediating device 30b. And
[0020]
In this system, the communication protocol system between the devices is not required. In this embodiment, a TCP / IP protocol suite is used. The TCP / IP protocol suite does not represent TCP and IP in a narrow sense, but means a broad protocol system including UDP, ARP, and the like.
[0021]
The high reliability server 20 is composed of one or more servers. In the example of FIG. 1, the high reliability server 20 includes three servers 21, 22, and 23. In response to the same request transmitted from the mediation device to each server, each server responds the same if it is operating normally. The servers 21, 22, and 23 may be implemented by software that operates on a computer or the like, or may be implemented by hardware. That is, the high reliability server 20 may be realized by a plurality of hardware, or may be realized by mounting a plurality of servers on one piece of hardware. In the example of FIG. 1, the servers 21, 22, and 23 are software running on computers 91, 92, and 93, respectively. Computers 91, 92, and 93 are assigned IP addresses 172.16.3.3, 172.16.3.4, and 172.16.3.5, respectively. The computers 91, 92, and 93 have MAC addresses cc: cc: cc: cc: cc: 03, cc: cc: cc: cc: cc: 04, cc: cc: cc: cc: cc: 05, respectively. ing.
[0022]
The client 70 is a device that receives a service provided by the high reliability server system 10. In the present embodiment, the client 70 is exemplified by a NAS (Network Access Server) such as a RAS (Remote Access Server). In the present embodiment, the client 70 is assigned 192.168.3.200 as an IP address. It also has a MAC address, dd: dd: dd: dd: dd: 00.
[0023]
The intermediary device 30 includes a NIC (Network Interface Card) 31 connected to a server 21, 22, 23 side network (hereinafter referred to as Uchigun network) 81, and a NIC 32 connected to a client side network (hereinafter referred to as external network) 82. It has. The intermediary device 30 includes an internal network side packet receiving unit 33 that receives packets from the internal network 81 via the NIC 31, an internal network side packet transmitting unit 34 that transmits packets to the internal network 81 via the NIC 31, and the NIC 32. An external network side packet receiving unit 35 that receives packets from the external network 82 via the network, and an external network side packet transmitting unit 36 that transmits packets to the external network 82 via the NIC 32. Further, the intermediary device 30 performs processing to be described later on the packets received from the internal network side packet receiving unit 33 and the external network side packet receiving unit 35, and the internal network side packet transmitting unit 34 and the external network side packet transmitting unit 36. A packet control unit 40 for transmitting packets using the.
[0024]
Each intermediary device 30 is connected via a NIC 31 to an internal network 81 connected to computers 91, 92, 93 on which servers 21, 22, 23 are operating. In the example of FIG. 1, the computers 91, 92, 93 and the NIC 32 are connected to a repeater hub 83. Each intermediary device 30 is connected via the NIC 32 to an external network 82 to which the client 70 is connected. In the example of FIG. 1, the client 70 and the NIC 32 are connected to a repeater hub 84.
[0025]
The NIC 32 connected to the external network 82 and the NIC 31 connected to the internal network 81 are assigned different IP addresses for each intermediary device 30, and each has a different MAC address (hardware address). In the example of FIG. 1, 192.168.3.1 is assigned as the IP address to the NIC 32a of the mediating apparatus 30a, and the MAC address is aa: aa: aa: aa: aa: 01. The NIC 32b of the mediation apparatus 30b is assigned 192.168.3.2 as an IP address, and the MAC address is aa: aa: aa: aa: aa: 02. In the example of FIG. 1, 172.16.3.3.1 is assigned to the NIC 31a of the intermediary device 30a as the IP address, and the MAC address is bb: bb: bb: bb: bb: 01. The NIC 31b of the intermediary device 30b is assigned 172.168.3.2 as an IP address, and the MAC address is bb: bb: bb: bb: bb: 02.
[0026]
Next, the virtual server and the virtual router will be described. The following two conditions must be satisfied in order to provide higher reliability while using the client or server without modification, which is the object of the present invention.
[0027]
(1) Even if a failure occurs in the high reliability server system 10, the failure is hidden from the client 70. That is, the client 70 does not need to change the operation or setting due to the failure, and can receive a service from the high-reliability server system 10 as before the failure.
[0028]
(2) If a failure occurs in any of the plurality of mediation devices 30, the failure is concealed in each of the servers 21, 22, and 23. That is, each server 21, 22 and 23 does not need to change the operation or setting due to the failure, and can communicate with the client 70 without changing from before the failure.
[0029]
In the present invention, a “virtual server” is defined for realizing the condition (1), and a “virtual router” is defined for realizing the condition (2).
[0030]
The virtual server is a server that hides the internal configuration of the high-reliability server system and appears virtually as one server when viewed from the client. For example, in the case of the high reliability server system 10 illustrated in FIG. 1, as illustrated in FIG. 2, the virtual IP address 192.168.3.100 and the virtual MAC address aa: aa: aa: aa: It is the virtual server 11 having aa: 0.
[0031]
Here, the virtual IP address is an IP address assigned to the virtual server 11, and the client 70 transmits a request packet to this IP address. The virtual MAC address is a MAC address assigned to the virtual server 11, and is a communication connected to the network to which the virtual server 11 is connected, that is, the external network 82 to which the high reliability server system 10 is connected. This is the MAC address used when the device communicates with the virtual server 11. That is, the virtual MAC address is the MAC (included in the ARP response packet) obtained when a communication device connected to the external network 82 makes an address resolution request (transmits an ARP request packet) to the virtual IP address. It is an address. The virtual IP address and the virtual MAC address need to be selected so as not to overlap with the IP address and the MAC address possessed by the communication device connected to the external network 82. It should be noted here that there is actually no communication device having a virtual IP address and a virtual MAC address. Therefore, the ARP response to the ARP request is normally executed by the Linux kernel of the communication device having the virtual IP address and the virtual MAC address, but there is no communication device having the virtual IP address and the virtual MAC address. The problem of not being solved arises. In order to solve this problem, the intermediary device 30 has a pseudo ARP response unit and realizes address resolution (details will be described later).
[0032]
With such a configuration, if one or more intermediary devices are normal and one or more servers are normal, the virtual server 11 functions normally. Therefore, by realizing the virtual server 11, the client 70 only needs to communicate with the virtual server 11 having the IP address 192.168.3.100 regardless of whether there is a failure in the high-reliability server system 10. good. That is, the above condition (1) can be satisfied.
[0033]
The virtual router is a router that hides the redundant configuration of the mediation device and looks like a virtual router when viewed from the server. For example, in the case of the high-reliability server system 10 of FIG. 1, as shown in FIG. 3, the virtual IP address 172.16.3.100, virtual MAC address on the internal network 81 side as seen from the servers 21, 22, 23. A virtual router 37 having bb: bb: bb: bb: bb: 00.
[0034]
Here, the virtual IP address is an IP address assigned to the virtual router 37. A communication device connected to the internal network 81 recognizes the IP address of the router when transferring the packet to the external network 82. On the other hand, the virtual MAC address is a MAC address assigned to the virtual router 37 and is a MAC address used when a communication device connected to the internal network 81 communicates with the virtual router 37. That is, the virtual MAC address is obtained when a communication device connected to the internal network 81 makes an address resolution request (that is, transmits an ARP request packet) to the virtual IP address (included in the ARP response packet). It is a MAC address. The virtual IP address and the virtual MAC address must be selected so as not to overlap with the IP address and MAC address of the communication device connected to the internal network 81. It should be noted here that there is actually no communication device having a virtual IP address and a virtual MAC address. Therefore, the ARP response to the ARP request is normally executed by the Linux kernel of the communication device having the virtual IP address and the virtual MAC address, but there is no communication device having the virtual IP address and the virtual MAC address. The problem of not being solved arises. In order to solve this problem, the intermediary device 30 has a pseudo ARP response unit and realizes address resolution (details will be described later).
[0035]
With such a configuration, if one or more intermediary devices 30 are normal, the virtual router 37 functions normally. Accordingly, the realization of the virtual router 37 makes it possible for the communication devices connected to the internal network 81 (in the example of FIG. 1, servers 21, 22, and 23) to have IP addresses, regardless of whether or not each mediating device 30 has a failure. It is only necessary to communicate with the virtual router 37 of 172.16.3.100. That is, the above condition (2) can be satisfied.
[0036]
Next, details for realizing a virtual server / virtual router will be described. Although the virtual server is visible from the client and the virtual router is visible from the server, both the virtual server and the virtual router can be realized by the method described below.
[0037]
First, a detailed configuration of the packet control unit 40 will be described with reference to FIG. As shown in FIG. 4, the packet control unit 40 includes a server management table 42 that manages the states of all the servers of the high reliability server 20 (in the example of FIG. 1, servers 21, 22, and 23), and an internal network. The internal network side pseudo ARP response unit 43 that returns a response to the IP address resolution request of the virtual router and the external network side pseudo ARP response unit 44 that returns a response to the IP address resolution request of the virtual server in the external network. And a server control unit 41 that receives a request from the client 70, transfers the request to the high-reliability server 20, checks the validity of the response from the high-reliability server 20, and returns a correct response to the client 70. ing.
[0038]
The server control unit 41 registers which server is normal or faulty with respect to the server management table 42 and refers to the server management table 42 to process the request from the client 70 to which server. Judge whether to make it.
[0039]
FIG. 5 shows an example of the server management table 42. As shown in FIG. 5, the server management table 42 includes a server ID for identifying each server, an IP address of a computer on which the server is operating, and an operating state of the server. In the example of FIG. 5, a case where the state of each server is normal is shown.
[0040]
When the server control unit 41 detects a server failure from the response packet from each server, the server control unit 41 changes the operating state of the corresponding server in the server management table 42 from “normal” to “failure”. As an example, FIG. 6 shows a server management table 42 when the server 23 is in a failure state.
[0041]
On the other hand, when the server control unit 41 detects that the server in the failure state is normal, the server control unit 41 changes the operation state of the server management table 42 from “failure” to “normal”. For example, when the server 23 recovers from a failure, the server control unit 41 changes the server management table 42 from that shown in FIG. 6 to that shown in FIG. As a method of recognizing that the server has become normal, for example, the server control unit 41 throws a packet to the server and judges from the response, or the server has started up to the server control unit 41 when the computer starts up. And a method for operating software for notifying the user on a computer.
[0042]
Next, packet transmission / reception processing on the internal network side will be described. Communication performed in the internal network is communication between the servers 21, 22, and 23 and the virtual router 37. In the example of FIG. 1, the computers 91, 92, and 93 set the default gateway in the virtual router 37.
[0043]
First, prior to communication, the computers 91, 92, 93 need to know the MAC address for the virtual IP address 172.16.3.100, so the computers 91, 92, 93 broadcast an ARP request packet. As described above, since there is actually no communication device having the virtual IP address 172.16.3.100, the address is not normally resolved, and the computers 91, 92, and 93 cannot communicate. appear. In order to avoid this problem, the internal network side packet receiving unit 33 sets all the packets arriving at the repeater hub 83 by setting the NIC 31 to the promiscuous mode (a mode for receiving all packets arriving at the NIC). The ARP request packet of the virtual IP address 172.16.3.100 among the received packets is transferred to the internal network side pseudo ARP response unit 43. The pseudo ARP response unit 43 returns a virtual MAC address selected in advance so as not to overlap with the MAC address of the device connected to the same network. All the pseudo ARP response units 43 must be set to return the same virtual MAC address. In this example, the pseudo ARP response units 43a and 43b return an ARP response packet including bb: bb: bb: bb: bb: 00 that does not overlap with the MAC addresses of the mediation device 30 and the computers 91, 92, 93. When a plurality of mediation devices are operating normally, a plurality of ARP response packets are returned to the computers 91, 92 and 93, respectively, but there is no problem because the packets have the same contents. In this way, address resolution for the virtual IP address is realized, and the computers 91, 92, 93 can transmit packets to the virtual router 37.
[0044]
To set the NIC to the promiscuous mode and filter (receive only necessary packets with raw socket), from the data link layer to the application layer without using the TCP / IP stack provided by the kernel. It is convenient to use a library libcapcap (ftp://ftp.ee.lbl.gov/libcapcap.tar.Z) that captures packets.
[0045]
Next, a response packet reception process of the mediation device 30 in the internal network 81 will be described. FIG. 7 illustrates a packet format that arrives at the virtual router 37 via the internal network 81. In the example of FIG. 7, the format of a packet transmitted from the computer 91 to the virtual router 37 is shown.
[0046]
As shown in FIG. 7, the destination MAC address of the packet is neither that of the mediating device 30a nor that of the mediating device 30b. Further, the destination IP address is neither that of the mediation device 30a nor that of the mediation device 30b. Therefore, as described above, the internal network side packet receiving unit 33 receives a packet by using libcapcap. When the destination IP address is the client 70, it is passed to the server control unit 41. This operation is performed simultaneously in parallel by the internal network side packet receiving unit 33a and the internal network side packet receiving unit 33b.
[0047]
Next, request packet transmission processing of the mediation device 30 in the internal network 81 will be described. FIG. 8 illustrates a format of a packet transmitted from the virtual router 37 to the server via the internal network 81. In the example of FIG. 8, the format is a packet transmitted from the mediating device 30 (both the mediating device 30a and the mediating device 30b) to the computer 91.
[0048]
As shown in FIG. 8, the source IP address of the packet is the client 70, not the mediation device 30a or the mediation device 30b. This is to make the intermediary device 30 appear to the server 21 as a simple router. Also, the source MAC address is neither the mediation device 30a nor the mediation device 30b. Therefore, the packet cannot be transmitted using a normal socket using a standard TCP / IP stack provided by the kernel. Therefore, the internal network side packet transmission unit 34 creates an Ethernet header, an IP header, and a UDP header and transmits them to the server 21 using a raw socket.
[0049]
When a plurality of mediation devices are operating normally, the server receives the number of mediation devices operating normally as shown in FIG. Since all packets are exactly the same, only the first one needs to be processed and the rest of the packets need to be discarded by the server. For example, in the case of an application using UDP such as RADIUS, there is a possibility that a plurality of the same packets are received in duplicate, so that the function of discarding the second and subsequent duplicate packets is usually originally provided. Therefore, the function of discarding unnecessary packets is already implemented, and there is no need to modify the server for the present invention.
[0050]
Next, packet transmission / reception processing on the external network side will be described. Communication performed in the external network 82 is communication between the client 70 and the virtual server 11.
[0051]
First, prior to communication, since the client 70 needs to know the MAC address for the virtual IP address 192.168.3.100, the client 70 broadcasts an ARP request packet. As described above, since there is actually no communication device having the virtual IP address 192.168.3.100, the address is not normally resolved, and there is a problem that the client 70 cannot perform communication. In order to avoid this problem, the external network side packet receiving unit 35 receives all packets arriving at the repeater hub 84 by raw socket by setting the NIC 32 to a promiscuous mode (a mode for receiving all packets arriving at the NIC). The ARP request packet of the virtual IP address 192.168.3.100 among the received packets is transferred to the external network side pseudo ARP response unit 44. The pseudo ARP response unit 44 returns a virtual MAC address selected in advance so as not to overlap with the MAC address of the device connected to the same network. All the pseudo ARP response units 44 must be set to return the same virtual MAC address. In this example, the pseudo ARP response units 44 a and 44 b return an ARP response packet including aa: aa: aa: aa: aa: 00 that does not overlap with the MAC addresses of the mediation device 30 and the client 70. When a plurality of mediation apparatuses are operating normally, a plurality of ARP response packets are returned to the client 70, but there is no problem because the packets have the same contents. In this way, address resolution for the virtual IP address is realized, and the client 70 can transmit a packet to the virtual server 11.
[0052]
To set the NIC to the promiscuous mode and filter (receive only necessary packets with raw socket), from the data link layer to the application layer without using the TCP / IP stack provided by the kernel. It is convenient to use a library libcapcap (ftp://ftp.ee.lbl.gov/libcapcap.tar.Z) that captures packets.
[0053]
Next, request packet reception processing of the mediation device 30 in the external network 82 will be described. FIG. 9 illustrates a packet format that arrives at the virtual server 11 via the external network 82. In the example of FIG. 9, the format is a packet transmitted from the client 70 to the virtual server 11.
[0054]
As shown in FIG. 9, the destination MAC address of the packet is neither that of the mediating device 30a nor that of the mediating device 30b. Therefore, as described above, the external network side packet receiving unit 35 receives a packet by using libcapcap. When the destination IP address is the virtual server 11, it is passed to the server control unit 41. This operation is simultaneously performed in parallel by the external network side packet receiving unit 35a and the external network side packet receiving unit 35b.
[0055]
Next, a response packet transmission process of the mediation device 30 in the external network 82 will be described. FIG. 10 illustrates a format of a packet transmitted from the virtual server 30 to the client 70 via the external network 82. In the example of FIG. 10, the format is a packet transmitted from the mediation device 30 (both the mediation device 30 a and the extension device 30 b) to the client 70.
[0056]
As shown in FIG. 10, neither the transmission source MAC address nor the mediation device 30a or the mediation device 30b. Therefore, the packet cannot be transmitted using a normal socket using a standard TCP / IP stack provided by the kernel. Therefore, the external network side packet transmission unit 36 creates an Ethernet header, an IP header, and a UDP header, and transmits them to the client 70 using a raw socket.
[0057]
When a plurality of mediation devices are operating normally, the client receives the number of mediation devices operating normally as shown in FIG. Since all packets are exactly the same, only the first one needs to be processed and the remaining packets need to be discarded by the client. For example, in the case of an application using UDP such as RADIUS, there is a possibility that a plurality of the same packets are received in duplicate, so that the function of discarding the second and subsequent duplicate packets is usually originally provided. Therefore, the function of discarding unnecessary packets has already been implemented, and there is no need to modify the client for the present invention.
[0058]
Next, the operation of the server control unit 41 will be described with reference to the drawings. It is assumed that the configuration and each device of the highly reliable server system taken as an example are in the state shown in FIG. FIG. 11 is a flowchart for explaining the operation of the server control unit 41. 12 and 13 are diagrams for explaining the operation of the high-reliability server system 10.
[0059]
The server control unit 41 checks whether the request packet from the client 70 has been received by the external network side packet receiving unit 35 (step SA1). If there is no request packet, the server control unit 41 checks the request packet reception again. If there is a request packet, the request packet is transmitted to the server whose operation state is “normal” in the server management table 42 by using the internal network side packet transmission unit 34 (step SA2). The flow of a request from the client by the above processing is indicated by a thick arrow in FIG.
[0060]
Next, a timer is set and a response packet from each server is checked (step SA3). If it is not time-out, it is checked whether or not the internal network side packet receiving unit 33 has received a response packet from the server (step SA4). If no response packet is received from the server, the timeout is checked again (step SA3). If a response packet is received from the server, it is checked whether response packets have been received from all the destination servers of the request packet (step SA5). If all response packets are not complete, a timeout check is performed again (step SA3).
[0061]
When all the response packets are prepared, it is checked whether there is a failed server (step SA6). As a method for determining whether or not there is a failed server, for example, there are a method of making a majority decision with a plurality of responses, a method of checking the validity of data included in the responses, and the like. The latter method of checking the validity of data includes, for example, determining that a failure is present when an impossible code is included, and determining a failure when a supposed code is not included. Is mentioned. If there is a failed server, the operating status of the corresponding server is registered as “failed” in the server management table 42 (step SA7). Thereafter, a normal response packet is transmitted to the client 70 using the external network side packet transmitter 36 (step SA8).
[0062]
If there is no failed server in step SA6, a normal response packet is transmitted to the client 70 using the external network side packet transmitter 36 (step SA8).
[0063]
If a time-out occurs in step SA3, that is, if there is a server that does not return a response packet, it is determined that the server is in failure, and the operating status of the corresponding server is set to “failure” in the server management table 42. Is registered (step SA9), and it is checked whether there is another failed server (step SA6). Then, a normal response packet is transmitted to the client 70 using the external network side packet transmitter 36 (step SA8).
[0064]
After transmitting the response packet to the client 70 (step SA8), the request from the client 70 is checked again (step SA1). The flow of the response packet from the server to the client 70 by the above processing is indicated by a thick arrow in FIG. Further, as described above, the server management table 42 when the server 23 becomes a failure is as shown in FIG.
[0065]
Through the processing as described above, the request packet from the client 70 is not transferred to the server that has become “failure” among the servers 21, 22, and 23 constituting the highly reliable server 20, and the highly reliable server system It was cut off from 10.
[0066]
The mediating devices 30a and 30b operate independently without being conscious of each other. Therefore, even if one of the mediating devices becomes a failure, the other mediating device is not affected. For example, when the mediation device 30a goes down due to a failure, the mediation device 30b continues to operate the above-described virtual server and virtual router without knowing whether the mediation device 30a is alive or dead.
[0067]
Similarly, even if a mediation device recovers from a failure, it does not affect the other mediation device. For example, even if the mediating device 30a that has been down due to a failure is recovered and the operations of the above-described virtual server and virtual router are started, the mediating device 30b does not know whether the mediating device 30a is alive or dead. Continue the operation.
[0068]
As described above, in order for the intermediary devices 30a and 30b to execute the same process independently in parallel, a mechanism that satisfies the condition that the same packet must be sent to the intermediary devices 30a and 30b is necessary. However, since the client 70 transmits only one packet to the virtual server 11 and the servers 21, 22, and 23 transmit only one packet to the virtual router 37, the above condition cannot be normally satisfied. In the present embodiment, the above conditions are satisfied by combining the repeater hubs 83 and 84 and the NICs 31 and 32 in the promiscuous mode. That is, the above condition is realized by combining the feature that the repeater hub transmits all packets to all ports and the feature that the NIC set to the promiscuous mode receives all packets that reach the port.
[0069]
Therefore, in this embodiment, for example, it is not possible to simply replace the switching hub with a switching hub. In addition, when the repeater hub cannot be used, a means for separately copying the packet and transferring it to all the intermediary devices is required.
[0070]
A highly reliable server system according to a second embodiment of the present invention will be described with reference to the drawings. FIG. 14 is a block diagram illustrating an overall configuration of a highly reliable server system according to the second embodiment.
[0071]
The present embodiment is different from the first embodiment in that three mediating devices 30 are provided. However, since the intermediary device 30 operates without being aware of each other, the operation does not change regardless of whether it is two, three, or more.
[0072]
The difference is the number of packets received by the server and the number of packets received by the client. In the first embodiment, since there are two intermediary devices 30, since the same two packets are received at the maximum, the second has to be discarded. In the second embodiment, since there are three intermediary devices 30, a maximum of three identical packets are received. Therefore, the server and client need to discard the second and third packets.
[0073]
A highly reliable server system according to a third embodiment of the present invention will be described with reference to the drawings. FIG. 15 is a block diagram illustrating a packet control unit 45 according to the third embodiment.
[0074]
This embodiment is different from the first and second embodiments in that a server control table correction unit 46 is provided in the packet control unit. Along with this, the following operations are added.
[0075]
The operation of the server management table correction unit 46 will be described with reference to FIG. FIG. 16 is a flowchart for explaining the operation of the server management table correction unit 46.
[0076]
First, the server management table correction unit 46 transmits the contents of the server management table 42 managed by itself to the virtual server 11 using the external network side packet transmission unit 36 (step SB1). Next, the server management table correction unit 46 receives the server management table 42 transferred using the external network side packet reception unit 35 (step SB2). The information in the server management table 42 received in this way is compared to determine whether they are the same (step SB3).
[0077]
If they are the same (YES in step SB3), after sleeping for a certain period without doing anything (step SB5), the contents of the server management table 42 managed by itself are again transmitted to the virtual server using the external network side packet transmitter 36. 11 (step SB1).
[0078]
If they are not the same (NO in step SB3), the server management table 42 managed by itself is modified by some algorithm (step SB4). For example, when the operating states are different such as “normal” and “failure”, the “failure” is determined to be the correct state and is corrected from “normal” to “failure”. Or you may decide by majority vote. The server changed to “failure” is disconnected from the system and does not transfer a request from the client thereafter. After the correction, after sleeping for a certain period (step SB5), the content of the server management table 42 managed by itself is transmitted to the virtual server 11 again using the external network side packet transmitter 36 (step SB1).
[0079]
In this way, the server management table 42 can be corrected when the state becomes inconsistent for some reason between the intermediary devices 30 operating independently of each other.
[0080]
A highly reliable server system according to a fourth embodiment of the present invention will be described with reference to the drawings. FIG. 17 is a block diagram illustrating the overall configuration of the high reliability server system 100 according to the fourth embodiment, and FIG. 18 is a block diagram illustrating the packet control unit 400 according to the fourth embodiment.
[0081]
The present embodiment is different from the first embodiment in that the internal network 81 does not exist and both the high reliability server 20 and the mediation apparatus 300 are connected to the same network 820.
[0082]
Accordingly, the intermediary device 300 includes a packet receiving unit 350 having both the internal network side packet receiving unit 33 and the external network side packet receiving unit 35, and the internal network side packet transmitting unit 34 and the external network side packet transmitting unit 36. A combined packet transmission unit 360 is provided. Further, the packet control unit 400 includes a pseudo ARP response unit 440 that includes both the internal network side pseudo ARP response unit 43 and the external network side pseudo ARP response unit 44.
[0083]
As described above, the configuration block diagram of the high-reliability server system changes by eliminating the internal network 81. However, if the network 820 is logically divided into the external network 82 and the internal network 81, the same as in the first embodiment. It is.
[0084]
Each server does not need to be the same implementation if it returns the same response. That is, the version, specifications, programming language, compiler type, compiler options, hardware or software, and the like may be different. Furthermore, the server may be composed of a single component or a plurality of components.
[0085]
In the above embodiment, the packet transmission / reception unit, the control unit, the server management table, the pseudo ARP response unit, and the server management table correction unit are mounted on one mediation device, and the server is mounted on another device. The physical positional relationship of each component of the reliability server system is arbitrary. That is, for example, each component may be mounted on one computer or may be mounted separately on different computers. Moreover, you may mount one part in the same computer.
[0086]
Furthermore, in the said Example, although the server was shown as an example, there may be three or more servers. In addition, the number of servers may be three or less as long as a decrease in reliability against a server failure is allowed.
[0087]
Furthermore, although the case where there is one client is assumed in the above embodiment, there may be a plurality of clients.
[0088]
Furthermore, in the first embodiment, the virtual IP address and the virtual MAC address of the virtual server 11 are selected that the communication device (including the mediation device 30) connected to the external network 82 does not have. The IP address of the NIC 32 of one intermediary device 30 may be selected as a virtual IP address, or the MAC address of the NIC 32 of one intermediary device 30 may be selected as the virtual MAC address. However, it is important that all the intermediary devices 30 must return the same ARP response to the ARP request for the virtual IP address.
[0089]
Furthermore, in the first embodiment, the virtual IP address and the virtual MAC address of the virtual router 37 are selected that the communication device (including the mediation device 30) connected to the internal network 81 does not have. The IP address of the NIC 31 of one intermediary device 30 may be selected as a virtual IP address, or the MAC address of one NIC 31 of one intermediary device 30 may be selected as the virtual MAC address. However, it is important that all the intermediary devices 30 must return the same ARP response to the ARP request for the virtual IP address.
[0090]
In addition, the said embodiment is an illustration and this invention is not limited to this. The scope of the present invention is defined by the terms of the claims, and all modifications that come within the meaning of the claims are intended to be embraced by the present invention.
[0091]
【The invention's effect】
As described above, according to the present invention, even if one intermediary device that transfers a request and a response between a client and a server becomes a failure, the transfer can be continued by another normal intermediary device. The entire system can be prevented from being down, and a more reliable client-server system can be constructed. Also, Virtual MAC address common to each intermediary device Any mediating device This virtual MAC address It can handle requests and responses addressed to it. Therefore, even if the mediation device is down due to a failure or the like, the server and the client need not be changed. That is, since existing servers and clients can be used without modification, a highly reliable client-server system can be constructed at low cost.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating an overall configuration of a highly reliable server system according to a first embodiment.
FIG. 2 is a diagram showing how a system looks when a mediation device is viewed from a client
FIG. 3 shows how the system looks when the mediation device is viewed from the server.
FIG. 4 is a block diagram illustrating the configuration of an intermediary device
FIG. 5 is a diagram illustrating an example of a server management table
FIG. 6 is a diagram for explaining another example of the server management table;
FIG. 7 is a diagram for explaining a packet format;
FIG. 8 is a diagram for explaining a packet format;
FIG. 9 is a diagram for explaining a packet format;
FIG. 10 is a diagram for explaining a packet format;
FIG. 11 is a diagram illustrating the operation of the mediation apparatus
FIG. 12 is a diagram for explaining the flow of requests from clients;
FIG. 13 is a diagram for explaining a response flow from the server;
FIG. 14 is a block diagram illustrating the overall configuration of a highly reliable server system according to the second embodiment.
FIG. 15 is a block diagram illustrating a packet control unit 45 according to the third embodiment.
FIG. 16 is a diagram for explaining the operation of the server management table correction unit according to the third embodiment;
FIG. 17 is a block diagram for explaining the overall configuration of a highly reliable server system according to the fourth embodiment;
FIG. 18 is a block diagram illustrating a packet control unit according to the fourth embodiment.
FIG. 19 is a configuration diagram of a conventional highly reliable server system.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... High reliability server system, 11 ... Virtual server, 20 ... High reliability server, 21, 22, 23 ... Server, 30a, 30b, 30c, 300a, 300b ... Intermediary device, 31a, 31b, 32a, 32b ... NIC 33a, 33b ... internal network side packet receiver, 34a, 34b ... internal network side packet transmitter, 35a, 35b ... external network side packet receiver, 350a, 350b ... packet receiver, 36a, 36b ... external network side packet Transmission unit, 360a, 360b ... packet transmission unit, 37 ... virtual router, 40a, 40b, 400a, 400b ... packet control unit, 41 ... server control unit, 42 ... server management table, 43 ... internal network side pseudo ARP response reception unit , 44 ... External network side pseudo ARP response receiving unit, 4 ... Server management table correction unit, 70 ... Client, 81 ... Internal network, 82 ... External network, 820 ... Network, 83, 84 ... Repeater HUB, 91, 92, 93 ... Computer, 1010 ... High reliability server system, 1111, 1112, 1113 ... copy, 1020 ... high reliability server, 1021, 1022, 1023 ... server, 1030 ... mediation device, 1031 ... control unit, 1032 ... server management table, 1041 ... client, 1050 ... network.

Claims (4)

In the server side system in the client server type system,
In addition to transferring a request from the client to the server, and providing a plurality of intermediary devices including transfer means for transferring a valid response to the request received from the server to the requesting client,
The mediation apparatus includes a packet transmission / reception unit that transmits and receives packets, and a single virtual IP address and a single virtual MAC address that are common to each mediation apparatus so that it can be seen by a client as a single server. Other virtual IP addresses and other virtual MAC addresses that are common to each intermediary device are pre-assigned so as to be seen as one router, and the virtual IP address is sent to the ARP request packet that asks for the MAC address for each virtual IP address. Response means for responding to the virtual MAC address corresponding to the IP address;
The packet transmitting / receiving unit receives a packet whose destination MAC address is related to each virtual MAC address, and uses the source address of the IP packet related to the processing request transferred from the mediation device to the server by the transfer means as the address of the client as well as, and passes to the transfer means takes in an IP packet according to the response results of the destination address is in the client's address,
The transfer means, response means, and packet transmission / reception unit of each intermediary device execute the same processing independently in parallel,
2. The server system according to claim 1, wherein the server and the client are provided with a packet discarding unit that discards the second and subsequent packets that overlap among the same packets received from the mediation apparatus . 2. The server system according to claim 1 , wherein the intermediary device includes a correcting unit that checks server management information with each other and corrects the same internal state when a mismatch occurs. The intermediary device comprises copy creation / transmission means that, when receiving a request and a response addressed to each virtual MAC address, creates a copy of the number of intermediary devices and transmits the copy to all intermediary devices. The server system according to claim 1 or 2 . In a method of concealing an error that has occurred in a server in a client-server system from a client,
Between the client and the server, a plurality of intermediary devices having transfer means for transferring a request from the client to the server and transferring a legitimate response to the request received from the server to the requesting client are interposed. ,
Each intermediary device has one virtual IP address and one virtual MAC address common to each intermediary device so that it can be seen from the client as a single server, and each intermediary device so that it can be seen as a single router from the server. Pre-assigning another common virtual IP address and other virtual MAC address, and responding to the virtual MAC address corresponding to the virtual IP address in response to an ARP request packet asking for the MAC address for each virtual IP address,
Each mediation device
The destination MAC address receives the packet related to each virtual MAC address, and the source address of the IP packet related to the processing request transferred from the intermediary device to the server by the transfer unit is the client address, and the destination address is was passed to the transfer means takes in an IP packet according to the response result that is the client's address, and executes each intermediary device independently the same process by respectively parallel,
An error concealment method in a client-server system , wherein the server and the client discard duplicate second and subsequent packets among a plurality of identical packets received from the mediation device .

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