JP5629281B2 - Management device and program - Google Patents

Description

  The present invention relates to a management apparatus that manages a plurality of servers constituting a cluster that performs data processing in a coordinated manner.

  In recent years, with the rise of cloud computing, it has been required to efficiently process and retain a large amount of data. Thus, distributed processing technology has been developed that realizes efficient processing by operating a plurality of servers in a coordinated manner.

  When performing distributed processing, it is necessary to distribute processing target (management target) data to each server constituting the cluster (hereinafter also referred to as “cluster member” or “member”). At this time, in order to increase the processing capacity of the entire cluster, it is desirable that the number of data (data amount) handled by each cluster member is averaged.

  As a typical data distribution method, a remainder obtained by dividing a value obtained by multiplying the key of each data by a hash function (hereinafter referred to as “hash (key)”) by the number N of cluster members, that is, “hash (key) mod N There is a method of distributing data to cluster members having "" as a number. In this case, it is assumed that numbers “0” to “N−1” are assigned to each cluster member in advance. When such a distribution method is used, if a cluster member is added, the value of N changes, and the cluster member in charge of a lot of data is changed, so that the data in charge must be rearranged.

  Therefore, as a method for suppressing the number of data that the cluster member in charge changes with the addition of the cluster member to about 1 / N, there is a distribution method using a consistent hashing method (see Non-Patent Document 1). is there.

  In this data distribution method using the consistent hash method, an ID (IDentifier) is assigned to both the cluster member and the data, and when the ID space is traced clockwise from the data ID, the first cluster member encountered is Take charge of data.

  In addition, when managing a large amount of data in a cluster-structured distributed processing system, data redundancy is maintained by maintaining a copy of the data so that even if a failure occurs in one cluster member, processing can be continued on other cluster members. Needs to be realized. The same applies to a distributed processing system that uses a data management technique based on the consistent hash method.

  As shown in FIG. 7, in the consistent hash method, IDs are assigned to both cluster members (members 1 to 4) and data (data A to D, indicated by black circles), and the ID space is clockwise from the data ID. As a result, the first cluster member encountered is determined to be responsible for the data. Then, the cluster member that is further to the right of the cluster member in charge (next clockwise) is assigned the duplicate data.

  For example, in FIG. 7, data A is traced clockwise in the ID space and is assigned to the member 1 that first encounters, and the duplicated data is assigned to the member 2 on the right side of the member 1 in the ID space. By determining the cluster member in charge of the original data / replicated data in this way, even if the cluster member leaves, the cluster member that owns the replicated data becomes the new cluster member in charge of the data. There is an advantage that it can respond. When a plurality of pieces of duplicate data are taken, the second duplicate data can be assigned to the cluster member on the right side.

  As a database server that can be used in such a method, for example, there is a distributed database server described in Cassandra (Non-Patent Document 2) or the like, in which a plurality of servers can dynamically join and leave a cluster. In the technique of Non-Patent Document 2, uniform distribution of data using the consistent hash method and high-speed access of O (1) are realized. In addition, fault tolerance is enhanced by providing duplicate information to a plurality of servers.

David Karger et al., “Consistent Hashing and Random Trees: Distributed Caching Protocols for Relieving Hot Spots on the World Wide Web”, [online], 1997, ACM, [searched February 20, 2012], Internet <URL: http://www.akamai.com/dl/technical_publications/ConsistenHashingandRandomTreesDistributedCachingprotocolsforrelievingHotSpotsontheworldwideweb.pdf> Avinash Lakshman et al., “Cassandra-A Decentralized Structured Storage System”, [online], [searched February 20, 2012], Internet <URL: http://www.cs.cornell.edu/projects/ladis2009 /papers/lakshman-ladis2009.pdf>

  However, in the conventional method described above, when a catastrophic disaster or the like occurs and a plurality of servers are down (failed) at the same time, there is a possibility that both the original data and the duplicated data are lost. In this case, a process using separate backup data or the like is required for recovery. This process is usually slow since it is a suction operation from the disk, and it is inevitable that the service is temporarily stopped.

  Therefore, in a distributed processing system using a plurality of general-purpose servers, a data replication method is studied to increase the possibility that processing can be continued without losing data even when a large-scale failure occurs due to a severe disaster or the like.

  For example, if multiple servers are placed only in the data center area with the Kanto area (the area under the control of the data center that manages the server), if a catastrophic disaster occurs in the entire Kanto area, all servers will go down, Data may be lost. Therefore, it is first necessary to distribute a plurality of servers in a wide area.

  Here, as shown in FIG. 8, consider a case where a plurality of servers belong to one of K types (here, five types) of data center areas across the country. In the ID space of FIG. 8, it is assumed that servers having the same symbol (black circle, white circle, black triangle, white triangle, white square) belong to the same data center area.

  In this case, even if a catastrophic disaster or the like occurs in the entire Kanto region, servers belonging to the Kanto data center area go down, but servers belonging to other data center areas do not go down. In other words, in the consistent hash method ID space, servers in the Kanto data center area leave, but servers in other data center areas do not leave.

  Normally, in the ID space of the consistent hash method, the servers are distributed (arranged) without considering the physical positions of the servers. Therefore, in FIG. 8, when servers belonging to the same data center area are adjacent to each other, such as two servers surrounded by a broken line at the top in the ID space, when a catastrophic disaster or the like occurs in the entire data center area, There is a possibility that both original data and duplicated data will be lost at the same time.

  Therefore, the present invention has been made in view of the circumstances described above, and the management apparatus in the distributed processing system performs server selection in consideration of the physical position of the server when adding servers (cluster members). It is an object to avoid a situation in which data is lost even if all servers in one of the three or more regions are down.

  In order to solve the above-described problem, the present invention allocates a plurality of data to be managed and a plurality of servers that manage the data and constitute a cluster in a circular ID space, and each of the servers includes: Managing the data located between itself and the next server around the predetermined direction in the ID space, and located between the next server and the next server around the predetermined direction. In a distributed processing system that stores a copy of data, a management device that determines to which of the plurality of servers a request from a client machine is distributed, and manages a server in charge of managing the data in the ID space Each of the servers including the ID space management information, the plurality of servers, and the waiting server is a predetermined number of three or more. A storage unit for storing, for each of the regions, server management information for managing the association with all the servers physically existing in the region; On the other hand, when the standby server is added, the servers on both sides of the insertion position in the ID space are identified with reference to the ID space management information based on the insertion position in the ID space for the added server. Then, referring to the server management information, selects a server that physically exists in an area to which the specified adjacent servers do not belong, and uses the selected server and the information on the insertion position to identify the ID space management information. And a processing unit for updating.

  According to this, when adding a standby server to the cluster, by selecting a server that physically exists in an area to which the server next to the insertion position of the server in the ID space does not belong, Since servers in the same region are not adjacent to each other, it is possible to avoid a situation where data is lost even if all servers existing in one region of three or more regions are down.

  Further, according to the present invention, a plurality of data to be managed and a plurality of servers that manage the data and constitute a cluster are allocated to the annular ID space, and each of the servers is assigned to itself in the ID space. Manages the data located between the next server around the predetermined direction and stores a copy of the data located between the next server and the next server around the predetermined direction. In a distributed processing system, a management apparatus that determines to which of the plurality of servers a request from a client machine is allocated, ID space management information for managing a server in charge of managing the data in the ID space, Each server including a plurality of servers and a standby server is one of a plurality of predetermined physical regions. A storage unit that stores, for each of the regions, server management information that manages associations with all the servers physically existing in the region, and is waiting for the cluster When adding a server, based on the insertion position in the ID space for the added server, if the number of regions is K (≧ 3), when K is an odd number, refer to the ID space management information. For each side of the insertion position in the ID space, {(K-1) / 2} servers are specified, and when K is an even number, the insertion position in the ID space is referred to with reference to the ID space management information (K / 2) units on one side of the server, and {(K-2) / 2} units on the other side are identified, and all of the identified servers belong to the server management information. Select the server physically present in the free area, and having a processing unit by using the selected server and information of the insertion position to update the ID space management information.

  According to this, when adding a standby server to the cluster, when the number of regions is a natural number K of 3 or more, and when K is an odd number, both sides of the insertion position of the server in the ID space { (K-1) / 2} servers are identified, and when K is an even number, (K / 2) units on one side of the insertion position of the server in the ID space and {(K-2) / 2} servers are specified. Then, a server that physically exists in an area to which all the specified servers do not belong is selected. Accordingly, when K is an odd number, any continuous {(K + 1) / 2} servers in the ID space belong to different regions. Further, when K is an even number, any continuous (K / 2) servers in the ID space belong to different areas. Therefore, if the redundancy number (total number of original data and duplicate data) is 3 or more, even if all the servers in one region are down, the duplicate data of the original data held by the down server is held. The expected value of the number of existing servers can be increased.

  Further, in the present invention, when the processing unit adds the standby server to the cluster, the center of the widest portion between the servers in the ID space is referred to with reference to the ID space management information. This position is specified as the insertion position.

  According to this, when adding a standby server to the cluster, by selecting a server physically present in an area corresponding to the center position of the widest portion between the servers in the ID space, Even if all the servers existing in one of the three or more regions are down, it is possible to avoid a situation where data is lost and to further average the processing load on each server. In the present specification and claims, the “center position” includes not only the exact center position but also the position near the center.

  Further, the present invention is a program for causing a computer to function as the management device.

  According to this, a computer in which such a program is installed can be caused to function as a management device.

  According to the present invention, when a management device in a distributed processing system adds a server (cluster member), it performs server selection in consideration of the physical location of the server, thereby allowing one of the three or more regions to be selected. Even if all the servers existing in the server are down, it is possible to avoid a situation where data is lost.

It is explanatory drawing of the outline | summary of this invention. It is a block diagram of the management apparatus etc. of this embodiment. It is a figure which shows the structure of ID space management information of this embodiment. It is a figure which shows the structure of the area name information of this embodiment. It is a figure which shows the server management information of this embodiment. It is a flowchart which shows the flow of the process by the management apparatus of this embodiment. It is explanatory drawing of the conventional consistent hash method. It is explanatory drawing of ID space and the physical position of a cluster member in the conventional consistent hash method.

  Hereinafter, modes for carrying out the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings (refer to drawings other than the referenced drawings as appropriate). In order to facilitate understanding, the outline of the present embodiment will be described first with reference to FIG. 1, and then the embodiment will be described.

(Outline of this embodiment)
As shown in FIG. 1, a case is considered where servers are arranged in data center areas (hereinafter also referred to as “regions”) of K types (three or more types, here five types). In the ID space of the consistent hash method, first, the servers in the same region are distributed as shown in the figure (in order for each region) so as not to be adjacent to each other.

  When a server is added, a new cluster member insertion destination (synonymous with “insertion position”, ID) in the ID space is determined ((1) in FIG. 1).

  After the insertion destination of a new cluster member in the ID space is determined ((1) in FIG. 1), the area of the K-1 servers around the insertion destination (at least, both neighbors are sufficient) is investigated ( (2) in FIG. Then, a server in a region to which none of the K-1 (at least, both adjacent) servers belong is selected ((3) in FIG. 1), and the server is added.

  With such an algorithm, servers in the same region are not adjacent to each other in the ID space, so that even if all the servers existing in one of the three or more regions are down, data is lost. It can be avoided. In addition, the processing load on each server can be further averaged.

  To explain again, due to the characteristics of the consistent hash method, the “probability of losing any one of the data (also with duplicates)” is “continuous M (redundant number (total number of original data and duplicated data))” It is equal to the probability that servers in the same area will be placed. According to the algorithm described above, the probability can always be 0% when M ≧ 2. That is, even if one area is completely destroyed (all servers existing in that area are down), if M is 2 or more, no data is lost (duplicated data always remains).

  In addition, in the case of a method of examining the area of the surrounding K−1 servers as well as the “neighbors” of the insertion destination, if K is an odd number, any continuous {(K + 1) / 2} units in the ID space All servers belong to different regions. Further, when K is an even number, any continuous (K / 2) servers in the ID space belong to different areas. As a result, if the number of redundancy is 3 or more, even if all the servers in one region are down, the expected value of the number of servers holding duplicate data of the original data held by the down server is more Can be bigger.

  For example, if K = 5 and M = 3, even if one area is completely destroyed, any server that holds duplicate data of the original data held by the server in that area is not in that area. They belong to different regions and keep replica data. That is, in this case, even if two areas are completely destroyed, one server always holds duplicate data.

  If the redundant number M of data is further increased, it is possible to increase the possibility that duplicated data is not lost even when more regions are completely destroyed. For example, when K = 7, if M = 4, even if three regions are completely destroyed, one server always holds duplicate data.

  In addition, when adding a server to a cluster, the center position of the place where the distance between cluster members is the widest is selected in the ID space, but this is only an example. That is, when adding a server to a cluster, the position (insertion position) selected in the ID space may be arbitrary, and the essential matter is that a server in an area to which neither of the servers adjacent to the selected position in the ID space belongs. Is to choose. This makes it possible to select a server in consideration of the physical location of the server, and to avoid a situation where data is lost even if all servers existing in one of three or more regions are down. Can do.

(Embodiment)
Next, this embodiment will be described. As illustrated in FIG. 2, the distributed processing system 1000 according to the present embodiment includes a load distribution device 3, a management device 4, and a plurality of servers 5 configuring the cluster 100. The load balancer 3 is connected to a plurality of client machines 1 via a network 2 such as the Internet.

  The main operation will be described. The data distribution request from the client machine 1 is received by the load balancer 3 via the network 2. The load balancer 3 distributes the request to one of a plurality of servers 5 that perform data processing based on the server allocation table (ID space management information) on the data ID space. The distributed server 5 processes the request. The management device 4 manages ID space management information.

Next, the configuration of the load distribution device 3 and the management device 4 will be described.
The load distribution device 3 includes a storage unit 31, a processing unit 32, and a communication unit 33.
The storage unit 31 is a means for storing information, and includes a memory such as a random access memory (RAM) or a read only memory (ROM), a hard disk drive (HDD), or the like. The storage unit 31 stores ID space management information 411 received from the management device 4 as ID space management information 311. The storage unit 31 also stores an operation program for the processing unit 32 (not shown).

  The processing unit 32 is means for performing arithmetic processing based on information stored in the storage unit 31, and is configured by, for example, a CPU (Central Processing Unit).

The communication unit 33 is a communication interface used for communication with an external device.
In addition, the load balancer 3 may further include an input unit for the user of the load balancer 3 to input information, a display unit for displaying information, and the like.

  The management device 4 is a computer device that determines to which of a plurality of servers 5 (cluster members) a request from the client machine 1 is distributed based on a consistent hash method. As described above, in this consistent hash method, a plurality of data to be managed and a plurality of servers 5 that manage the data and constitute the cluster 100 are allocated to the circular ID space, The server 5 manages (in charge) data positioned between itself and the next server 5 in the clockwise direction (predetermined direction) in the ID space, and from the next server 5 to the next server 5 in the clockwise direction. It is assumed that a copy of the data located in between is stored.

The management device 4 includes a storage unit 41, a processing unit 42, an input unit 43, a display unit 44, and a communication unit 45.
The storage unit 41 is a means for storing information, and includes a memory such as a RAM or a ROM, an HDD, or the like. The storage unit 41 stores ID space management information 411, area name information 412, server management information 413, number of areas 414, and number of redundancy 415. The storage unit 41 also stores an operation program for the processing unit 42 (not shown).

  The ID space management information 411 is information for managing the server 5 in charge of data using an ID calculated by performing predetermined hash value conversion on the management target data (described later in FIG. 3).

  The area name information 412 is information for managing the association between the area ID and the area name corresponding to the area ID (described later in FIG. 4).

  The server management information 413 is information for managing the association with all the servers 5 physically existing in the area for each area (area ID) (described later in FIG. 5). In the present embodiment, all the servers 5 (a plurality of servers that already constitute the cluster 100 and a standby server) belong to one of a plurality of predetermined three or more physical regions. It is assumed that

The number of areas 414 is information on the number of areas (K) preset by the user of the management apparatus 4.
The redundancy number 415 is information on the redundancy number (M) preset by the user of the management apparatus 4.

  The processing unit 42 is a unit that performs arithmetic processing based on information stored in the storage unit 41, and is configured by a CPU, for example. When adding the standby server 5 to the cluster 100, the processing unit 42 first determines an insertion position in the ID space for the server 5 to be added. Next, the processing unit 42 refers to the ID space management information 411 and identifies the servers 5 on both sides of the insertion position in the ID space. Next, the processing unit 42 refers to the server management information 413, selects the server 5 that physically exists in the area to which the specified adjacent servers 5 do not belong, and information on the selected server 5 and the insertion position. Is used to update the ID space management information 411. Details will be described later with reference to FIG.

  Further, the processing unit 42 may perform the following processing when adding the standby server 5 to the cluster 100. First, when the number of regions is K (≧ 3), when K is an odd number, the ID space management information 411 is referred to and {{K−1) / 2} units on both sides of the insertion position in the ID space. The server 5 is specified. In addition, when K is an even number, the processing unit 42 refers to the ID space management information 411 and (K / 2) units on one side of the insertion position in the ID space and {(K-2) / 2 on the other side } Identify the servers 5. Next, the processing unit 42 refers to the server management information 413, selects a server 5 that physically exists in an area to which none of the specified servers 5 belongs, and selects the selected server and the insertion position. The ID space management information 411 is updated using the information. Details will be described later with reference to FIG.

The input unit 43 is a means for the user of the management device 4 to input information, and is realized by, for example, a keyboard or a mouse.
The display unit 44 is a means for displaying information, and is realized by an LCD (Liquid Crystal Display), for example.
The communication unit 45 is a communication interface used for communication with an external device.

Next, the ID space management information 411 will be described. As shown in FIG. 3, the ID space management information 411 includes ID and server columns, and is sorted according to the size of the ID value.
The ID is an ID in the ID space, and is stored in order to specify the data area that the server 5 is responsible for.

  The server represents an identifier of the server 5 constituting the cluster 100. For example, when the ID value in the first row shown in FIG. 3 is “0056”, this indicates that “server A” is in charge of data belonging to the area having identifiers “0000” to “0056”. When the ID value of the second row is “0172”, the data belonging to the identifiers “0057” to “0172” obtained by adding 1 to the ID value of the previous row is assigned to “Server G”. Indicates that you are in charge.

Next, the area name information 412 will be described. As shown in FIG. 4, the region name information 412 is composed of columns of region ID and region name.
The region ID represents an identifier of a predetermined plurality of physical regions.
The region name represents the name of the region corresponding to the region ID of the row.

Next, the server management information 413 will be described. As shown in FIG. 5, the server management information 413 is composed of each column of area ID and server.
The region ID represents an identifier of a predetermined plurality of physical regions.
The server represents the identifier of the server 5 that physically exists in the area of the corresponding area ID. The server 5 includes servers that have not been used as the cluster 100 yet.

Next, processing by the management device 4 will be described.
As shown in FIG. 6, in step S1, the processing unit 42 of the management device 4 determines whether or not there is a cluster configuration change request. If Yes, the process proceeds to step S2, and if No, the process returns to step S1. . The cluster configuration change request here may be, for example, an input to that effect by the user of the management apparatus 4 or a request to that effect from another apparatus.

  In step S2, the processing unit 42 determines whether or not the cluster configuration change request is to add a cluster member. If Yes, the process proceeds to step S3, and if No, the process proceeds to step S7.

  In step S3, the processing unit 42 determines the insertion destination (ID) of the cluster member to be added in the ID space.

  Where to insert may be designated by the maintenance person through the input unit 43, or the processing unit 42 can calculate by any method. The position to be selected in the ID space may be arbitrary, and the essential matter is to select a server 5 in a region to which neither of the servers 5 adjacent to the selected position in the ID space belongs. As a result, the server can be selected in consideration of the physical location of the server 5, and even if all the servers 5 existing in one of the three or more regions are down, data is not lost. can do.

  For example, the processing unit 42 refers to the ID space management information 411 stored in the storage unit 41 to search (specify) a location where the distance between cluster members (distance on the ID space) is the largest in the ID space, and The center position between the cluster members is determined as the insertion destination of the new cluster member ID. The reason for selecting such a position is that, in the cluster configuration distributed processing system 1000, it is desirable that the load among the cluster members be averaged as much as possible. Statistically, the number of data is much more than the number of cluster members. This is because the number of data handled by each cluster member is almost proportional to the distance between the cluster members in the ID space.

  Subsequently, in step S4, the processing unit 42 refers to the ID space management information 411 and the number of regions 414 in the storage unit 41, and investigates the data center area to which the K-1 servers 5 around the central point belong. The unused data center area (area ID) is specified.

  In step S4, specifically, when K is an odd number, the processing unit 42 refers to the ID space management information 411 and the number of regions 414 for each side of the position in the ID space {(K−1) / 2. } Identify the servers 5. When K is an even number, referring to the ID space management information 411 and the number of regions 414, (K / 2) units on one side of the position in the ID space and {(K-2) / 2} units on the other side The server 5 is specified. Next, referring to the server management information 413, the data center area to which none of the specified servers 5 belongs is specified. When there are a plurality of “data center areas to which none of them belong”, for example, a data center area with the smallest total number of servers 5 used may be selected. However, the present invention is not limited to this.

  Subsequently, in step S5, the processing unit 42 refers to the server management information 413 in the storage unit 41, and physically exists in the data center area (that is, corresponds to the area ID specified in step S). 5 is selected.

  In step S6, the processing unit 42 updates the ID space management information 411 and ends the process. In step S7, specifically, if the process goes through steps S3 to S5, a new line is inserted in the ID space management information 411, and the corresponding ID and the identifier of the server 5 to be added are written. (The added server 5 is activated by a known means). For example, when a part of the cluster member is deleted due to a failure or the like without going through steps S3 to S5, processing such as deleting the corresponding line in the ID space management information 411 is performed.

  Thereafter, the load distribution device 3 receives the latest ID space management information 411 from the management device 4 and stores it as the ID space management information 311 in the storage unit 31. Then, the load balancer 3 distributes the request received from the client machine 1 to one of the plurality of servers 5 by the consistent hash method based on the ID space management information 311. The distributed server 5 processes the request.

  Further, the plurality of servers 5 receive the latest ID space management information 411 and the redundancy number 415 from the management device 4 and store them in a storage unit (not shown), and copy the data described above based on the consistent hash method. Do.

  As described above, according to the management device 4 of the present embodiment, when the standby server 5 is added to the cluster 100, the K-1 servers 5 around the position of the server 5 in the ID space belong. By investigating the data center area and selecting a server 5 that physically exists in an unused data center area, servers in the same region in the ID space are not adjacent to each other. In this case, even if all the servers 5 existing in one data center area out of the five data center areas are down, it is possible to avoid a situation in which duplicate data is lost. In addition, by checking not only “both neighbors” of the insertion destination in the ID space but also the data center area to which “K−1 neighboring servers” belong, the copy data of the original data held by the down server 5 is held. It is possible to increase the expected value of the number of servers 5 (see “Summary of the present embodiment”).

  Further, when adding standby servers 5 to the cluster 100, by selecting a server 5 that physically exists in an area corresponding to the center position of the widest portion between the servers 5 in the ID space. The processing load on each server 5 can be further averaged.

  As described above, even if “both neighbors” is used instead of “periphery K−1”, the servers 5 in the same data center area are not adjacent to each other in the ID space. Even if all the servers 5 existing in one data center area are down, a situation in which data is lost can be avoided.

Although description of this embodiment is finished above, the aspect of the present invention is not limited to these.
For example, the management device 4 and the load distribution device 3 may be configured to coexist on the same hardware.

  Further, without using the load balancer 3, each client machine 1 holds the ID space management information 411 received from the management device 4 and directly accesses any of the plurality of servers 5 via the network 2. Also good.

  Moreover, although the case where the data center area is used as a unit as an area has been described as an example, another unit such as a further divided data center area or a prefecture may be adopted.

In the present embodiment, the consistent hash method is assumed, but another method may be assumed.
The present invention can also be embodied as a program for causing a computer to function as the management device 4.
In addition, about a concrete structure, it can change suitably in the range which does not deviate from the main point of this invention.

DESCRIPTION OF SYMBOLS 1 Client machine 2 Network 3 Load distribution apparatus 4 Management apparatus 5 Server 31 Storage part 32 Processing part 33 Communication part 41 Storage part 42 Processing part 43 Input part 44 Display part 45 Communication part 100 Cluster 311 ID space management information 411 ID space management information 412 Area name information 413 Server management information 414 Area count 415 Redundancy count 1000 Distributed processing system

Claims (4)

In a circular ID (IDentifier) space, a plurality of data to be managed and a plurality of servers that manage the data and constitute a cluster are allocated, and each of the servers rotates in a predetermined direction from itself in the ID space. A distributed processing system for managing the data located between the next server and storing a copy of the data located between the next server and the next server around the predetermined direction. In the management device for determining which of the plurality of servers the request from the client machine is distributed,
ID space management information for managing a server in charge of managing the data in the ID space;
Each of the servers including the plurality of servers and the standby server belongs to one of a plurality of predetermined three or more physical regions, and for each region, all the servers physically existing in the region A storage unit for storing server management information for managing the association with
When adding the standby server to the cluster, based on the insertion position in the ID space for the server to be added, the ID space management information is referred to and the both sides of the insertion position in the ID space are The server is identified, the server management information is referred to, a server that physically exists in an area to which the identified two adjacent servers do not belong is selected, and the ID is obtained using information on the selected server and the insertion position A processing unit for updating the space management information;
A management apparatus comprising: In a circular ID (IDentifier) space, a plurality of data to be managed and a plurality of servers that manage the data and constitute a cluster are allocated, and each of the servers rotates in a predetermined direction from itself in the ID space. A distributed processing system for managing the data located between the next server and storing a copy of the data located between the next server and the next server around the predetermined direction. In the management device for determining which of the plurality of servers the request from the client machine is distributed,
ID space management information for managing a server in charge of managing the data in the ID space;
Each of the servers including the plurality of servers and the standby server belongs to one of a plurality of predetermined three or more physical regions, and for each region, all the servers physically existing in the region A storage unit for storing server management information for managing the association with
When adding the standby server to the cluster, based on the insertion position in the ID space for the added server,
When the number of the areas is K (≧ 3),
When K is an odd number, {(K-1) / 2} servers are specified for each of both sides of the insertion position in the ID space with reference to the ID space management information;
When K is an even number, with reference to the ID space management information, (K / 2) servers on one side of the insertion position in the ID space and {(K-2) / 2} servers on the other side Identify,
The server management information is referenced to select a server physically present in an area to which none of the specified servers belongs, and the ID space management information is determined using the selected server and the information on the insertion position. A processing unit to be updated;
A management apparatus comprising: The processor is
When adding the standby server to the cluster,
The management apparatus according to claim 1 or 2, wherein a reference position of a center of the widest portion between the servers in the ID space is specified as the insertion position with reference to the ID space management information. .   The program for functioning a computer as a management apparatus as described in any one of Claim 1- Claim 3.

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