JP2000057033A - Distributed exclusive control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exclusive control system with which a load is distributed and fault resistance is improved. SOLUTION: Concerning this exclusive control system, plural exclusive control servers S1-S4 are provided and among these servers, the server S1 is defined as a preferential exclusive control server concerning the data of the remainder but the other servers S2-S4 have priority concerning the other different data. On the assumption that the request of remainder data operation is inputted from a client C1 to the server S1, this server is set as the preferential exclusive control server so that processing such as remainder updating is performed as it is. On the assumption that the remainder data operation is requested from a client C2 and accepted by the server S4, the request is transferred from the server 84 to the preferential exclusive control server S1. Namely, since only the preferential server processes the relevant request, the confirmation of exclusive control right of confirming whether all the other exclusive control servers have the exclusive control right already or not is not required and the entire exclusive control is not down.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a processing method between a server and a client when exclusive control is required at the time of data operation such as updating the contents of a database.

[0002]

2. Description of the Related Art In a distributed system, simultaneous processing of data may be caused by different processes, which may cause "contention" which breaks data consistency. In order to cope with this contention, a process having an operation right is always required. Exclusive control is performed so that the order is set to one. This will be described with reference to FIG.

FIG. 1 is a time chart showing an example in which the Tokyo branch (Client 1) and the Osaka branch (Client 2) simultaneously issue balance data operation requests. That is, the balance of 1,000 yen is read out at the request of the Tokyo branch, and 500 yen is added to the balance at the Tokyo branch to add 1,500
It is assumed that there is a data operation for updating to 0 yen and writing it to the database. At that time, if there is a request from the Osaka branch at the same time, 1,000 yen before the update will be read out,
The Osaka branch will add 1,000 yen to this and update it to 2,000 yen. As a result of the simultaneous operation, the total balance of the Tokyo branch and the Osaka branch should normally be 2,500 yen, but the actual final balance is 2,000 yen.

[0004] If data operations occur at the same time, an erroneous result will be generated. To prevent this, exclusive control is executed. That is, as shown in FIG.
One server S for executing exclusive control is set, and a request for data requiring exclusive control such as the above balance is received by the exclusive control server S. If there is a request from one client C1 involving exclusive control and a transaction has occurred, the other client C1
The same request from 2 is not accepted. By processing the exclusive control request in this way, the problem caused by the simultaneous operation is eliminated.

[0005]

In the exclusive control system as described above, there is a limit for centralized management with one exclusive control server, and it is easy to reach a performance limit due to centralized control. When a failure occurs, the entire exclusive control service goes down. In view of the above, the present invention provides an exclusive control method capable of distributing a load and improving fault tolerance.

[0006]

In order to solve the problem caused by the concentration of a single pole, there is a method using a distributed exclusive control method in which a plurality of exclusive control servers are set. According to this, the exclusive control request from the client is notified to any one of the plurality of exclusive control servers, and the exclusive control server that has received the request confirms with the other exclusive control servers, and If none has exclusive control, process the request. If there is a server already having the exclusive control right, it waits for the processing to be completed. With this method, load distribution can be achieved.

However, this alone does not provide sufficient fault tolerance. That is, if a failure occurs in any one of the exclusive control servers and the communication path between them, the exclusive control right cannot be confirmed, and all exclusive control cannot be continued. At that point, the system is down.

In the present invention, as a distributed exclusion control method which solves such a problem, a priority exclusion control server which operates preferentially for each request accompanied by exclusion control is set, and a subordinate exclusion which receives a request which is not a priority target is received. The control server provides a distributed exclusion control method characterized by delegating the request to a priority exclusion control server set in the request.
In this method, a client request is first accepted by a load balancing mechanism to one of a plurality of exclusive control servers. Then, the server that has received the request checks the exclusive control server that has been set with priority by referring to the attribute value of the target data, etc., and if it is applicable, continues the processing as it is, while performing other exclusive control. If the server has priority settings, delegate to it.

In other words, the priority server is determined, and the corresponding request is processed only by the priority server. Therefore, it is not necessary to confirm the exclusive control right for confirming whether or not the exclusive control right already exists with all other exclusive control servers. Become. Therefore,
Even if a failure occurs in any one of the exclusive control servers or the communication path, only the operation of the data in charge of the server cannot be performed, and the other data can be operated without any trouble. In other words, even if a failure occurs, only some of the exclusive control processing cannot be performed, but other exclusive control can be continued, and the entire exclusive control does not go down.

In such a distributed exclusion control method, when the request transfer from the subordinate exclusion control server to the priority exclusion control server fails, failure information indicating the failure is sent from the subordinate exclusion control server to the request source. By replying and suspending or terminating the transaction, it is possible to prevent waiting for delegation to the exclusive control server in which the failure has occurred, and to prevent the client and server from proceeding to the next processing promptly. It becomes possible.

Further, each exclusive control server may be formed as a group of a plurality of servers, and the server having the largest capacity among them may receive the request, whereby the load is further distributed. Also, at this time, if the server having the largest capacity accepts the request, it is confirmed that there is no server that has already accepted the same request in the exclusive control server group to which the server belongs, and then the process is executed. Prevent simultaneous processing of data. It is preferable that all servers belonging to the same exclusive control server group confirm each other's status and agree on each other. That is, when a failure occurs in one of the servers in the group, another server in the same group can take over.

[0012]

FIG. 3 shows an example of a system according to the distributed exclusion control method of the present invention. As illustrated, four exclusive control servers S1, S2, S3, and S4 are provided, of which the exclusive control server S1 is a priority exclusive control server for balance data. Therefore, for the balance data, the other exclusive control servers S2 to S4 are subordinate exclusive control servers. The other exclusive control servers S2 to S4 have a priority for different types of data, for example, data such as accounts receivable and inventory, and when a request to operate the data is received, the exclusive control servers S2 to S4 have a priority.
1 is a subordinate exclusive control server.

Each exclusive control server S comprises a group of three servers Sa, Sb, Sc as exemplified in FIG. These servers Sa to Sc communicate with each other to confirm each other's state, and always agree on the content of the exclusive control. For example, according to the load balancing mechanism, the server Sa having the highest margin is
Is received by another server S
It is checked whether processing has already been performed in steps b and Sc, and then the processing is executed. The contents of the confirmation are recorded in all the servers Sa to Sc, and the same state is always maintained. As a result, even if a failure occurs in the server Sa and communication becomes impossible, one of the other servers Sb and Sc can act on behalf of the server Sa.

The servers Sa to Sc are unable to communicate for roughly the following reasons. That is, stop due to operator intervention, stop due to obvious failure, or unknown.
In these cases, the stop can be clearly confirmed, so that it can be performed by another server in the group. However, in this case, it is not clear whether or not the operation is stopped. Therefore, it is dangerous to substitute at this time because the situation shown in FIG. 1 may occur. Therefore, if it is not clear whether the transaction is stopped, the transaction is terminated. With such a method, the function of one server group can be reliably maintained, and the entire exclusive control server group can be kept running even when the server configuration or hardware is changed. Further, even if the process is aborted due to the unknown, since the requests other than the request of the priority target are processed by another exclusive control server group, only some data cannot be operated, and the risk is dispersed. .

Returning to the example of FIG. 3, if a request for balance data operation from the client C1 enters the exclusive control server S1 according to the data attribute value, the exclusive control server S1 performs priority exclusive control on the balance data. Since it is set in the server, processing such as updating the balance is performed as it is. At another time, if there is a request for balance data operation from the client C2 and the exclusive control server S4 receives the request by the load balancing mechanism, the exclusive control server S4 becomes a subordinate exclusive control server for the balance data. The request is transferred to the control server S1.

When the subordinate exclusive control server S4 delegates to the preferential exclusive control server S1, if a failure occurs in the communication path, the delegation will fail. At this time, the exclusive control server S4 returns failure information to the client C2 as failure to transfer and suspends or terminates the transaction. Therefore client C2
Can immediately move on to another process, and do not stop waiting for a request to be processed. Also, if the transfer cannot be performed because a failure has occurred in the preferential exclusion control server S1, the failure information is similarly returned and the transaction is suspended or terminated. Only for the exclusive control server S1 having a failure, and for the other exclusive control servers S2
In S4, the request can be processed.

[0017]

According to the present invention, by setting a priority exclusive control server for each request in the distributed exclusive control method, the load is distributed and the exclusive control server confirms the exclusive control right between the exclusive control servers. And the fault tolerance is improved. Further, by forming each exclusive control server into a group of a plurality of servers, the load can be further distributed, and proxy processing within the group can be performed, so that fault tolerance can be further improved.

[Brief description of the drawings]

FIG. 1 is a time chart illustrating a data operation requiring exclusive control.

FIG. 2 is an explanatory diagram of a conventional exclusive control method.

FIG. 3 is an explanatory diagram of a distributed exclusion control method according to the present invention.

FIG. 4 is an explanatory diagram of an exclusive control server according to the present invention.

Claims (5)

[Claims] 1. A priority exclusive control server that operates preferentially for each request accompanied by exclusive control is set, and a subordinate exclusive control server that receives a request that is not its own priority target sets the request in the request. A decentralized exclusive control method characterized by delegating to a priority exclusive control server. 2. When the request transfer from the subordinate exclusive control server to the priority exclusive control server fails, failure information indicating the failure is returned from the subordinate exclusive control server to the request source, and the transaction is interrupted or 2. The distributed exclusion control method according to claim 1, wherein the control is terminated. 3. The distributed exclusion control method according to claim 1, wherein each exclusion control server is a group of a plurality of servers, and a server having the largest capacity among the plurality of servers receives a request. 4. The process according to claim 3, wherein, when the server with the largest capacity accepts the request, it confirms that there is no server that has already accepted the same request in the exclusive control server group to which the server belongs, and then executes the processing. Distributed exclusion control method. 5. The distributed exclusion control method according to claim 4, wherein all servers belonging to the same exclusion control server group mutually confirm the status and mutually agree.