Arbitrating an appropriate back-end server to receive channels of a client session

• US 20070061329A1
• Filed: 11/10/2005
• Published: 03/15/2007
• Est. Priority Date: 09/12/2005
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Moutafov, Kamen
• Granted Patent: US 7,720,971 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 9/505 considering the load
• CPC Class Codes: G06F 9/52 Program synchronisation; Mutual exclusion, e.g. by means of semaphores
• CPC Class Codes: G06F 9/547 Remote procedure calls [RPC]; Web services

Abstract

The present invention extends to methods, systems, and computer program products for arbitrating an appropriate back-end server to receive channels of a client connection. Each front-end server in a server farm specifies a back-end server in the server farm that it deems appropriate for receiving channels of a client connection. Each specified back-end server is represented by an arbitration order, for example, a universally unique identifier. A relevant set of potential back-end servers that can receive channels of a client connection is selected according to function configured to minimize performance impact. A load balancing service compares arbitration orders for different back-end servers in the set of potential back-end servers to determine an appropriate back-end server for receiving channels of the client connection.

Claims

1. At a computer system including a load balancing service, a method for arbitrating an appropriate back-end server to receive channels of a client session, the method comprising:

an act of the load balancing service receiving an first arbitration order value from a first front-end server that received a first channel of the client session, the first arbitration order value representing an arbitration mechanism for a first back-end server that the first front-end server is promoting as the appropriate back-end server to receive channels of the client session, the first arbitration order being a first universally unique identifier;

an act of the load balancing service receiving an second arbitration order value from a second front-end server that received a second channel of the client session, the second arbitration order value representing an arbitration mechanism for a second back-end server that the second front-end server is promoting as the appropriate back-end server to receive channels of the client session, the second arbitration order being a second universally unique identifier;

an act of the load balancing service comparing the first arbitration order value to the second arbitration order value; and

an act of the load balancing service selecting the first back-end server as the appropriate backend server to receive channels of the client session based on the results of the comparison by the load balancing service.

2. The method as recited in claim 1, wherein the computer system includes a second load balancing service, the method further comprising:

an act of the second load balancing service receiving an first arbitration order value from a first front-end server that received a first channel of the client session, the first arbitration order value representing an arbitration mechanism for a first back-end server that the first front-end server is promoting as the appropriate back-end server to receive channels of the client session, the first arbitration order being a first universally unique identifier;

an act of second load balancing service receiving an second arbitration order value from a second front-end server that received a second channel of the client session, the second arbitration order value representing an arbitration mechanism for a second back-end server that the second front-end server is promoting as the appropriate back-end server to receive channels of the client session, the second arbitration order being a second universally unique identifier;

an act of second load balancing service comparing the first arbitration order value to the second arbitration order value; and

an act of second load balancing service selecting the first back-end server as the appropriate backend server to receive channels of the client session based on the results of the comparison by the second load balancing service such that the selection made by the first load balancing service and the second load balancing service are consistent.

3. The method as recited in claim 2, wherein the computer system includes one or more additional load balancing services, the method further comprising:

an act of each of the additional load balancing services receiving the first arbitration order value, the second arbitration order value, and one or more additional arbitration order values representing an arbitration mechanisms for a corresponding one or more additional back-end servers that are being promoted as the appropriate back-end server;

an act of each additional load balancing service comparing the first arbitration order value to the second arbitration order value and to the one or more additional arbitration order values; and

an act of each additional load balancing service selecting the first back-end server as the appropriate backend server to receive channels of the client session based on the results of the comparison by each additional load balancing service such that the selection made by the first load balancing service, the second load balancing service, and each of the additional load balancing servers are consistent.

4. The method as recited in claim 3, further comprising:

an act of at least one of the additional loading balancing services granting a lock to a back-end server other than the first back-end sever for committing the arbitration order for the appropriate back-end server to other load balancing services of the computer system.

5. The method as recited in claim 1, further comprising:

an act of the first load balancing service determining that the promotion process has not yet begun for the session; and

an act of granting the first back-end server a lock for committing the arbitration order for the appropriate back-end server to other load balancing services of the computer system.

6. The method as recited in claim 1, wherein the computer system is a server farm including a plurality of front-end servers and a plurality of back-end servers.

7. The method as recited in claim 1, further comprising:

an act of denying a lock to the second-back-end server based on the results of the comparison by the load balancing service.

8. The method as recited in claim 7, further comprising:

an act of the second back-end server revoking any previously obtained locks received from other load balancing services.

9. The method as recited in claim 1, wherein the an act of the load balancing service selecting the first back-end server as the appropriate backend server to receive channels of the client session comprises an act of installing the first back-end server as the highest ranking contender.

10. The method as recited in claim 1, further comprising an act of granting a third back-end server a lock for committing the arbitration order for the appropriate back-end server to other load balancing services of the computer system prior to comparing the first arbitration or to the second arbitration order;

and

wherein the act of comparing the first arbitration order value to the second arbitration order value is for determining if the first back-end server should replace the second back-end server as the highest ranking contender.

11. The method as recited in claim 10, further comprising:

an act of denying a lock to the second-back-end server based on the results of the comparison by the load balancing service.

12. The method as recited in claim 1, wherein the first and second front-end servers are proxy servers.

13. The method as recited in claim 1, further comprising:

an act of the load balancing service comparing the first arbitration order value and the second arbitration order value to one or more additional arbitration order values prior to selecting the first back-end server as the appropriate backend server.

14. A system for arbitrating an appropriate back-end server for receiving channels of a client session, the system comprising:

a plurality of front-end servers,

a plurality of back-end servers configured to receive channels of client sessions from the plurality of front-end servers;

a plurality of load balancing services communicatively coupled to he plurality of front-end servers and communicatively coupled to the plurality of back-end servers;

each front-end server configured to;

create a desired order of one or more back-end servers from the plurality of back-end servers, a back-end server'"'"'s position in the desired order indicating the back-end server'"'"'s appropriateness, from the perspective of the front-end server, for receiving channels of the client session;

extract a relevant set of back-end servers from the desired order, the relevant set being a subset of the back-end servers included in the desired order;

promote a specified contender back-end server to one or more load balance services from the plurality of load balancing services as the most appropriate back-end server to receive channels of the client session; and

accept and rollback locks at load balancing services; and

each load balancing service configured to;

grant and deny locks to front-end servers for contender back-end servers selected for receiving channels of the client connection;

receive arbitration orders from front-end servers, the arbitration orders promoting contender back-end servers, arbitration orders being universally unique identifiers representing the appropriateness of a contender back-end server for receiving channels of the client session;

compare arbitration orders corresponding to different contender back-end servers; and

install a highest ranking contender back-end server based on the results of comparing arbitration orders.

15. The system as recited in claim 14, wherein each load balancing service is further configured to return an already committed status when promotion is complete.

16. The system as recited in claim 14, wherein each load balancing service is further configured to:

determine that the promotion process has not yet begun for a session when no session is found; and

grant a first back-end server a lock for committing its arbitration order for the appropriate back-end server for the session to other load balancing services of the computer system when its arbitration order value is the first received arbitration value.

17. In a server farm including at least one front-end server, a method for identifying a relevant set of back-end servers to use in arbitrating an appropriate back-end server to receive channels of a client connection, the method comprising:

an act of creating a desired order of a plurality of back-end servers according to a global function, the global function configured to receive a client ID and Server ID as input and configured to provide an indication of how appropriate a back-end server is for receiving channels of a client session as output; and

an act of selecting a relevant set of one or more appropriate back-end servers from the desired order of back-end servers, the relevant set being a subset of the back-end servers included in the desired order, the relevant set selected according to a second function that limits the size of the relevant set such that the performance impact on the server farm is minimized.

18. The method as recited in claim 17, wherein each back-end server includes an instance of a load balancing service.

19. The method as recited in claim 17, further comprising:

an act of the front-end server adding a local load balancing service to the relevant set.

20. The method as recited in claim 20, wherein each of the front-end servers and back-end servers are included in a common server farm.