Selecting a server to service client requests

• US 6,898,633 B1
• Filed: 10/04/2000
• Issued: 05/24/2005
• Est. Priority Date: 10/04/2000
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Lyndersay, Sean, Hopmann, Alex, Deen, Brian, Soderberg, Joel
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): DELGADO, MICHAEL A
• Application Number:
  US09/680,120
• Time in Patent Office: 1,693 Days
• Field of Search: 709/224, 709/331, 709/229, 700/2, 707/4, 707/10, 718/105
• US Class Current: 709/226
• CPC Class Codes: H04L 63/08 for authentication of entities cryptographic mechanisms or cryptographic arrangements for entity authentication H04L9/32
• CPC Class Codes: H04L 67/1001 for accessing one among a plurality of replicated servers
• CPC Class Codes: H04L 67/1014 based on the content of a request
• CPC Class Codes: H04L 67/1023 based on a hash applied to IP addresses or costs

Abstract

Systems and methods for directing client requests and for selecting a back end server to service client requests. A front end server receives client requests and based on the URI of the requests, directs the request to a back end server. The client request can be for a private or a public folder and each back end server typically stores both private and public folders. If the request is for a private folder, then the front end server determines which server stores that user'"'"'s private folder and directs the client request to that folder. If the request is for a home public folder, the front end server directs the client request to the server that is associated with the private folders of the users. If the request is for an application public folder, then the front end server selects one of the back end servers to service the client request. Advantageously, the front end server always directs the client request to the same server. If the selected server is unavailable, then the front end server is capable of redirecting the client request to an available server.

Claims

1. In a system including a client and a server system including a front end server and one or more back end servers, a method for directing a client request to a particular back end server, the method comprising the acts of:

identifying the particular back end server from a directory if the client request is for a private folder, wherein only the particular back end server stores the private folder of the client;

identifying the particular back end server from the directory if the client request is for a home public folder, wherein only the particular back end server stores the home public folder of the client;

identifying the particular back end server, from a list of a plurality of back end servers capable of servicing the client request, using a selection module if the client request is for an application public folder, wherein the selection module identifies the same particular back end server from the list for each client request of a particular user; and

directing the client request to the particular back end server.

2. A method as defined in claim 1, wherein the directory includes configuration information.

3. A method as defined in claim 1, wherein the directory associates a URI of the client request with the private folder, associates the private folder with the home public folder, and associates each of the one or more back end servers that have a replica of the home public folder.

4. A method as defined in claim 1, wherein the act of identifying the particular back end server from a directory if the client request is for a private folder further comprises the act of examining the URI to determine a username.

5. A method as defined in claim 1, wherein the act of identifying the particular back end server from the directory if the client request is for a home public folder further comprises the act of identifying a string in the directory to determine that the client request is for a home public folder.

6. A method as defined in claim 1, wherein the selection module performs a hash function using the list of back end servers and a security token of a user to select the particular back end server.

7. A method as defined in claim 2, further comprising the act of servicing the client request with the particular back end server.

8. A method as defined in claim 2, wherein the configuration information associates a username with the private folder, and wherein the username is identified from one of the URI of the client request or authentication information of a user.

9. A method as defined in claim 2, wherein the configuration information associates the home public folder with the private folder.

10. A method as defined in claim 2, wherein the back end servers include ghosted folders.

11. A method as defined in claim 5, wherein the string is “

public folder.”

12. A method as defined in claim 6, wherein one or more of the back end servers included in the list of back end servers is marked as unavailable, wherein the hash function does not exclude a back end server that is marked as unavailable unless the particular back end server selected by the hash function is marked as unavailable.

13. A method as defined in claim 10, further comprising the act or returning a subset of servers to the front end server if the particular back end server ghosts a content requested in the client request.

14. A method as defined in claim 13, wherein the selection module selects a new back end server from the subset of servers to service the client request.

15. A method as defined in claim 14, wherein each of one or more back end servers included in the subset of servers actually store the content requested in the client request.

16. A method as defined in claim 14, further comprising the act of directing the client request to the new back end server.

17. In a system including a client and a server system including a front end server and one or more back end servers, a method for directing a client request for content in an application public folder to a particular back end server, the method comprising the acts of:

identifying a security token of a user associated with the client request;

identifying a list of back end servers from a directory, wherein each back end server in the list of back end servers has a replica of the application public folder;

selecting the particular back end server from the list using a selection module, wherein the selection module hashes the security token of the user to identify the same particular back end server within the list of back end servers for each of a plurality of requests to be received from the user; and

directing the client request to the particular back end server selected by the selection module.

18. A method as defined in claim 17, wherein the particular back end server selected by the selection module ghosts the content requested in the client request.

19. A method as defined in claim 18, further comprising the acts of:

the particular back end server sending a subset list of back end servers to the front end server, wherein the subset list includes each of the one or more back end servers that actually stores the content;

selecting a new back end server from the subset list with the selection module; and

directing the client request to the new back end server.

20. A method as defined in claim 17, wherein the particular back end server is unavailable.

21. A method as defined in claim 20, further comprising the acts of:

marking the particular server as unavailable in the list of back end servers;

selecting a new particular server from the list of back end servers with the selection module, wherein the unavailable back end server is not excluded from the list of back end servers unless the unavailable back end server is selected by the selection module; and

directing the client request to the new particular server.

22. A method as defined in claim 17, wherein at least one of the back end servers included in the list of back end servers is marked as unavailable and wherein the act of selecting the particular back end server comprises the act of keeping the marked back end servers in the list of back end servers when the selection module selects the particular back end server.

23. A computer readable medium containing computer executable instructions for executing the acts recited in claim 17.

24. In a system including a client and a server system, the server system including a front end server and one or more back end servers, a computer program product for implementing a method for directing a client request to a particular back end server, the computer program product comprising:

a computer-readable medium carrying executable instructions for performing the method, wherein the method includes the acts of;

identifying the particular back end server from a directory if the client request is for a private folder, wherein only one of the one or more back end servers stores the private folder of the client;

identifying the particular back end server from the directory if the client request is for a home public folder, wherein only one of the one or more back end servers stores the home public folder of the client;

identifying the particular back end server, from a list of a plurality of back end servers capable of servicing the client request, using a selection module if the client request is for an application public folder, wherein the selection module identifies the same particular back end server from the list for each client request of a particular user; and

directing the client request to the particular back end server.

25. A computer program product as defined in claim 24, wherein the directory associates a URI of the client request with the private folder, associates the private folder with the home public folder, and associates each of the one or more back end servers that have a replica of the home public folder.

26. A computer program product as defined in claim 24, wherein the act of identifying the particular back end server from a directory if the client request is for a private folder further comprises the act of examining the URI to determine a username.

27. A computer program product as defined in claim 24, wherein the act of identifying the particular back end server from the directory if the client request is for a home public folder further comprises the act of identifying a string in the directory to determine that the client request is for a home public folder.

28. A computer program product as defined in claim 24, herein the string is “

public folder.”

29. A computer program product as defined in claim 24 wherein the selection module performs a hash function using the list of back end servers and a security token of a user to select the particular back end server.