Internet server session backup apparatus

• US 6,539,494 B1
• Filed: 06/17/1999
• Issued: 03/25/2003
• Est. Priority Date: 06/17/1999
• Status: Expired due to Term

• Current Assignee: Oracle OTC Subsidiary LLC (Oracle Corporation)
• Original Assignee: Art Technology Group Incorporated (Oracle Corporation)
• Inventors: Chung, Joseph T., Abramson, Nathan
• Primary Examiner(s): LE, DIEU MINH T
• Application Number:
  US09/335,004
• Time in Patent Office: 1,377 Days
• Field of Search: 714/4, 714/6, 714/11, 714/13
• US Class Current: 714/4.3
• CPC Class Codes: G06F 11/203 using migration
• CPC Class Codes: G06F 11/2038 with a single idle spare processing component
• CPC Class Codes: G06F 11/2046 where the redundant components share persistent storage G06F11/2043 takes precedence
• CPC Class Codes: H04L 67/02 based on web technology, e.g. hypertext transfer protocol [HTTP]
• CPC Class Codes: H04L 67/14 Session management for real-time applications in data packet communications networks H04L65/1066
• CPC Class Codes: H04L 67/142 Managing session states for stateless protocols; Signalling session states; State transitions; Keeping-state mechanisms
• CPC Class Codes: H04L 69/40 for recovering from a failure of a protocol instance or entity, e.g. service redundancy protocols, protocol state redundancy or protocol service redirection management of faults, events, alarms or notifications in data switching networks H04L41/06

Abstract

A computer system for a web site uses three tiers of servers, web (or HTTP) servers, application servers, and backup servers. The backup servers are responsible for backing up the session data for particular application servers. The system assigns to each web session a session ID, which encodes the IP addresses of the application server and its backup server, and provides an identifier that uniquely identifies the session within that application server. A session is automatically routed to a second application server to process a request if the application server handling the session should fail or not have the requested application. However, the request uses the original session ID. The second application server detects from the session ID that the session may have been handled by the first application server. The second application server decodes the IP address for the backup server for the first application server, and connects to that backup server. The user'"'"'s session data is recovered from that backup server and reconstituted into a new session, with a new session ID. If the session had previously existed on the second application server, the session ID used by the second application server and the session data for that session are used, updated with the session data from the first backup server.

Claims

1. A computer system comprising:

a plurality of application servers, wherein each of the plurality of application servers is programmed to maintain session data for a user session assigned to such application server; and

a backup server coupled to the application servers;

wherein the backup server is programmed to maintain a backup of the session data for a first of the application servers;

wherein a second of the application servers is programmed to obtain the backup of session data from the backup server when the second of the application servers receives a request for service not corresponding to a user session hosted by the second of the application servers; and

wherein the transition of the backup session data from the first server to the second server is transparent to the user.

2. The computer system of claim 1, wherein each of the plurality of application servers is programmed to assign a session ID to a user session not previously assigned to such application server.

3. The computer system of claim 2, wherein the session ID provides a unique identifier for the user session.

4. The computer system of claim 2, wherein the session ID identifies the application server to which the user session is assigned.

5. The computer system of claim 4, wherein the session ID further identifies the backup server.

6. The computer system of claim 4, wherein the second of the application servers is programmed to assign a new session ID to the user session if the second of the application servers is not hosting a user session with the session ID.

7. The computer system of claim 6, wherein the new session ID identifies the second of the application servers and provides a unique identifier for the user session.

8. The computer system of claim 4, wherein the second of the application servers is programmed to assign a new session ID to the user session if the session ID does not identify the second of the application servers, the new session ID identifying the second of the application servers.

9. The computer system of claim 1, wherein the second of the application servers is programmed to replace the session ID with a new session ID if the second of the application servers receives a request for service not corresponding to a user session hosted by the second of the application servers, wherein the new session ID identifies a user session assigned to the second of the application servers.

10. The computer system of claim 9, further comprising a session alias server coupled to the plurality of application servers, wherein the session alias server is programmed to maintain a table indicating equivalence of session IDs from different ones of the plurality of application servers.

11. The computer system of claim 9, wherein the backup server is programmed to maintain a table indicating equivalence of session IDs from different ones of the plurality of application servers.

12. The computer system of claim 11, wherein the second of the application servers is programmed to obtain from the backup server a list of equivalent session IDs to the current session ID of the user session, and to determine whether the list of equivalent session IDs includes a session ID corresponding to the second of the application servers.

13. The computer system of claim 1, further comprising a web server coupled to the plurality of application servers, wherein the web server is programmed to route requests for service from the user session to the first of the plurality of application servers.

14. The computer system of claim 13, wherein the web server is programmed to route a request for service from the user session to the second of the application servers when the first of the application servers has failed.

15. The computer system of claim 14, further comprising a load manager coupled to the plurality of application servers, wherein the load manager is programmed to obtain load information from the plurality of application servers.

16. A computer system comprising:

a web server;

a plurality of application servers coupled to the web server, wherein a user session is assigned to one of the plurality of application servers and the one of the plurality of application servers maintains session data for the user session; and

a group of at least one backup server coupled to the application servers;

wherein each application server is assigned to one backup server from the group of backup servers, and each backup server in the group of backup servers is programmed to maintain a backup of the session data for at least one of the application servers;

wherein a user session assigned to a first of the application servers is assigned a session ID;

wherein the second of the application servers assigns a different session ID to the user session;

wherein a second of the application servers is programmed to obtain the backup of session data from the backup server to which the first of the application servers is assigned when the second of the application servers receives a request for service from the web server, the request for service not corresponding to a user session hosted by the second of the application servers; and

wherein the transition of the backup session data from the first server to the second server is transparent to the user.

17. A method for transferring a session on a computer network comprising the steps of:

assigning a user session to a first application server;

assigning a first session ID to the user session;

sending a request for service to a second application server, the request for service including the first session ID;

determining whether the request for service corresponds to a user session hosted by the second application server;

retrieving session data for the user session from a backup server assigned to the first application server;

assigning a second session ID to the user session; and

wherein the retrieval of the session data from the first server to the second server is transparent to the user.

18. The method of claim 17, wherein the retrieving step includes identifying, from the first session ID, the backup server assigned to the first application server.

19. The method of claim 17, wherein the step of assigning a second session ID includes determining whether the user session had previously been assigned to the second application server.

20. The method of claim 19, wherein the step of determining whether the user session had previously been assigned to the second application server includes obtaining a list of session IDs that are equivalent to the first session ID.

21. The method of claim 20, wherein the list of session IDs is obtained from the backup server assigned to the first application server.

22. The method of claim 20, wherein the list of session IDs is obtained from a session alias server.

23. The method of claim 20, further comprising the step of providing to a backup server assigned to the second application server the second session ID, the first session ID, and the list of session IDs that are equivalent to the first session ID, if the user session had not previously been assigned to the second application server.

24. The method of claim 23, further comprising the step of providing to the backup server assigned to the first application server the second session ID, if the user session had not previously been assigned to the second application server.

25. The method of claim 19, wherein the step of assigning a second session ID further includes re-assigning a session ID previously assigned to the user session for the second application server if the user session had previously been assigned to the second application server.

26. The method of claim 25, further comprising the step of recovering session data corresponding to the period during which the user session had been assigned to the second application server.

27. The method of claim 26, further comprising the step of updating the recovered session data with the session data retrieved from the backup server.

28. A computer system comprising:

an application server programmed to maintain session data for user sessions assigned to the application server and to assign a session ID to each user session assigned to the application server; and

a backup server coupled to the application server, wherein the backup server is programmed to maintain a backup of session data for a user session on the computer system;

wherein the application server is programmed to obtain from the backup server the backup of session data for the user session if the application server is not hosting the user session;

wherein the application server is programmed to determine if the application server is not hosting the user session by comparing the session ID of the user session to a list of session ID'"'"'s currently being hosted by the application server; and

wherein the transfer of session data to the application server is transparent to the user.