| 摘要 |
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.
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