Transparent failover

摘要

Described are embodiments directed at persistent handles that are used to retain state across network failures and server failovers. Persistent handles are requested by a client after a session has been established with a file server. The request for the persistent handle includes a handle identifier generated by the client. The server uses the handle identifier to associate with state information. When there is a network failure or a server failover, and a reconnection to the client, the handle identifier is used to identify replayed requests that if replayed would create an inconsistent state on the server. The replayed requests are then appropriately handled.

主权项

1. A computer implemented method of providing consistent availability to clients accessing a shared file system on a server cluster, the method comprising:
receiving at a file server a request to connect to the file server to access file information in a shared file system, the request to connect being formatted according to a file access protocol, wherein the file server is one of a plurality of servers in a server cluster; sending a first response from the file server, the first response establishing a session with a client for allowing access to file information in the shared file system, the first response being formatted according to the file access protocol; receiving a request at the file server to open a persistent handle on the file server for accessing a file in the shared file system by the client, the request to open a persistent handle including a handle identifier provided by the client; in response to receiving the request to open a persistent handle, the file server:
storing first state information about the session in association with the handle identifier; andsending a second response to the client granting access to the file; after a client disconnect, receiving a request to reestablish the session using the persistent handle; reestablishing the session using the first state information; after reestablishing the session, receiving a new request from the client, the new request including the handle identifier; determining, using the handle identifier, that the new request is a replay of a previously sent request.