CLIENT-BASED CACHING OF REMOTE FILES

• US 20100185704A1
• Filed: 01/15/2009
• Published: 07/22/2010
• Est. Priority Date: 01/15/2009
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Jolly, Thomas E., George, Mathew, Pinkerton, James T., Kruse, David M.
• Granted Patent: US 8,185,566 B2
• Time in Patent Office: Days
• US Class Current: 707/821
• CPC Class Codes: G06F 12/0813 with a network or matrix configuration
• CPC Class Codes: G06F 12/0815 Cache consistency protocols
• CPC Class Codes: G06F 12/0866 for peripheral storage systems, e.g. disk cache
• CPC Class Codes: G06F 16/172 Caching, prefetching or hoarding of files
• CPC Class Codes: G06F 16/182 Distributed file systems
• CPC Class Codes: G06F 16/183 Provision of network file services by network file servers, e.g. by using NFS, CIFS network file access protocols H04L67/1097
• CPC Class Codes: G06F 21/6218 to a system of files or objects, e.g. local or distributed file system or database
• CPC Class Codes: G06F 2212/264 Remote server
• CPC Class Codes: G06F 2212/463 File
• CPC Class Codes: G06F 2221/2141 Access rights, e.g. capability lists, access control lists, access tables, access matrices
• CPC Class Codes: H04L 67/01 Protocols
• CPC Class Codes: H04L 67/1097 for distributed storage of data in networks, e.g. transport arrangements for network file system [NFS], storage area networks [SAN] or network attached storage [NAS]
• CPC Class Codes: H04L 67/568 Storing data temporarily at an intermediate stage, e.g. caching

Abstract

A lease system is described herein that allows clients to request a lease to a remote file, wherein the lease permits access to the file across multiple applications using multiple handles without extra round trips to a server. When multiple applications on the same client (or multiple components of the same application) request access to the same file, the client specifies the same lease identifier to the server for each open request or may handle the request from the cache based on the existing lease. Because the server identifies the client'"'"'s cache at the client level rather than the individual file request level, the client receives fewer break notifications and is able to cache remote files in more circumstances. Thus, by providing the ability to cache data in more circumstances common with modern applications, the lease system reduces bandwidth, improves server scalability, and provides faster access to data.

Claims

1. A computer-implemented method for caching information at a client related to remote files stored at a server, the method comprising:

receiving information from a software application indicating a remote file to open in an open request

determining whether a lease exists on the client for the indicated remote file, wherein a lease provides cache coherency information associated with the remote file independent of zero or more open handles to the remote file;

if no existing lease exists,

sending a lease request to open the file and request a lease that identifies one or more cache intentions of the client based on the access information received from the application; and

receiving a lease response indicating whether the requested lease was granted,

wherein the preceding steps are performed by at least one processor.

2. The method of claim 1 wherein the open request comprises a UNC path to a remote file accessible over a network.

3. The method of claim 1 wherein determining whether a lease exists comprises looking up a UNC path associated with the remote file in a table of leases.

4. The method of claim 1 wherein sending a lease request comprises generating a lease identifier and sending the identifier to the server with the request.

5. The method of claim 1 wherein sending a lease request comprises providing one or more cache intentions in the lease request, wherein the cache intentions specify a manner in which the client will access the remote file.

6. The method of claim 1 further comprising receiving file data and metadata for the requested remote file and storing the data and meta data in a local cache for later use.

7. The method of claim 1 further comprising determining whether a user associated with the current request is the same as a user associated with an existing lease, and when the user is different, requesting a new lease from the server.

8. The method of claim 1 further comprising, if an existing lease exists,

determining whether a scope of access requested to the remote file is compatible with a scope of the existing lease;

and

if the scope of access requested is the same as the scope of the existing lease, collapsing the current open request onto the existing lease, without making a round trip to the server.

9. A computer system at a client for providing access to remote files stored on a server that are shared with other clients, the system comprising:

a processor and memory configured to execute software instructions;

an application interface configured to provide an interface through which applications submit requests to open remote files on the server and receive file data;

a lease request component configured to send lease requests to a remote server and handle received lease responses;

a communication component configured to transmit requests and receive responses over a network that connects one or more clients and servers;

a cache component configured to cache data at the client based on information received from the server; and

a break handling component configured to respond to break notifications received from the server, wherein a break notification indicates that access that the server previously granted is no longer compatible with access requests of other clients accessing the same file.

10. The system of claim 9 wherein the application interface provides a kernel mode interface for communicating with the server.

11. The system of claim 9 wherein the application interface is further configured to receive requests to access remote files, use the lease request component to send open requests to remote servers that include a lease identifier, and cache data received from the remote servers based on the terms of received leases.

12. The system of claim 9 wherein the application interface is further configured to provide file data to an application directly from the cache component without additional communication with the remote server when the file data is available in the cache.

13. The system of claim 9 wherein the lease request component is further configured to receive responses from the server that either grant or deny a lease and when a lease is denied suggest a lease scope of access that is lower than a requested access level based on existing client access to a file.

14. The system of claim 9 wherein the communication component is further configured to use extensions to the Server Message Block version 2 network protocol.

15. The system of claim 9 wherein the cache component is further configured to associate a lease identifier with each cache so that the server can distinguish one cache provider from another.

16. The system of claim 9 wherein the break handling component is further configured to update the server based on use of a remote file related to the break notification by applications on the client.

17. A computer-readable storage medium comprising instructions for controlling a computer system to handle a lease break notification from a server, wherein the instructions, when executed, cause a processor to perform actions comprising:

receiving a break notification from the server, wherein the break includes a lease identifier provided by the client when the client opened a remote file managed by the server to which the break applies, wherein the break notification is not based on concurrent access to the remote file by applications on the client;

flushing cached data that can no longer be cached based on the received break notification;

sending an acknowledgement request to the server that indicates that the client has handled the break and requests a new scope of access to the remote file based on application requests on the client;

receiving an acknowledgement response from the server that indicates whether the server granted the new scope of access to the remote file.

18. The computer-readable medium of claim 17 wherein the break notification includes a current lease state of the lease held by the client and a new lease state available to the client based on the access of one or more other clients to the remote file.

19. The computer-readable medium of claim 17 wherein the client was caching writes to the remote file before the break notification and wherein flushing cached data comprises flushing pending written data to the server before responding to the break notification.

20. The computer-readable medium of claim 17 further comprising, after receiving and handling the break notification, handling application requests from the cache that are compatible with the new scope of access and sending other requests to the server without caching.