METHOD AND APPARATUS FOR CACHE VALIDATION FOR PROXY CACHES

• US 20030061272A1
• Filed: 12/30/1997
• Published: 03/27/2003
• Est. Priority Date: 06/02/1997
• Status: Active Grant

• Current Assignee: AT&T Corporation (AT&T, Inc.)
• Original Assignee: AT&T Corporation (AT&T, Inc.)
• Inventors: KRISHNAMURTHY, BALACHANDER, WILLS, CRAIG ELLIS
• Granted Patent: US 6,578,113 B2
• Time in Patent Office: Days
• US Class Current: 709/203
• CPC Class Codes: G06F 16/9574 of access to content, e.g. by caching

Abstract

A proxy cache maintains a copy of multiple resources from various servers in a network. When the proxy cache must generate a validation request for at least one resource at one of the servers, the proxy cache piggybacks one or more additional cache validation requests related to documents presently stored in the cache but originating from or associated with the server in question. Upon receipt of an indication of the freshness or validity of the cached copy of the document, the proxy cache can then make a determination as to whether to request an update of the document.

Claims

1. A method for maintaining consistency in a cache in a data communication network, the method comprising the steps of:

receiving a request for a data resource;

determining whether the cache holds the requested data resource;

detecting a freshness of the requested data resource if determined to be held by the cache;

when said freshness of said requested data resource falls outside a predetermined range, generating a change-status request relating to said requested data resource to a source of that requested data resource;

when generating said change-status request, identifying at least one other data resource held by the cache and from said source and generating a change-status request relating to said at least one other data resource to said source.

2. The method of claim 1 comprising the further step of receiving notice that said at least one other data source has changed.

3. The method of claim 1 comprising the further steps of:

receiving a notice that said requested data resource has changed;

receiving the changed requested data resource; and

receiving notice that said at least one other data resource has changed.

4. The method of claim 2 comprising the further step of:

rendering said at least one other data resource in said cache invalid in response to said notice that said at least one other data resource has changed.

5. The method of claim 2 comprising the further steps of:

requesting a transmission of the changed said at least one other data resource from said source.

6. The method of claim 1 wherein said step of identifying said at least one other data resource comprises the substeps of:

detecting all data resources in said cache identified as being from said source of the requested data resource;

examining a freshness of each of the detected data resources; and

selecting a subset of the detected data resources based on the examination of freshness;

wherein said subset corresponds to the identified at least one other data resource.

7. In a data communication system including a plurality of servers and a proxy server that includes a proxy cache, a method for maintaining cache consistency comprising the steps of:

receiving a request for a data resource at said proxy server;

determining whether said proxy cache holds the requested data resource;

identifying a source of said requested data resource;

identifying other data resources from said source in said proxy cache;

selecting a subset of the identified other data resources;

requesting, from said source, information regarding the requested data resource and the subset of identified other data resources.

8. The method of claim 7 wherein said step of requesting comprises:

generating a first change-status request identifying said requested data resource; and

generating a second change-status request identifying said subset of identified other data resources.

9. The method of claim 7 comprising the further step of rendering invalid each one of the subset of identified other data resources that is indicated to have changed.

10. The method of claim 7 comprising the further step of re-loading each one of the subset of identified other data resources that is indicated to have changed.

11. The method of claim 7, comprising the further step of receiving information regarding differences between a version of one of the subset of identified other data resources in the cache and a version of said one of the subset of identified other data resources at the source.

12. The method of claim 7 comprising the further step of updating a freshness of each data resource in said subset of identified other data resources that is indicated to be unchanged.

13. A method for checking the validity of contents of a cache memory in a data network, the method comprising the steps of:

detecting a need to verify at a source a data resource requested of the cache memory;

identifying a plurality of other data resources stored in the cache memory and associated with the source; and

querying the source for information regarding said data resource and to determine if any of said plurality of other data resources have changed since the most recent previous query.

14. The method of claim 13, wherein in response to an indication that one or more data resources have changed the method further comprises the step of:

re-loading any data resource indicated to have changed.

15. The method of claim 14 wherein said step of detecting a need to verify comprises the substeps of:

identifying a data resource of interest in the cache memory;

detecting a time duration identifying the time since a most recent re-loading of the data resource;

determining a need to verify when the detected time duration exceeds a predetermined value.

16. A method for maintaining consistency in a cache in a data communication network, the method comprising the steps of:

receiving a request for a data resource;

determining whether the cache holds a fresh copy of the requested data resource;

when it is determined that the cache does not hold a fresh copy of the requested data resource, transmitting a request relating to said requested data resource to a source of that requested data resource; and

when transmitting that request, also transmitting a change status request relating to at least one other data resource from said source held by the cache.

17. The method of claim 16 comprising the further step of receiving notice that said at least one other data source has changed.