USING ENTITY TAGS (ETAGS) IN A HIERARCHICAL HTTP PROXY CACHE TO REDUCE NETWORK TRAFFIC

• US 20130198313A1
• Filed: 01/30/2012
• Published: 08/01/2013
• Est. Priority Date: 01/30/2012
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Lobo, Alwyn R., Nicholson, Robert B., Hayton, Stuart J., Jones, David R., Vetterlein, Graeme P.
• Granted Patent: US 9,253,278 B2
• Time in Patent Office: Days
• US Class Current: 709/213
• CPC Class Codes: G06F 21/64 Protecting data integrity, e.g. using checksums, certificates or signatures
• CPC Class Codes: H04L 63/123 received data contents, e.g. message integrity
• CPC Class Codes: H04L 63/1466 Active attacks involving interception, injection, modification, spoofing of data unit addresses, e.g. hijacking, packet injection or TCP sequence number attacks
• CPC Class Codes: H04L 67/02 based on web technology, e.g. hypertext transfer protocol [HTTP]
• CPC Class Codes: H04L 67/56 Provisioning of proxy services store-and-forward switching systems in data switching networks H04L12/54
• CPC Class Codes: H04L 67/5681 Pre-fetching or pre-delivering data based on network characteristics
• CPC Class Codes: H04L 67/5682 Policies or rules for updating, deleting or replacing the stored data
• CPC Class Codes: H04L 69/04 Protocols for data compression, e.g. ROHC

Abstract

Disclosed is a program for validating a web cache independent of an origin server. A computer in between a client computer and the origin server computer receives a request for a resource and an entity tag (ETag) corresponding to the request. The computer forwards the request to the origin server and subsequently receives the resource. The computer generates an ETag for the received resource and compares the generated ETag to the ETag corresponding to the request. If the ETags match, the computer sends an indication toward the client computer that the resource has not been modified.

Claims

1. A method for validating a web cache, the method comprising the steps of:

a first computer, connectedly disposed between a second computer and a third computer, receiving a request for a resource stored on the second computer from the third computer, the request having an entity tag (ETag) corresponding to a cached version of the resource stored on the third computer;

the first computer forwarding the request for the resource to the second computer and receiving a copy of the resource from the second computer;

the first computer generating an ETag for the copy of the resource received from the second computer; and

the first computer comparing the generated ETag with the ETag corresponding to the cached version of the resource, and in response to determining that the generated ETag and the ETag corresponding to the cached version match, the first computer sending a response to the third computer indicating that the cached version of the resource is the same as the resource on the second computer.

2. The method of claim 1, further comprising the steps of:

prior to the first computer receiving the request for the resource;

the first computer receiving a previous request for the resource stored on the second computer from the third computer;

the first computer forwarding the previous request to the second computer and receiving a first copy of the resource;

the first computer determining that the second computer did not generate an ETag for the first copy of the resource, and in response, the first computer generating an ETag for the first copy of the resource; and

the first computer sending the first copy of the resource and the generated ETag for the first copy of the resource to the third computer, wherein the first copy of the resource and the generated ETag for the first copy of the resource are subsequently stored on the third computer as the cached version of the resource and the ETag corresponding to the cached version of the resource.

3. The method of claim 1, further comprising the step of, subsequent to the first computer receiving the ETag corresponding to the cached version of the resource, the first computer determining that the received ETag is an ETag generated by the first computer.

4. The method of claim 1, further comprising the step of, subsequent to the first computer receiving the ETag corresponding to the cached version of the resource stored on the third computer from the third computer, the first computer determining that a cached version of the resource stored on the first computer has an ETag matching the ETag corresponding to the cached version of the resource stored on the third computer;

5. The method of claim 1, further comprising the steps of:

subsequent to the step of the first computer comparing the generated ETag with the ETag corresponding to the cached version of the resource;

in response to determining that the generated ETag and the ETag corresponding to the cached version do not match, the first computer sending the copy of the resource and the generated ETag for the copy of the resource to the third computer.

6. The method of claim 1, wherein the request for the resource originates at the third computer.

7. The method of claim 1, wherein the request for the resource originates at a fourth computer.

8. The method of claim 7, wherein the third computer receives the request for the resource from the fourth computer and inserts the ETag corresponding to the cached version of the resource into a header of the request.

9. A computer program product for validating a web cache, the computer program product comprising:

one or more computer-readable tangible storage devices and program instructions stored on at least one of the one or more storage device, the program instructions comprising;

program instructions to receive a request for a resource stored on a first computer from a second computer, the request having an entity tag (ETag) corresponding to a cached version of the resource stored the second computer;

program instructions to forward the request for the resource to the first computer and receive a copy of the resource from the first computer;

program instructions to generate an ETag for the copy of the resource received from the first computer; and

program instructions to compare the generated ETag with the ETag corresponding to the cached version of the resource, and in response to determining that the generated ETag and the ETag corresponding to the cached version match, program instructions to send a response to the second computer indicating that the cached version of the resource is the same as the resource stored on the first computer.

10. The computer program product of claim 9, further comprising program instructions, stored on at least one of the one or more storage devices, to:

receive a previous request for the resource from the second computer;

forward the previous request to the first computer and receive a first copy of the resource;

determine that the first computer did not generate an ETag for the first copy of the resource, and in response, generate an ETag for the first copy of the resource; and

send the first copy of the resource and the generated ETag for the first copy of the resource to the second computer, wherein the first copy of the resource and the generated ETag for the first copy of the resource are subsequently stored on the second computer as the cached version of the resource and the ETag corresponding to the cached version of the resource.

11. The computer program product of claim 9, further comprising program instructions, stored on at least one of the one or more storage devices, to, subsequent to receiving the ETag corresponding to the cached version of the resource from the second computer, determine that the received ETag is an ETag generated by a computer executing the computer program product of claim 9.

12. The computer program product of claim 9, further comprising program instructions, stored on at least one of the one or more storage devices, to, subsequent to receiving the ETag corresponding to the cached version of the resource from the second computer, determine that a cached version of the resource stored on a computer executing the computer program product of claim 9 has an ETag matching the ETag corresponding to the cached version of the resource;

13. The computer program product of claim 9, further comprising program instructions, stored on at least one of the one or more storage devices, to:

in response to determining that the generated ETag and the ETag corresponding to the cached version do not match, send the copy of the resource and the generated ETag for the copy of the resource to the second computer.

14. The computer program product of claim 9, wherein the request for the resource originates at the second computer.

15. The computer program product of claim 9, wherein the request for the resource originates at a third computer and is subsequently received by the second computer.

16. A computer system for validating a web cache, the computer system comprising:

one or more processors, one or more computer-readable tangible storage devices, and program instructions stored on at least one of the one or more storage device for execution by at least one of the one or more processors, the program instructions comprising;

program instructions to receive a request for a resource stored on a first computer from a second computer, the request having an entity tag (ETag) corresponding to a cached version of the resource stored the second computer;

program instructions to forward the request for the resource to the first computer and receive a copy of the resource from the first computer;

program instructions to generate an ETag for the copy of the resource received from the first computer; and

program instructions to compare the generated ETag with the ETag corresponding to the cached version of the resource, and in response to determining that the generated ETag and the ETag corresponding to the cached version match, program instructions to send a response to the second computer indicating that the cached version of the resource is the same as the resource stored on the first computer.

17. The computer system of claim 16, further comprising program instructions, stored on at least one of the one or more storage devices for execution by at least one of the one or more processors, to:

receive a previous request for the resource from the second computer;

forward the previous request to the first computer and receive a first copy of the resource;

determine that the first computer did not generate an ETag for the first copy of the resource, and in response, generate an ETag for the first copy of the resource; and

send the first copy of the resource and the generated ETag for the first copy of the resource to the second computer, wherein the first copy of the resource and the generated ETag for the first copy of the resource are subsequently stored on the second computer as the cached version of the resource and the ETag corresponding to the cached version of the resource.

18. The computer system of claim 16, further comprising program instructions, stored on at least one of the one or more storage devices for execution by at least one of the one or more processors, to, subsequent to receiving the ETag corresponding to the cached version of the resource from the second computer, determine that the received ETag is an ETag generated by the computer system of claim 16.

19. The computer system of claim 16, further comprising program instructions, stored on at least one of the one or more storage devices for execution by at least one of the one or more processors, to, subsequent to receiving the ETag corresponding to the cached version of the resource from the second computer, determine that a cached version of the resource stored on the computer system of claim 16 has an ETag matching the ETag corresponding to the cached version of the resource;

20. The computer system of claim 16, further comprising program instructions, stored on at least one of the one or more storage devices for execution by at least one of the one or more processors, to:

in response to determining that the generated ETag and the ETag corresponding to the cached version do not match, send the copy of the resource and the generated ETag for the copy of the resource to the second computer.