System and method for transparently redirecting client requests for content using a front-end indicator to preserve the validity of local caching at the client system

• US 6,865,605 B1
• Filed: 10/04/2000
• Issued: 03/08/2005
• Est. Priority Date: 10/04/2000
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Hopmann, Alex, Deen, Brian, Soderberg, Joel
• Primary Examiner(s): Dharia, Rupal
• Assistant Examiner(s): Nguyen, Quang N.
• Application Number:
  US09/679,716
• Time in Patent Office: 1,616 Days
• Field of Search: 709/200, 709/217, 709/219, 709/224, 709/226, 709/229, 709/239
• US Class Current: 709/226
• CPC Class Codes: H04L 63/0807 using tickets, e.g. Kerberos cryptographic mechanisms or cryptographic arrangements for entity authentication using tickets or tokens H04L9/3213
• CPC Class Codes: H04L 67/63 Routing a service request depending on the request content or context

Abstract

Methods and computer program products for transparently redirecting a request for content such that a client system is unaware of the redirection. A client requests content through a front-end server that provides a single point of access for content stored on one or more back-end servers. The single point of access makes it so the client does not know and does not care which particular back-end server stores the requested content. When a back-end server provides a redirect response for content that the back-end server does not store, the front-end server receives the redirect response and reissues the request to a server identified in the redirect response. A front-end server indicator is added to requests so that the back-end server knows the request is from a front-end server. This allows the back-end server to provide a list of servers in the redirect response without causing errors in clients making direct requests to back-end servers when the clients are unable to process a list of servers contained in a redirect response.

Claims

1. In a computerized system that includes a client system, a front-end server, and one or more back-end servers, all interconnected with a communication link, a method of transparently redirecting a request for content such that the client system is unaware of the redirection, the method comprising the front-end server performing the acts of:

receiving a request for the content from the client system, the front-end server making it appear as if the front-end server is the source of the content, which actually is stored at a back-end server;

directing the request to a particular back-end server;

receiving from the particular back-end server, a redirect response identifying one or more other back-end servers where the content is stored;

automatically and without client system intervention, redirecting the request to a redirect back-end server, the redirect back-end server being one of the one or more other back-end servers identified in the redirect response;

receiving the requested content from the redirect back-end server; and

sending the requested content to the client system from the front-end server so that any local caching of the content received from the front-end server remains valid at the client system regardless of which of the one or more back-end servers actually stores the content.

2. A method as recited in claim 1 further comprising the act of adding a front-end indicator to the request in order to indicate that the front-end server is making the request on behalf of the client system, wherein the front-end indicator is added to a hypertext transfer protocol User Agent header.

3. A method as recited in claim 1 wherein the redirect response identifies a list of back-end servers where the content is stored.

4. A method as recited in claim 3 wherein the list of back-end servers is identified in a hypertext transfer protocol 305 Use Proxy response from the particular back-end server.

5. A method as recited in claim 3, further comprising the acts of:

requesting authentication credentials from the client system; and

receiving proper authentication credentials from the client system.

6. A method as recited in claim 5 further comprising the acts of:

receiving an authentication token that is associated with the authentication credentials; and

using the authentication token as a key for a hash operation to identify the redirect back-end server from the list of back-end servers identified in the redirect response.

7. A method as recited in claim 1 wherein the redirect response identifies a single back-end server where the content is stored.

8. A method as recited in claim 7, wherein the single back-end server is identified in either a hypertext transfer protocol 301 Moved Permanently or 302 Moved Temporarily response from the particular server.

9. A method as recited in claim 1, further comprising the acts of:

receiving the requested content from the redirect back-end server; and

sending the requested content to the client system.

10. In a computerized system that includes a client system, a front-end server, and one or more back-end servers, all interconnected with a communication link, a method of redirecting a request for content directed to a particular back-end server when the content is not stored at the particular back-end server, the method comprising the back-end server performing the acts of:

receiving a content request from the client system through the front-end server, the content request including a front-end indicator in order to indicate that the front-end server is making the content request on behalf of the client system;

examining the content request for the front-end indicator;

if the front-end indicator is present in the content request, creating a redirect response to the content request that includes a list identifying a plurality of redirect back-end servers where the content is stored so that the front-end server can load balance among the plurality of redirect back-end servers capable of satisfying the content request, and otherwise creating a redirect response to the content request that includes a single redirect back-end server where the content is stored; and

sending the redirect response to the front-end server so that the front-end server can redirect the request to one or more redirect back-end servers.

11. A method as recited in claim 10 wherein the front-end indicator is added to a hypertext transfer protocol User Agent header.

12. A method as recited in claim 10 wherein the list of one or more redirect back-end servers is identified in a hypertext transfer protocol 305 Use Proxy response from the particular back-end server.

13. In a computerized system that includes a client system, a front-end server, and one or more back-end servers, all interconnected with a communication link, a method of transparently redirecting a request for content such that the client system is unaware of the redirection, the method comprising the front-end server performing:

an act of receiving a request for the content from the client system as if the front-end server were the source of content stored at the one or more back-end servers;

a step for querying a particular back-end server for the requested content, wherein the response to the query identifies one or more other back-end servers where the content is stored, the one or more other back-end servers being either inaccessible or unknown to the client system;

a step for, automatically and without user intervention, retrieving the requested content from a redirect back-end server, the redirect back-end server being one of the one or more other back-end servers identified in the query response; and

an act of sending the requested content to the client system from the front-end server so that any local caching of the requested content received from the front-end server remains valid at the client system even if the requested content later moves from the redirect back-end server or is retrieved from a back-end server other than the redirect back-end server.

14. A method as recited in claim 13 further comprising a step for authenticating the client system.

15. A method as recited in claim 14 wherein the query response identifies a list of back-end servers where the content is stored, the method further comprising a step for distributing the request to the redirect back-end server based on the client system authentication.

16. A method as recited in claim 13 wherein the query response identifies a single back-end servers where the content is stored.

17. In a computerized system that includes a client system, a front-end server, and one or more back-end servers, all interconnected with a communication link, a computer program product for implementing a method of transparently redirecting a request for content such that the client system is unaware of the redirection, comprising:

a computer readable medium for carrying machine-executable instructions for implementing the method; and

wherein said method is comprised of machine-executable instructions for the front-end server performing the acts of;

receiving a request for the content from the client system, the front-end server making it appear as if the front-end server is the source of the content, which actually is stored at a back-end server;

directing the request to a particular back-end server;

receiving from the particular back-end server, a redirect response identifying one or more other back-end servers where the content is stored;

automatically and without client system intervention, redirecting the request to a redirect back-end server, the redirect back-end server being one of the one or more other back-end servers identified in the redirect response;

receiving the requested content from the redirect back-end server; and

sending the requested content to the client system from the front-end server so that any local caching of the content received from the front-end server remains valid at the client system regardless of which of the one or more back-end servers actually stores the content.

18. A computer program product as recited in claim 17, wherein the redirect response identifies a list of back-end servers where the content is stored.

19. A computer program product as recited in claim 18, the method comprised further of machine-executable instructions for performing the acts of:

requesting authentication credentials from the client system; and

receiving proper authentication credentials form the client system.

20. A computer program product as recited in claim 19, the method comprised further of machine-executable instructions for performing the acts of:

receiving an authentication token that is associated with the authentication credentials; and

using the authentication token as a key for a hash operation to identify the redirect back-end server from the list of back-end servers identified in the redirect response.

21. A computer program product as recited in claim 17, wherein the redirect response identifies a single back-end server where the content is stored.

22. A computer program product as recited in claim 17, the method comprised further of machine-executable instructions for performing the act of adding a front-end indicator to the request in order to indicate that the front-end server is making the request on behalf of the client system.

23. In a computerized system that includes a client system, a front-end server, and one or more back-end servers, all interconnected with a communication link, a computer program product for implementing a method of redirecting a request for content directed to a particular back-end server when the content is not stored at the particular back-end server, comprising:

a computer readable medium for carrying machine-executable instructions for implementing the method; and

wherein said method is comprised of machine-executable instructions for the particular back-end server performing the acts of;

receiving a request for the content from the client system through the front-end server, the request including a front-end indicator in order to indicate that the front-end server is making the request on behalf of the client system;

examining the content request for the front-end indicator;

if the front-end indicator is present in the content request, creating a redirect response to the request that includes a list identifying a plurality of redirect back-end servers where the content is stored so that the front-end server can load balance among the plurality of redirect back-end servers capable of satisfying the content request, and otherwise creating a redirect response to the content request that includes a single redirect back-end server where the content is stored; and

sending the redirect response to the front-end server so that the front-end server can redirect the request to one or more redirect back-end servers.

24. A method as recited in claim 23 wherein the front-end indicator is added to a hypertext transfer protocol User Agent header.

25. A method as recited in claim 23 wherein the list of one or more redirect in a hypertext transfer protocol 305 Use Proxy response from the particular back-end server.