Managing web tier session state objects in a content delivery network (CDN)

• US 7,254,634 B1
• Filed: 03/10/2003
• Issued: 08/07/2007
• Est. Priority Date: 03/08/2002
• Status: Active Grant

• Current Assignee: Akamai Technologies, Inc.
• Original Assignee: Akamai Technologies, Inc.
• Inventors: Thirumalai, Srikanth, Weihl, William E., Parikh, Jay G., Tsimelzon, Mark, Davis, Andrew T.
• Primary Examiner(s): Dharia; Rupal
• Assistant Examiner(s): Gillis; Brian J.
• Application Number:
  US10/384,824
• Time in Patent Office: 1,611 Days
• Field of Search: 709/217, 709/227, 709/228, 709/238, 709/249
• US Class Current: 709/228
• CPC Class Codes: G06F 11/203 using migration
• CPC Class Codes: G06F 11/2097 maintaining the standby controller/processing unit updated initialisation or re-synchronisation thereof G06F11/1658 and subgroups
• CPC Class Codes: H04L 67/1095 Replication or mirroring of data, e.g. scheduling or transport for data synchronisation between network nodes
• CPC Class Codes: H04L 67/14 Session management for real-time applications in data packet communications networks H04L65/1066
• CPC Class Codes: H04L 67/142 Managing session states for stateless protocols; Signalling session states; State transitions; Keeping-state mechanisms
• CPC Class Codes: H04L 67/148 Migration or transfer of sessions

Abstract

Business applications running on a content delivery network (CDN) having a distributed application framework can create, access and modify state for each client. Over time, a single client may desire to access a given application on different CDN edge servers within the same region and even across different regions. Each time, the application may need to access the latest “state” of the client even if the state was last modified by an application on a different server. A difficulty arises when a process or a machine that last modified the state dies or is temporarily or permanently unavailable. The present invention provides techniques for migrating session state data across CDN servers in a manner transparent to the user. A distributed application thus can access a latest “state” of a client even if the state was last modified by an application instance executing on a different CDN server, including a nearby (in-region) or a remote (out-of-region) server.

Claims

1. A method of managing user session state during execution of platform-independent code in a content delivery network (CDN) deployed and operated by a content delivery network service provider (CDNSP), the content delivery network comprising a set of edge servers organized into distinct and separate regions and a DNS-based request handling mechanism for mapping client DNS queries to the edge servers, at least some of the edge servers provisioned with a runtime container and application server code for executing the platform-independent code, comprising:

at a first edge server provisioned with the runtime container and application server code and located in a first CDN region, establishing and maintaining a user session state in association with the execution of the platform-independent code at the first edge server; and

migrating the user session state to a second edge server provisioned with the runtime container and application server code, the second edge server being located in a second CDN region geographically distinct from the first CDN region;

wherein, as a result of the migrating step, the user session state is available to the platform-independent code on the second edge server if the CDN DNS-based request handling mechanism maps a given DNS query associated with the execution of the platform-independent code to the second edge server.

2. The method as described in claim 1 wherein the user session state is migrated to the second edge server if execution of the platform-independent code is transferred to the second edge server.

3. The method as described in claim 2 wherein execution of the platform-independent code is transferred to the second edge server because of a failure at the first edge server.

4. The method as described in claim 2 wherein execution of the platform-independent code is transferred to the second edge server to share load across the first and second CDN regions.

5. The method as described in claim 1 wherein the user session state is migrated to the second edge server before execution of the platform-independent code is transferred to the second edge server.

6. The method as described in claim 1 wherein the user session state is associated with a data structure.

7. The method as described in claim 6 wherein the data structure comprises a region number, and a session state identifier, wherein the region number represents a CDN region of the given edge server on which the platform-independent code is currently executing.

8. The method as described in claim 7 wherein the data structure also includes a session state version number that is incremented upon an update to the user session state.

9. The method as described in claim 6 wherein the data structure is a cookie.

10. The method as described in claim 1 wherein the runtime container is a Web-tier container or an Enterprise-tier container.

11. A method of managing user session state during execution of platform-independent code in a content delivery network (CDN) deployed and operated by a content delivery network service provider (CDNSP), the content delivery network comprising a set of edge servers organized into distinct and separate regions and a DNS-based request handling mechanism for mapping client DNS queries to the edge servers, at least some of the edge servers provisioned with a runtime container and application server code for executing the platform-independent code, comprising:

at a first edge server provisioned with the runtime container and application server code and located in a first CDN region and in response to a request from a given client, establishing and maintaining a user session state in association with the execution of the platform-independent code at the first edge server;

if the given client is mapped by the CDN DNS-based request handling mechanism to a second edge server provisioned with the runtime container and application server code, the second edge server being located in a second CDN region geographically distinct from the first CDN region, determining if the user session state is available at the second edge server;

if the user session state is not available at the second edge server, migrating the user session state from the first edge server to the second edge server, wherein, as a result of the migrating step, the user session state is available to the platform-independent code on the second edge server; and

executing the platform-independent code on the second edge server in association with the user session state to generate a result.

12. The method as described in claim 11 wherein the user session state is associated with a data structure comprising a region number, a session state version number, and a session state identifier, wherein the region number represents a CDN region of the given edge server on which the platform-independent code is currently executing, and the session state version number is a number that is incremented upon an update to the user session state.

13. A method of managing user session state during execution of platform-independent code in a content delivery network (CDN) deployed and operated by a content delivery network service provider (CDNSP), the content delivery network comprising a set of edge server regions organized into distinct and separate regions and a DNS-based request handling mechanism for mapping DNS queries to the edge servers, each edge server region comprising a set of edge servers, and at least some of the edge servers in the CDN provisioned with a runtime container and application server code for executing the platform-independent code, comprising:

for a given CDN region, associating a set of one or more replica regions;

at a first edge server provisioned with the runtime container and application server code and located in the given CDN region, establishing and maintaining a user session state object in association with the execution of the platform-independent code at the first edge server; and

replicating the user session state object to a given replica region in the set of replica regions associated with the given CDN region;

wherein, as a result of the replicating step, the user session state object is available to the platform-independent code on a second edge server in the given replica region if the CDN DNS-based request handling mechanism maps a given DNS query associate with the execution of the platform-independent code to the second edge server.

14. The method as described in claim 13 wherein the given replica region in the set of replica regions is identified as a function of where an end user request originates.

15. The method as described in claim 13 wherein the user session state object is replicated to the given replica region upon a given update to the user session state.