Transparent session migration across servers

• US 20050038848A1
• Filed: 08/12/2004
• Published: 02/17/2005
• Est. Priority Date: 08/14/2003
• Status: Active Grant

• Current Assignee: Oracle International Corporation (Oracle Corporation)
• Original Assignee: Oracle International Corporation (Oracle Corporation)
• Inventors: Gollapudi, Sreenivas, Chatterjee, Debashish, Kaluskar, Sanjay
• Granted Patent: US 7,552,218 B2
• Time in Patent Office: Days
• US Class Current: 709/201
• CPC Class Codes: G06F 16/27 Replication, distribution or synchronisation of data between databases or within a distributed database system; Distributed database system architectures therefor
• CPC Class Codes: G06F 16/275 Synchronous replication
• CPC Class Codes: H04L 67/148 Migration or transfer of sessions

Abstract

Techniques allow a client to be switched from a session on a server to another session on another server in a way that is a transparent to the application for which the initial session was established. Thus, under transparent session migration, a client is switched between sessions without executing application instructions tailored to accomplish the migration. Instead, a client-side interface component, through which the application interacts with the server, handles details of migration, modifying the internal state of the client-side interface component to effect the same. Legacy applications do not have to be modified in order to institute techniques described herein.

Claims

1. A method, the method comprising the computer-implemented steps of:

receiving a request to establish a certain session for a client of a multi-node system;

establishing as the certain session a first session on a first node of the multi-node system;

determining to transfer the certain session to a second node of the multi-node system;

transferring first session state of the first session from the first node to a second session on the second node; and

establishing the second session as the certain session for the client on the multi-node system.

2. The method of claim 1, wherein the step of transferring first session state includes:

the first node generating and storing a copy of a portion of the first session state; and

sending a copy of the portion of the first session state to the second node via a connection established between the first node and the second node.

3. The method of claim 1, wherein:

the step of determining to transfer includes determining whether one or more migration criteria are satisfied; and

wherein the step of transferring first session state is commenced only if the one or more migration criteria are satisfied.

4. The method of claim 3, wherein the one or more migration criteria are based on whether a transaction associated with the first session has terminated.

5. The method of claim 3, wherein:

each component of a plurality of software components executed on the first node accesses a respective portion of the first session state;

the step of determining whether the one or more migration criteria are satisfied includes for each component of the plurality of components, invoking a function of the each component, the function returning a value indicating whether the respective portion of the first session state can be transferred to another node; and

wherein the one or more migration criteria are based on the values returned by the function of each component of the plurality of components.

6. The method of claim 4, the steps further including:

sending a first message to the client to cause the client to create the second session;

the client transmitting a second message to the first node indicating that the second session has been created; and

in response to receiving the second message, the first node commencing transferring first session state.

7. The method of claim 6, wherein:

the second message contains connection data for establishing a connection to the second node; and

transferring first session state includes transferring the first session state via the connection.

8. The method of claim 6, wherein the steps further include:

in response to receiving the first message from the first node, the client transmitting to the second node a certain request to create the second session; and

after creating the second session;

the second node establishing a port for a connection to the first node, and

the second node transmitting to the client a message that contains connection data for establishing a connection to the port.

9. The method of claim 8, wherein the steps further include:

the client transmitting to the second node a message that contains a copy of the connection data for establishing the connection to the port; and

in response to receiving the message that contains a copy of the connection data;

the first node establishing a connection based on the connection data, and commencing the step of transferring first session state.

10. The method of claim 6, the steps further including after transferring the first session state, sending a third message to the client to cause the client to use the second session as the certain session.

11. The method of claim 1, the steps further including receiving a request to migrate the first session to the second node.

12. The method of claim 11, the steps further including:

tracking progress of migrating the first session;

based on the progress of migrating the first session and a period of time,

ceasing to migrate the first session,

generating data that indicates that migration of the first session was attempted unsuccessfully.

13. The method of claim 1, wherein:

the client resides on a computer and executes an application;

the application invokes a interface component to interact with a server that resides on the multi-node system;

the application makes a call to the server; and

the step of transferring first session state and establishing the second session as the certain session are performed within the call.

14. The method of claim 1, the steps further including:

the first node receiving a request to migrate the first session to the second node;

after determining that a period of time has elapsed, the first node causing the client to call a server hosted one the second node; and

the step of transferring first session state and establishing the second session as the certain session are performed within the call.

15. The method of claim 1, wherein:

the step of transferring first session state and establishing the second session are performed as an operation to migrate the first session to the second node;

the steps further include, as a response to detecting a migration failure event;

ceasing to migrate the first session,

relinquishing resources allocated to migrating the first session, and

generating data that indicates that migration of the first session was attempted unsuccessfully.