METHOD AND SYSTEM FOR LOAD BALANCING WITH AFFINITY

• US 20110252127A1
• Filed: 04/13/2010
• Published: 10/13/2011
• Est. Priority Date: 04/13/2010
• Status: Abandoned Application

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Wright, Charles P., Iyengar, Arun K., Tantawi, Asser N., Jiang, Hongbo, Nahum, Erich M., Segmuller, Wolfgang
• Application Number:
  US12/759,390
• Publication Number:
  US 20110252127A1
• Time in Patent Office: Days
• US Class Current: 709/224
• CPC Class Codes: G06F 2209/5016 Session
• CPC Class Codes: G06F 9/5033 considering data affinity
• CPC Class Codes: G06F 9/505 considering the load
• CPC Class Codes: H04L 67/1008 based on parameters of servers, e.g. available memory or workload monitoring of computer activity G06F11/30
• CPC Class Codes: H04L 67/1027 Persistence of sessions during load balancing
• CPC Class Codes: H04L 67/1029 using data related to the state of servers by a load balancer
• CPC Class Codes: H04L 67/1036 Load balancing of requests to servers for services different from user content provisioning, e.g. load balancing across domain name servers

Abstract

A method and system for distributing requests to multiple back-end servers in client-server environments. A front-end load balancer is used to send requests to multiple back-end servers. In appropriate cases, the load balancer will send requests to the servers based on affinity requirements, while maintaining load balance among servers.

Claims

1. In a client-server system comprising a load balancer for sending requests to a plurality of servers, a method for sending requests to the servers comprising the steps of:

establishing affinity between a session and at least one server s1 in which state information maintained at the load balancer indicates that requests corresponding to the session should preferably be sent to server s1;

determining a load on server s1;

determining a load on at least one other server;

in response to the load balancer receiving a request corresponding to said session, sending the request to a server different from server s1 if the load on server s1 exceeds the load on the at least one other server by a threshold.

2. The method of claim 1 further comprising the step of, in response to the load balancer receiving a request corresponding to said session, sending the request to server s1 if the load on server s1 does not exceed the load on the at least one other server by a threshold.

5. The method of claim 1 in which said session corresponds to SIP requests which are part of a same call.

6. The method of claim 1 in which said session corresponds to TLS (SSL) requests from a same client.

7. The method of claim 1 in which said session corresponds to requests associated with a same application which maintains state information on server s1.

11. The method of claim 1 in which said load on server s1 is determined using one of a number of requests currently assigned to s1;

an estimated amount of work s1 has to do to satisfy remaining requests assigned to it;

CPU load on s1; and

recent response times exhibited by s1.

12. The method of claim 1 in which said load on server s1 and at least one other server is determined using one of a number of requests currently assigned to s1 and said at least one other server;

an estimated amount of work s1 and said at least one other server have to do to satisfy remaining requests assigned to it;

CPU load on s1 and said at least one other server; and

recent response times exhibited by s1 and said at least one other server.

3. In a client-server system comprising a load balancer sending requests to a plurality of servers, a method for sending requests to the servers comprising the steps of:

designating a server s1 to handle requests corresponding to a session;

storing session state on s1;

determining a load on s1;

determining a load on at least one other server;

in response to the load on server s1 exceeding the load on the at least one other server by a threshold, migrating session state from s1 to a second server s2;

sending at least one subsequent request corresponding to the session to s2.

4. The method of claim 3 further comprising the step of the load balancer selecting one of s1 and s2 to handle a request corresponding to said session based on determined load.

8. The method of claim 3 in which said session corresponds to SIP requests which are part of a same call.

9. The method of claim 3 in which said session corresponds to TLS (SSL) requests from a same client.

10. The method of claim 3 in which said session corresponds to requests associated with a same application which maintains state information on server s1.

13. A client-server system comprising:

at least one client for generating requests;

a plurality of servers for handling client requests; and

at least one load balancer for receiving client requests, for designating a server s1 to handle requests corresponding to a session;

for storing session state on s1;

for determining a load on s1 and at least one other server;

for, in response to a load on server s1 exceeding the load on the at least one other server by a threshold, migrating session state from s1 to a second server s2; and

for sending at least one subsequent request corresponding to the session to s2.

14. A program storage device readable by machine storing a program of instructions for causing a load balancer to perform a method for sending client requests to a plurality of servers, said method comprising the steps of:

designating a server s1 to handle requests corresponding to a session;

storing session state on s1;

determining a load on s1;

determining a load on at least one other server;

in response to the load on server s1 exceeding the load on the at least one other server by a threshold, migrating session state from s1 to a second server s2;

sending at least one subsequent request corresponding to the session to s2.

15. A client server system comprising:

at least one client for generating requests;

a plurality of servers for handling client requests; and

at least one load balancer adapted to perform steps of;

establishing affinity between a session and at least one server s1 in which state information maintained at the load balancer indicates that requests corresponding to the session should preferably be sent to server s1;

determining a load on server s1;

determining a load on at least one other server;

in response to the load balancer receiving a request corresponding to said session, sending the request to a server different from server s1 if the load on server s1 exceeds the load on the at least one other server by a threshold.

16. A program storage device readable by machine storing a program of instructions for causing a load balancer to perform a method for sending client requests to servers in a client server system comprising the steps of:

establishing affinity between a session and at least one server s1 in which state information maintained at the load balancer indicates that requests corresponding to the session should preferably be sent to server s1;

determining a load on server s1;

determining a load on at least one other server;

in response to the load balancer receiving a request corresponding to said session, sending the request to a server different from server s1 if the load on server s1 exceeds the load on the at least one other server by a threshold.