Setting up node replication and failover for the cluster

This optional procedure sets up node replication to provide high availability and fail-over support for the cluster. If one member of the cluster goes down, other nodes can continue to process the SIP request. Use this procedure only if you require high availability and fail-over support.

Before you begin

Before you begin, you must install IBM® Sametime® Gateway on each node, add the nodes to a cluster, and then start the cluster and the SIP proxy server.

Enabling high availability uses additional memory which reduces your server's session capacity. For more information about enabling high availability, see the IBM Sametime Gateway sizing guide in the Sametime wiki:

Sametime Gateway 8.5.0 and 8.5.1 sizing guidelines

About this task

Sametime Gateway offers a comprehensive high availability (HA) solution. High availability means an environment that doesn't have a single point of failure, and therefore prevents the users from loosing presence awareness in the event of a Gateway server instance failure.

Replication domains

A SIP cluster with replication and failover can consist of many server instances. Each replication domain contains a set of two servers. Therefore, the number of replication domains needed is half the number of server instances. You need to create a new replication domain for each pair of Sametime Gateway instances (deployment manager and proxy server do not count). For example: if you have eight Sametime Gateway instance, you will be creating four replication domains. In case one server instance fails, the remaining server instance begins servicing the replicated SIP sessions of the failed instance. Therefore, IBM recommends that you pair server instances that are NOT likely to fail at the same time. For example, you should not pair server instances if both are running on the same physical host.

Procedure

  1. Validate that the environment is ready:
    1. Click Servers > clusters and verify that the Sametime Gateway cluster is started and the status is green.
    2. Click Servers > Proxy Servers and verify that the SIP proxy is started and the status is green.
    3. Click SIP proxy > SIP Proxy Server Settings > SIP proxy settings and verify that the specified cluster is the same Sametime Gateway cluster defined in the previous step.
  2. Create your new replication domains:
    1. Click Environment > Replication Domains, and then click New. Note: Disregard the GatewayCache. This is the DynaCache used to propagate the configuration across the cluster, and is not used for SIP session replication.
    2. Type a name for the new replication domain. For example: SIPRD1.
    3. In the Number of Replicas section, select Entire Domain so that the SIP session is replicated to both Gateway instances, and click OK.
    4. Repeat this process for each replication domain you wish to create.
  3. Assign replication domains to server instances:
    1. Click Servers > Application Servers, and then select a member of the cluster.
    2. In the "Container Settings" section, click Session management.
    3. In the "Additional Properties" section, click Distributed environment settings.
    4. In the "Distributed sessions" section, click Memory-to-memory replication. The distributed session option will become enabled once configured.
    5. In the "Replication domain" section, select one of the replication domains that you created in previous steps. Remember, each replication domain must be assigned to exactly two server instances.
    6. In the Replication mode field, select Both client and server, then click OK, and Save. Memory to memory replication is now enabled for this member of the cluster.
    7. Repeat the previous step for each member of the cluster.
  4. When High Availability is configured, you may see redundant SIP Container printouts in the log files, such as these:
    [6/7/11 18:34:45:409 IDT] 0000006d RepCommand I RepCommand _replication updates=2 removes = 1 in the last 1439735 milliseconds
[6/7/11 18:57:45:321 IDT] 0000006d RepCommand I RepCommand _replication updates=4 removes = 2 in the last 1379911 milliseconds

    Add a SIP Container custom property to suppress these messages:

    1. Click Servers > Server Types > WebSphere application servers.
    2. Click the Gateway server (for example, GWServer1).
    3. Select SIP Container in the Container Settings > SIP Container Settings section.
    4. Select Custom properties in the "Additional Properties" section.
    5. Click New to add a new custom property.
    6. Give the property the following name and value:

      Name: enable.replication.debug.mode

      Value: false

    7. Click OK.
    8. Update the master configuration by clicking Save in the "Messages" box at the beginning of the page.