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High availability of messaging engines connected to IBM MQ

For a WebSphere Application Server messaging engine to connect with an IBM MQ queue manager in a highly available manner, we must add support for changes of IP address.

An IBM MQ link connects a service integration messaging engine to an IBM MQ queue manager. To IBM MQ, the messaging engine appears to be another queue manager. To service integration, the IBM MQ network appears to be a foreign bus.

The IBM MQ gateway queue manager uses one IP address to reach the WAS gateway messaging engine, and the WAS gateway messaging engine uses one IP address to reach the IBM MQ gateway queue manager. In a high availability configuration, if the gateway messaging engine fails over to a different application server, or the gateway queue manager fails and is replaced by a failover gateway queue manager, the connection to the original IP address for the failed component is lost. We must ensure that both products are able to reinstate their connection to the component in its new location.

To ensure that the connection to a failover WAS gateway messaging engine is reinstated, choose one of the following options:

  1. If we are using a version of IBM MQ that is earlier than v7.0.1, install the SupportPac R01 for IBM MQ. This SupportPac provides the IBM MQ queue manager with a list of alternative IP addresses and ports, so that the queue manager can connect with the WAS gateway messaging engine after the messaging engine fails over to a different IP address and port. In WAS we must set a high availability policy of "One of N" for the gateway messaging engine. For more information about the IBM MQ MR01 SupportPac, see MR01: Creating a HA Link between IBM MQ and a Service Integration Bus.

  2. If we are using IBM MQ Version 7.0.1, use the connection name (CONNAME) to specify a connection list. Although typically only one machine name is required, we can provide multiple machine names to configure multiple connections with the same properties. The connections are tried in the order in which they are specified in the connection list until a connection is successfully established. If no connection is successful, the channel starts retry processing. When using this option, specify the CONNAME as a comma-separated list of names of machines for the stated TransportType, making sure that all the WebSphere Application Server cluster member IPs are listed directly in the CONNAME. For further information about using the CONNAME, see the IBM MQ information center.

    IBM MQ Version 7.0.1 does not require SupportPac MR01 because this release includes the equivalent function to that provided by SupportPac MR01 for earlier releases. The ability to use the CONNAME to specify a connection list was added as part of the support for multi-instance queue managers in IBM MQ v7.0.1, however, it can also be used as another option to ensure that the connection to a failover WAS gateway messaging engine is reinstated.

  3. Use an external high availability framework, such as HACMP™, to manage a resource group containing the gateway messaging engine. When we use an external high availability framework, the IP address can be failed over to the machine that runs the application server to which the gateway messaging engine has moved. Follow this procedure to handle the IP address correctly:

    • Set a high availability policy of "No operation" for the messaging engine, so that the external high availability framework controls when and where the messaging engine runs.

    • Create resources for the messaging engine and its IP address in the resource group managed by the external high availability framework.
    • Consider locating the messaging engine data store in the same resource group as the resource that represents the messaging engine.

To ensure that the connection to a failover IBM MQ gateway queue manager is reinstated, choose one of the following options:

  1. Set up multi-instance queue managers in IBM MQ, as described in the IBM MQ information center. In your definition for the IBM MQ link sender channel, select Multiple Connection Names List, and specify the host names (or IP addresses) and ports for the servers where the active and standby queue managers are located. If the active gateway queue manager fails, the service integration bus uses this information to reconnect to the standby gateway queue manager.

  2. Create the IBM MQ high-availability cluster using an external high availability framework, such as HACMP, that supports IP address takeover. IP address takeover ensures that the gateway queue manager in its new location appears as the same queue manager to the service integration bus.

The gateway queue manager and the gateway messaging engine store status information that they use to prevent loss or duplication of messages when they restart communication following a failure. This means that the gateway messaging engine must always reconnect to the same gateway queue manager.

If we use IBM MQ for z/OS queue sharing groups, we can configure the IBM MQ link to use shared channels for the connection. Shared channels provide superior availability compared to the high-availability clustering options available on other IBM MQ platforms, because shared channels can reconnect to a different queue manager in the same queue sharing group. Reconnecting in the same queue sharing group is typically faster than waiting to restart the same queue manager in the same or a different location.


Related:

  • External high availability frameworks and service integration
  • Create a High Availability Link between IBM MQ and a Service Integration Bus
  • Create a new IBM MQ link
  • Configure a core group policy for messaging engines