About uniform clusters

The objective of a uniform cluster deployment is that applications can be designed for scale and availability, and can connect to any of the queue managers within the uniform cluster. This removes any dependency on a specific queue manager, resulting in better availability and workload balancing of messaging traffic. Uniform clusters are not available on IBM® MQ for z/OS®; queue sharing groups provide many of the capabilities of a uniform cluster.

Uniform clusters are a specific pattern of an IBM MQ cluster that provides a highly available and horizontally scaled small collection of queue managers. These queue managers are configured almost identically, so that an application can interact with them as a single group. This makes it easier to ensure each queue manager in the cluster is being used, by automatically ensuring application instances are spread evenly across the queue managers.

Uniform clusters remove some of the manual steps an administrator has to go through to create and administer a group of independent, interconnected queue managers. They move some client connection logic from the client to the queue manager, where information about levels of application activity can inform decisions at the clients, as to which queue managers they should connect to.

You can simplify both initial creation of a uniform cluster, and subsequently keeping the configuration between the uniform cluster members identical, by using the automatic configuration and automatic clustering support. When using this capability, one configuration file describes the cluster and another represents the MQSC configuration to apply to all queue managers in the uniform cluster. On each queue manager restart, the configuration is reapplied and the cluster automatically forms. See Creating a uniform cluster for more details on using this feature.

To take full advantage of a uniform cluster, each application should also be scaled into multiple matching instances, preferably with at least as many instances as there are queue managers, if not many more.

In a uniform cluster pattern, all queue managers in the cluster offer the same messaging services. For example, you might configure all cluster members to have the same local queues defined, and allow client applications to connect to any member of the cluster. You might also have the same server connection channels defined, and possibly the same authority records, channel authentication rules, and so on. However, members of the cluster can still have some differences in objects and configuration. For example, some applications might create temporary dynamic queues while they are connected to a queue manager. Also, some configuration updates might be rolled out across the members over a period of time; for example, new or updated certificates. As with regular IBM MQ clusters, two of the queue managers will require additional configuration to make them full repository queue managers.

The following diagram shows that the queue managers have similar configurations. They define the same queue called Q1 and the same server connection channel SVRCONN1.

Note that, for multiple queue managers with identical server connection channel names to work with a single client-channel definition table (CCDT), you must use the updated CCDT format introduced in IBM MQ 9.1.2. See client channel definition table in JSON format.