Using queues on an IBM MQ uniform cluster

A uniform cluster is a specific type of 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 approach makes it easier to ensure that each queue manager in the cluster is being used, by automatically ensuring that application instances are spread evenly across the queue managers.

Uniform clusters differ from other IBM MQ clusters in several respects. For example, a uniform cluster typically has a smaller number of queue managers in the cluster and is used by a single application or a group of related applications. In a uniform cluster, client connections are grouped together based on the application name. Applications that connect to any member of the uniform cluster using the same application name are considered to be equivalent to any other applications using the same application name. All connections from an App Connect Enterprise integration server currently use the same MQ application name.

By using uniform clusters, applications can be designed for scale and availability, and can connect to any of the queue managers within the uniform cluster. As a result, there is no dependency on a specific queue manager, which improves availability and workload balancing of messaging traffic. For more information, see Uniform clusters in the IBM MQ product documentation online.

In some scenarios, it is important that the connection that is made between an IBM App Connect Enterprise integration node or server and an IBM MQ queue manager is maintained with that same queue manager, and not changed to an alternative queue manager. In these circumstances, uniform clusters are not appropriate. For example, in some MQ request/reply scenarios, reply messages must be returned to the same App Connect Enterprise integration server, which can be problematic if the connection is moved to a different queue manager. Another situation in which it is necessary to maintain access to a specific queue manager is when a flow contains nodes that require access to information about the state of in-flight messages, such as Aggregation, Sequence, Resequence, Collector, and Timeout nodes. Information about the state of in-flight messages is held on storage queues that are owned by the queue manager that is associated with the integration server. If the connection is moved to a different queue manager, the required information will no longer be accessible. Uniform clusters are also unsuitable for connections that are made from locally-bound applications; uniform clusters cannot achieve even workload distribution with locally bound applications, because they cannot connect to any other member of the cluster. For more information, see Limitations and considerations for uniform clusters.

In scenarios where one-way messaging is required, it can be beneficial to use queues that are defined on an IBM MQ uniform cluster. For information about configuring App Connect Enterprise to use uniform clusters, see Configuring App Connect Enterprise to use IBM MQ uniform clusters.