A publish/subscribe application can consist of a network of one or more brokers connected together. The brokers can all be on the same physical system, or they can be distributed over several physical systems. By connecting brokers together, publications can be received by a client on any broker in the network.
Publications are sent only to brokers that have subscribers that have expressed an interest in the topics being published. This helps to optimize network traffic.
A collective is a set of brokers that are fully interconnected and form part of a multi-broker network for publish/subscribe applications.
A broker cannot belong to more than one collective. Brokers within the same collective can exist on physically separate computers. Each pair of broker queue managers must be connected together by a pair of WebSphere MQ channels.
A broker can belong to only one collective.
Brokers within a collective can all be on one physical system, or they can be on separate physical systems.
Clients that share common topics can connect to brokers within a collective. The common publications are transported efficiently within the collective, because they do not pass through brokers that do not have at least one client with an interest in those common topics.
The performance of a client application is also improved for other services that are requested from this broker, or from this broker's queue manager. A client application can use both publish/subscribe and point-to-point messaging.
The following diagram shows a network of six collectives grouped in a hierarchical structure.
When you create a collective, the workbench ensures that the connections that you make to other collectives and brokers are valid. You are prevented from making connections that would cause messages to cycle forever within the network. You are also prevented from creating a collective of brokers that does not have the required WebSphere MQ connections already defined.
The queue manager of each broker in a collective must have a connection to every other queue manager in the collective.
Each broker in the collective maintains a list of its neighbors.
A neighbor can be one of the following:
The complete list of neighboring brokers forms a broker's neighborhood.
Related concepts
Broker
Related tasks
Developing publish/subscribe applications
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