WebSphere MQ messaging services
A service represents a destination that applications send messages to or receive messages from.
In WebSphere® MQ a destination is called a message queue. A queue resides in a queue manager. The parameters that describe the messages on a queue are defined in a service by the systems administrator.
In a point-to-point application, the sending application knows the destination of the message. Point-to-point applications can be send and forget, or datagrams, in which a reply to the message is not required. Point-to-point applications can be request or response messages, where the message specifies the destination for the response message. For example, the correlation identifier in the Table 3 configuration table, is used for a request/reply type of application in MQ user defined functions
Publish or subscribe application
In a publish/subscribe application, the providers of information (publishers) are separate from the consumers of that information (subscribers).
Publishers supply information about a subject by sending it to a broker. The subject is identified by a topic. A publisher can publish information on more than one topic, and many publishers can publish information on a particular topic.
Subscribers decide what information might be of interest, and subscribes to the relevant topics by sending a message to the broker. When information is published on one or the topics of interest, the broker sends it to the subscriber.
There can be many brokers in a publish or subscribe system. The brokers communicate with each other to exchange subscription requests and publications. A publication is propagated to another broker if a subscription to that topic exists on the other broker.
Types of service
- Senders and receivers establish one-way communication pipes for sending and receiving messages.
- A publisher contains a sender that is used to publish messages to a publish or subscribe broker.
- A subscriber contains a sender, that is used to subscribe to a publish or subscribe broker, and a receiver, that is used to receive publications from the broker.