Cluster Communication 

Use

The SAP J2EE Engine cluster communication is represented by a communication engine, which is used to send messages between the elements in the cluster. You can send messages to one cluster element, to a group of elements or to all elements in the cluster.

Several ways for sending messages are available:

·        One-way – it is sent without waiting for a response.

·        Request-response – a response to this message is expected. The response type depends on the request and can be either a confirmation that the message was received, or a response that the request was processed.

The messages can be used to send events between the elements in the cluster, as well as to transport greater amounts of data.

Features

The Cluster Manager offers several ways for communicating within the cluster. These options differ depending on the abilities they provide for transferring messages between the cluster elements:

·        Message Server Communication – the communication is established through the message server used as a dispatcher when sending messages. This way of communication has one advantage – it has a failover function that avoids the loss of information. For more information, see Message Server Communication.

·        Session Communication – this is used between the elements in one cluster group. Its advantage is that there are constantly opened connections between the elements, and the data is transferred directly without a mediator. For more information, see Session Communication.

·        Lazy Communication – lazy communication is used when transferring large messages. For more information, see Lazy Communication.

At Cluster Manager level, it is decided whether the connection will pass through the message server or through a lazy connection – the services are not interested in the way the message is send.

The successful message delivery is guaranteed, except in cases when the corresponding element stops or is timed out.