The Message Transport and Communication between Nodes

This topic introduces the Message Transport and the concept of communication between Nodes.

Nodes communicate with other Nodes . Nodes normally use asynchronous communication, but Flow Nodes in the Data Plane use synchronous communication to communicate with other Flow Nodes.

Nodes use messages and message queues to communicate asynchronously. Nodes use direct function calls to communicate synchronously. The Node API is the set of messages to which a Node responds.

You can do operations on Nodes. The following list gives some of the features of an operation on a Node:

• an operation is a sequence of messages sent to the Node.

• a Node can run many operations at the same time

• an operation can define if another operation can run on the Node at the same time.

• a Node can define the order that operations must occur.

A Node normally sends a message to second Node and expects a reply from the second Node. The first Node stops the operation until the first Node receives the reply. Some messages do not require a reply. For example, a message that signals that a Node must destroy itself does not require a reply.