A message flow can perform a wide
range of operations, depending on your business and operational requirements.
For best performance and capability, you must design it to include
the most appropriate nodes.
When you design a message flow,
consider the following questions and options:
- Which nodes provide the function that you require. In many cases,
you can choose between several nodes that provide a suitable function.
You might have to consider other factors listed here to determine
which node is best for your overall needs. You can include built-in
nodes, user-defined nodes, and subflow nodes. For more information,
see Deciding which nodes to use.
- Whether it is appropriate to include more than one input node.
For more information, see Using more than one input node.
- How to specify the characteristics of the input message.
For more information, see Defining input message characteristics.
- Whether to determine the path that a message follows
through the message flow, based on the content or the characteristics
of the message. Several nodes provide checks or examination of the
message, and have output terminals that can be connected to direct
certain messages to different nodes. For more information, see Using nodes for decision making.
- Whether you can use subflows that provide a well-defined
subset of processing. You might be able to reuse subflows that were
created for another project (for example, an error processing routine),
or you might create a subflow in your current project, and reuse it
in several places within the same message flow. For more information,
see Using subflows.
- What response times your applications expect from the message
flow. This factor is influenced by several aspects of how you configure
your nodes and the message flow. For more information, see Optimizing message flow response times.
- Whether your message flow processing makes demands on
system resources such as stack size. For more information, see System considerations for message flow development.
- Whether you can use the destination list within the
LocalEnvironment that is associated with the message to determine
the processing within the message flow (for example, using RouteToLabel and Label nodes), or the target
for the output messages (for example, by setting the Destination Mode property of the MQOutput node to Destination List). For more
information, see Creating destination lists.
- Whether to use WebSphere MQ cluster queues.
For more information, see Using WebSphere MQ cluster queues for input and output.
- Whether to use WebSphere MQ shared
queues on z/OS® . For more information, see Using WebSphere MQ shared queues for input and output (z/OS).
- Whether to validate input messages that are received
by the input node, or output messages that are generated by the Compute node, or both. For
more information, see Validating messages.
- Whether to view or record message structure in Trace node output. For more
information, see Viewing the logical message tree in trace output.
- Whether your message flows access data in databases.
You must configure brokers, databases, and database connections to
enable this function, as described in Configuring broker and user databases.
You must also configure your message flows; see Accessing databases from message flows.
If you include nodes
that use ESQL, for information about how to code the appropriate statements,
see Accessing databases from ESQL.
You can also access databases
through the Data perspective in
the workbench; see Connecting to databases using the Data perspective.
- Whether your messages must be handled within a transaction.
You can set the properties of some built-in nodes to control how transactions
are managed, and how messages are processed within a transaction.
For more information, see Configuring globally coordinated message flows.
If you want to include JMSInput and JMSOutput nodes in your message
flow transactions, you must consider the additional information in Configuring JMSInput and JMSOutput nodes to support global transactions.
- Whether you want your messages to go through data conversion.
For information about the available options, see Configuring message flows for data conversion.
- Whether you want to use the MQGet node. For more information
about how messages are processed by the MQGet node, and a description
of a request-reply scenario using this node, see Using MQGet nodes.
- How your message flows can benefit from
user exits. For more information, see Exploiting user exits.
- What steps to take to ensure that messages are not lost. For more
information, see Ensuring that messages are not lost.
- How errors are handled within the message flow. You can use the
facilities provided by the broker to handle any errors that arise
during message flow execution (for example, if the input node fails
to retrieve an input message, or if writing to a database results
in an error). However, you might prefer to design your message flow
to handle errors in a specific way. For more information, see Handling errors in message flows.
For a basic introduction to developing message flows, see
the IBM® Redbooks® publication WebSphere Message Broker Basics. (This link works
only if you are connected to the Internet.)