When you design a message flow,
consider the following questions and options:
- The mode that your broker is working in
can affect the types of node that you can use and the number of message
flows you can deploy. For more information, see Restrictions that apply in each operation mode.
- 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 in the same message flow. For more information, see 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 resources for message flow development.
- Whether you can use the destination list in the local environment
that is associated with the message to determine the processing in
the message flow (for example, by 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 Working with 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. If you want to access databases from Java™ nodes by using JDBC, see Interacting with databases by using the JavaCompute node or Extending the capability of a Java message processing or output node.
- Whether your message flows access data in files. By
using the FileInput and FileOutput nodes, your message
flows can read messages from files and write messages to files in
the local file system, or on a network file system that appears local
to the broker. For more information, see Connecting client applications.
- Whether your messages must be handled in a transaction. You can
set the properties of some built-in nodes to control how transactions
are managed, and how messages are processed in a transaction. For
more information, see Configuring transactionality for message flows.
If
you want to include JMSInput and JMSOutput nodes in your message
flow transactions, you must consider the additional information in Configuring JMS and SOAP nodes to support XA coordinated 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 that uses 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 in 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.
- Whether you want a systems monitoring tool to be able
to query, discover, and set certain user-defined properties at run
time. For more information, see Setting message flow user-defined properties at run time in a CMP application.
For a basic introduction to developing message flows, see
the IBM Redbooks® publication IBM Integration Bus Basics. (This link works
only if you are connected to the Internet.)