You can add subflows created as a
.msgflow file
into your message flows if either of the following statements is true:
- The subflow that you want to add to a message flow is defined
in a library.
Applications and integration services can reference
libraries.
Note: A library is a logical grouping of related code, data,
or both that typically contains reusable subflows, and other type
of resources.
- The subflow that you want to add to a message flow is defined
in the same Integration project, application, or integration service
as the message flow.
During the development phase, in the
IBM Integration Toolkit,
you can define a subflow once, and then reuse it in more than one
message flow.
- If you use a subflow in multiple message flows that are defined
in one or more Integration projects, you can define the subflow within
a library. This library can be referenced by any Integration project
that needs access to the resources it contains.
- If you use a subflow in multiple message flows that are defined
within the same Integration project, you can define the subflow within
the Integration project.
Note: When the IBM Integration Bus run
time encounters a subflow within a message flow, it creates a copy
of all the message flow nodes that define that subflow. If the subflow
is used more than once, it creates a copy of all the message flow
nodes that define the subflow every time it occurs. This increases
resource usage, which can affect your overall message flow performance.
Types of subflows supported
In IBM Integration Bus, you
can create a subflow as a .subflow file or as
a .msgflow file.
Note: If you have migrated
subflows from earlier versions of IBM Integration Bus, you
have subflows created as .msgflow files.
Subflow content
You define subflow content
in the same way as you define message flow content, by adding, configuring,
and connecting message flow nodes.
A subflow can have one or
more input nodes, and zero, one or more output nodes.
- If you want to use a subflow as the first node in your message
flow, you need to add at least one Input node, such as the MQInput
node, and one generic Output node.
- If you want to use a subflow in the middle of a message flow,
you need to add at least one generic Input node. You only need to
add a generic Output node if you want to connect additional nodes
in the message flow after you add the subflow.
- If you want to use a subflow as the last node in a message flow,
you need to add at least one generic Input node, and at least one
Output node, such as the MQOutput node.
Subflows created as .msgflow files
are grouped in the folder named Message Flow within
your application, integration service, or Integration project. The
following figure illustrates where you can find subflows created as .msgflow files:

For subflows
created as a .msgflow file, IBM Integration Bus creates
a blank flow to which you can add the message flow nodes that you
need.
Design considerations
When you define the
message flow nodes in a subflow created as a
.msgflow file,
you should consider the following recommendations:
- Define subflows in libraries. Create references to a library from
your Integration projects to be able to reuse the common logic.
- Limit the number of nested subflows.
- Group logic that is defined in consecutive compute nodes into
one single compute node. This will improve performance, since the
number of nodes loaded at runtime will be reduced.
- Add a version to the subflow.
- Do not nest subflows of different types, that is, do not add a
subflow created as a .msgflow file into a subflow
created as a .subflow file or vice versa.
Development considerations
In earlier versions
of
IBM Integration Bus,
you create message flows and other resources within Integration projects.
Note: Message
flow projects have been renamed to Message Broker projects in WebSphere® Message Broker Version
8. Message Broker projects have been renamed to Integration projects
in IBM Integration
Bus Version 9.0.
You
create reusable logic as a message flow. You embed message flows into
message flows.
Note: WebSphere Message
Broker releases earlier than version 8 only supported subflows created
as a .msgflow file. If you plan to develop new
integration solutions in IBM Integration Bus, you
should create subflows created as a .subflow file.
You should convert your subflows created as .msgflow files
into subflows created as .subflow files.