When an integration server is initialized, the appropriate loadable
implementation library (LIL) files
and Plug-in Archive
(PAR) files are made available to the runtime environment. The
integration server runtime process starts, and creates a dedicated configuration
thread. You are responsible for ensuring that a user-defined node
is thread-safe. If a node updates a variable across multiple threads,
appropriate locking must be in place. Do not compromise this threading
model in your implementation of user-defined nodes. Consider the following
points:
- An input message sent to a message flow is processed only by the
thread that received it.
- A single instance of a user-defined extension might be invoked
on several threads concurrently.
- The message flow execution environment is conceptually like procedural
programming. Nodes that you insert into a message flow are like subroutines
called using a function call interface. However, rather than a call-return
interface, in which parameters are passed in the form of input message
data, the execution model is referred to as a propagation-and-return
model.
As an example, consider a message flow in which you use both user-defined
nodes and parsers. You use a user-defined node to process messages,
and a user-defined parser to parse messages; both the node and parser
contain implementation functions. The broker calls the implementation
functions, or callback functions, when certain events occur:
- When an input message is received by the message flow and is propagated
to the user-defined node:
- For C nodes, the broker calls the cniEvaluate function
for the user-defined node. See cniEvaluate.
- For Java™ nodes, the broker
calls the evaluate method that is implemented by
the user-defined node.
- If the user-defined node wants to query the message to decide
what to do with it, the node calls a C utility function or a Java method, as appropriate for
the language in which the node is written.
The broker invokes the user-defined parser on one of its implementation
functions, for example cpiParseFirstChild. This
function instructs the parser to build the parse tree. The parser
builds the tree by invoking utility functions that create elements
in the parse tree, for example cpiCreateElement.
The parser can be called many times by the broker.
Last updated Friday, 21 July 2017