This function dispatches a new message flow thread to invoke another
thread instance to run the user-defined message flow input node. This message
flow thread is allocated from a pool of threads maintained for each message
flow, under control of the
Additional Instances property
of the message flow. If there are no threads available because they are all
in use, CCI_SUCCESS is returned and
returnCode is
set to CCI_NO_THREADS_AVAILABLE. This is not an error, but means one of the
following:
- The message flow was not configured to run with additional threads.
- All additional threads configured are currently running.