Thread Creation Loop
While the processing threads are running, the thread that invoked mtaDequeueStart() executes a loop containing a brief pause (that is, a sleep request). Each time the mtaDequeueStart() thread awakens, it communicates with the Job Controller to see if it should create more processing threads. In addition, the Job Controller itself has logic to determine if more threads are needed in the currently running channel program, or if it should create additional processes to run the same channel program.
To demonstrate, the following code fragment shows pseudo code of the mtaDequeueStart() loop.
threads_running = 0
threads_max = MTA_THREAD_MAX_THREADS
attemtps = MTA_JBC_MAX_ATTEMPTS
LOOP:
while (threads_running < threads_max)
{
Go to DONE if a shut down has been requested
pending_messages = Ask the Job Controller how many
messsages there are to be processed
// If there are no pending messages
// then consider what to do next
if (pending_messages = 0)
{
// Continue to wait?
if (attempts <= 0)
go to DONE
// Decrement attempts and wait
attempts = attempts - 1;
go to SLEEP
}
// Reset the attempts counter
attempts = MTA_JBC_MAX_ATTEMPTS
threads_needed = Ask the Job Controller how many
processing threads are needed
// Cannot run more then threads_max threads per process
if (threads_needed \> threads_max)
threads_needed = threads_max
// Create additional threads if needed
if (threads_needed \> threads_running)
{
Create (threads_needed - threads_running) more threads
threads_running = threads_needed
}
}
SLEEP:
Sleep for MTA_JBC_RETRY_INTERVAL seconds
-- a shut down request will cancel the sleep
go to LOOP
DONE:
Wait up to MTA_THREAD_WAIT_TIMEOUT seconds
for all processing threads to exit
Return to the caller of mtaDequeueStart()
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