Checking up on a `concurrent.futures.ThreadPoolExecutor`

Question

I've got a live concurrent.futures.ThreadPoolExecutor. I want to check its status. I want to know how many threads there are, how many are handling tasks and which tasks, how many are free, and which tasks are in the queue. How can I find out these things?

Answer 1

There is some visibility into the Pool, and the pending workitem queue. To find out what's available, print poolx.__dict__ to see the structure. Read the ThreadPool code, it's pretty good: concurrent.futures.thread

The following creates a pool with one thread. It then creates two jobs: one sleeps for 3 seconds, the other immediately returns. The pool's number of pending work items is then printed.

Following that, we print out items from the work queue. In this case, a thread is already executing the time.sleep(3) function, so that's not in the queue. The function sleep with args [0] and kwargs {} is printed, because that's the next work item for the pool to run.

Kudos to @dano for the nondestructive queue insight, and @abarnert.

source

import concurrent.futures, time

poolx = concurrent.futures.ThreadPoolExecutor(max_workers=1)
poolx.submit(time.sleep, 3)
poolx.submit(time.sleep, 0)   # very fast

print('pending:', poolx._work_queue.qsize(), 'jobs')
print('threads:', len(poolx._threads))
print()

# TODO: make thread safe; work on copy of queue?
print('Estimated Pending Work Queue:')
for num,item in enumerate(poolx._work_queue.queue):
    print('{}\t{}\t{}\t{}'.format(
        num+1, item.fn, item.args, item.kwargs,
        ))

poolx.shutdown(wait=False)

output

pending: 1 jobs
threads: 1

Pending Work Queue:
1   <built-in function sleep>   (0,)    {}