title: How to monitor python's concurrent.futures.ProcessPoolExecutor?
body: <p>We are using the <a href="https://docs.python.org/3/library/concurrent.futures.html#concurrent.futures.ProcessPoolExecutor" rel="noreferrer">ProcessPoolExecutor</a> from <code>concurrent.futures</code> in a service that asynchronously receives requests, and does the actual, synchronous processing in the process pool.</p>
  
  <p>Once we ran into the case that the process pool was exhausted, so new requests had to wait until some other processes were finished.</p>
  
  <p>Is there a way to interrogate the process pool for its current usage? That would allow us to monitor their state and do proper capacity planning.</p>
  
  <p>If there isn't, is there any good alternative process pool implementation with an asynchronous interface that supports such monitoring/capacity planning?</p>