title: Tracking progress of joblib.Parallel execution
body: <p>Is there a simple way to track the overall progress of a <a href="https://pythonhosted.org/joblib/generated/joblib.Parallel.html">joblib.Parallel</a> execution?</p>
  
  <p>I have a long-running execution composed of thousands of jobs, which I want to track and record in a database. However, to do that, whenever Parallel finishes a task, I need it to execute a callback, reporting how many remaining jobs are left.</p>
  
  <p>I've accomplished a similar task before with Python's stdlib multiprocessing.Pool, by launching a thread that records the number of pending jobs in Pool's job list.</p>
  
  <p>Looking at the code, Parallel inherits Pool, so I thought I could pull off the same trick, but it doesn't seem to use these that list, and I haven't been able to figure out how else to "read" it's internal status any other way.</p>