classification
Title: Futures are not marked as completed
Type: Stage:
Components: Versions:
process
Status: closed Resolution:
Dependencies: Superseder:
Assigned To: Nosy List: Sebastian.Kreft.Deezer
Priority: normal Keywords:

Created on 2014-07-01 14:29 by Sebastian.Kreft.Deezer, last changed 2014-07-16 14:56 by Sebastian.Kreft.Deezer. This issue is now closed.

Messages (2)
msg222034 - (view) Author: Sebastian Kreft (Sebastian.Kreft.Deezer) Date: 2014-07-01 14:29
With Python 3.4.1 compiled from source, I'm having an issue in which every now and then some Futures are not marked as completed even though the underlying workload is done.

My workload is launching two subprocess in parallel, and whenever one is ready, launches another one. In one of the runs, the whole process got stuck after launching about 3K subprocess, and the underlying processes had in fact finished.

To wait for the finished subprocesses, I'm using FIRST_COMPLETED. Below is the core of my workload:

for element in element_generator:
    while len(running) >= max_tasks:
        done, pending = concurrent.futures.wait(running, timeout=15.0, return_when=concurrent.futures.FIRST_COMPLETED)
        process_results(done)
        running = pending

    running.add(executor.submit(exe_subprocess, element)) 
 

Replicating the issue takes time, but I've been able to successfully reproduce it with 2 and 3 processes in parallel.

Note: this was already posted in comments to http://bugs.python.org/issue20319, however it did not receive the proper atention as that issue is already closed.

As suggested there I printed the status of the never finished futures and this is the result:

State: RUNNING, Result: None, Exception: None, Waiters: 0, Cancelled: False, Running: True, Done: False

The information does not seem very relevant. However, I can attach a console and debug from there.
msg223218 - (view) Author: Sebastian Kreft (Sebastian.Kreft.Deezer) Date: 2014-07-16 14:56
After more testing I finally found that in fact the process is not being killed. That means that there is no problem with the futures. But instead it is probably related with subprocess deadlocking, as the problematic process does not consume any CPU.

Sorry for the false report.
History
Date User Action Args
2014-07-16 14:56:39Sebastian.Kreft.Deezersetstatus: open -> closed
nosy: - bquinlan
messages: + msg223218

2014-07-01 20:47:35ned.deilysetnosy: + bquinlan
2014-07-01 14:29:26Sebastian.Kreft.Deezercreate