playground update blocks if bzr produces a lot of output

[Maciej Muehleisen]

If a huge commit changed a lot of files playground.py upgrade will produce a lot of output. wnbsbase/rcs/Output.py uses stderr and stdout directly from the subprocess, causing blocking as described in http://docs.python.org/library/subprocess.html 17.1.2 Unfortunately I have no idea how to use communicate() to prevent the subprocess from blocking.

[Daniel Bültmann (daniel.bueltmann)]

I am not sure if this is easy to fix. I have tried to remove the call to subprocess.wait() in wnsbase.rcs.Bazaar which causes the blocking. At the moment I cannot verify that it fixes the problem. Could you provide a test or something, so that I can reproduce the bug?

[Maciej Muehleisen (mue-comnets)]

import subprocess
p = subprocess.Popen("ls -R ./", shell=True, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE, close_fds=True)
p.wait()

This subprocess (listing directories recursively) produces a lot of output and therefore blocks when nobody "collects" it from stderr and stdin. In the shell "ls -R" takes a few seconds and is done. Above code results in a deadlock.