wait_procs won't wait for timeout

[giampaolo]

From crusade...@gmail.com on January 27, 2014 12:40:10

When waiting for 2 or more processes, as soon as the gone processes are more 
than the alive processes, wait_procs() will return, irregardless of the 
remaining timeout.

Attaching patch to psutil-1.2.1; however the same problem affects the latest 
version in mercurial as of Jan 19 2014 (adapting the patch is trivial).

Attachment: psutil_wait_procs.patch

Original issue: http://code.google.com/p/psutil/issues/detail?id=470

[giampaolo]

From g.rodola on January 27, 2014 17:02:48

I'm not sure I understand.
Are you saying wait_procs() returns immediately even if there are still 
processess to wait for?

[giampaolo]

From crusade...@gmail.com on January 27, 2014 17:16:21

Yes exactly. The current algorithm goes:

try:
    max_timeout = 1.0 / (len(alive) - len(gone))
except ZeroDivisionError:
    max_timeout = 1.0
timeout = min((deadline - timer()), max_timeout)

So whenever len(gone) > len(alive), the loop breaks and the whole method exits 
prematurely. Also, the algorithm as it is now fails in its intent of having the 
whole loop take a total of 1 cumulative second.

[giampaolo]

From g.rodola on January 27, 2014 17:52:25

Ah, I see what you mean. I think your patch is incorrect though in that it 
needs to take ZeroDivionError into account.
AFAIU it should just be:

diff --git a/psutil/__init__.py b/psutil/__init__.py
--- a/psutil/__init__.py
+++ b/psutil/__init__.py
@@ -1272,7 +1272,7 @@
             # processes may disappear in the meantime and their PID
             # reused.
             try:
-                max_timeout = 1.0 / (len(alive) - len(gone))
+                max_timeout = 1.0 / len(alive)
             except ZeroDivisionError:
                 max_timeout = 1.0  # one alive remaining
             if timeout is not None:

[giampaolo]

From g.rodola on January 28, 2014 05:24:59

Inogre my last comment about ZeroDivisionError.
I committed your patch as-is in revision 07229e0f40bd .
Thanks.

Status: FixedInHG
Labels: Milestone-2.0.0

[giampaolo]

From g.rodola on March 10, 2014 04:36:50

Closing out as fixed as 2.0.0 version is finally out.

Status: Fixed