BIND 10 #1828: Python tests print warnings about unclosed file handles / sockets

[BIND 10 Development]

#1828: Python tests print warnings about unclosed file handles / sockets
-------------------------------------+-------------------------------------
                   Reporter:  muks   |                 Owner:  jinmei
                       Type:         |                Status:  reviewing
  defect                             |             Milestone:
                   Priority:         |  Sprint-20120612
  medium                             |            Resolution:
                  Component:         |             Sensitive:  0
  Unclassified                       |           Sub-Project:  DNS
                   Keywords:         |  Estimated Difficulty:  4
            Defect Severity:  N/A    |           Total Hours:  0
Feature Depending on Ticket:         |
        Add Hours to Ticket:  0      |
                  Internal?:  0      |
-------------------------------------+-------------------------------------
Changes (by muks):

 * owner:  muks => jinmei


Comment:

 Replying to [comment:13 jinmei]:
 > I'm afraid I don't understand this...
 >
 > - In "the object goes out of scope" case, the underlying FD should be
 >   immediately closed (with the warning), so it basically shouldn't
 >   cause the descriptor exhaustion (as long as the scope is
 >   sufficiently small), right?
 > - "these don't happen in a recu(r)sive style..." is not clear to me.
 >   Are these the points that actually cause the FD exhaustion?

 None of the cases that print these warnings should cause fd exhaustion
 with CPython.

 > But since it's not so obvious why we need to do the seemingly
 > redundant close(), I'd suggest updating the coding guideline page
 > http://bind10.isc.org/wiki/CodingGuidelines#PythonStyle
 > to explain this issue and what we generally should do in our code.  I
 > also suggest raising this at the bind10-dev list so other developers
 > can recognize it.

 http://bind10.isc.org/wiki/CodingGuidelines#Closeallfileandsocketobjects

 I have mailed bind10-dev too.

 > Regarding the branch itself...
 >
 > - (repeating my original comment) I'd suggest using 'file' or
 >   at least something different from 'fd' to represent file object.
 > - it would probably be even better to use the `with` idiom so the code
 >   is more exception safe in terms of the timing of close().  That is,
 >   instead of
 > {{{#!python
 >     file = open(self.pid_file, "w")
 >     file.write('dummy data\n')
 >     file.close()
 > }}}
 >   do this:
 > {{{#!python
 >     # or in this simple case it could be a one-liner.
 >     with open(self.pid_file, "w") as file:
 >         file.write('dummy data\n')
 > }}}

 This still doesn't call `.close()`.

-- 
Ticket URL: <http://bind10.isc.org/ticket/1828#comment:15>
BIND 10 Development <http://bind10.isc.org>
BIND 10 Development