[Python-Dev] Internal counter to debug leaking file descriptors

[Guido van Rossum]

If you wanted to do something like this in the Python stdlib, you'd
have to monkey-patch (with a proxy/wrapper) all places that can open
or close a filedescriptor -- os.open, os.popen, os.close, file
open/close, socket open/close, and probably a bunch more that I've
forgotten. Also some extension modules may open file descriptors
directly through the C interfaces.

I don't know if the Windows libc has some kind of tracking feature for
file descriptors; of course it complicates things by using separate
(numeric) namespaces for sockets and files.

On Linux you can look somewhere in /proc, but I don't know that it
would help you find where a file was opened.

--Guido

On Mon, Aug 30, 2010 at 11:49 PM, anatoly techtonik <techtonik at gmail.com> wrote:
> Hi,
>
> Is there any kind of internal file descriptor counter that can be
> queried to debug issues with leaking resources?
> It can be used in tests to check that all tests are finish with 0
> opened descriptors.
> It will be very useful while porting Python applications from Unix to
> Windows. Unix is more tolerant to open files and can overwrite them
> and do other nasty things. See the thread from comment #17 -
> https://bugs.edge.launchpad.net/dulwich/+bug/557585/ - there is an
> example of mmap that starts holding file descriptor somewhere long
> before an error occurs. How could one debug this?
>
> Right now I have to use FileMon. It includes information about
> operated filenames, but no info about source code where this happens.
> It will be nice to have some kind of counter with filename information
> inside Python, so that it can be possible to get the full log of
> events without manually messing with external system-specific tools
> like FileMon.
>
> --
> anatoly t.
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-- 
--Guido van Rossum (python.org/~guido)