[mapserver-dev] python mapscript and msCleanup issues

[Umberto Nicoletti]

Fabian,
if you could put together a test case that I can run to reproduce the
problem I will take a look into it.

Regards,
Umberto

On Thu, Jun 28, 2012 at 1:44 PM, thomas bonfort <thomas.bonfort at gmail.com>wrote:

> Fabian,
> can you get a backtrace of the segfaults?
>
> Aside from that, I would personally refrain from using threads with
> mapscript and stick to a prefork mpm in apache to accomplish this. It
> is also my understanding that calling msCleanup() should be limited to
> when a process is actually exiting, and not at the end of each
> request, i.e. if I were you I would investigate where memory is
> leaking when freeing your request/map objects.
>
> regards,
> thomas
>
> On Thu, Jun 28, 2012 at 11:28 AM, Fabian Schindler
> <fabian.schindler at eox.at> wrote:
> > Hi all,
> >
> > Has anyone had issues with Python MapScript and the msCleanup() in
> > WSGI-Apache applications? Using msCleanup() results in strange
> > errors/segfaults in multi-threaded setups but not using it quickly eats
> up
> > memory.
> >
> > We are developing a Django application to serve enhanced WCS responses
> > (according to the EO-WCS extension). For this purpose, we use MapScript
> to
> > receive a basic WCS response, which we are extending with additional
> > metadata.
> >
> > Our mapserver dispatch code is like this:
> >
> > mapscript.msIO_installStdoutToBuffer()
> > dispatch_status = map.OWSDispatch(ows_req)
> > content_type = mapscript.msIO_stripStdoutBufferContentType()
> > mapscript.msIO_stripStdoutBufferContentHeaders()
> > result = mapscript.msIO_getStdoutBufferBytes()
> > mapscript.msCleanup(1)
> > return result, content_type, dispatch_status
> >
> > Unfortunately we experienced several weird errors (segfaults, hit
> assertions
> > within GEOS, etc) when dispatching requests, especially in multi-threaded
> > environments (such as a deployment with Apache). We traced this down and
> > found that a call to `msCleanup` right after the OWSDispatch was causing
> the
> > problems.
> >
> > Taken from the mapscript documentation:
> >
> > "msCleanup() attempts to recover all dynamically allocated resources
> > allocated by MapServer code and dependent libraries. It it used primarily
> > for final cleanup in scripts that need to do memory leak testing to get
> rid
> > of “noise” one-time allocations. It should not normally be used by
> > production code."
> >
> > When we remove the call to msCleanup, no segfaults and other errors occur
> > within Apache. Unfortunately, while running our test cases (including
> > several hundreds MapServer dispatches) we quickly run out of memory (e.g:
> > memory consumption after 30 test cases was over 2.2 GiB instead of about
> 150
> > MB).
> >
> > Any ideas are welcome :)
> >
> > Thanks,
> > Fabian
> >
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