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Re: [Maposmatic-dev] File descriptor leak problem

From: Thomas Petazzoni
Subject: Re: [Maposmatic-dev] File descriptor leak problem
Date: Mon, 16 Apr 2012 23:07:36 +0200


Le Mon, 16 Apr 2012 21:39:50 +0200,
David MENTRE <address@hidden> a écrit :

> I am glad to see that your are making progress in locating this
> annoying bug. Locating it is half fixing it. ;-)

I had a discussion with Dane Springmeyer on the #mapnik IRC channel,
and he said that the behaviour is expected: Mapnik keeps the shape
files opened as a cache. We need to disable this at compile time by
setting the SHAPE_MEMORY_MAPPED_FILE=False value when calling the
configure script.

> I think this option is the most tolerant to this error and other
> similar errors that would certainly occur in the future. While it
> might not be the cleanest from an idealistic point of view, it uses
> the isolation features of our underlying OS and ensures that
> everything is properly cleaned-up. In fact, I thought it was the way
> the rendering pipeline was implemented. :-)
> Regarding performance, I think (but not measured) that the overhead of
> forking a process is negligible compared to other overheads we have,
> like database queries.

I agree that we should use one process for each rendering. It
guarantees the isolation between renderings, and the cost of the
fork/exec compared to the rendering itself is negligible.

Maxime told me today that he would work tomorrow on implementing this.


Thomas Petazzoni      
Logiciels Libres à Toulouse
Embedded Linux        

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