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List:       graphviz-interest
Subject:    Re: [graphviz-interest] Shapefile image caching
From:       John Ellson <ellson () research ! att ! com>
Date:       2009-02-04 16:35:30
Message-ID: 4989C3D2.7000608 () research ! att ! com
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Jussi,

The only "caching" in graphviz (in libgvc) is of the decoded image file 
for the current
invocation of dot.   There is no persistent caching across invocations.
Dot's caching is to speed up the reuse of the same image in a single 
graph, and/or the same image in multiple
renderings of the same graph in a single invocation.

I think the issue you are seeing must be from either the web server 
using dot, or from the client's image caching.

One way to ensure that the caching works for you is to never reuse a 
file name for images.   For example, perhaps
you could use the md5sum of the image as its file name?

John


Juhani Eronen wrote:
> Hello,
>
> I'm using Graphviz in a MoinMoin wiki extension Graphingwiki to
> autogenerate graphs of page metadata and links.
>
> http://graphingwiki.python-hosting.com/
>
> Attachments on pages can be used as shapefiles for the nodes
> representing the pages. This is something I've recently had some
> difficuties with: as the images are replaced with other images, the
> original shapefiles sometimes still persist.
>
> I'm using Graphviz via the Python SWIG bindings, and the installations
> I've seen the problems on use the mod_python Apache module, which
> makes the used Python interpreter,s as well as much of the session
> data, persistent across requests.
>
> As my code only supplies the paths of the shapefiles to Graphviz, I
> started thinking that this behaviour could be a result of caching of
> loaded images in Graphviz or Cairo. The section 6.3 of the Drawing
> Graphs with Graphviz -document suggests that some caching might be
> done by Graphviz.
>
> Is there any basis to my reasoning on caching, and if so, how could I
> avoid this behaviour?
>
> Best Regards,
>
> -Jussi
> _______________________________________________
> graphviz-interest@research.att.com
> https://mailman.research.att.com/mailman/listinfo/graphviz-interest
>   

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