[mapserver-users] mapcache seed speed optimization

[Travis Kirstine]

I may not be unrealistic for it take mapserver to 4-6 seconds to generate
4096px image depending on the amount data being rendered and the complexity
of your styles / expressions / labels.  If your mapserver is able to
generate a 1024x1024 in under a second that is pretty good.  Like Jukka and
other suggest I would look at translating the files to shp files with
spatial indexes or postgis tables with spatial and attribute indexes if
necessary.  Preprocessing the data (simplification / prefiltering / point
thinning cluster) and using SCALETOKENs to reference different source
layers at different scales can lead to big performance boosts at the
mapserver end.

For us the biggest limiting factor has been the write blocking to sqlite
cache when seeding tiles, if you increase the number of threads / process
in mapcache seed those process will just end up waiting to write to the
cache.  You can generally figure out what the max number of processes the
cache can handle by running a seed on a test area and look at the number of
tiles seeded per second, as some point -n will have no effect which your
process are just waiting to write the cache.  I would look at using this
method to test sqlite vs disk or other backends.  The GeoTiff cache may be
promising as it appears to be non-blocking but experimental...

We use a riak cache with a riak leveldb backend which works well for us but
is a bit of a pain to manage as it difficult to delete objects so it's not
great for caches that need to be refreshed.

Finally you may want to test MapProxy as an alternative to MapCache (we use
both).  MapProxy supports a non-blocking compact cache that could solve
your inode problem

Regards









On Fri, 8 Nov 2019 at 11:48, Sebastiano Laini <
Sebastiano.Laini at buchanancomputing.co.uk> wrote:

> We don’t create the data, we rely on OS (ordnance survey) to supply us the
> maps files and then we publish them in our service but I assume that
> probably we will need to create some flow to improve it or download it in
> other format that is faster.
>
>
>
> Sebastiano Laini
>
> Web Developer
>
> Buchanan Computing
>
>
>
> *From:* Fawcett, David (MNIT) [mailto:david.fawcett at state.mn.us]
> *Sent:* 08 November 2019 16:41
> *To:* Sebastiano Laini <Sebastiano.Laini at BuchananComputing.co.uk>;
> 'Rahkonen Jukka (MML)' <jukka.rahkonen at maanmittauslaitos.fi>; '
> mapserver-users at lists.osgeo.org' <mapserver-users at lists.osgeo.org>
> *Subject:* RE: mapcache seed speed optimization
>
>
>
> For data formats that are slower to read, would it add fit your workflow
> to convert it to different data format before creating the tiles?
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> mapserver-users mailing list
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