[mapserver-users] high memory usage on map draw

Wed Nov 30 07:50:59 PST 2011

All, 

I've been following this thread with some interest. 

Another option for print work flow may be to tile some data as separate calls, and then to call cartographic stuff like large labels with a transparent background and overlay this on the base tiles.  We do this type of operation in the PDF printer for GeoMoose for handling high resolution output. 

bobb 

>>> Adam Eskreis <aeskreis at gmail.com> wrote:

If you have a piece of text with a buffer that spans 10 tiles, and assuming you are using 2048x2048 tiles to do your tiling, I wonder what kind of text this is that can literally span 20000 pixels, and whether displaying that text on the map, rather than just overlaying that text on the map post-render, is the right call.

Anyway, best of luck.

-Adam

On Wed, Nov 30, 2011 at 10:22 AM, Daniele Debernardi <daniele at geosar.ch> wrote:

I've already tried with that solution but the problem is how to know how much buffer I need.
Suppose that i have a very long label that cover 10 tiles, I have to generate tiles with a buffer of the size of 10 tiles to
get my text correctly. But how can I know what my label text will be long?
Now I'm going in the direction of vector outputs hoping that they support all my needs (symbols and labels).

Daniele

Il 30.11.2011 16:03, Adam Eskreis ha scritto: 

You can still buffer even if you draw in a tile based manner. Suppose your buffer is 100 pixels and tile size is 256x256. Just pull 100 pixels more in each direction than you need, and then when you weave your tiles together, only draw from 100,100 to 356,356 and cut out the rest. See what I mean?

On Wed, Nov 30, 2011 at 3:06 AM, Daniele Debernardi <daniele at geosar.ch> wrote:

Tiling the map is a good idea, but the problem is the symbology and label that are drawn between 2 tiles,
with a buffer can't be possible why there is no possibility to know how the symbol or text will be.

I'm trying to configure php mapscript to output directly in pdf with CAIRO but with no success.

MapServer version 6.1-dev OUTPUT=GIF OUTPUT=PNG OUTPUT=JPEG SUPPORTS=PROJ SUPPORTS=AGG SUPPORTS=CAIRO SUPPORTS=FREETYPE SUPPORTS=ICONV SUPPORTS=WMS_SERVER SUPPORTS=WMS_CLIENT SUPPORTS=WFS_CLIENT SUPPORTS=GEOS INPUT=POSTGIS INPUT=OGR INPUT=GDAL INPUT=SHAPEFILE

setting output format driver CAIRO/PDF mimetype application/x-pdf imagemode RGB and extension pdf i get this error:

[MapServer Error]: msSaveRasterBuffer(): unsupported image format

Failed writing image to /tmp/4ed5e30c_4d9_0.pdf

In php i have the support of pdflib lite enabled (PDFlib GmbH Version 7.0.5)

Is there something particular in the configuration that I'm missing to get pdf output work correctly?

Thanks in advance

Daniele

Il 29.11.2011 19:00, Adam Eskreis ha scritto: 

Why don't you try requesting the images in a tile-based manner so that the requests are managable, and then weave them together in your software? Mapserver isn't intended to pull in tiles that big. You should be able to pull in 2048x2048 tiles just fine.

-Adam

On Tue, Nov 29, 2011 at 10:51 AM, Stephen Woodbridge <woodbri at swoodbridge.com> wrote:

On 11/29/2011 10:02 AM, Daniele Debernardi wrote:

The solution is not pumping up the memory limit of the server, because
if i get 2 request at the same time
I still have memory problem.

It sounds like you have not adequately sized the server for the tasks you are asking it to perform. Mapserver is designed for performance so that it can handle requests quickly and free up the memory it is using for the next request. If you start swapping or paging data to disk that slows down all processes and can overwhelm the system with too many slow requests that are all consuming memory and not exiting as fast as new requests are coming in.

If you are making an enhancement request for say making mapserver use less memory and temporary disk files or swap space at the cost of performance, then you should add a ticket to the tracking system. This is not a short term solution. 

Which is the best way (output format) to generate high resolution map
images with full symbology support?

I defer to Thomas on this one. But he has already mentioned that probably doing something like direct pdf output and converting any pixmap symbols into scalable symbols is the best way to go.

-Steve W 

Il 29.11.2011 15:49, Stephen Woodbridge ha scritto:

On 11/29/2011 3:20 AM, Daniele Debernardi wrote:

Hi,
with mapserver trunk version (but i think with others too) I have to
generate very big map to be imported in a pdf file.
I use php mapscript to generate maps with 300 dpi for an A1/A0 pdf page
or bigger.
This mean that the map has dimensions like 15000x25000 pxl and when I
call the MapObj->draw method i get this error:

PHP Warning: mapObj::draw(): [MapServer Error]: agg2CreateImage():
mapagg.cpp: 708: Out of memory allocating 1550851152 bytes.

Map server is configured with the AGG/PNG driver with imagemode RGBA.

Is it normal that need so much memory to generate the image?

Just for the image buffer you need 15000x25000x4 pixels = 1500,000,000
and AGG might actually allocate a slight larger image buffer so it
does not create edge effects while antialiasing objects close to the
edges. So the above request does not seem unreasonable.

I already tryied the php ini_set memory_limit but with a limit of 2048M
i still have some problem with memory.

Try setting the limit a little higher like to 2564-3072M can see if
your memory problems go away. Of course this assumes you have a system
with a lot of memory.

-Steve W

I checked other possible outputs but generating maps in pdf through
Cairo driver but doc says that polygons filled with symbols are not
supported, and for that reason I cant use it.
SVG output has some limitations too like line drawn without symbols or
pixmap symbols not supported.

Is there a better way to generate so big map images and imported in a
pdf file?

Hope you guys can help me.

Daniele
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