[mapserver-users] Designing a wrapper around mapserv which can be used with fcgi

[Andy Colson]

> Andy Colson wrote:
>> Adrian Popa wrote:
>>> Hello everyone,
>>>
>>> I am currently using a wrapper around mapserv which receives the URL 
>>> parameters, builds the map file (actually I only need to set some 
>>> filters in the map file, but the filters need to be built after 
>>> running some SQL queries with the passed in parameters). After the 
>>> map file is built, mapserv is called (as a shell script), and the map 
>>> gets sent to the user. Currently this wrapper is written in perl - so 
>>> it's not terribly fast as a cgi process.
>>>
>>> While this approach works, it is terribly inefficient. I would like 
>>> to use mapserv as a fcgi process (or something faster than plain 
>>> cgi). My question is - how can I /should I build a wrapper around 
>>> mapserv that can "customize" the MAP file on the fly and run as a 
>>> fcgi process?
>>>
>>> Any ideas on where I should start? An example of such a wrapper?
>>>
>>> Also, I suspect I can send parameters to mapserver and use some sort 
>>> of variables in the map file to set up my filters - but I haven't 
>>> seen an example. Can someone point me to such a documentation?
>>>
>>> Thanks,
>>> Adrian
>>
>> Have you seen mapscript?  You can use mapserver directly from perl.  
>> And perl can do fast-cgi.  Here is a little, ad-hoc, non-tested, perl 
>> fcgi:
>>
>>
>> #!/usr/bin/perl
>>
>> use strict;
>> use mapscript;
>> use FCGI;
>>
>>
>> my $request = FCGI::Request( );
>> while($request->Accept() >= 0)
>> {
>>         my($req, $x, $at, $xmap, $xpin, $sid, $y, $q);
>>
>>         $req = new mapscript::OWSRequest();
>>         $req->loadParams();
>>
>>         $xmap = $req->getValueByName('map');
>>         $xpin = $req->getValueByName('pin');
>>
>>         my $map = new mapscript::mapObj( "/maps/$xmap.map" );
>>         if (! $map)
>>         {
>>                 #print STDERR "----- Error loading map: $xmap.map\n";
>>                 print("Content-type: text/text\r\n\r\n");
>>                 print "cant load $xmap.map";
>>                 $request->Finish();
>>                 next;
>>         }
>>
>>         mapscript::msIO_installStdoutToBuffer();
>>
>>         $x = $map->OWSDispatch( $req );
>>         if ($x)
>>         {
>>                 print STDERR "OWSDispatch: $x\n";
>>                 my $errObj = new mapscript::errorObj();
>>                 while ($errObj) {
>>                         print STDERR "ERROR: 
>> $errObj->{code}:$errObj->{message}:$errObj->{routine} \n";
>>                         $errObj = $errObj->next();
>>                 }
>>         }
>>
>>         my $content_type = 
>> mapscript::msIO_stripStdoutBufferContentType();
>>
>>         $x = mapscript::msIO_getStdoutBufferBytes();
>>
>>
>>         print("Content-type: $content_type\r\n\r\n");
>>         if (mapscript::msGetVersionInt() >= 50500)
>>         {
>>                 print $$x;
>>         } else {
>>                 print $x;
>>         }
>>
>>         mapscript::msIO_resetHandlers();
>>         $request->Finish();
>> }
>>
>>
>>
>> I'd recommend using mapserver 5.6.0.
>>
>> -Andy
>>
> 

Adrian Popa wrote:
 > Thank you,
 >
 > I will look into it. I guess through mapscript I can redefine the
 > parameters that get sent to mapserver? Or do I rewrite the whole map?
 >


You can load a map into memory (I assume you were already doing that). 
You said "..perl.. receives the URL parameters ...and... builds the map 
file".


I assume your perl does: use mapscript?

and at some point: my $map = new mapscript::mapObj( "/maps/$xmap.map" );

You kind of imbed mapserver into your perl script, and can call its 
functions and what not.  After you load the map you can do things to it, 
in memory.

In my example above, I'm using the WMS features ($map->OWSDispatch), but 
you can also generate an image:

my $img = $map->draw();
$img->save('x.jpg', $mapscript::MS_JPG);

-Andy