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

[Adrian Popa]

Thank you Andy for explaining.

Actually my wrapper is very hard-core, meaning I don't use mapscript 
(because I had to build it quickly and didn't have time to research 
which was the best approach). Now I have more time and I'd like to tune 
things up, so I will definitely start studying mapscript (If you have a 
link to a good tutorial/function reference for it I am in your debt).

My wrapper just copied over a template map file, edited it (rewrites 
some filters) and then it set
$ENV{'QUERY_STRING'} = $ENV{'QUERY_STRING'}."&map=$file";

...and then called

print `/var/www/cgi-bin/mapserv`;


It's barbaric, I know, but it worked for me. :)
It will take a bit of rewrite to add fcgi support and mapscript, but in 
the long run it will be more mantainable... :)

Thanks again,
Adrian

Andy Colson wrote:
>> 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
>


-- 
--- 
Adrian Popa
NOC Division
Network Engineer
Divizia Centrul National de Operare Retea
Departament Transport IP & Metro
Compartiment IP Core & Backbone
Phone: +40 21 400 3099