[MAPSERVER-USERS] msProcessProjection(): Projection library error.

[Frank Warmerdam]

rich.fromm wrote:
> I'm not sure if anyone is going to be able to be of any help with this, since
> I am not able to consistently reproduce the problem.  Nevertheless, based on
> previous instructions, just in case, I am reporting a rare problem seen
> under
> heavy load.
> 
> I am stress testing a custom webapp using java mapscript.  On several
> occasions, I have observed mapserver logging an error, which caused tomcat
> to
> return a 500 (Internal Server Error), but NOT crash.  The error is as
> follows:
> 
> --- begin ---
> java.lang.UnknownError: msProcessProjection(): Projection library error. no
> system list, errno: 22
> 
>         at edu.umn.gis.mapscript.mapscriptJNI.new_mapObj(Native Method)
>         at edu.umn.gis.mapscript.mapObj.<init>(mapObj.java:288)
> --- end ---

Rich,

Looking at the code in mapfile.c I see:


     msAcquireLock( TLOCK_PROJ );
     if( !(p->proj = pj_init(numargs, args)) ) {
         int *pj_errno_ref = pj_get_errno_ref();
         msReleaseLock( TLOCK_PROJ );
         msSetError(MS_PROJERR, pj_strerrno(*pj_errno_ref),
                    "msProcessProjection()");	
         return(-1);
     }

     msReleaseLock( TLOCK_PROJ );

I suspect the msReleaseLock( TLOCK_PROJ ) ought to be after the
msSetError() instead of before it, though it is also possible this
would introduce a deadlock condition if something else that is
waiting for the PROJ lock already holds the error lock.  You might
want to experiment with this if you are comfortable rebuilding things.

If this sequence turns out to be the issues there are certainly ways
to restructure the code a bit to be safe.

But this wouldn't explain why you are only occationally getting this
error, so I suspect it is a red herring - not your real issue for which
I have no useful advice.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | President OSGeo, http://osgeo.org