[mapguide-internals] Raster provider problems...

[Frank Warmerdam]

Robert Bray wrote:
> Frank,
> 
> Yes I am suggesting the server should take responsibility. At the same 
> time I wonder if GDAL is not per connection thread safe. What that means 
> is that the server will never use the same connection to GDAL on more 
> than one thread at any give time.
> 
> When you say GDALDataSet you mean the C++ object right? 

Yes

 > Is a single
> instance of that ever shared between FDO Connection objects? If not then 
>  the GDAL Provider can be marked as "Per Connection Threaded".
> 
> The server as designed today will never assign an FDO Connection object 
> to more than one thread at a time.

Frank wrote:
>> I will note that GDAL is threadsafe under certain restricted 
>> circumstances:
>>
>>  o Using only threadsafe vetted drivers (ie. GeoTIFF, HFA).
>>  o Only having a single thread touch any given GDALDataset at any
>>    one time.

So, to reiterate, GDAL could be marked as per connection threaded if
we know that only vetted drivers were going to be used.  But GDAL has
many format drivers, most of which have not been meaningfully vetted
for multi-thread safety.

Best regards,
-- 
---------------------------------------+--------------------------------------
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