[mapguide-internals] Raster provider problems...

[Robert Bray]

Ah thats too bad. I thought there was some way to limit the upper 
connection limit on a per provider basis.

Bob

Bruce Dechant wrote:
> Limiting the pooling to 1 won't solve this as the server will simply use un unpooled connection on the 2nd GDAL request if the 1st is already in use.
>  
> Bruce
> 
> 	-----Original Message----- 
> 	From: mapguide-internals-bounces at lists.osgeo.org on behalf of Robert Bray 
> 	Sent: Sat 4/7/2007 12:03 AM 
> 	To: MapGuide Internals Mail List 
> 	Cc: 
> 	Subject: Re: [mapguide-internals] Raster provider problems...
> 	
> 	
> 
> 	Yea, guess you are right. For the vetted providers it could be marked
> 	per connection threaded, but we cannot blindly mark it that way.
> 	
> 	So that means there can never be more than one instance of the GDAL
> 	provider in use within the server. I wonder if we simply limit pooling
> 	on that provider to 1 if that would do the trick.
> 	
> 	Bruce what do you think?
> 	
> 	Bob
> 	
> 	Frank Warmerdam wrote:
> 	> 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,
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> 
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