[Gdal-dev] ECW Hanging

[srweal]

Hi,

I'm experiencing intermittent problems running the FWTools 2.2.6 version of
GDAL, including ECW support.  

I'm using the library to render maps (or map tiles) produced using the
SharpMap library, an open-source mapping library written in C#.NET. 
SharpMap access the standard GDAL operations via a wrapper, but this is not
where the problem lies.

I am rendering the ECW maps/tiles out through a web application running
under IIS6.0 and this works fine most of the time, but there are times when
the ECW library hangs.

I've identified this using Process Monitor, which shows that when all is
going well and the ECW files are being read, the calls to GDAL run an
IRP_MJ_CREATE operation on the system kernel to open the files
NCSUtil_fw.dll, NCSEcw_fw.dll.  Then the process seems to read from the
source ECW using gdal_fw.dll.

However, when the rendering hangs and I investigate Process Monitor, all
that gets listed is a 'Thread Create' which runs NCSUtil_fw.dll.  There is
no subsequent references to NCSEcw_fw.dll, gdal_fw.dll or anything similar. 
Instead, this thread stays open and every 40 seconds there are other threads
opened and then closed that just refer to main kernel files (i.e. no ECW
references in them).  This hangs indefinitely, which in turn causes my web
apps to hang (and because no error gets thrown or the process is completely
inactive, automatically rebooting them is tricky). 

I'm trying to understand what is happening when this occurs and would
appreciate some further guidance on what the issue might be here and a
potential way around it.  I had thought it was an issue with using a 64bit
operating system, but have moved all my applications onto 32bit and have
just discovered this problem is still occurring (but not as frequently as on
the 64bit system).  

I would love to hear from anyone who's had issues with the ECW library in a
similar way and got around them (or avoided them somehow).  Unfortunately,
due to file sizes, other file formats like TIF are not feasible.  

Thanks, Steve
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