Is it possible that the error is related to something else?

No.

By default, Perl can open 2048 files concurrently. Excluding the 3 standard files (stdin,stdout,stderr) that leaves 2045 for program use:

perl -E"say(),open $fh[$_], '>', qq[file$_] or die $! for 1 .. 1e5"
1
2
3
...
2040
2041
2042
2043
2044
2045
2046
Too many open files at -e line 1.
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Any tips on how to debug this?

You could modify all the open and close lines something like this:

open $fh, .... or die ...;
close $fh;
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To

open $fh, ... and printf( LOG "%s(%u) opening %u\n", __FILE__, __LINE_
+_, fileno( $fh ) ) or die ...;
printf( LOG "%s(%u) closing %u\n", __FILE__, __LINE__, fileno( $fh ) )
+ and close $fh;
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Once the program fails it should be simple to find which opens do not have or are not reaching their associated close statements.

Have you checked OS (you don't say which version) documentaiton for limits on such things? Has the user hit a resource limit? Perhaps there is something wrong with your code, or it's not doing what you think. Have you attempted to debug your code while recreating the problem? Tutorials -> Debugging and Optimization.

Thanks marto for the reply.

The application is used for batch processing, so the user had 2700 objects (files) to process, and it's the repeated processing of these objects that cause the failure. The user is using windows 7.

I'm almost certain that our code is wrong, but am not sure where to start debugging. Creating a repeatable case is difficult as the objects that the user are using are sensitive. I've tested the app at the high level (process monitor and explorer) and I can't see a file handle leak so I was hoping to do something at the perl level?

Probably you already thought of this, but just in case: even if the opens and closes are paired you will run into trouble if you have too many files open concurrently - you open new files while old files are still open. A subtle way that could happen is if you have recursion (perhaps by accident) so check sub calls for that possibility.

Thanks to all who replied, your suggestions were much appreciated.

For any one who reads this thread in the future:

The user's data (once we got a copy) was causing recoverable failures which left file handles open (in XS code).

improve the bug reporting to detect bugs in your bug reporting ?

try to duplicate the problem?

$ perl -le " print $!=$_ for 23 .. 24 "
Too many open files in system
Too many open files
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