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This queue is for tickets about the AnyData CPAN distribution.

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The Basics
Id: 19223
Status: new
Priority: 0/
Queue: AnyData

People
Owner: Nobody in particular
Requestors: zmousm [...] admin.grnet.gr
Cc:
AdminCc:

Bug Information
Severity: Important
Broken in: 0.10
Fixed in: (no value)



Subject: adExport to XML hangs while flock($fh, LOCK_EX)
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I experienced this while attempting to adExport from an in-memory ARRAY table to an XML file. Calling adExport($arraytable, "XML", $filename) hangs indefinitely. Running my program through a debugger I noticed that Perl is waiting for flock($fh, LOCK_EX), which happens in AnyData::Storage::File::open_local_file, line 104. The complete stack trace at this point looks like this: $ = AnyData::Storage::File::open_local_file(ref(AnyData::Storage::PassThru), '/home/zmousm/rstab.xml', 'o') called from file `/usr/lib/perl5/site_perl/5.8.5/AnyData/Format/XML.pm' line 876 @ = AnyData::Format::XML::export(ref(AnyData::Format::XML), ref(AnyData::Storage::PassThru), '/home/zmousm/rstab.xml') called from file `/usr/lib/perl5/site_perl/5.8.5/AnyData.pm' line 100 @ = AnyData::export(ref(AnyData), '/home/zmousm/rstab.xml') called from file `/usr/lib/perl5/site_perl/5.8.5/AnyData.pm' line 664 @ = AnyData::adConvert('adHash', ref(AnyData), 'XML', '/home/zmousm/rstab.xml', undef, undef) called from file `/usr/lib/perl5/site_perl/5.8.5/AnyData.pm' line 608 @ = AnyData::adExport(ref(HASH), 'XML', '/home/zmousm/rstab.xml') called from file `/home/zmousm/rgrWalk.pl' line 271 While stepping through the calling stack, I realized this happens because Perl has already opened this file and obtained an exclusive lock on $fh. This happens because: my $target_ad = adTable( $target_format,$target_file_name,'o',undef,$target_flags ); is called, in AnyData::adConvert, line 649. Once again, the stack trace at the time this (first) lock is obtained looks like this: $ = AnyData::Storage::File::open_local_file(ref(AnyData::Storage::PassThru), '/home/zmousm/rstab.xml', 'o') called from file `/usr/lib/perl5/site_perl/5.8.5/AnyData/Format/XML.pm' line 876 @ = AnyData::Format::XML::export(ref(AnyData::Format::XML), ref(AnyData::Storage::PassThru), '/home/zmousm/rstab.xml') called from file `/usr/lib/perl5/site_perl/5.8.5/AnyData.pm' line 100 @ = AnyData::export(ref(AnyData), '/home/zmousm/rstab.xml') called from file `/usr/lib/perl5/site_perl/5.8.5/AnyData.pm' line 664 @ = AnyData::adConvert('adHash', ref(AnyData), 'XML', '/home/zmousm/rstab.xml', undef, undef) called from file `/usr/lib/perl5/site_perl/5.8.5/AnyData.pm' line 608 @ = AnyData::adExport(ref(HASH), 'XML', '/home/zmousm/rstab.xml') called from file `/home/zmousm/rgrWalk.pl' line 271 A few lines after the previous call to adTable, AnyData::export is called, which subsequently calls AnyData::Format::XML::export, but this last function ignores the already open file handle, available at $storage->{fh}, overwriting $fh by reopening the file at line 876, as shown in the first trace. In order to fix this, I believe there are a couple of possibilities: 1) The adTable call should restrict itself to a shared lock, opening the file read-only, since it seems it only wants to prepare $target_ad and it is not going to write to the file yet. 2) The file handle should be closed before opening the file again, at some time between the two calls to adTable and export. 3) AnyData::Format::XML::export should check if the file is already open before attempting to open it again. I'm sorry for not providing a patch, but my knowledge of Perl and specifically my familiarity with the complex data structures in AnyData code is far too limited, in other words I am totally lost wrt the implications applying any of the above fixes may have. I hope this (first) bug report makes sense ;)


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