DBIx::Timeout

DESCRIPTION

This module provides a safe method of timing out DBI requests. An unsafe method is described in the DBI docs:

http://search.cpan.org/~timb/DBI/DBI.pm#Signal_Handling_and_Canceling_Operations

The problem with using POSIX sigaction() is that it relies on unsafe signals to work. Unsafe signals are well known to cause instability. For example, imagine your DB client code is in the middle of updating some global state when the signal arrives. That global state could be left in an inconsitent state, just wait for the next time it is needed to cause problems. Since this will likely occur far from the cause, and only ocur rarely, it can be a very difficult problem to track down.

Instead, this module:

• Forks a child process which sleeps for $timeout seconds.
• Runs your long-running query in the parent process.
• If the parent process finishes first it kills the child and returns.
• If the child process wakes up it kills the parent's DB thread and exits with a code so the parent knows it was timed out.

NOTE: After this call your database connection may be killed even if no timeout occurred. This is due to a race condition - the child may wake up just as parent process finishes. Patches addressing this bug are welcome. Until this is fixed you should be ready to reconnect after call_with_timeout().

DATABASE SUPPORT

This release supports only MySQL. I would appreciate patches from users of other databases. Your patch will need to provide code to kill a running query. In MySQL this uses the KILL command.

PREREQUISITES

DBI 1.49
Test::More
Params::Validate

INSTALLATION

To install this module, run the following commands:

perl Makefile.PL
make
make test
make install

SUPPORT AND DOCUMENTATION

After installing, you can find documentation for this module with the perldoc command.

perldoc DBIx::Timeout

COPYRIGHT AND LICENCE

Copyright (C) 2006 Sam Tregar

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.