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.
