NAME

Sys::RunUntil - make sure script only runs for the given time

VERSION

This documentation describes version 0.05.

SYNOPSIS

 use Sys::RunUntil '30mW';
 # code which may only take 30 minutes to run

 use Sys::RunUntil '30sC';
 # code which may only take 30 seconds of CPU time

DESCRIPTION

Provide a simple way to make sure the script from which this module is loaded, is running only for either the given wallclock time or a maximum amount of CPU time.

METHODS

There are no methods.

RUNTIME SPECIFICATION

The maximum runtime of the script can be specified in seconds, or with any combination of the following postfixes:

 - S seconds
 - M minutes
 - H hours
 - D days

The string "1H30M" would therefor indicate a runtime of 5400 seconds.

The letter C indicates that the runtime is specified in CPU seconds used. The (optional) letter W indicates that the runtime is specified in wallclock time.

THEORY OF OPERATION

The functionality of this module basically depends on alarm and fork, with some pipes and selects mixed in when checking for CPU time.

Wallclock Time

When the "import" class method is called (which happens automatically with use), that method forks the process and sets an alarm in the parent process and waits for the child process to return. If the process returns before the alarm is activated, that's ok. If the alarm is triggered, it means that the child process is taking to long: the parent process will then kill the child by sending it a TERM (15) signal and exit.

CPU time

When the "import" class method is called (which happens automatically with use), that method creates a pipe and forks the process. In the child process a signal handler is installed on the INFO (29) signal which prints the total CPU time used on the pipe to the parent. The parent then waits for the minimum amount of time that would need to expire before the CPU limit in the child process is reached. It then sends the INFO signal to the child process to obtain the amount of CPU used by the child. The parent then decides to wait longer or to kill the child process by sending it a TERM (15) signal.

REQUIRED MODULES

 (none)

SEE ALSO

Sys::RunAlone, Sys::RunAlways.

AUTHOR

 Elizabeth Mattijsen

COPYRIGHT

Copyright (c) 2005, 2012 Elizabeth Mattijsen <liz@dijkmat.nl>. All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.