NAME

Schedule::Load::Schedule - Functions for choosing a host among many

SYNOPSIS

use Schedule::Load::Schedule;

my $scheduler = Schedule::Load::Schedule->fetch();
print "Best host for a new job: ", $scheduler->best();

DESCRIPTION

This package will allow the most lightly loaded host to be choosen for new jobs across many machines across a entire network.

It is also a superclass of Schedule::Load::Hosts, so any functions that work for that module also work here.

METHODS

best (...)

Returns the hostname of the best host in the network for a new job.

fixed_load (load=>load_value, [pid=>$$], [host=>localhost])

Sets the current process and all children as always having at least the load value specified. This prevents undercounting CPU utilization when a large batch job is running which is just paused in the short term to do disk IO or sleep.

hold_release (hold_key=>key)

Releases the temporary hold placed with the best function.

hosts_of_class (class=>name)

Returns Schedule::Load::Hosts::Host objects for every host that matches the given class.

jobs (...)

Returns the maximum number of jobs suggested for the given scheduling parameters. Presumably this will be used to spawn parallel jobs for one given user, such as the make -j command. Jobs() takes the same arguments as best(), in addition to the max_jobs parameter.

release (host=>hostname)

Releases the machine from exclusive use of any user. The user doing the release does not have to be the same user that reserved the host.

reserve (host=>hostname, [comment=>comment])

Reserves the machine for exclusive use of the current user. The host choosen must have the reservable flag set. rschedule hosts will show the host as reserved, along with the provided comment.

PARAMETERS

Parameters for the new and fetch calls are shown in Schedule::Load::Hosts.

allow_none

If allow_none is true, if there is less then a free CPU across the entire network, then no cpu will be choosen. This is useful for programs that can dynamically adjust their outstanding job count. (Presumably you would only set allow_none if you already have one job running, or you can get livelocked out of getting anything!)

classes

An array reference of which classes the host must support to allow this job to be run on that host. Defaults to [], which allows any host.

favor_host

The hostname to try and choose if all is equal, under the presumption that there are disk access time benefits to doing so. Defaults to the current host.

hold_key

A hold key will reserve a job slot on the choosen CPU until a release_hold function is called. This prevents overscheduling a host due to the delay between choosing a host with a light load and starting the job on it which rases the CPU load of that choosen host.

hold_time

Number of seconds to allow the hold to remain before being removed automatically.

hold_load

Number of cpu loads the hold_key should reserve, defaults to one.

max_jobs

Maximum number of jobs that jobs() can return. Defaults to 6 jobs during the day, unlimited at night.

night_hours_cb

Reference to Function for determining if this is night time, defaults to M-F 6am-10pm. When it is nighttime hours, every class passed to the best option has a new class with _night appended.

SEE ALSO

Schedule::Load, Schedule::Load::Hosts, rschedule

DISTRIBUTION

The latest version is available from CPAN.

AUTHORS

Wilson Snyder <wsnyder@wsnyder.org>