NAME
Gearman::Driver - Manages Gearman workers
SYNOPSIS
package My::Workers::One;
# Yes, you need to do it exactly this way
use base qw(Gearman::Driver::Worker);
use Moose;
# this method will be registered with gearmand as 'My::Workers::One::scale_image'
sub scale_image : Job {
my ( $self, $job, $workload ) = @_;
# do something
}
# this method will be registered with gearmand as 'My::Workers::One::do_something_else'
sub do_something_else : Job : MinProcesses(2) : MaxProcesses(15) {
my ( $self, $job, $workload ) = @_;
# do something
}
# this method wont be registered with gearmand at all
sub do_something_internal {
my ( $self, $job, $workload ) = @_;
# do something
}
1;
package My::Workers::Two;
use base qw(Gearman::Driver::Worker);
use Moose;
# this method will be registered with gearmand as 'My::Workers::Two::scale_image'
sub scale_image : Job {
my ( $self, $job, $workload ) = @_;
# do something
}
1;
package main;
use Gearman::Driver;
my $driver = Gearman::Driver->new(
namespaces => [qw(My::Workers)],
server => 'localhost:4730,otherhost:4731',
interval => 60,
);
$driver->run;DESCRIPTION
Having hundreds of Gearman workers running in separate processes can consume a lot of RAM. Often many of these workers share the same code/objects, like the database layer using DBIx::Class for example. This is where Gearman::Driver comes in handy:
You write some base class which inherits from Gearman::Driver::Worker. Your base class loads your database layer for example. Each of your worker classes inherit from that base class. In the worker classes you can register single methods as jobs with gearmand. It's even possible to control how many workers doing that job/method in parallel. And this is the point where you'll save some RAM: Instead of starting each worker in a separate process Gearman::Driver will fork each worker from the main process. This will take advantage of copy-on-write on Linux and save some RAM.
There's only one mandatory parameter which has to be set when calling the constructor: namespaces
use Gearman::Driver;
my $driver = Gearman::Driver->new( namespaces => [qw(My::Workers)] );See also: namespaces. If you do not set server (gearmand) attribute the default will be used: localhost:4730
Each module found in your namespaces will be loaded and introspected, looking for methods having the 'Job' attribute set:
package My::Workers::ONE;
sub scale_image : Job {
my ( $self, $job, $workload ) = @_;
# do something
}This method will be registered as job function with gearmand, verify it by doing:
plu@mbp ~$ telnet localhost 4730
Trying ::1...
Connected to localhost.
Escape character is '^]'.
status
My::Workers::ONE::scale_image 0 0 1
.
^]
telnet> Connection closed.If you dont like to use the full package name you can also specify a custom prefix:
package My::Workers::ONE;
sub prefix { 'foo_bar_' }
sub scale_image : Job {
my ( $self, $job, $workload ) = @_;
# do something
}This would register 'foo_bar_scale_image' with gearmand.
See also: prefix
ATTRIBUTES
See also "ATTRIBUTES" in Gearman::Driver::Loader.
server
A list of Gearman servers the workers should connect to. The format for the server list is: host[:port][,host[:port]]
See also: Gearman::XS
default:
localhost:4730isa:
Str
console_port
Gearman::Driver has a telnet management console, see also:
default:
47300isa:
Int
Set this to 0 to disable management console at all.
interval
Each n seconds Net::Telnet::Gearman is used in Gearman::Driver::Observer to check status of free/running/busy workers on gearmand. This is used to fork more workers depending on the queue size and the MinProcesses/MaxProcesses attribute of the job method. See also: Gearman::Driver::Worker
default:
5isa:
Int
max_idle_time
Whenever Gearman::Driver::Observer notices that there are more processes running than actually necessary (depending on min_processes and max_processes setting) it will kill them. By default this happens immediately. If you change this value to 300, a process which is not necessary is killed after 300 seconds.
Please remember that this also depends on what value you set "interval" to. The max_idle_time is only checked each n seconds where n is "interval". Besides that it makes only sense when you have workers where "MinProcesses" in Gearman::Driver::Worker is set to 0.
default:
0isa:
Int
logfile
Path to logfile.
isa:
Strdefault:
gearman_driver.log
loglayout
See also Log::Log4perl.
isa:
Strdefault:
[%d] %p %m%n
loglevel
See also Log::Log4perl.
isa:
Strdefault:
INFO
unknown_job_callback
Whenever Gearman::Driver::Observer sees a job that isnt handled it will call this CodeRef, passing following arguments:
$driver$status
my $driver = Gearman::Driver->new(
namespaces => [qw(My::Workers)],
unknown_job_callback => sub {
my ( $driver, $status ) = @_;
# notify nagios here for example
}
);$status might look like:
$VAR1 = {
'busy' => 0,
'free' => 0,
'name' => 'GDExamples::Sleeper::unknown_job',
'queue' => 6,
'running' => 0
};INTERNAL ATTRIBUTES
This might be interesting for subclassing Gearman::Driver.
jobs
Stores all Gearman::Driver::Job instances. The key is the name the job gets registered with gearmand. There are also two methods: get_job and has_job.
Example:
{
'My::Workers::ONE::scale_image' => bless( {...}, 'Gearman::Driver::Job' ),
'My::Workers::ONE::do_something_else' => bless( {...}, 'Gearman::Driver::Job' ),
'My::Workers::TWO::scale_image' => bless( {...}, 'Gearman::Driver::Job' ),
}isa:
HashRefreadonly:
True
observer
Instance of Gearman::Driver::Observer.
isa:
Gearman::Driver::Observerreadonly:
True
console
Instance of Gearman::Driver::Console.
isa:
Gearman::Driver::Consolereadonly:
True
METHODS
add_job
There's one mandatory param (hashref) with following keys:
decode (optionally)
Name of a decoder method in your worker object.
encode (optionally)
Name of a encoder method in your worker object.
method (mandatory)
Reference to a Class::MOP::Method object which will get invoked.
min_processes (mandatory)
Minimum number of processes that should be forked.
max_processes (mandatory)
Maximum number of processes that may be forked.
name (mandatory)
Job name/alias that method should be registered with Gearman.
object (mandatory)
Object that should be passed as first parameter to the job method.
Basically you never really need this method if you use "namespaces". But "namespaces" depend on method attributes which some people do hate. In this case, feel free to setup your $driver this way:
package My::Workers::One;
use Moose;
use JSON::XS;
extends 'Gearman::Driver::Worker::Base';
sub scale_image {
my ( $self, $job, $workload ) = @_;
# do something
}
# this method will be registered with gearmand as 'My::Workers::One::do_something_else'
sub do_something_else {
my ( $self, $job, $workload ) = @_;
# do something
}
sub encode_json {
my ( $self, $result ) = @_;
return JSON::XS::encode_json($result);
}
sub decode_json {
my ( $self, $workload ) = @_;
return JSON::XS::decode_json($workload);
}
1;
package main;
use Gearman::Driver;
use My::Workers::One;
my $driver = Gearman::Driver->new(
server => 'localhost:4730,otherhost:4731',
interval => 60,
);
my $worker = My::Workers::One->new();
foreach my $method (qw(scale_image do_something_else)) {
$driver->add_job(
decode => 'decode_json',
encode => 'encode_json',
max_processes => 5,
method => $worker->meta->find_method_by_name($method)->body,
min_processes => 1,
name => $method,
object => $worker,
);
}
$driver->run;get_jobs
Returns all Gearman::Driver::Job objects ordered by jobname.
run
This must be called after the Gearman::Driver object is instantiated.
shutdown
Sends TERM signal to all child processes and exits Gearman::Driver.
has_job
Params: $name
Returns true/false if the job exists.
get_job
Params: $name
Returns the job instance.
SCRIPT
There's also a script gearman_driver.pl which is installed with this distribution. It just instantiates Gearman::Driver with its default values, having most of the options exposed to the command line using MooseX::Getopt.
usage: gearman_driver.pl [long options...]
--loglevel Log level (default: INFO)
--lib Example: --lib ./lib --lib /custom/lib
--server Gearman host[:port][,host[:port]]
--logfile Path to logfile (default: gearman_driver.log)
--console_port Port of management console (default: 47300)
--interval Interval in seconds (see Gearman::Driver::Observer)
--loglayout Log message layout (default: [%d] %p %m%n)
--namespaces Example: --namespaces My::Workers --namespaces My::OtherWorkersAUTHOR
Johannes Plunien <plu@cpan.org>
CONTRIBUTORS
Uwe Voelker, <uwe.voelker@gmx.de>
COPYRIGHT AND LICENSE
Copyright 2009 by Johannes Plunien
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.