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,
);
#or should save all config into a YAML config file, then read config from it.
my $driver = Gearman::Driver->new(configfile => '/etc/gearman-driver/config.yml');
$driver->run;
DESCRIPTION
Warning: This framework is still EXPERIMENTAL!
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
console_port
Gearman::Driver has a telnet management console, see also:
Gearman::Driver::Console
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
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.
logfile
Path to logfile.
loglayout
See also Log::Log4perl.
loglevel
See also Log::Log4perl.
unknown_job_callback
Whenever Gearman::Driver::Observer sees a job that isnt handled it will
call this CodeRef, passing following arguments:
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::Convert::unknown_job',
'queue' => 6,
'running' => 0
};
worker_options
You can pass runtime options to the worker module, these will pass to
the worker constructor.
has worker_options => (
default => sub {
{
'My::App::Worker::MysqlPing' => {
'dsn' => 'DBI:mysql:database=test;host=localhost;mysql_auto_reconnect=1;mysql_enable_utf8=1;mysql_server_prepare=1;',
},
'My::App::Worker::ImageThumbnail' => {
'default_format' => 'jpeg',
'default_size => '133x100',
}
}
}
);
You should define these in a runtime config (See also "configfile"), might be:
---
worker_options:
'My::App::Worker::MysqlPing':
'dsn': 'DBI:mysql:database=test;host=localhost;mysql_auto_reconnect=1;mysql_enable_utf8=1;mysql_server_prepare=1;'
'user': 'root'
'password:': ''
'My::App::Worker::ImageThumbnail':
'default_format': 'jpeg'
'default_size': '133x100'
Job runtime attributes
You can override a job attribute by its name here. This help to tuning
job some runtime-related options (like max_processes, min_processes)
handy. You just change the options in a config file, no need to modify
the worker code anymore.
Currently only 'max_processes', 'min_processes' make sense. The hash key is "worker_module::job_key", job_key is ProcessGroup attribute or job method name.
max_processes: 25 min_processes: 2 #job has a ProcessGroup attribute named 'group1' 'My::App::Worker::group1':
max_processes: 10 min_processes: 2 #then run as: gearman_driver.pl --configfile /etc/gearman_driver.yml
configfile
Runtime config file path, You can provide a default configfile pathname
like so:
has +configfile ( default => '/etc/gearman-driver.yaml' );
You can pass an array of filenames if you want, like:
has +configfile ( default => sub { [ '/etc/gearman-driver.yaml','/opt/my-app/etc/config.yml' ] });
INTERNAL ATTRIBUTES
This might be interesting for subclassing Gearman::Driver.
jobs
Stores all Gearman::Driver::Job instances. There are also two methods:
{
'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' ),
}
observer
Instance of Gearman::Driver::Observer.
console
Instance of Gearman::Driver::Console.
METHODS
add_job
There's one mandatory param (hashref) with following keys:
Maximum number of processes that may be forked.
Minimum number of processes that should be forked.
Job name/alias that method should be registered with Gearman.
ArrayRef of HashRefs containing following keys:
CodeRef to the job method.
The name this method should be registered with gearmand.
Name of a decoder method in your worker object.
Name of a encoder method in your worker object.
Worker 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" depends 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';
# this method will be registered with gearmand as 'My::Workers::One::scale_image'
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, $result ) = @;
return JSON::XS::encodejson($result);
}
sub decode_json {
my ( $self, $workload ) = @;
return JSON::XS::decodejson($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();
# run each method in an own process
foreach my $method (qw(scale_image do_something_else)) {
$driver->add_job(
{
max_processes => 5,
min_processes => 1,
name => $method,
worker => $worker,
methods => [
{
body => $w1->meta->find_method_by_name($method)->body,
decode => 'decode_json',
encode => 'encode_json',
name => $method,
},
]
}
);
}
# share both methods in a single process
$driver->add_job(
{
max_processes => 5,
min_processes => 1,
name => 'some_alias',
worker => $worker,
methods => [
{
body => $w1->meta->find_method_by_name('scale_image')->body,
decode => 'decode_json',
encode => 'encode_json',
name => 'scale_image',
},
{
body => $w1->meta->find_method_by_name('do_something_else')->body,
decode => 'decode_json',
encode => 'encode_json',
name => 'do_something_else',
},
]
}
);
$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::OtherWorkers
--configfile Read options from this file. Example: --configfile ./etc/gearman-driver-config.yml
AUTHOR
Johannes Plunien <plu@cpan.org>
CONTRIBUTORS
Uwe Voelker, <uwe.voelker@gmx.de>
Night Sailer <nightsailer@gmail.com>
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.
SEE ALSO
REPOSITORY
<http://github.com/plu/gearman-driver/> <http://github.com/nightsailer/gearman-driver/>