Index

NAME

Gearman::Driver::Worker - Base class for workers

SYNOPSIS

    package My::Worker;

    use base qw(Gearman::Driver::Worker);
    use Moose;

    sub begin {
        my ( $self, $job, $workload ) = @_;
        # called before each job
    }

    sub prefix {
        # default: return ref(shift) . '::';
        return join '_', split /::/, __PACKAGE__;
    }

    sub do_something : Job : MinProcesses(2) : MaxProcesses(15) {
        my ( $self, $job, $workload ) = @_;
        # $job => Gearman::XS::Job instance
    }

    sub end {
        my ( $self, $job, $workload ) = @_;
        # called after each job
    }

    sub spread_work : Job {
        my ( $self, $job, $workload ) = @_;

        my $gc = Gearman::XS::Client->new;
        $gc->add_servers( $self->server );

        $gc->do_background( 'some_job_1' => $job->workload );
        $gc->do_background( 'some_job_2' => $job->workload );
        $gc->do_background( 'some_job_3' => $job->workload );
        $gc->do_background( 'some_job_4' => $job->workload );
        $gc->do_background( 'some_job_5' => $job->workload );
    }

    1;

ATTRIBUTES

server

Gearman::Driver connects to the server passed to its constructor. This value is also stored in this class. This can be useful if a job uses Gearman::XS::Client to add another job. See 'spread_work' method in SYNOPSIS above.

METHODATTRIBUTES

Job

This will register the method with gearmand.

MinProcesses

Minimum number of processes working parallel on this job/method.

MaxProcesses

Maximum number of processes working parallel on this job/method.

Encode

This will automatically look for a method encode in this object which has to be defined in the subclass. It will call the encode method passing the return value from the job method. The return value of the encode method will be returned to the Gearman client. This is useful to serialize Perl datastructures to JSON before sending them back to the client.

    sub do_some_job : Job : Encode : Decode {
        my ( $self, $job, $workload ) = @_;
        return { message => 'OK', status => 1 };

        # calls 'encode' and returns JSON string: {"status":1,"message":"OK"}
    }

    sub custom_encoder : Job : Encode(enc_yaml) : Decode(dec_yaml) {
        my ( $self, $job, $workload ) = @_;
        return { message => 'OK', status => 1 };

        # calls 'enc_yaml' and returns YAML string:
        # ---
        # message: OK
        # status: 1
    }

    sub encode {
        my ( $self, $result ) = @_;
        return JSON::XS::encode_json($result);
    }

    sub decode {
        my ( $self, $workload ) = @_;
        return JSON::XS::decode_json($workload);
    }

    sub enc_yaml {
        my ( $self, $result ) = @_;
        return YAML::XS::Dump($result);
    }

    sub dec_yaml {
        my ( $self, $workload ) = @_;
        return YAML::XS::Load($workload);
    }

Decode

This will automatically look for a method decode in this object which has to be defined in the subclass. It will call the decode method passing the workload value ($job->workload). The return value of the decode method will be passed as 3rd argument to the job method. This is useful to deserialize JSON workload to Perl datastructures for example. If this attribute is not set, $job->workload and $workload is the same.

Example, workload is this string: {"status":1,"message":"OK"}

    sub decode {
        my ( $self, $workload ) = @_;
        return JSON::XS::decode_json($workload);
    }

    sub job1 : Job {
        my ( $self, $job, $workload ) = @_;
        # $workload eq $job->workload eq '{"status":1,"message":"OK"}'
    }

    sub job2 : Job : Decode {
        my ( $self, $job, $workload ) = @_;
        # $workload ne $job->workload
        # $job->workload eq '{"status":1,"message":"OK"}'
        # $workload = { status => 1, message => 'OK' }
    }

ProcessGroup

Forking each job method in an own process may not always be the way to go. It's possible to run many job methods in a single process by defining ProcessGroup attribute. This process group alias will also show up in Gearman::Driver::Console instead of the single method names. The workers process name will also be affected.

    sub process_name {
        my ( $self, $orig, $job_name ) = @_;
        return "$orig ($job_name)";
    }

    sub scale_image : Job : ProcessGroup(image_worker) {
        my ( $self, $job, $workload ) = @_;
    }

    sub convert_image : Job : ProcessGroup(image_worker) {
        my ( $self, $job, $workload ) = @_;
    }

    # $ ~/Gearman-Driver$ ps ux|grep image_worker
    # plu   2608   0.0  0.1  2466720   4200 s001  S    12:46PM   0:00.01 script/gearman_driver.pl (XxX::image_worker)

    # $ ~/Gearman-Driver$ telnet localhost 47300
    # Trying ::1...
    # telnet: connect to address ::1: Connection refused
    # Trying fe80::1...
    # telnet: connect to address fe80::1: Connection refused
    # Trying 127.0.0.1...
    # Connected to localhost.
    # Escape character is '^]'.
    # status
    # XxX::image_worker  1  1  1  1970-01-01T00:00:00  1970-01-01T00:00:00

It's possible to combine ProcessGroup and MinProcesses + MaxProcesses. But there's one small caveat: Because one single process shares many methods, you can only set the min/max process amount once per ProcessGroup:

    sub scale_image : Job : ProcessGroup(image_worker) : MinProcesses(5) : MaxProcesses(10) {
        my ( $self, $job, $workload ) = @_;
    }

    sub convert_image : Job : ProcessGroup(image_worker) {
        my ( $self, $job, $workload ) = @_;
    }

If you do not obey this restriction, Gearman::Driver will barf:

    sub scale_image : Job : ProcessGroup(image_worker) : MinProcesses(5) : MaxProcesses(10) {
        my ( $self, $job, $workload ) = @_;
    }

    sub convert_image : Job : ProcessGroup(image_worker) : MinProcesses(6) : MaxProcesses(12) {
        my ( $self, $job, $workload ) = @_;
    }

MinProcesses redefined in ProcessGroup(image_worker) at XxX::convert_image at lib/Gearman/Driver.pm line 850.

METHODS

prefix

Having the same method name in two different classes would result in a clash when registering it with gearmand. To avoid this, all jobs are registered with the full package and method name (e.g. My::Worker::some_job). The default prefix is ref(shift . '::'), but this can be changed by overriding the prefix method in the subclass, see SYNOPSIS above.

begin

This method is called before a job method is called. In this base class this methods just does nothing, but can be overridden in a subclass.

The parameters are the same as in the job method:

* $self
* $job

end

This method is called after a job method has been called. In this base class this methods just does nothing, but can be overridden in a subclass.

The parameters are the same as in the job method:

* $self
* $job

process_name

If this method is overridden in the subclass it will change the process name after a job has been forked.

The following parameters are passed to this method:

* $self
* $orig - the original process name ( $0 )
* $job_name - the name of the job

Example:

    sub process_name {
        my ( $self, $orig, $job_name ) = @_;
        return "$orig ($job_name)";
    }

This may look like:

    plu       2034  0.0  1.7  22392 17948 pts/2    S    21:17   0:00 gearman_driver.pl (GDExamples::Convert::convert_to_jpeg)
    plu       2035  0.0  1.7  22392 17944 pts/2    S    21:17   0:00 gearman_driver.pl (GDExamples::Convert::convert_to_gif)

override_attributes

If this method is overridden in the subclass it will change all attributes of your job methods. It must return a reference to a hash containing valid attribute keys. E.g.:

    sub override_attributes {
        return {
            MinProcesses => 1,
            MaxProcesses => 1,
        }
    }

    sub job1 : Job : MinProcesses(10) : MaxProcesses(20) {
        my ( $self, $job, $workload ) = @_;
        # This will get MinProcesses(1) MaxProcesses(1) from override_attributes
    }

default_attributes

If this method is overridden in the subclass it can supply default attributes which are added to all job methods. This is useful if you want to Encode/Decode all your jobs:

    sub default_attributes {
        return {
            Encode => 'encode',
            Decode => 'decode',
        }
    }

    sub decode {
        my ( $self, $workload ) = @_;
        return JSON::XS::decode_json($workload);
    }

    sub encode {
        my ( $self, $result ) = @_;
        return JSON::XS::encode_json($result);
    }

    sub job1 : Job {
        my ( $self, $job, $workload ) = @_;
    }

AUTHOR

See Gearman::Driver.

COPYRIGHT AND LICENSE