NAME

Gearman::JobScheduler::AbstractFunction - An abstract class for a Gearman "function" which is to be derived by working Gearman "functions".

LINGO

• Gearman function

  A function to be run by Gearman or locally, e.g. add_default_feeds.

• Gearman job

  An instance of the Gearman function doing the actual job with specific parameters.

ABSTRACT INTERFACE

The following subroutines must be implemented by the subclasses of this class.

REQUIRED

run($self, $args)

Run the job.

Parameters:

• $self, a reference to the instance of the Gearman function class
• (optional) $args (hashref), arguments needed for running the Gearman function

An instance (object) of the class will be created before each run. Class instance variables (e.g. $self->_my_variable) will be discarded after each run.

Returns result on success (serializable by the Storable module). The result will be discarded if the job is ordered on Gearman as a background process.

Provides progress reports when available:

• by calling $self->set_progress($numerator, $denominator)

die()s on error.

Writes log to STDOUT or STDERR (preferably the latter).

OPTIONAL

(static) timeout()

Return the timeout of each job.

Returns the timeout (in seconds) of each job or 0 if there's no timeout.

Default implementation of this subroutine returns 0 (no timeout).

(static) retries()

Return the number of retries for each job.

Returns a number of retries each job will be attempted at. For example, if the number of retries is set to 3, the job will be attempted 4 four times in total.

Returns 0 if the job should not be retried (attempted only once).

Default implementation of this subroutine returns 0 (no retries).

(static) unique()

Return true if the function is "unique" (only for Gearman requests).

Returns true if two or more jobs with the same parameters can not be run at the same and instead should be merged into one.

Default implementation of this subroutine returns "true".

(static) notify_on_failure()

Return true if the client / worker should send error report by email when the function fails.

Returns true if the GJS client (in case run_locally() is used) or worker (in case run_on_gearman() or enqueue_on_gearman() is being used) should send an email when the function fails to run.

Default implementation of this subroutine returns "true".

(static) priority()

Return priority of the job ("low", "normal" or "high"). This will influence Gearman's queueing mechanism and prioritize "high priority" jobs.

Returns one of the three constants:

• GJS_JOB_PRIORITY_LOW(), if the job is considered of "low priority".
• GJS_JOB_PRIORITY_NORMAL() if the job is considered of "normal priority".
• GJS_JOB_PRIORITY_HIGH() if the job is considered of "high priority".

Default implementation of this subroutine returns GJS_JOB_PRIORITY_NORMAL() ("normal priority" job).

HELPER SUBROUTINES

The following subroutines can be used by the deriving class.

$self->set_progress($numerator, $denominator)

Provide progress report while running the task (from run()).

Examples:

• $self->set_progress(3, 10)

  3 out of 10 subtasks are complete.

• $self->set_progress(45, 100)

  45 out of 100 subtasks are complete (or 45% complete).

CLIENT SUBROUTINES

The following subroutines can be used by "clients" in order to issue a Gearman function.

(static) $class->run_locally([$args, $config])

Run locally and right away, blocking the parent process until it gets finished.

Parameters:

• (optional) $args (hashref), arguments required for running the Gearman function (serializable by the Storable module)
• (optional) instance of Gearman::JobScheduler::Configuration to be used by the worker
• (optional, internal) instance of Gearman::XS::Job to be later used by send_progress()

Returns result (may be false of undef) on success, die()s on error

(static) $class->run_on_gearman([$args, $config])

Run on Gearman, wait for the task to complete, return the result; block the process until the job is complete.

Parameters:

• (optional) $args (hashref), arguments needed for running the Gearman function (serializable by the Storable module)
• (optional) Instance of Gearman::JobScheduler::Configuration to be used by the client.

Returns result (may be false of undef) on success, die()s on error

(static) $class->enqueue_on_gearman([$args, $config])

Enqueue on Gearman, do not wait for the task to complete, return immediately; do not block the parent process until the job is complete.

Parameters:

• (optional) $args (hashref), arguments needed for running the Gearman function (serializable by the Storable module)
• (optional) Instance of Gearman::JobScheduler::Configuration to be used by the client.

Returns Gearman-provided string job identifier (Gearman job ID) if the job was enqueued successfully, die()s on error.

TODO

• code formatting
• test timeout
• store Gearman queue in PostgreSQL?
• unit tests
• remove the requirement to pass a function name parameter to log_path_for_gearman_job()