NAME¶
TheSchwartz - reliable job queue
SYNOPSIS¶
# MyApp.pm
package MyApp;
sub work_asynchronously {
my %args = @_;
my $client = TheSchwartz->new( databases => $DATABASE_INFO );
$client->insert('MyWorker', \%args);
}
# myworker.pl
package MyWorker;
use base qw( TheSchwartz::Worker );
sub work {
my $class = shift;
my TheSchwartz::Job $job = shift;
print "Workin' hard or hardly workin'? Hyuk!!\n";
$job->completed();
}
package main;
my $client = TheSchwartz->new( databases => $DATABASE_INFO );
$client->can_do('MyWorker');
$client->work();
DESCRIPTION¶
TheSchwartz is a reliable job queue system. Your application can put jobs into
the system, and your worker processes can pull jobs from the queue atomically
to perform. Failed jobs can be left in the queue to retry later.
Abilities specify what jobs a worker process can perform. Abilities are
the names of "TheSchwartz::Worker" subclasses, as in the synopsis:
the "MyWorker" class name is used to specify that the worker script
can perform the job. When using the "TheSchwartz" client's
"work" functions, the class-ability duality is used to automatically
dispatch to the proper class to do the actual work.
TheSchwartz clients will also prefer to do jobs for unused abilities before
reusing a particular ability, to avoid exhausting the supply of one kind of
job while jobs of other types stack up.
Some jobs with high setup times can be performed more efficiently if a group of
related jobs are performed together. TheSchwartz offers a facility to
coalesce jobs into groups, which a properly constructed worker can find
and perform at once. For example, if your worker were delivering email, you
might store the domain name from the recipient's address as the coalescing
value. The worker that grabs that job could then batch deliver all the mail
for that domain once it connects to that domain's mail server.
USAGE¶
"TheSchwartz->new( %args )"¶
Optional members of %args are:
- •
- "databases"
An arrayref of database information. TheSchwartz workers can use multiple
databases, such that if any of them are unavailable, the worker will
search for appropriate jobs in the other databases automatically.
Each member of the "databases" value should be a hashref
containing:
- •
- "dsn"
The database DSN for this database.
- •
- "user"
The username to use when connecting to this database.
- •
- "pass"
The password to use when connecting to this database.
- •
- "verbose"
A value indicating whether to log debug messages. If "verbose" is
a coderef, it is called to log debug messages. If "verbose" is
not a coderef but is some other true value, debug messages will be sent to
"STDERR". Otherwise, debug messages will not be logged.
- •
- "prioritize"
A value indicating whether to utilize the job 'priority' field when
selecting jobs to be processed. If unspecified, jobs will always be
executed in a randomized order.
- •
- "driver_cache_expiration"
Optional value to control how long database connections are cached for in
seconds. By default, connections are not cached. To re-use the same
database connection for five minutes, pass driver_cache_expiration =>
300 to the constructor. Improves job throughput in cases where the work to
process a job is small compared to the database connection set-up and
tear-down time.
- •
- "retry_seconds"
The number of seconds after which to try reconnecting to apparently dead
databases. If not given, TheSchwartz will retry connecting to databases
after 30 seconds.
"$client->list_jobs( %args )"¶
Returns a list of "TheSchwartz::Job" objects matching the given
arguments. The required members of %args are:
- •
- "funcname"
the name of the function or a reference to an array of functions
- •
- "run_after"
the value you want to check <= against on the run_after column
- •
- "grabbed_until"
the value you want to check <= against on the grabbed_until column
- •
- "coalesce_op"
defaults to '=', set it to whatever you want to compare the coalesce field
too if you want to search, you can use 'LIKE'
- •
- "coalesce"
coalesce value to search for, if you set op to 'LIKE' you can use '%' here,
do remember that '%' searches anchored at the beginning of the string are
much faster since it is can do a btree index lookup
- •
- "want_handle"
if you want all your jobs to be set up using a handle. defaults to true.
this option might be removed, as you should always have this on a Job
object.
It is important to remember that this function doesnt lock anything, it just
returns as many jobs as there is up to amount of databases *
FIND_JOB_BATCH_SIZE
"$client->lookup_job( $handle_id )"¶
Returns a "TheSchwartz::Job" corresponding to the given handle ID.
"$client->set_verbose( $verbose )"¶
Sets the current logging function to $verbose if it's a coderef. If not a
coderef, enables debug logging to "STDERR" if $verbose is true;
otherwise, disables logging.
POSTING JOBS¶
The methods of TheSchwartz clients used by applications posting jobs to the
queue are:
"$client->insert( $job )"¶
Adds the given "TheSchwartz::Job" to one of the client's job
databases.
"$client->insert( $funcname, $arg )"¶
Adds a new job with funcname $funcname and arguments $arg to the queue.
"$client->insert_jobs( @jobs )"¶
Adds the given "TheSchwartz::Job" objects to one of the client's job
databases. All the given jobs are recorded in
one job database.
"$client->set_prioritize( $prioritize )"¶
Set the "prioritize" value as described in the constructor.
WORKING¶
The methods of TheSchwartz clients for use in worker processes are:
"$client->can_do( $ability )"¶
Adds $ability to the list of abilities $client is capable of performing.
Subsequent calls to that client's "work" methods will find jobs
requiring the given ability.
"$client->work_once()"¶
Find and perform one job $client can do.
"$client->work_until_done()"¶
Find and perform jobs $client can do until no more such jobs are found in any of
the client's job databases.
"$client->work( [$delay] )"¶
Find and perform any jobs $client can do, forever. When no job is available, the
working process will sleep for $delay seconds (or 5, if not specified) before
looking again.
"$client->work_on($handle)"¶
Given a job handle (a scalar string)
$handle, runs the job,
then returns.
"$client->find_job_for_workers( [$abilities] )"¶
Returns a "TheSchwartz::Job" for a random job that the client can do.
If specified, the job returned matches one of the abilities in the arrayref
$abilities, rather than $client's abilities.
"$client->find_job_with_coalescing_value( $ability, $coval )"¶
Returns a "TheSchwartz::Job" for a random job for a worker capable of
$ability and with a coalescing value of $coval.
"$client->find_job_with_coalescing_prefix( $ability, $coval )"¶
Returns a "TheSchwartz::Job" for a random job for a worker capable of
$ability and with a coalescing value beginning with $coval.
Note the "TheSchwartz" implementation of this function uses a
"LIKE" query to find matching jobs, with all the attendant
performance implications for your job databases.
"$client->get_server_time( $driver )"¶
Given an open driver
$driver to a database, gets the
current server time from the database.
COPYRIGHT, LICENSE & WARRANTY¶
This software is Copyright 2007, Six Apart Ltd, cpan@sixapart.com. All rights
reserved.
TheSchwartz is free software; you may redistribute it and/or modify it under the
same terms as Perl itself.
TheScwhartz comes with no warranty of any kind.