Difference between revisions of "TheSchwartz"

Revision as of 18:21, 19 September 2011

TheSchwartz is a worker manager system that runs things like the importer, the private messaging function, the crossposter, and all of the event notifications. It makes it so that the web servers don't have to spend CPU timing doing work that doesn't have to be done instantly.

Setting up TheSchwartz

See TheSchwartz Setup.

Queueing a job for TheSchwartz from Dreamwidth

Generic Job

The following example queues a pony-feeding job, passing it amounts of hay and oats to use.

use TheSchwartz;
my $sclient = LJ::theschwartz(); # LJ::theschwartz( { role => "mass" } ) for very large stables
die "Can't get TheSchwartz client" unless $sclient;
my $job = TheSchwartz::Job->new_from_array("DW::Worker::FeedPonies",
                                           [ hay => $hay, oats => $oats ]);
die "Can't create job" unless $job;
$sclient->insert($job) or die "Can't queue feeding job";

LJ::theschwartz is defined in cgi-bin/ljlib.pl, so if you're not in web context (command-line program, Gearman worker, TheSchwartz worker), you'll need to require "ljlib.pl"; as well.

You should be able to adapt this to your specific job and data.

Notifying users of ESN events they subscribed to

Don't use the above. See Firing ESN events and delivering notifications instead.

Sending non-ESN email to a user

Use LJ::send_mail from cgi-bin/ljmail.pl. Note that doing so correctly is fiddly, if you want to respect all of the user's email-related preferences. See bug 3946 for more.

Writing a worker for Dreamwidth TheSchwartz jobs

The following implements the DW::Worker::FeedPonies worker used in the example above:

<syntaxhighlighting lang="perl"> use LJ::Worker::TheSchwartz; schwartz_decl( "DW::Worker::FeedPonies" ); schwartz_work(); # Never returns.

package DW::Worker::FeedPonies; use base 'TheSchwartz::Worker'; sub schwartz_capabilities { return ( __PACKAGE__ ); } sub max_retries { 5 } # Try feeding ponies 5 times before giving up sub grab_for { 600 } # Give the stable hand 600 seconds (10 minutes) to finish sub keep_exit_status_for { 86400 } # Keep the result of the feeding attempt for 24 hours

sub retry_delay { # How long to wait before retrying on after an attempt fails

   my ($class, $fails) = @_;

   return (10, 30, 60, 300, 600)[$fails];

}

sub work { # Do the actual work

   my ($class, $job) = @_;
   my %arg = %{$job->arg};

   $job->permanent_failure( "Amount of hay and or oats negative" )
       if $arg{hay} < 0 || $arg{oats} < 0;
   $job->debug( "Feeding the ponies $arg{hay} bales of hay and $arg{oats} bushels of oats" );
   Ponies->feed( %arg ) or return $job->failed( "Unable to feed ponies, retrying" );

   $job->completed;

} </syntaxhighlighting>

You should be able to adapt this to your specific job and data.