PerfectSched is a highly available distributed cron built on top of RDBMS.
It provides at-least-once semantics; Even if a worker node fails during process a task, the task is retried by another worker.
PerfectSched also guarantees that only one worker server processes a task if the server is alive.
All you have to consider is implementing idempotent worker programs. It's recommended to use PerfectQueue with PerfectSched.
# open a schedule collection
PerfectSched.open(config, &block) #=> #<ScheduleCollection>
# add a schedule
ScheduleCollection#add(task_id, type, options)
# poll a scheduled task
# (you don't have to use this method directly. see following sections)
ScheduleCollection#poll #=> #<Task>
# get data associated with a task
Task#data #=> #<Hash>
# finish a task
Task#finish!
# retry a task
Task#retry!
# create a schedule reference
ScheduleCollection#[](key) #=> #<Schedule>
# chack the existance of the schedule
Schedule#exists?
# delete a schedule
Schedule#delete!
ScheduleError < StandardError
##
# Workers may get these errors:
#
AlreadyFinishedError < ScheduleError
NotFoundError < ScheduleError
PreemptedError < ScheduleError
ProcessStopError < RuntimeError
##
# Client or other situation:
#
ConfigError < RuntimeError
AlreadyExistsError < ScheduleError
NotSupportedError < ScheduleError
# submit a task
PerfectSched.open(config) {|sc|
data = {'key'=>"value"}
options = {
:cron => '0 * * * *',
:delay => 30,
:timezone => 'Asia/Tokyo',
:next_time => Time.parse('2013-01-01 00:00:00 +0900').to_i,
:data => data,
}
sc.add("sched-id", "type1", options)
}class TestHandler < PerfectSched::Application::Base
# implement run method
def run
# do something ...
puts "acquired task: #{task.inspect}"
# call task.finish!, task.retry! or task.release!
task.finish!
end
endclass Dispatch < PerfectSched::Application::Dispatch
# describe routing
route "type1" => TestHandler
route /^regexp-.*$/ => :TestHandler # String or Regexp => Class or Symbol
endIn a launcher script or rake file:
system('perfectsched run -I. -rapp/schedules/dispatch Dispatch')or:
require 'perfectsched'
require 'app/schedules/dispatch'
PerfectSched::Worker.run(Dispatch) {
# this method is called when the worker process is restarted
raw = File.read('config/perfectsched.yml')
yml = YAJL.load(raw)
yml[ENV['RAILS_ENV'] || 'development']
}- TERM,INT,QUIT: shutdown
- USR1,HUP: restart
- USR2: reopen log files
- type: backend type (required; see following sections)
- log: log file path (default: use stderr)
- poll_interval: interval to poll tasks in seconds (default: 1.0 sec)
- timezone: default timezone (default: 'UTC')
- alive_time: duration to continue a heartbeat request (default: 300 sec)
- retry_wait: duration to retry a retried task (default: 300 sec)
additional configuration:
- url: URL to the RDBMS (example: 'mysql://user:password@host:port/database')
- table: name of the table to use
Not implemented yet.
Usage: perfectsched [options] <command>
commands:
list Show list of registered schedules
add <key> <type> <cron> <data> Register a new schedule
delete <key> Delete a registered schedule
run <class> Run a worker process
init Initialize a backend database
options:
-e, --environment ENV Framework environment (default: development)
-c, --config PATH.yml Path to a configuration file (default: config/perfectsched.yml)
options for add:
-d, --delay SEC Delay time before running a schedule (default: 0)
-t, --timezone NAME Set timezone (default: UTC)
-s, --start UNIXTIME Set the first schedule time (default: now)
-a, --at UNIXTIME Set the first run time (default: start+delay)
options for run:
-I, --include PATH Add $LOAD_PATH directory
-r, --require PATH Require files before starting
# assume that the config/perfectsched.yml exists
$ perfectsched init
$ perfectsched add s1 user_task '* * * * *' '{}'
$ perfectsched list
key type cron delay timezone next_time next_run_time data
s1 user_task * * * * * 0 UTC 2012-05-18 22:04:00 UTC 2012-05-18 22:04:00 UTC {}
1 entries.
$ perfectsched delete s1
$ perfectsched run -I. -Ilib -rconfig/boot.rb -rapps/schedules/schedule_dispatch.rb ScheduleDispatch