class Sidekiq::Scheduled::Poller

The Poller checks Redis every N seconds for jobs in the retry or scheduled set have passed their timestamp and should be enqueued. If so, it just pops the job back onto its original queue so the workers can pick it up like any other job.

Constants

INITIAL_WAIT

Public Class Methods

new() click to toggle source
# File lib/sidekiq/scheduled.rb, line 45
def initialize
  @enq = (Sidekiq.options[:scheduled_enq] || Sidekiq::Scheduled::Enq).new
  @sleeper = ConnectionPool::TimedStack.new
  @done = false
  @thread = nil
end

Public Instance Methods

enqueue() click to toggle source
# File lib/sidekiq/scheduled.rb, line 75
def enqueue
  begin
    @enq.enqueue_jobs
  rescue => ex
    # Most likely a problem with redis networking.
    # Punt and try again at the next interval
    logger.error ex.message
    handle_exception(ex)
  end
end
start() click to toggle source
# File lib/sidekiq/scheduled.rb, line 63
def start
  @thread ||= safe_thread("scheduler") do
    initial_wait

    while !@done
      enqueue
      wait
    end
    Sidekiq.logger.info("Scheduler exiting...")
  end
end
terminate() click to toggle source

Shut down this instance, will pause until the thread is dead.

# File lib/sidekiq/scheduled.rb, line 53
def terminate
  @done = true
  if @thread
    t = @thread
    @thread = nil
    @sleeper << 0
    t.value
  end
end

Private Instance Methods

initial_wait() click to toggle source
# File lib/sidekiq/scheduled.rb, line 160
def initial_wait
  # Have all processes sleep between 5-15 seconds.  10 seconds
  # to give time for the heartbeat to register (if the poll interval is going to be calculated by the number
  # of workers), and 5 random seconds to ensure they don't all hit Redis at the same time.
  total = 0
  total += INITIAL_WAIT unless Sidekiq.options[:poll_interval_average]
  total += (5 * rand)

  @sleeper.pop(total)
rescue Timeout::Error
end
poll_interval_average() click to toggle source

We do our best to tune the poll interval to the size of the active Sidekiq cluster. If you have 30 processes and poll every 15 seconds, that means one Sidekiq is checking Redis every 0.5 seconds - way too often for most people and really bad if the retry or scheduled sets are large.

Instead try to avoid polling more than once every 15 seconds. If you have 30 Sidekiq processes, we'll poll every 30 * 15 or 450 seconds. To keep things statistically random, we'll sleep a random amount between 225 and 675 seconds for each poll or 450 seconds on average. Otherwise restarting all your Sidekiq processes at the same time will lead to them all polling at the same time: the thundering herd problem.

We only do this if poll_interval_average is unset (the default).

# File lib/sidekiq/scheduled.rb, line 143
def poll_interval_average
  Sidekiq.options[:poll_interval_average] ||= scaled_poll_interval
end
process_count() click to toggle source
# File lib/sidekiq/scheduled.rb, line 154
def process_count
  pcount = Sidekiq::ProcessSet.new.size
  pcount = 1 if pcount == 0
  pcount
end
random_poll_interval() click to toggle source
# File lib/sidekiq/scheduled.rb, line 100
def random_poll_interval
  # We want one Sidekiq process to schedule jobs every N seconds.  We have M processes
  # and **don't** want to coordinate.
  #
  # So in N*M second timespan, we want each process to schedule once.  The basic loop is:
  #
  # * sleep a random amount within that N*M timespan
  # * wake up and schedule
  #
  # We want to avoid one edge case: imagine a set of 2 processes, scheduling every 5 seconds,
  # so N*M = 10.  Each process decides to randomly sleep 8 seconds, now we've failed to meet
  # that 5 second average. Thankfully each schedule cycle will sleep randomly so the next
  # iteration could see each process sleep for 1 second, undercutting our average.
  #
  # So below 10 processes, we special case and ensure the processes sleep closer to the average.
  # In the example above, each process should schedule every 10 seconds on average. We special
  # case smaller clusters to add 50% so they would sleep somewhere between 5 and 15 seconds.
  # As we run more processes, the scheduling interval average will approach an even spread
  # between 0 and poll interval so we don't need this artifical boost.
  #
  if process_count < 10
    # For small clusters, calculate a random interval that is ±50% the desired average.
    poll_interval_average * rand + poll_interval_average.to_f / 2
  else
    # With 10+ processes, we should have enough randomness to get decent polling
    # across the entire timespan
    poll_interval_average * rand
  end
end
scaled_poll_interval() click to toggle source

Calculates an average poll interval based on the number of known Sidekiq processes. This minimizes a single point of failure by dispersing check-ins but without taxing Redis if you run many Sidekiq processes.

# File lib/sidekiq/scheduled.rb, line 150
def scaled_poll_interval
  process_count * Sidekiq.options[:average_scheduled_poll_interval]
end
wait() click to toggle source
# File lib/sidekiq/scheduled.rb, line 88
def wait
  @sleeper.pop(random_poll_interval)
rescue Timeout::Error
  # expected
rescue => ex
  # if poll_interval_average hasn't been calculated yet, we can
  # raise an error trying to reach Redis.
  logger.error ex.message
  handle_exception(ex)
  sleep 5
end