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(options) click to toggle source
# File lib/sidekiq/scheduled.rb, line 73
def initialize(options)
  @config = options
  @enq = (options[:scheduled_enq] || Sidekiq::Scheduled::Enq).new
  @sleeper = ConnectionPool::TimedStack.new
  @done = false
  @thread = nil
  @count_calls = 0
end

Public Instance Methods

enqueue() click to toggle source
# File lib/sidekiq/scheduled.rb, line 107
def enqueue
  @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
start() click to toggle source
# File lib/sidekiq/scheduled.rb, line 95
def start
  @thread ||= safe_thread("scheduler") {
    initial_wait

    until @done
      enqueue
      wait
    end
    logger.info("Scheduler exiting...")
  }
end
terminate() click to toggle source

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

# File lib/sidekiq/scheduled.rb, line 83
def terminate
  @done = true
  @enq.terminate if @enq.respond_to?(:terminate)

  if @thread
    t = @thread
    @thread = nil
    @sleeper << 0
    t.value
  end
end

Private Instance Methods

cleanup() click to toggle source

A copy of Sidekiq::ProcessSet#cleanup because server should never depend on sidekiq/api.

# File lib/sidekiq/scheduled.rb, line 195
def cleanup
  # dont run cleanup more than once per minute
  return 0 unless Sidekiq.redis { |conn| conn.set("process_cleanup", "1", nx: true, ex: 60) }

  count = 0
  Sidekiq.redis do |conn|
    procs = conn.sscan_each("processes").to_a
    heartbeats = conn.pipelined { |pipeline|
      procs.each do |key|
        pipeline.hget(key, "info")
      end
    }

    # the hash named key has an expiry of 60 seconds.
    # if it's not found, that means the process has not reported
    # in to Redis and probably died.
    to_prune = procs.select.with_index { |proc, i|
      heartbeats[i].nil?
    }
    count = conn.srem("processes", to_prune) unless to_prune.empty?
  end
  count
end
initial_wait() click to toggle source
# File lib/sidekiq/scheduled.rb, line 219
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 @config[:poll_interval_average]
  total += (5 * rand)

  @sleeper.pop(total)
rescue Timeout::Error
ensure
  # periodically clean out the `processes` set in Redis which can collect
  # references to dead processes over time. The process count affects how
  # often we scan for scheduled jobs.
  cleanup
end
poll_interval_average(count) 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 176
def poll_interval_average(count)
  @config[:poll_interval_average] || scaled_poll_interval(count)
end
process_count() click to toggle source
# File lib/sidekiq/scheduled.rb, line 187
def process_count
  pcount = Sidekiq.redis { |conn| conn.scard("processes") }
  pcount = 1 if pcount == 0
  pcount
end
random_poll_interval() click to toggle source
# File lib/sidekiq/scheduled.rb, line 130
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.
  #
  count = process_count
  interval = poll_interval_average(count)

  if count < 10
    # For small clusters, calculate a random interval that is ±50% the desired average.
    interval * rand + interval.to_f / 2
  else
    # With 10+ processes, we should have enough randomness to get decent polling
    # across the entire timespan
    interval * rand
  end
end
scaled_poll_interval(process_count) 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 183
def scaled_poll_interval(process_count)
  process_count * @config[:average_scheduled_poll_interval]
end
wait() click to toggle source
# File lib/sidekiq/scheduled.rb, line 118
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