Add logic to self-tune the poll_interval based on available

heartbeat info.

Fixes #1630

Changes.md

@@ -1,3 +1,12 @@
+3.1.4
+-----------
+
+- Happy π release!
+- Self-tuning Scheduler polling, we use heartbeat info to better tune poll\_inteval [#1630]
+- Remove all table column width rules, hopefully get better column formatting [#1747]
+- Handle rare case where YAML can't be decoded in dev mode [#1761]
+- Fix lingering jobs in Busy page on Heroku [#1764]
+
 3.1.3
 -----------
 

lib/sidekiq.rb

@@ -118,9 +118,7 @@ module Sidekiq
     Sidekiq::Logging.logger = log
   end
 
-  # The default poll interval is 15 seconds.  This should generally be set to
-  # (Sidekiq process count * 5).  So if you have a dozen Sidekiq processes, set
-  # poll_interval to 60.
+  # See sidekiq/scheduled.rb for an in-depth explanation of this value
   def self.poll_interval=(interval)
     self.options[:poll_interval] = interval
   end

lib/sidekiq/scheduled.rb

@@ -5,7 +5,7 @@ require 'sidekiq/actor'
 module Sidekiq
   module Scheduled
 
-    POLL_INTERVAL = 15
+    INITIAL_WAIT = 15
 
     ##
     # The Poller checks Redis every N seconds for messages in the retry or scheduled
@@ -20,7 +20,7 @@ module Sidekiq
 
       def poll(first_time=false)
         watchdog('scheduling poller thread died!') do
-          add_jitter if first_time
+          initial_wait if first_time
 
           begin
             # A message's "score" in Redis is the time at which it should be processed.
@@ -51,19 +51,35 @@ module Sidekiq
             logger.error ex.backtrace.first
           end
 
-          after(poll_interval) { poll }
+          after(poll_interval * rand) { poll }
         end
       end
 
       private
 
+      # We do our best to tune 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 set poll_interval to 30 * 15 * 2 or 900 seconds.
+      # To keep things statistically random, we'll sleep a random amount between
+      # 0 and 900 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 is unset (the default).
       def poll_interval
-        Sidekiq.options[:poll_interval] || POLL_INTERVAL
+        Sidekiq.options[:poll_interval] ||= begin
+          pcount = Sidekiq.redis {|c| c.scard('processes') } || 1
+          pcount * 15 * 2
+        end
       end
 
-      def add_jitter
+      def initial_wait
         begin
-          sleep(poll_interval * rand)
+          sleep(INITIAL_WAIT)
         rescue Celluloid::Task::TerminatedError
           # Hit Ctrl-C when Sidekiq is finished booting and we have a chance
           # to get here.

lib/sidekiq/version.rb

@@ -1,3 +1,3 @@
 module Sidekiq
-  VERSION = "3.1.3"
+  VERSION = "3.1.4"
 end