Implement process lifecycle events, fixes #1534

lib/sidekiq.rb

@@ -20,6 +20,11 @@ module Sidekiq
     :timeout => 8,
     :profile => false,
     :error_handlers => [],
+    :lifecycle_events => {
+      :boot => [],
+      :quiet => [],
+      :shutdown => [],
+    },
   }
 
   def self.❨╯°□°❩╯︵┻━┻
@@ -121,6 +126,11 @@ module Sidekiq
     self.options[:error_handlers]
   end
 
+  def self.on(event, &block)
+    raise ArgumentError, "Symbols only please: #{event}" if !event.is_a?(Symbol)
+    raise ArgumentError, "Invalid event name: #{event}" if !options[:lifecycle_events].keys.include?(event)
+    options[:lifecycle_events][event] << block
+  end
 end
 
 require 'sidekiq/extensions/class_methods'

lib/sidekiq/cli.rb

@@ -74,6 +74,8 @@ module Sidekiq
       logger.info "Running in #{RUBY_DESCRIPTION}"
       logger.info Sidekiq::LICENSE
 
+      fire_event(:boot)
+
       if !options[:daemon]
         logger.info 'Starting processing, hit Ctrl-C to stop'
       end
@@ -96,6 +98,7 @@ module Sidekiq
       rescue Interrupt
         logger.info 'Shutting down'
         launcher.stop
+        fire_event(:shutdown)
         # Explicitly exit so busy Processor threads can't block
         # process shutdown.
         exit(0)
@@ -104,6 +107,16 @@ module Sidekiq
 
     private
 
+    def fire_event(event)
+      Sidekiq.options[:lifecycle_events][event].each do |block|
+        begin
+          block.call
+        rescue => ex
+          handle_exception(ex, { :event => event })
+        end
+      end
+    end
+
     def handle_signal(sig)
       Sidekiq.logger.debug "Got #{sig} signal"
       case sig
@@ -124,6 +137,7 @@ module Sidekiq
       when 'USR1'
         Sidekiq.logger.info "Received USR1, no longer accepting new work"
         launcher.manager.async.stop
+        fire_event(:quiet)
       when 'USR2'
         if Sidekiq.options[:logfile]
           Sidekiq.logger.info "Received USR2, reopening log file"

myapp/config/initializers/sidekiq.rb

@@ -3,6 +3,9 @@ Sidekiq.configure_client do |config|
 end
 Sidekiq.configure_server do |config|
   config.redis = { :size => 25, :namespace => 'foo' }
+  config.on(:boot) { puts "Hello!" }
+  config.on(:quiet) { puts "Quiet down!" }
+  config.on(:shutdown) { puts "Goodbye!" }
 end
 
 class EmptyWorker

test/test_sidekiq.rb

@@ -34,4 +34,17 @@ class TestSidekiq < Sidekiq::Test
       assert_equal "Calm down, bro\n", $stdout.string
     end
   end
+
+  describe 'lifecycle events' do
+    it 'handles invalid input' do
+      e = assert_raises ArgumentError do
+        Sidekiq.on(:bot)
+      end
+      assert_match /Invalid event name/, e.message
+      e = assert_raises ArgumentError do
+        Sidekiq.on('boot')
+      end
+      assert_match /Symbols only/, e.message
+    end
+  end
 end