Support manual starting/stopping of the clock.

lib/sidetiq/clock.rb

@@ -12,7 +12,7 @@ module Sidetiq
 
     START_TIME = Sidetiq.config.utc ? Time.utc(2010, 1, 1) : Time.local(2010, 1, 1)
 
-    attr_reader :schedules
+    attr_reader :schedules, :thread
 
     def self.method_missing(meth, *args, &block)
       instance.__send__(meth, *args, &block)
@@ -42,6 +42,26 @@ module Sidetiq
       Sidetiq.config.utc ? clock_gettime.utc : clock_gettime
     end
 
+    def start!
+      return if ticking?
+
+      Sidekiq.logger.info "Sidetiq::Clock start"
+      @thread = Thread.start { clock { tick } }
+      @thread.abort_on_exception = true
+      @thread.priority = Sidetiq.config.resolution
+    end
+
+    def stop!
+      if ticking?
+        @thread.kill
+        Sidekiq.logger.info "Sidetiq::Clock stop"
+      end
+    end
+
+    def ticking?
+      @thread && @thread.alive?
+    end
+
     private
 
     def enqueue(worker, time)
@@ -73,13 +93,6 @@ module Sidetiq
       end
     end
 
-    def start!
-      Sidekiq.logger.info "Sidetiq::Clock start"
-      thr = Thread.start { clock { tick } }
-      thr.abort_on_exception = true
-      thr.priority = Sidetiq.config.resolution
-    end
-
     def clock
       loop do
         yield

test/test_clock.rb

@@ -9,6 +9,25 @@ class TestClock < Sidetiq::TestCase
     Sidetiq::Clock.foo
   end
 
+  def test_start_stop
+    refute clock.ticking?
+    assert_nil clock.thread
+
+    clock.start!
+    Thread.pass
+    sleep 0.01
+
+    assert clock.ticking?
+    assert_kind_of Thread, clock.thread
+
+    clock.stop!
+    Thread.pass
+    sleep 0.01
+
+    refute clock.ticking?
+    refute clock.thread.alive?
+  end
+
   def test_gettime_seconds
     assert_equal clock.gettime.tv_sec, Time.now.tv_sec
   end