Allow TimerTask to be safely restarted after shutdown and avoid duplicate tasks

Creates a new @running object on shutdown while the ScheduledTask is checking the previously set @running object which will remain false

Author: bensheldon

lib/concurrent-ruby/concurrent/timer_task.rb

@@ -278,24 +278,26 @@ def ns_initialize(opts, &task)
     # @!visibility private
     def ns_shutdown_execution
       @running.make_false
+      @running = Concurrent::AtomicBoolean.new(false)
       super
     end
 
     # @!visibility private
     def ns_kill_execution
       @running.make_false
+      @running = Concurrent::AtomicBoolean.new(false)
       super
     end
 
     # @!visibility private
     def schedule_next_task(interval = execution_interval)
-      ScheduledTask.execute(interval, args: [Concurrent::Event.new], &method(:execute_task))
+      ScheduledTask.execute(interval, args: [Concurrent::Event.new, @running], &method(:execute_task))
       nil
     end
 
     # @!visibility private
-    def execute_task(completion)
-      return nil unless @running.true?
+    def execute_task(completion, continue_running)
+      return nil unless continue_running.true?
       _success, value, reason = @executor.execute(self)
       if completion.try?
         self.value = value

spec/concurrent/timer_task_spec.rb

@@ -1,5 +1,6 @@
 require_relative 'concern/dereferenceable_shared'
 require_relative 'concern/observable_shared'
+require 'concurrent/atomic/atomic_fixnum'
 require 'concurrent/timer_task'
 
 module Concurrent
@@ -94,12 +95,24 @@ def trigger_observable(observable)
       end
 
       context '#shutdown' do
-
         it 'returns true on success' do
           task = TimerTask.execute(run_now: false) { nil }
           sleep(0.1)
           expect(task.shutdown).to be_truthy
         end
+
+        it 'will cancel pre-shutdown task even if restarted to avoid double-runs' do
+          counter = Concurrent::AtomicFixnum.new(0)
+          task = TimerTask.execute(execution_interval: 0.2, run_now: true) { counter.increment }
+          sleep 0.05
+          expect(counter.value).to eq 1
+
+          task.shutdown
+          task.execute
+
+          sleep 0.25
+          expect(counter.value).to eq 3
+        end
       end
     end