Implemented pure-Ruby monotonic clock.

Author: jdantonio

lib/concurrent/atomic/condition.rb

@@ -1,4 +1,4 @@
-require 'concurrent/utility/clock_time'
+require 'concurrent/utility/monotonic_time'
 
 module Concurrent
 
@@ -44,13 +44,13 @@ def initialize
     # @param [Object] timeout nil means no timeout
     # @return [Result]
     def wait(mutex, timeout = nil)
-      start_time = Concurrent::clock_time
+      start_time = Concurrent.monotonic_time
       @condition.wait(mutex, timeout)
 
       if timeout.nil?
         Result.new(nil)
       else
-        Result.new(start_time + timeout - Concurrent::clock_time)
+        Result.new(start_time + timeout - Concurrent.monotonic_time)
       end
     end
 

lib/concurrent/executor/ruby_thread_pool_executor.rb

@@ -3,7 +3,7 @@
 require 'concurrent/atomic/event'
 require 'concurrent/executor/executor'
 require 'concurrent/executor/ruby_thread_pool_worker'
-require 'concurrent/utility/clock_time'
+require 'concurrent/utility/monotonic_time'
 
 module Concurrent
 
@@ -92,7 +92,7 @@ def initialize(opts = {})
       @largest_length       = 0
 
       @gc_interval  = opts.fetch(:gc_interval, 1).to_i # undocumented
-      @last_gc_time = Concurrent::clock_time - [1.0, (@gc_interval * 2.0)].max
+      @last_gc_time = Concurrent.monotonic_time - [1.0, (@gc_interval * 2.0)].max
     end
 
     # @!macro executor_module_method_can_overflow_question
@@ -226,13 +226,13 @@ def ensure_capacity?
     #
     # @!visibility private
     def prune_pool
-      if Concurrent::clock_time - @gc_interval >= @last_gc_time
+      if Concurrent.monotonic_time - @gc_interval >= @last_gc_time
         @pool.delete_if { |worker| worker.dead? }
         # send :stop for each thread over idletime
         @pool.
-            select { |worker| @idletime != 0 && Concurrent::clock_time - @idletime > worker.last_activity }.
+            select { |worker| @idletime != 0 && Concurrent.monotonic_time - @idletime > worker.last_activity }.
             each { @queue << :stop }
-        @last_gc_time = Concurrent::clock_time
+        @last_gc_time = Concurrent.monotonic_time
       end
     end
 

lib/concurrent/executor/ruby_thread_pool_worker.rb

@@ -1,6 +1,6 @@
 require 'thread'
 require 'concurrent/logging'
-require 'concurrent/utility/clock_time'
+require 'concurrent/utility/monotonic_time'
 
 module Concurrent
 
@@ -13,7 +13,7 @@ def initialize(queue, parent)
       @queue = queue
       @parent = parent
       @mutex = Mutex.new
-      @last_activity = Concurrent::clock_time
+      @last_activity = Concurrent.monotonic_time
       @thread = nil
     end
 
@@ -65,7 +65,7 @@ def run(thread = Thread.current)
           # let it fail
           log DEBUG, ex
         ensure
-          @last_activity = Concurrent::clock_time
+          @last_activity = Concurrent.monotonic_time
           @parent.on_end_task
         end
       end

lib/concurrent/utilities.rb

@@ -1,4 +1,4 @@
-require 'concurrent/utility/clock_time'
+require 'concurrent/utility/monotonic_time'
 require 'concurrent/utility/processor_count'
 require 'concurrent/utility/timeout'
 require 'concurrent/utility/timer'

lib/concurrent/utility/clock_time.rb

@@ -0,0 +1,45 @@
+module Concurrent
+
+  if defined?(Process::CLOCK_MONOTONIC)
+    def monotonic_time
+      Process.clock_gettime(Process::CLOCK_MONOTONIC)
+    end
+  elsif RUBY_PLATFORM == 'java'
+    def monotonic_time
+      java.lang.System.nanoTime() / 1_000_000_000.0
+    end
+  else
+
+    require 'thread'
+    class << self
+
+      # @!visibility private
+      @@global_monotonic_clock = Class.new {
+        def initialize
+          @mutex = Mutex.new
+          @correction = 0
+          @last_time = Time.now.to_f
+        end
+        def get_time
+          @mutex.synchronize do
+            @correction ||= 0 # compensating any back time shifts
+            now = Time.now.to_f
+            corrected_now = now + @correction
+            if @last_time < corrected_now
+              return @last_time = corrected_now 
+            else
+              @correction += @last_time - corrected_now + 0.000_001
+              return @last_time = @correction + now
+            end
+          end
+        end
+      }.new
+    end
+
+    def monotonic_time
+      @@global_monotonic_clock.get_time
+    end
+  end
+
+  module_function :monotonic_time
+end

lib/concurrent/utility/monotonic_time.rb

@@ -1 +1 @@
-Subproject commit db7483b80f6efb7df9930f0031508d7e2eb6bad0
+Subproject commit 5aff4706f70d757c15830edd66d74759ff364eda