Add Helpers::Time module to access a monotonic clock

lib/rackstash/helpers/time.rb

@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+# Copyright 2017 Holger Just
+#
+# This software may be modified and distributed under the terms
+# of the MIT license. See the LICENSE.txt file for details.
+
+module Rackstash
+  module Helpers
+    module Time
+      protected
+
+      if defined?(Process::CLOCK_MONOTONIC)
+        # Get the current timestamp as a numeric value. If supported by the
+        # current platform, we use a monitonic clock.
+        #
+        # @return [Float] the current timestamp
+        def clock_time
+          Process.clock_gettime(Process::CLOCK_MONOTONIC)
+        end
+      else
+        # Get the current timestamp as a numeric value
+        #
+        # @return [Float] the current timestamp
+        def clock_time
+          Time.now.to_f
+        end
+      end
+    end
+  end
+end

spec/rackstash/helpers/time_spec.rb

@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+# Copyright 2017 Holger Just
+#
+# This software may be modified and distributed under the terms
+# of the MIT license. See the LICENSE.txt file for details.
+
+require 'spec_helper'
+
+require 'rackstash/helpers/time'
+
+describe Rackstash::Helpers::Time do
+  it 'only defines protected methods' do
+    expect(described_class.public_instance_methods(false)).to be_empty
+  end
+
+  describe '#clock_time' do
+    def clock_time(*args)
+      Object.new.extend(described_class).send(:clock_time, *args)
+    end
+
+    it 'returns the numeric timestamp' do
+      expect(clock_time).to be_a Float
+    end
+
+    it 'is monotinically increasing' do
+      expect(clock_time).to be < clock_time
+    end
+  end
+end