Monotonic clock

lib/ddtrace/contrib/active_support/notifications/subscription.rb

@@ -76,8 +76,8 @@ def start_span(name, id, payload, start = nil)
 
             # Start a trace
             tracer.trace(@span_name, @options.dup).tap do |span|
-              # Assign start time if provided
-              span.start_time = start unless start.nil?
+              # Start span if time is provided
+              span.start(start) unless start.nil?
               payload[:datadog_span] = span
             end
           end

lib/ddtrace/contrib/grape/endpoint.rb

@@ -1,3 +1,4 @@
+
 require 'ddtrace/ext/http'
 require 'ddtrace/ext/errors'
 require 'ddtrace/contrib/analytics'
@@ -95,7 +96,7 @@ def endpoint_run(name, start, finish, id, payload)
               span.set_tag(Ext::TAG_ROUTE_ENDPOINT, api_view) unless api_view.nil?
               span.set_tag(Ext::TAG_ROUTE_PATH, path)
             ensure
-              span.start_time = start
+              span.start(start)
               span.finish(finish)
             end
           rescue StandardError => e
@@ -134,7 +135,7 @@ def endpoint_render(name, start, finish, id, payload)
 
               span.set_error(payload[:exception_object]) unless payload[:exception_object].nil?
             ensure
-              span.start_time = start
+              span.start(start)
               span.finish(finish)
             end
           rescue StandardError => e
@@ -169,7 +170,7 @@ def endpoint_run_filters(name, start, finish, id, payload)
               span.set_error(payload[:exception_object]) unless payload[:exception_object].nil?
               span.set_tag(Ext::TAG_FILTER_TYPE, type.to_s)
             ensure
-              span.start_time = start
+              span.start(start)
               span.finish(finish)
             end
           rescue StandardError => e

lib/ddtrace/span.rb

@@ -8,6 +8,8 @@
 require 'ddtrace/analytics'
 require 'ddtrace/forced_tracing'
 require 'ddtrace/diagnostics/health'
+require 'ddtrace/span/duration'
+require 'ddtrace/utils/time'
 
 module Datadog
   # Represents a logical unit of work in the system. Each trace consists of one or more spans.
@@ -36,12 +38,12 @@ class Span
     NUMERIC_TAG_SIZE_RANGE = (-2**53..2**53)
 
     attr_accessor :name, :service, :resource, :span_type,
-                  :start_time, :end_time,
                   :span_id, :trace_id, :parent_id,
                   :status, :sampled,
-                  :tracer, :context
+                  :tracer, :context, :duration, :start_time, :end_time
 
     attr_reader :parent
+
     # Create a new span linked to the given tracer. Call the \Tracer method <tt>start_span()</tt>
     # and then <tt>finish()</tt> once the tracer operation is over.
     #
@@ -72,11 +74,14 @@ def initialize(tracer, name, options = {})
       @parent = nil
       @sampled = true
 
-      @start_time = nil # set by Tracer.start_span
-      @end_time = nil # set by Span.finish
-
       @allocation_count_start = now_allocations
       @allocation_count_finish = @allocation_count_start
+
+      @start_time = nil
+      @duration_start = nil
+      @end_time = nil
+      @duration_end = nil
+      @wall_clock_duration = false
     end
 
     # Set the given key / value tag pair on the span. Keys and values
@@ -160,6 +165,36 @@ def set_error(e)
       set_tag(Ext::Errors::STACK, e.backtrace) unless e.backtrace.empty?
     end
 
+    # Mark the span started at the current time.
+    def start(start_time = nil)
+      # A span should not be started twice. Note that this is not thread-safe,
+      # start is called from multiple threads, a given span might be started
+      # several times. Again, one should not do this, so this test is more a
+      # fallback to avoid very bad things and protect you in most common cases.
+      return if started?
+
+      if start_time
+        @start_time = start_time
+        @duration_start = start_time
+        @wall_clock_duration = true
+      else
+        @start_time = Time.now.utc
+        @duration_start = duration_marker
+      end
+
+      self
+    end
+
+    # for backwards compatibility
+    def start_time=(time)
+      time.tap { start(time) }
+    end
+
+    # for backwards compatibility
+    def end_time=(time)
+      time.tap { finish(time) }
+    end
+
     # Mark the span finished at the current time and submit it.
     def finish(finish_time = nil)
       # A span should not be finished twice. Note that this is not thread-safe,
@@ -170,12 +205,22 @@ def finish(finish_time = nil)
 
       @allocation_count_finish = now_allocations
 
-      # Provide a default start_time if unset, but this should have been set by start_span.
-      # Using now here causes 0-duration spans, still, this is expected, as we never
-      # explicitely say when it started.
-      @start_time ||= Time.now.utc
+      now = Time.now.utc
 
-      @end_time = finish_time.nil? ? Time.now.utc : finish_time # finish this
+      # Provide a default start_time if unset.
+      # Using `now` here causes duration to be 0; this is expected
+      # behavior when start_time is unknown.
+      start(finish_time || now) unless started?
+
+      if finish_time
+        @end_time = finish_time
+        @duration_start = @start_time
+        @duration_end = finish_time
+        @wall_clock_duration = true
+      else
+        @end_time = now
+        @duration_end = @wall_clock_duration ? now : duration_marker
+      end
 
       # Finish does not really do anything if the span is not bound to a tracer and a context.
       return self if @tracer.nil? || @context.nil?
@@ -195,11 +240,6 @@ def finish(finish_time = nil)
       self
     end
 
-    # Return whether the span is finished or not.
-    def finished?
-      !@end_time.nil?
-    end
-
     # Return a string representation of the span.
     def to_s
       "Span(name:#{@name},sid:#{@span_id},tid:#{@trace_id},pid:#{@parent_id})"
@@ -232,7 +272,7 @@ def allocations
 
     # Return the hash representation of the current span.
     def to_hash
-      h = {
+      {
         span_id: @span_id,
         parent_id: @parent_id,
         trace_id: @trace_id,
@@ -244,21 +284,18 @@ def to_hash
         metrics: @metrics,
         allocations: allocations,
         error: @status
-      }
-
-      if !@start_time.nil? && !@end_time.nil?
-        h[:start] = (@start_time.to_f * 1e9).to_i
-        h[:duration] = ((@end_time - @start_time) * 1e9).to_i
+      }.tap do |h|
+        if complete?
+          h[:start] = (start_time.to_f * 1e9).to_i
+          h[:duration] = (duration.to_f * 1e9).to_i
+        end
       end
-
-      h
     end
 
     # Return a human readable version of the span
     def pretty_print(q)
-      start_time = (@start_time.to_f * 1e9).to_i rescue '-'
-      end_time = (@end_time.to_f * 1e9).to_i rescue '-'
-      duration = ((@end_time - @start_time) * 1e9).to_i rescue 0
+      start_time = (start_time.to_f * 1e9).to_i rescue '-'
+      end_time = (end_time.to_f * 1e9).to_i rescue '-'
       q.group 0 do
         q.breakable
         q.text "Name: #{@name}\n"
@@ -271,7 +308,7 @@ def pretty_print(q)
         q.text "Error: #{@status}\n"
         q.text "Start: #{start_time}\n"
         q.text "End: #{end_time}\n"
-        q.text "Duration: #{duration}\n"
+        q.text "Duration: #{duration.to_f}\n"
         q.text "Allocations: #{allocations}\n"
         q.group(2, 'Tags: [', "]\n") do
           q.breakable
@@ -288,8 +325,34 @@ def pretty_print(q)
       end
     end
 
+    # Return whether the duration is started or not
+    def started?
+      !@start_time.nil?
+    end
+
+    # Return whether the duration is finished or not.
+    def finished?
+      !@end_time.nil?
+    end
+
+    def complete?
+      started? && finished?
+    end
+
+    def duration
+      if @wall_clock_duration
+        (@start_time - @end_time).to_f rescue 0.0
+      else
+        (@duration_end - @duration_start).to_f rescue 0.0
+      end
+    end
+
     private
 
+    def duration_marker
+      Utils::Time.get_time
+    end
+
     if defined?(JRUBY_VERSION) || Gem::Version.new(RUBY_VERSION) < Gem::Version.new(VERSION::MINIMUM_RUBY_VERSION)
       def now_allocations
         0

lib/ddtrace/tracer.rb

@@ -186,8 +186,7 @@ def guess_context_and_parent(child_of)
     # * +start_time+: when the span actually starts (defaults to \now)
     # * +tags+: extra tags which should be added to the span.
     def start_span(name, options = {})
-      start_time = options.fetch(:start_time, Time.now.utc)
-
+      start_time = options[:start_time]
       tags = options.fetch(:tags, {})
 
       span_options = options.select do |k, _v|
@@ -212,9 +211,10 @@ def start_span(name, options = {})
         # child span
         span.parent = parent # sets service, trace_id, parent_id, sampled
       end
+
       span.set_tags(@tags) unless @tags.empty?
       span.set_tags(tags) unless tags.empty?
-      span.start_time = start_time
+      span.start(start_time)
 
       # this could at some point be optional (start_active_span vs start_manual_span)
       ctx.add_span(span) unless ctx.nil?

spec/ddtrace/contrib/active_support/notifications/subscription_spec.rb

@@ -30,7 +30,7 @@
 
         it do
           expect(tracer).to receive(:trace).with(span_name, options).and_return(span).ordered
-          expect(span).to receive(:start_time=).with(start).and_return(span).ordered
+          expect(span).to receive(:start).with(start).and_return(span).ordered
           expect(spy).to receive(:call).with(span, name, id, payload).ordered
           expect(span).to receive(:finish).with(finish).and_return(span).ordered
           is_expected.to be(span)
@@ -47,7 +47,7 @@
 
           it 'finishes tracing anyways' do
             expect(tracer).to receive(:trace).with(span_name, options).and_return(span).ordered
-            expect(span).to receive(:start_time=).with(start).and_return(span).ordered
+            expect(span).to receive(:start).with(start).and_return(span).ordered
             expect(span).to receive(:finish).with(finish).and_return(span).ordered
             is_expected.to be(span)
           end