Merge pull request #1458 from DataDog/feature/trace_completed_event

Add trace_completed event to Tracer

.rubocop.yml

@@ -231,6 +231,14 @@ RSpec/LeadingSubject:
 RSpec/ImplicitSubject:
   Enabled: false
 
+# Enforces empty line after subject declaration.
+RSpec/EmptyLineAfterSubject:
+  Enabled: false
+
+# Enforces empty line after last let declaration.
+RSpec/EmptyLineAfterFinalLet:
+  Enabled: false
+
 # TODO: Disabling until we categorize which file are safe to do so.
 Style/FrozenStringLiteralComment:
   Enabled: false
@@ -250,6 +258,12 @@ Lint/EmptyBlock:
 RSpec/ContextWording:
   Enabled: false
 
+# Checks for multiple top-level example groups.
+# Multiple descriptions for the same class or module should either
+# be nested or separated into different test files.
+RSpec/MultipleDescribes:
+  Enabled: false
+
 # Enforces that examples should only have a limited amount of assertions.
 RSpec/MultipleExpectations:
   Enabled: false

lib/ddtrace/tracer.rb

@@ -10,6 +10,7 @@
 require 'ddtrace/sampler'
 require 'ddtrace/sampling'
 require 'ddtrace/correlation'
+require 'ddtrace/event'
 require 'ddtrace/utils/only_once'
 
 # \Datadog global namespace that includes all tracing functionality for Tracer and Span classes.
@@ -315,6 +316,10 @@ def trace(name, options = {})
       end
     end
 
+    def trace_completed
+      @trace_completed ||= TraceCompleted.new
+    end
+
     # Record the given +context+. For compatibility with previous versions,
     # +context+ can also be a span. It is similar to the +child_of+ argument,
     # method will figure out what to do, submitting a +span+ for recording
@@ -366,6 +371,22 @@ def write(trace)
       end
 
       @writer.write(trace)
+      trace_completed.publish(trace)
+    end
+
+    # Triggered whenever a trace is completed
+    class TraceCompleted < Datadog::Event
+      def initialize
+        super(:trace_completed)
+      end
+
+      # NOTE: Ignore Rubocop rule. This definition allows for
+      #       description of and constraints on arguments.
+      # rubocop:disable Lint/UselessMethodDefinition
+      def publish(trace)
+        super(trace)
+      end
+      # rubocop:enable Lint/UselessMethodDefinition
     end
 
     # TODO: Move this kind of configuration building out of the tracer.

spec/ddtrace/tracer_spec.rb

@@ -532,9 +532,12 @@
 
   describe '#record' do
     subject(:record) { tracer.record(context) }
-
     let(:context) { instance_double(Datadog::Context) }
 
+    before do
+      allow(tracer.trace_completed).to receive(:publish)
+    end
+
     context 'with trace' do
       let(:trace) { [Datadog::Span.new(tracer, 'dummy')] }
 
@@ -545,19 +548,49 @@
         subject
       end
 
-      it { expect(writer.spans).to eq(trace) }
+      it 'writes the trace' do
+        expect(writer.spans).to eq(trace)
+
+        expect(tracer.trace_completed)
+          .to have_received(:publish)
+          .with(trace)
+      end
     end
 
     context 'with empty trace' do
       let(:trace) { [] }
 
-      it { expect(writer.spans).to be_empty }
+      it 'does not write a trace' do
+        expect(writer.spans).to be_empty
+
+        expect(tracer.trace_completed)
+          .to_not have_received(:publish)
+      end
     end
 
     context 'with nil trace' do
       let(:trace) { nil }
 
-      it { expect(writer.spans).to be_empty }
+      it 'does not write a trace' do
+        expect(writer.spans).to be_empty
+
+        expect(tracer.trace_completed)
+          .to_not have_received(:publish)
+      end
     end
   end
+
+  describe '#trace_completed' do
+    subject(:trace_completed) { tracer.trace_completed }
+    it { is_expected.to be_a_kind_of(described_class::TraceCompleted) }
+  end
+end
+
+RSpec.describe Datadog::Tracer::TraceCompleted do
+  subject(:event) { described_class.new }
+
+  describe '#name' do
+    subject(:name) { event.name }
+    it { is_expected.to be :trace_completed }
+  end
 end