Fixes check for shutdown method so that traces send when buffer is cl…

…eared but the traces are still being sent. Updates test to use a thread to make sure shutdown is not called more than once

lib/ddtrace/workers.rb

@@ -78,7 +78,7 @@ def stop
 
       # Closes all available queues and waits for the trace and service buffer to flush
       def shutdown!
-        return if @shutting_down || (@trace_buffer.empty? && @service_buffer.empty?)
+        return false if @shutting_down
         @shutting_down = true
         @trace_buffer.close
         @service_buffer.close
@@ -91,6 +91,7 @@ def shutdown!
         stop
         join
         @shutting_down = false
+        true
       end
 
       # Block until executor shutdown is complete or until timeout seconds have passed.

test/integration_test.rb

@@ -72,9 +72,10 @@ def agent_receives_short_span(tracer)
     span.service = 'my.service'
     span.finish()
 
-    tracer.shutdown!
+    first_shutdown = tracer.shutdown!
 
     stats = tracer.writer.stats
+    assert(first_shutdown, 'should have run through the shutdown method')
     assert(span.finished?, 'span did not finish')
     assert_equal(1, stats[:traces_flushed], 'wrong number of traces flushed')
     assert_equal(1, stats[:services_flushed], 'wrong number of services flushed')
@@ -88,19 +89,27 @@ def shutdown_exec_only_once(tracer)
     span = tracer.start_span('my.short.op')
     span.service = 'my.service'
     span.finish()
+    first_shutdown = nil
+    second_shutdown = nil
+    worker = Thread.new() do
+      first_shutdown = tracer.shutdown!
+    end
+
+    100.times do
+      break if tracer.writer.worker.shutting_down # wait until first shutdown is halfway through execution
+      sleep(0.01)
+    end
 
-    first_point = Time.now.utc
-    tracer.shutdown!
-    second_point = Time.now.utc
-    tracer.shutdown!
-    third_point = Time.now.utc
+    second_worker = Thread.new() do
+      second_shutdown = tracer.shutdown!
+    end
 
-    first_shutdown = second_point - first_point
-    second_shutdown = third_point - second_point
+    worker.join(2)
+    second_worker.join(2)
 
     stats = tracer.writer.stats
-    assert(first_shutdown >= 0.1, 'should have executed shutdown')
-    assert_equal(true, second_shutdown < 0.1, 'should not have executed second shutdown')
+    assert(first_shutdown, 'should have run through the shutdown method')
+    assert_equal(false, second_shutdown, 'should not have executed shutdown')
     assert_equal(true, span.finished?, 'span did not finish')
     assert_equal(1, stats[:traces_flushed], 'wrong number of traces flushed')
     assert_equal(1, stats[:services_flushed], 'wrong number of services flushed')