tracer: fix leaking spans when submission is disabled

ddtrace/tracer.py

@@ -91,9 +91,6 @@ def current_span(self):
 
     def record(self, span):
         """ Record the given finished span. """
-        if not self.enabled:
-            return
-
         spans = []
         with self._spans_lock:
             self._spans.append(span)
@@ -108,12 +105,16 @@ def record(self, span):
 
     def write(self, spans):
         """ Submit the given spans to the agent. """
-        if spans:
-            if self.debug_logging:
-                log.debug("submitting %s spans", len(spans))
-                for span in spans:
-                    log.debug("\n%s", span.pprint())
+        if not spans:
+            return  # nothing to do
+
+        if self.debug_logging:
+            log.debug("writing %s spans (enabled:%s)", len(spans), self.enabled)
+            for span in spans:
+                log.debug("\n%s", span.pprint())
 
+        if self.enabled:
+            # only submit the spans if we're actually enabled.
             self._writer.write(spans, self._services)
 
     def set_service_info(self, service, app, app_type):

tests/test_tracer.py

@@ -90,6 +90,20 @@ def test_tracer_disabled():
         s.set_tag("a", "b")
     assert not writer.pop()
 
+def test_tracer_disabled_mem_leak():
+    # ensure that if the tracer is disabled, we still remove things from the
+    # span buffer upon finishing.
+    writer = DummyWriter()
+    tracer = Tracer(writer=writer)
+    tracer.enabled = False
+    s1 = tracer.trace("foo")
+    s1.finish()
+    p1 = tracer.current_span()
+    s2 = tracer.trace("bar")
+    assert not s2._parent, s2._parent
+    s2.finish()
+    assert not p1, p1
+
 def test_sampling():
     writer = DummyWriter()
     tracer = Tracer(writer=writer, sample_rate=0.5)