Moar accurate noop tracer (#207)

Author: dhendry

opencensus/trace/tracers/base.py

@@ -67,9 +67,10 @@ class NullContextManager(object):
     """Empty object as a helper for faking Trace and Span when tracing is
     disabled.
     """
-    def __init__(self, span_id=None):
+    def __init__(self, span_id=None, context_tracer=None):
         self.name = None
         self.span_id = span_id
+        self.context_tracer = context_tracer
 
     def __enter__(self):
         return self  # pragma: NO COVER
@@ -78,4 +79,4 @@ def __exit__(self, exc_type, exc_value, traceback):
         pass  # pragma: NO COVER
 
     def span(self, name='span'):
-        return NullContextManager()
+        return NullContextManager(context_tracer=self.context_tracer)

opencensus/trace/tracers/noop_tracer.py

@@ -34,7 +34,7 @@ def span(self, name='span'):
         :rtype: :class:`~opencensus.trace.trace_span.Span`
         :returns: The Span object.
         """
-        return base.NullContextManager()
+        return base.NullContextManager(context_tracer=self)
 
     def start_span(self, name='span'):
         """Start a span.
@@ -45,18 +45,18 @@ def start_span(self, name='span'):
         :rtype: :class:`~opencensus.trace.trace_span.Span`
         :returns: The Span object.
         """
-        return base.NullContextManager()
+        return base.NullContextManager(context_tracer=self)
 
     def end_span(self):
         """End a span. Remove the span from the span stack, and update the
         span_id in TraceContext as the current span_id which is the peek
         element in the span stack.
         """
-        return base.NullContextManager()
+        return base.NullContextManager(context_tracer=self)
 
     def current_span(self):
         """Return the current span."""
-        return base.NullContextManager()
+        return base.NullContextManager(context_tracer=self)
 
     def add_attribute_to_current_span(self, attribute_key, attribute_value):
         """Add attribute to current span.

tests/unit/trace/ext/grpc/test_client_interceptor.py

@@ -17,6 +17,7 @@
 import mock
 from opencensus.trace import execution_context
 from opencensus.trace.ext.grpc import client_interceptor
+from opencensus.trace.tracers.noop_tracer import NoopTracer
 
 
 class TestOpenCensusClientInterceptor(unittest.TestCase):
@@ -95,6 +96,28 @@ def test__intercept_call_metadata_none(self):
 
         self.assertEqual(expected_metadata, client_call_details.metadata)
 
+    def test__intercept_call_noop_tracer(self):
+        tracer = NoopTracer()
+        test_header = 'test header'
+        mock_propagator = mock.Mock()
+        mock_propagator.to_header.return_value = test_header
+
+        interceptor = client_interceptor.OpenCensusClientInterceptor(
+            tracer=tracer, host_port='test')
+        interceptor._propagator = mock_propagator
+        mock_client_call_details = mock.Mock()
+        mock_client_call_details.metadata = None
+        mock_client_call_details.method = '/hello'
+
+        client_call_details, request_iterator, current_span = interceptor._intercept_call(
+            mock_client_call_details,
+            mock.Mock(),
+            'unary_unary')
+
+        expected_metadata = (('grpc-trace-bin', test_header),)
+
+        self.assertEqual(expected_metadata, client_call_details.metadata)
+
     def test__intercept_call_metadata_list(self):
         tracer = mock.Mock()
         tracer.span_context = mock.Mock()