Merge pull request #39 from honeycombio/tredman.propagate_custom_context

[tracing] propagate trace fields to earlier spans

Author: tredman

beeline/test_trace.py

@@ -311,6 +311,26 @@ def _presend_hook(fields):
             },
         )
 
+    def test_run_hooks_and_send_adds_trace_fields(self):
+        ''' ensure trace fields are propagated backwards '''
+        m_client = Mock()
+        tracer = SynchronousTracer(m_client)
+        m_span = Mock()
+        m_span.event = Event()
+        m_span.event.start_time = datetime.datetime.now()
+        # set an existing trace field
+        m_span.event.add_field('app.a', 1)
+
+        with patch('beeline.trace._should_sample') as m_sample_fn:
+            m_sample_fn.return_value = True
+            # add some trace fields
+            tracer.add_trace_field('a', 0)
+            tracer.add_trace_field('b', 2)
+            tracer.add_trace_field('c', 3)
+            tracer.finish_span(m_span)
+        
+        # ensure we only added fields b and c and did not try to overwrite a
+        self.assertDictContainsSubset({'app.a': 1, 'app.b': 2, 'app.c': 3}, m_span.event.fields())
 
 class TestTraceContext(unittest.TestCase):
     def test_marshal_trace_context(self):

beeline/trace.py

@@ -115,6 +115,12 @@ def finish_span(self, span):
         # send the span's event. Even if the stack is in an unhealthy state,
         # it's probably better to send event data than not
         if span.event:
+            # propagate trace fields that may have been added in later spans
+            for k, v in self._state.trace_fields.items():
+                # don't overwrite existing values because they may be different
+                if k not in span.event.fields():
+                    span.event.add_field(k, v)
+
             duration = datetime.datetime.now() - span.event.start_time
             duration_ms = duration.total_seconds() * 1000.0
             span.event.add_field('duration_ms', duration_ms)

beeline/version.py

@@ -1 +1 @@
-VERSION = '2.2.0'
+VERSION = '2.3.0'

setup.py

@@ -4,7 +4,7 @@
 setup(
     python_requires='>=2.7',
     name='honeycomb-beeline',
-    version='2.2.0',
+    version='2.3.0',
     description='Honeycomb library for easy instrumentation',
     url='https://github.com/honeycombio/beeline-python',
     author='Honeycomb.io',