Merge branch 'master' into issue_958

docs/getting-started.rst

@@ -174,6 +174,29 @@ Now run the above script, hit the root url (http://localhost:5000/) a few times,
    python flask_example.py
 
 
+Configure Your HTTP Propagator (b3, CorrelationContext)
+-------------------------------------------------------
+
+A major feature of distributed tracing is the ability to correlate a trace across
+multiple services. However, those services need to propagate information about a
+trace from one service to the other.
+
+To enable this, OpenTelemetry has the concept of `propagators <https://github.com/open-telemetry/opentelemetry-specification/blob/master/specification/context/api-propagators.md>`_,
+which provide a common method to encode and decode span information from a request and response,
+respectively.
+
+By default, opentelemetry-python is configured to use the `W3C Trace Context <https://www.w3.org/TR/trace-context/>`_
+HTTP headers for HTTP requests. This can be configured to leverage different propagators. Here's
+an example using Zipkin's `b3 propagation <https://github.com/openzipkin/b3-propagation>`_:
+
+.. code-block:: python
+
+    from opentelemetry import propagators
+    from opentelemetry.sdk.trace.propagation.b3_format import B3Format
+
+    propagators.set_global_httptextformat(B3Format())
+
+
 Adding Metrics
 --------------