Add documentation for Tornado distributed tracing

Author: LotharSee

ddtrace/contrib/tornado/__init__.py

@@ -54,6 +54,7 @@ def notify(self):
         'datadog_trace': {
             'default_service': 'my-tornado-app',
             'tags': {'env': 'production'},
+            'distributed_tracing': True,
         },
     }
 
@@ -66,8 +67,11 @@ def notify(self):
 * ``default_service`` (default: `tornado-web`): set the service name used by the tracer. Usually
   this configuration must be updated with a meaningful name.
 * ``tags`` (default: `{}`): set global tags that should be applied to all spans.
-* ``enabled`` (default: `true`): define if the tracer is enabled or not. If set to `false`, the
+* ``enabled`` (default: `True`): define if the tracer is enabled or not. If set to `false`, the
   code is still instrumented but no spans are sent to the APM agent.
+* ``distributed_tracing`` (default: `False`): enable distributed tracing if this is called
+remotely from an instrumented application.
+We suggest to enable it only for internal services where headers are under your control.
 * ``agent_hostname`` (default: `localhost`): define the hostname of the APM agent.
 * ``agent_port`` (default: `8126`): define the port of the APM agent.
 """

docs/index.rst

@@ -286,7 +286,7 @@ Supported web frameworks:
 
 - Django
 - Flask
-
+- Tornado
 
 HTTP client/server
 ~~~~~~~~~~~~~~~~~~