Create README.rst for the Datadog trace exporter (#799)

Author: nbutton23

contrib/opencensus-ext-datadog/README.rst

@@ -0,0 +1,80 @@
+OpenCensus Datadog Exporter
+============================================================================
+
+|pypi|
+
+.. |pypi| image:: https://badge.fury.io/py/opencensus-ext-datadog.svg
+   :target: https://pypi.org/project/opencensus-ext-datadog/
+
+Installation
+------------
+
+::
+
+    pip install opencensus-ext-datadog
+
+Usage
+-----
+
+Trace
+~~~~~
+
+The **Datadog Trace Exporter** allows you to export `OpenCensus`_ traces to `Datadog`_.
+
+This example shows how to send a span "hello" to Datadog.
+
+* Set up a `Datadog Agent <https://docs.datadoghq.com/agent/>`_ that is accessible to your app.
+* Place the URL for the agent in the `trace_addr` of the configuration options.
+
+ .. code:: python
+
+    from opencensus.ext.datadog.traces import DatadogTraceExporter, Options
+    from opencensus.trace.samplers import ProbabilitySampler
+    from opencensus.trace.tracer import Tracer
+
+    tracer = Tracer(
+        exporter=DatadogTraceExporter(Options(service='app-name',trace_addr='my-datdog-agent:8126`)),
+        sampler=ProbabilitySampler(1.0)
+    )
+
+    with tracer.span(name='hello'):
+        print('Hello, World!')
+
+OpenCensus also supports several `integrations <https://github.com/census-instrumentation/opencensus-python#integration>`_ which allows OpenCensus to integrate with third party libraries.
+
+This example shows how to integrate with the `requests <https://2.python-requests.org/en/master/>`_ library.
+
+* Set up a `Datadog Agent <https://docs.datadoghq.com/agent/>`_ that is accessible to your app.
+* Place the URL for the agent in the `trace_addr` of the configuration options.
+
+.. code:: python
+
+    import requests
+
+    from opencensus.ext.datadog.traces import DatadogTraceExporter, Options
+    from opencensus.trace.samplers import ProbabilitySampler
+    from opencensus.trace.tracer import Tracer
+
+    config_integration.trace_integrations(['requests'])
+    tracer = Tracer(
+        exporter=DatadogTraceExporter(
+            Options(
+                service='app-name',
+                trace_addr='my-datdog-agent:8126`
+                )
+        ),
+        sampler=ProbabilitySampler(1.0),
+    )
+    with tracer.span(name='parent'):
+        response = requests.get(url='https://www.wikipedia.org/wiki/Rabbit')
+
+
+References
+----------
+
+* `Datadog <https://www.datadoghq.com/product/>`_
+* `Examples <https://github.com/census-instrumentation/opencensus-python/tree/master/contrib/opencensus-ext-datadog/examples>`_
+* `OpenCensus Project <https://opencensus.io/>`_
+
+.. _Datadog: https://www.datadoghq.com/product/
+.. _OpenCensus: https://github.com/census-instrumentation/opencensus-python/

contrib/opencensus-ext-datadog/examples/datadog.py

@@ -1,8 +1,8 @@
 from flask import Flask
 
+from opencensus.ext.datadog.traces import DatadogTraceExporter, Options
 from opencensus.ext.flask.flask_middleware import FlaskMiddleware
 from opencensus.trace.samplers import AlwaysOnSampler
-from traces import DatadogTraceExporter, Options
 
 app = Flask(__name__)
 middleware = FlaskMiddleware(app,