Move DD code into its own directory (#6)

reference/ddtrace/helpers.py

@@ -0,0 +1,37 @@
+import ddtrace
+
+
+def get_correlation_ids(tracer=None):
+    """Retrieves the Correlation Identifiers for the current active ``Trace``.
+    This helper method can be achieved manually and should be considered
+    only a shortcut. The main reason is to abstract the current ``Tracer``
+    implementation so that these identifiers can be extracted either the
+    tracer is an OpenTracing tracer or a Datadog tracer.
+
+    OpenTracing users can still extract these values using the ``ScopeManager``
+    API, though this shortcut is a simple one-liner. The usage is:
+
+        from ddtrace import helpers
+
+        trace_id, span_id = helpers.get_correlation_ids()
+
+    :returns: a tuple containing the trace_id and span_id
+    """
+    # Consideration: currently we don't have another way to "define" a
+    # GlobalTracer. In the case of OpenTracing, ``opentracing.tracer`` is exposed
+    # and we're doing the same here for ``ddtrace.tracer``. Because this helper
+    # must work also with OpenTracing, we should take the right used ``Tracer``.
+    # At the time of writing, it's enough to support our Datadog Tracer.
+
+    # If no tracer passed in, use global tracer
+    if not tracer:
+        tracer = ddtrace.tracer
+
+    # If tracer is disabled, skip
+    if not tracer.enabled:
+        return None, None
+
+    span = tracer.current_span()
+    if not span:
+        return None, None
+    return span.trace_id, span.span_id