updated docs for tracing

docs/features/configuration.rst

@@ -61,7 +61,8 @@ Here is an example ReRoute configuration, You don't need to set all of these thi
             },
             "HttpHandlerOptions": {
                 "AllowAutoRedirect": true,
-                "UseCookieContainer": true
+                "UseCookieContainer": true,
+                "UseTracing": true
             },
             "UseServiceDiscovery": false
         }

docs/features/tracing.rst

@@ -0,0 +1,31 @@
+Tracing
+=======
+
+Ocelot providers tracing functionality from the excellent `Butterfly <https://github.com/ButterflyAPM>`_ project. 
+
+In order to use the tracing please read the Butterfly documentation.
+
+In ocelot you need to do the following if you wish to trace a ReRoute.
+
+In your ConfigureServices method
+
+.. code-block:: csharp
+
+    services
+        .AddOcelot(Configuration)
+        .AddOpenTracing(option =>
+        {
+            //this is the url that the butterfly collector server is running on...
+            option.CollectorUrl = "http://localhost:9618";
+            option.Service = "Ocelot";
+        });
+
+Then in your configuration.json add the following to the ReRoute you want to trace..
+
+.. code-block:: json
+
+      "HttpHandlerOptions": {
+            "UseTracing": true
+        },
+
+Ocelot will now send tracing information to Butterfly when this ReRoute is called.