improv: add tracing documentation

README.md

@@ -1,6 +1,7 @@
 # pm2-io-apm-python
 
 ## Getting started
+
 ```python
 from pm2_io_apm_python import pm2io
 from pm2_io_apm_python import config
@@ -10,13 +11,15 @@ pm2.start()
 ```
 
 ## Add action
+
 ```python
 pm2.actionService.addAction(
   pm2.actionManager.Action("i'm an action", lambda data: "i'm the answer\n")
 )
 ```
 
 ## Add metric
+
 ```python
 randMetric = pm2.metricManager.Metric('random', 'r', 'rand')
 pm2.metricService.addMetric(randMetric)
@@ -25,6 +28,28 @@ randMetric.setValue(random.randint(1, 1000))
 ```
 
 ## Logging
+
 ```python
 pm2.notifier.log("Completely started")
+```
+
+## Tracing
+We are using OpenCensus for Transaction Tracing in Python. You can check integrations available on [https://github.com/census-instrumentation/opencensus-python#integration](OpenCensus python integration).
+
+The exporter is automatically configured when you init the agent with httplib integration.
+
+### Example (MySQL)
+
+#### Install
+
+```python
+pip install opencensus-ext-mysql
+```
+
+#### Add tracing
+
+```python
+from opencensus.trace import config_integration
+
+config_integration.trace_integrations(['httplib', 'mysql'])
 ```