To receive events raised from the tracing API, you are required to register a listener by implementing the ITraceListener interface. The initialization code in Optimizely Search & Navigation searches assemblies located in the current app domain and registers the implementations, if any, that exist.

Below is an example of a trace events listener which sends an email in case of an error.

The interface of `ITraceEvent` looks like this:

## Use cases

These are some examples of how to work with event tracing.

### Network issues when connecting to the index

You can use tracing to generate notifications of service exceptions. To do so, handle the following exceptions like this:

### Document storage limit reached

This example generates a notification when the number of indexed items is reaching the limit configured in your Optimizely Search & Navigation service subscription.