# Additional instrumentation

LLMS index: [llms.txt](/llms.txt)

---

The OpenTelemetry Spring Boot starter provides
[out of the box instrumentation](../out-of-the-box-instrumentation) that you can
augment with additional instrumentations.

## Log4j2 Instrumentation

You have to add the OpenTelemetry appender to your `log4j2.xml` file:

```xml
<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="WARN" packages="io.opentelemetry.instrumentation.log4j.appender.v2_17">
    <Appenders>
        <OpenTelemetry name="OpenTelemetryAppender"/>
    </Appenders>
    <Loggers>
        <Root>
            <AppenderRef ref="OpenTelemetryAppender" level="All"/>
        </Root>
    </Loggers>
</Configuration>
```

You can find more configuration options for the OpenTelemetry appender in the
[Log4j](https://github.com/open-telemetry/opentelemetry-java-instrumentation/blob/main/instrumentation/log4j/log4j-appender-2.17/library/README.md)
instrumentation library.

| System property                               | Type    | Default | Description                                                                                     |
| --------------------------------------------- | ------- | ------- | ----------------------------------------------------------------------------------------------- |
| `otel.instrumentation.log4j-appender.enabled` | Boolean | true    | Enables the configuration of the Log4j OpenTelemetry appender with an `OpenTelemetry` instance. |

## Instrumentation libraries

You can configure other instrumentations using
[OpenTelemetry instrumentation libraries](https://github.com/open-telemetry/opentelemetry-java-instrumentation/blob/main/docs/supported-libraries.md#libraries--frameworks).