# ContextData Instrumentation for Log4j2 version 2.17 and higher
This module provides a Log4j2 `ContextDataProvider` that injects trace context from active spans
into log context.
## Quickstart
### Add these dependencies to your project
Replace `OPENTELEMETRY_VERSION` with the [latest
release](https://search.maven.org/search?q=g:io.opentelemetry.instrumentation%20AND%20a:opentelemetry-log4j-context-data-2.17-autoconfigure).
For Maven, add to your `pom.xml` dependencies:
```xml
io.opentelemetry.instrumentation
opentelemetry-log4j-context-data-2.17-autoconfigure
OPENTELEMETRY_VERSION
runtime
```
For Gradle, add to your dependencies:
```groovy
runtimeOnly("io.opentelemetry.instrumentation:opentelemetry-log4j-context-data-2.17-autoconfigure:OPENTELEMETRY_VERSION")
```
### Usage
`OpenTelemetryContextDataProvider` implements the Log4j2 `ContextDataProvider` SPI, and injects the
trace ID and span ID from an active span into
Log4j's [context data](https://logging.apache.org/log4j/2.x/manual/thread-context.html).
Log4j will automatically pick up the integration when you include this module. The following keys
will be added to the context when a log statement is made when a span is active:
- `trace_id`
- `span_id`
- `trace_flags`
If the `otel.instrumentation.log4j-context-data.add-baggage` system property (or the
`OTEL_INSTRUMENTATION_LOG4J_CONTEXT_DATA_ADD_BAGGAGE` environment variable) is set to `true`,
key/value pairs in [baggage](https://opentelemetry.io/docs/concepts/signals/baggage/) will be added to the context too.
- `baggage.`
You can use these keys when defining an appender in your `log4j.xml` configuration, for example:
```xml
```