library-autoconfigure

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.

For Maven, add to your pom.xml dependencies:

<dependencies>
  <dependency>
    <groupId>io.opentelemetry.instrumentation</groupId>
    <artifactId>opentelemetry-log4j-context-data-2.17-autoconfigure</artifactId>
    <version>OPENTELEMETRY_VERSION</version>
    <scope>runtime</scope>
  </dependency>
</dependencies>

For Gradle, add to your dependencies:

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.

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

These keys can be customized using the following system properties or environment variables:

System property	Environment variable
otel.instrumentation.common.logging.trace-id	OTEL_INSTRUMENTATION_COMMON_LOGGING_TRACE_ID
otel.instrumentation.common.logging.span-id	OTEL_INSTRUMENTATION_COMMON_LOGGING_SPAN_ID
otel.instrumentation.common.logging.trace-flags	OTEL_INSTRUMENTATION_COMMON_LOGGING_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 will also be added to the context data.

• baggage.<entry_name>

You can use these keys when defining an appender in your log4j.xml configuration, for example:

<?xml version="1.0" encoding="UTF-8"?>
<Configuration>
  <Appenders>
    <Console name="Console" target="SYSTEM_OUT">
      <PatternLayout
          pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} trace_id=%X{trace_id} span_id=%X{span_id} trace_flags=%X{trace_flags} - %msg%n"/>
    </Console>
  </Appenders>
  <Loggers>
    <Root>
      <AppenderRef ref="Console" level="All"/>
    </Root>
  </Loggers>
</Configuration>