library

MDC Instrumentation for Logback version 1.0 and higher

This module integrates instrumentation with Logback by injecting the trace ID and span ID from a mounted span using a custom Logback appender.

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-logback-mdc-1.0</artifactId>
    <version>OPENTELEMETRY_VERSION</version>
  </dependency>
</dependencies>

For Gradle, add to your dependencies:

dependencies {
  runtimeOnly("io.opentelemetry.instrumentation:opentelemetry-logback-mdc-1.0:OPENTELEMETRY_VERSION")
}

Usage

The following demonstrates how you might configure the appender in your logback.xml configuration:

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
  <appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
    <encoder>
      <pattern>%d{HH:mm:ss.SSS} trace_id=%X{trace_id} span_id=%X{span_id} trace_flags=%X{trace_flags} %msg%n</pattern>
    </encoder>
  </appender>

  <!-- Just wrap your logging appender, for example ConsoleAppender, with OpenTelemetryAppender -->
  <appender name="OTEL" class="io.opentelemetry.instrumentation.logback.mdc.v1_0.OpenTelemetryAppender">
    <appender-ref ref="CONSOLE"/>
  </appender>

  <!-- Use the wrapped "OTEL" appender instead of the original "CONSOLE" one -->
  <root level="INFO">
    <appender-ref ref="OTEL"/>
  </root>

</configuration>

It's important to note you can also use other encoders in the ConsoleAppender like logstash-logback-encoder. This can be helpful when the Span is invalid and the trace_id, span_id, and trace_flags are all null and are hidden entirely from the logs.

Logging events will automatically have context information from the span context injected. The following attributes are available for use:

• trace_id
• span_id
• trace_flags

These keys can be customized in your logback.xml configuration, for example:

<appender name="OTEL" class="io.opentelemetry.instrumentation.logback.mdc.v1_0.OpenTelemetryAppender">
  <traceIdKey>example_trace_id</traceIdKey>
  <spanIdKey>example_span_id</spanIdKey>
  <traceFlagsKey>example_trace_flags</traceFlagsKey>
</appender>

If you set <addBaggage>true</addBaggage> in your logback.xml configuration, key/value pairs in baggage will also be added to the MDC.

• baggage.<entry_name>