OpenTelemetry Tracing Span Event Logback configuration. Based on a Spring Boot application.

application.properties

# Adds trace_id, span_id and trace_flags to log message, so when you read the logs, you can also find the trace
# Those are MDC properties and automatically added by opentelemetry-javaagent-all.jar javaagent
logging.pattern.console = %d{yyyy-MM-dd HH:mm:ss} - %logger{36} - %msg trace_id=%X{trace_id} span_id=%X{span_id} trace_flags=%X{trace_flags} %n

Dockerfile

# Example Dockerfile for java application with OpenTelemetry java agent added

FROM openjdk:11-jre-slim-stretch

RUN apt update && apt install -y libtcnative-1 && rm -rf /var/lib/apt/lists/*

# mount container /tmp to host /var/lib/docker (or whatever is set on runtime)
# /tmp is the default working directory for Tomcat in Sprint Boot application
VOLUME /tmp

EXPOSE 8080

COPY ./target/myapplication.jar /app/myapplication.jar

COPY ./opentelemetry-javaagent-all.jar /app/opentelemetry-javaagent-all.jar
WORKDIR /app

#https://github.com/open-telemetry/opentelemetry-java/blob/main/sdk-extensions/autoconfigure/README.md
ENTRYPOINT ["java", \
"-javaagent:/app/opentelemetry-javaagent-all.jar", \
"-Dotel.traces.exporter=jaeger", \
"-Dotel.exporter.jaeger.endpoint=http://jaeger:14250", \
"-Dotel.metrics.exporter=logging", \
"-Dotel.resource.attributes=service.name=myapplication", \
"-Dapplication.home=/app/", \
"-Dapplication.name=myapplication", \
"-jar","/app/myapplication.jar"]

logback-spring.xml

<?xml version="1.0" encoding="UTF-8"?>

<!--
Base logback configuration provided for compatibility with Spring Boot 1.1
-->

<configuration>
    <include resource="org/springframework/boot/logging/logback/defaults.xml" />
    <include resource="org/springframework/boot/logging/logback/console-appender.xml" />

    <!-- Adds log to current trace span event -->
    <appender name="SPAN_EVENT_APPENDER" class="my.pkg.LogbackSpanEventAppender"></appender>

    <root level="INFO">
        <appender-ref ref="SPAN_EVENT_APPENDER" />
        <appender-ref ref="CONSOLE" />
    </root>
</configuration>

LogbackSpanEventAppender.java

package my.pkg;
  
import ch.qos.logback.classic.spi.LoggingEvent;
import ch.qos.logback.core.AppenderBase;
import io.opentelemetry.api.common.Attributes;
import io.opentelemetry.api.common.AttributesBuilder;
import io.opentelemetry.api.trace.Span;
import org.slf4j.Marker;

import java.util.concurrent.TimeUnit;

/**
* Logback appender which adds a log to current trace span event
*/
public class LogbackSpanEventAppender extends AppenderBase<LoggingEvent> {
    @Override
    protected void append(LoggingEvent event) {
        Span span = Span.current();

        AttributesBuilder attributesBuilder = Attributes.builder();
        // copy all MDC properties, you can leave it out or take only useful information to avoid storing unnecessary data
        event.getMDCPropertyMap().forEach(attributesBuilder::put);

        Marker marker = event.getMarker();
        attributesBuilder.put("marker", marker != null ? marker.getName() : null);

        Attributes attributes = attributesBuilder.build();
        span.addEvent(event.getFormattedMessage(), attributes, event.getTimeStamp(), TimeUnit.MILLISECONDS);
    }
}

pom.xml

        <dependency>
            <groupId>io.opentelemetry</groupId>
            <artifactId>opentelemetry-api</artifactId>
            <version>1.2.0</version>
        </dependency>