Logger MDC auto-instrumentation with opentelemetry-spring-boot-starter

[birkoni5]

Hello,

I have a problem with a correlation between logs and traces, log statements don't contain any tracing information when opentelemetry-spring-boot-starter 1.22.0-alpha is used with Logback 1.2.11 and Spring Boot 2.7.2. Is it possible to inject trace_id and span_id into MDC to be included in produced log statements?

Any suggestion on how tracing information can be appended to each log statement is appreciated.

Thank you.

[mateuszrzeszutek]

Hey @birkoni5 ,

Unfortunately the spring boot starter is missing this feature right now; it can be added very easily though. You'll have to include one more dependency, and then configure your logging pattern to include the trace_id/span_id information.

[trajano]

It appears to be working with Spring Boot 3.1.x with the current instrumentation and works with the Logstash JSON encoder as well

{"@timestamp":"2023-11-07T23:55:37.814277259-05:00","@Version":"1","message":"whomami 2 requested","logger_name":"net.trajano.simpleauth.RootController","thread_name":"lettuce-nioEventLoop-5-1","level":"INFO","level_value":20000,"trace_id":"6c896aab0066650b36cd5a09f8188f69","trace_flags":"00","span_id":"7e1d76ca2865f464"}

[antechrestos]

I dunno whether it is appropriate but I instanciated the initializer as follow

public class OtelLogbackMdcAppenderApplicationInitializer implements GenericApplicationListener {
    @Override
    public boolean supportsEventType(ResolvableType eventType) {
        return eventType.isAssignableFrom(ApplicationEnvironmentPreparedEvent.class);
    }

    @Override
    public void onApplicationEvent(ApplicationEvent event) {
        if(event instanceof ApplicationEnvironmentPreparedEvent) {
            Logger logger = (Logger) LoggerFactory.getILoggerFactory().getLogger("ROOT");
            OpenTelemetryAppender openTelemetryAppender = new OpenTelemetryAppender();
            List<Appender<ILoggingEvent>> existingAppelders = new ArrayList<>();
            logger.iteratorForAppenders().forEachRemaining(existingAppelders::add);
            existingAppelders.forEach(logger::detachAppender);
            AtomicBoolean appenderAddedToOpenTelemetry = new AtomicBoolean();
            existingAppelders.forEach(existingAppender -> {
                if(existingAppender instanceof OpenTelemetryAppender
                || existingAppender instanceof io.opentelemetry.instrumentation.logback.appender.v1_0.OpenTelemetryAppender) {
                    logger.addAppender(existingAppender);
                } else {
                    openTelemetryAppender.addAppender(existingAppender);
                    appenderAddedToOpenTelemetry.set(true);
                }
            });
            if(appenderAddedToOpenTelemetry.get()) {
                openTelemetryAppender.start();
                logger.addAppender(openTelemetryAppender);
            }
        }
    }
}

and add it in a spring.factoriesfile; this inspired from the LogbackAppenderInstaller..