MDC attributes not captured with spring boot application using log4j.

[nityanandagohain]

I am using log4j in my spring boot application. The issue that I am facing is that the MDC attributes are not captured even after adding otel.instrumentation.log4j-appender.experimental.capture-mdc-attributes=* . Do I need to configure anything else ?

The other settings like otel.instrumentation.log4j-appender.experimental-log-attributes work as as expected.

---

update: I am able to get mdc attributes if I add them

ThreadContext.put("userId", "myid");
ThreadContext.put("requestId", "reqID");

But how do I capture attributes like className / LoggerName ?

[trask]

hi @nityanandagohain, are you using the OpenTelemetry Spring Boot starter or the OpenTelemetry Java agent or the OpenTelemetry Log4j Appender artifact?

[nityanandagohain]

hi @trask I am using the otel java agent

here is the code that I am using to test it https://github.com/nityanandagohain/otel_log4j

this is the run command I am using

OTEL_METRICS_EXPORTER=none OTEL_LOGS_EXPORTER=otlp OTEL_EXPORTER_OTLP_ENDPOINT="http://localhost:4317"  OTEL_RESOURCE_ATTRIBUTES=service.name=test java -javaagent:"/Users/nityanandagohain/Downloads/opentelemetry-javaagent.jar" -Dotel.instrumentation.log4j-appender.experimental.capture-marker-attribute=true -Dotel.instrumentation.log4j-appender.experimental.capture-mdc-attributes='*' -jar target/*.jar

[trask]

-Dotel.instrumentation.log4j-appender.experimental.capture-mdc-attributes='*'

my first guess would be that it's a shell quoting issue, maybe try

'-Dotel.instrumentation.log4j-appender.experimental.capture-mdc-attributes=*'

[laurit]

But how do I capture attributes like className / LoggerName ?

Capturing the class/method/line that logged the message is currently not implemented for log4j. It is implemented for logback. Logger name is set as InstrumentationScope.

[nityanandagohain]

Thanks @trask , the custom mdc attributes were captured but I wanted cass/method/line etc for log4j which doesn't seem to be supported as per @laurit .

Do we have any roadmap if it will be added for log4j ?
Thanks :)

[trask]

hi @nityanandagohain, if you can create a new issue targeted at that feature (and closing this issue), we will tag it as "contribution welcome".