Configure the javaagent to log to a file (instead of stderr)#3413

[mfridljand]

I have a question in relation to the following issue/feature:
Configure the javaagent to log to a file (instead of stderr)#3413

as well as
Logging agent logs separately #7179

My apologies if I had to comment on one of above instead of opening a topic in Discussions.

I have 2.22.0 agent running in an Application Server with 1.8.0.351 JVM with the following JVM parameters.

-Dotel.javaagent.configuration-file=<otel java agent path>/otel.properties 
-Dio.opentelemetry.javaagent.slf4j.simpleLogger=<otel java agent path>/otel.log
-Dotel.javaagent.logging=simple
-Dotel.javaagent.debug=true
-Dotel.javaagent.logging.file=<otel java agent path>/otel.log

The "-Dotel.javaagent.logging.file" is a ChatGPT’s idea :))

In general, the agent is doing fine. The data is being collected according to the agent’s configuration file. However, no separate logging file otel.log is created. The agent’s log messages appear in a JVM’s process log file instead.

Is io.opentelemetry.javaagent.slf4j.simpleLogger implemented?
Is any additional configuration required?
The environment is particularly irky about logging. No standard logging framework like Java Logging or slf4j is used. Thus, issues were expected.

I’d like to redirect the agent logs because the (my app server’s) proprietary infrastructure seems to kill agent’s logging after some time. In the server’s (JVM’s) log file the agent’s logging is presented but stops eventually after the server start. The last log message is a
AgentInstaller$TransformLoggingListener - Transformed ...

[laurit]

Javaagent debug log isn't particularly useful, consider whether you want it at all. You can see the available configuration options in https://www.slf4j.org/api/org/slf4j/simple/SimpleLogger.html You will have to slightly rename the properties so the property for setting the log file is io.opentelemetry.javaagent.slf4j.simpleLogger.logFile.

[mfridljand]

Oh, my fault. It works now. Thank you!

The Javaagent debug log seems to be quite useful. There are few errors from BeanAttributeExtractor on DEBUG. It may explain why some JVM metrics are missing.

Due to errors the log has grown to several hundred MBs in ten seconds or so. It is Ok with relevant modules disabled, but ... it is tricky.
Is there perhaps a rolling log?!
Any father configuration except the -Dio.opentelemetry.javaagent.slf4j.simpleLogger.defaultLogLevel ?

[laurit]

There are few errors from BeanAttributeExtractor on DEBUG. It may explain why some JVM metrics are missing.

If you believe you have found a bug create an issue, include a minimal application that reproduces the problem along with any necessary instructions.

Due to errors the log has grown to several hundred MBs in ten seconds or so. It is Ok with relevant modules disabled, but ... it is tricky.

In our tests the logs usually don't grow that fast. If you wish someone to take a look consider providing a minimal application that reproduces the issue.

Is there perhaps a rolling log?!

There isn't.