Logging agent logs separately

[maverick-devil]

Currently opentelemetry agent logs in the application logs itself. This pollutes the application logs, and also if there are any errors, they spam the application logs.
Currently agent uses slf4j simple to log these logs.
Can the logs be moved to a log file? It would be a cleaner approach. I would like to know if above approach was done due to some issues faced.
I'm thinking if we can add slf4j-api with logback. Let me know what can be the complications involved if I do so.

[maverick-devil]

Hello! Can I get any response please!

[laurit]

You should be able to redirect agent logs to file with -Dio.opentelemetry.javaagent.slf4j.simpleLogger.logFile=path-to-log-file

[maverick-devil]

Thanks for the info. But as I see, agent uses a simple logger, and does not have rolling policy. Some times, in case otel collector goes down, logs would pile up in single application file. Are there any plans to make changes to simple logger? Would like to know and contribute if there are any such plans. Thanks!

[mateuszrzeszutek]

Are there any plans to make changes to simple logger? Would like to know and contribute if there are any such plans. Thanks!

This topic has come up multiple times (#3413, #7257, #5059 and more) - I'm planning to clear up some time and prepare a POC of #5059, this should resolve your issue too.

[michaeltcoelho]

Hey folks!

Is it possible to, when working with logback in spring, specify somehow via property -Dio.opentelemetry.javaagent.slf4j.*** to route logs messages to a specific Appender? Considering I have an appender which formats my log in JSON. If I do not turn the agent's logging off like -Dio.opentelemetry.javaagent.slf4j.simpleLogger.defaultLogLevel=off" my logs parser fails as it gets the log texts from the javaagent.

[mateuszrzeszutek]

Hey @michaeltcoelho ,
Right now it is not possible to redirect agent logs into application logging system. Once #7339 is merged (and probably a couple follow-up PRs as well) it will become an option.

[apanasevich]

You should be able to redirect agent logs to file with -Dio.opentelemetry.javaagent.slf4j.simpleLogger.logFile=path-to-log-file

It works perfect if specified as JVM argument. Is it possible to specify this property in an javaagent configuration file?
I have tried but with no result, javaagent started to write its logs to stderr back.

UPD: Looks like only system properties is the way to configure at the moment
https://github.com/open-telemetry/opentelemetry-java-instrumentation/blob/main/javaagent-internal-logging-simple/src/main/java/io/opentelemetry/javaagent/logging/simple/Slf4jSimpleLoggingCustomizer.java

[mateuszrzeszutek]

Is it possible to specify this property in an javaagent configuration file?
I have tried but with no result, javaagent started to write its logs to stderr back.

Nope - the reason for that is that logging is initialized as one of the first javaagent subsystems, way before full configuration is assembled.

[lgext06]

Hi @mateuszrzeszutek ,
any news about your pending changes?

[mateuszrzeszutek]

Hey @lgext06 ,
Still pending -- I'll ping all the parties involved and try to get it merged before the next release.

[hajekt2]

Is it possible to, when working with logback in spring, specify somehow via property -Dio.opentelemetry.javaagent.slf4j.*** to route logs messages to a specific Appender? Considering I have an appender which formats my log in JSON. If I do not turn the agent's logging off like -Dio.opentelemetry.javaagent.slf4j.simpleLogger.defaultLogLevel=off" my logs parser fails as it gets the log texts from the javaagent.
Hi @michaeltcoelho, I am dealing with the same issue, logs in text format, but I need JSON formated instead. Have you found the solution on that?