Use MDC Tags to fill user context information

[dhufnagel]

It would be great if it is possible to use MDC Tags to add user context information. We do not want to make our application dependent on sentry, so we fill the MDC with user information. The log appender could pick up special tags and create a user context object.
For example it could be sentry.user.id for the ID oder sentry.user.username for the username. This would help us make use of the great user features.

[marandaneto]

I believe this works already, there are even tets for that, see:

https://github.com/getsentry/sentry-java/blob/f6949d1eb41d87b7b9f064423999053e9ce55412/sentry-logback/src/test/kotlin/io/sentry/logback/SentryAppenderTest.kt

have you tried it? could be because you are adding contexts from one thread and capturing an exception on another thread?

[dhufnagel]

Yes, using the MDC is already working. But unfortunately they only result additional context data or tags in the sentry backend, so that there is always 0 affected users of an event.
What I like to use is the great user features of sentry backend and add special tags or MDC properties to the user object. This could be done by filtering the MDC properties and create an user object for special property keys.

[marandaneto]

@dhufnagel interesting use case, thanks for that.

I'll discuss this internally, but it's actually documented that for this type of uses cases you'd need to use the Sentry static API: https://docs.sentry.io/platforms/java/guides/logback/

[maciejwalkowiak]

I like this idea. Currently it is possible to implement it with a custom event processor, but it also means that users would have to init Sentry manually. We could make it easier and resolve certain MDC properties directly on user object. What do you think @bruno-garcia?

[dhufnagel]

I created a log4j12 appender PoC with this "feature" (see also #1055). This could easily be integrated into the logging appenders.
More general this could also be integrated to the Sentry backend, but I guess this would be more work to do and would take longer to finally be integrated.
I created a gist for the PoC: https://gist.github.com/dhufnagel/2f42264c93f3900f2a22dfa0602d76b9

This PoC also includes a way to handle the "in-app-include" system property and introduces a special MDC prefix for sentry tags: "sentry.tag.*". It also keeps the "sentry.mdctags" system property that seems to be removed in the new log4j2 handler?!
There should be a better way to handle the properties, because I only access System.properties, and do not handle the other ways sentry properties could be set.