Add GC causes to jvm GC related metric

[steverao]

Area(s)

area:jvm

What's missing?

The GC log in Java is very helpful for users to understand the GC status of the application. I found that there are already definitions and implementations of related metric. I found that GC cause is also very helpful to users. Sometimes users don’t understand why GC occurs, so they need to use GC logs to get more detailed information. If we can include GC causes(such as System.gc(), Allocation Failure, Metadata GC Threshold etc.) information, it will be valuable to users.

Describe the solution you'd like

Add GC causes information to semantic convention.

[trask]

cc @open-telemetry/semconv-jvm-approvers

[trask]

I think this is a great idea.

It may need to be opt-in due to #722.

Or better we could introduce it as "opt-in" for existing instrumentations, but "recommended" for new instrumentations or instrumentation that are willing to take a major version bump.

Then we could enable it by default when we do a major version bump of the Java instrumentation.

[jack-berg]

If we can include GC causes(such as System.gc(), Allocation Failure, Metadata GC Threshold etc.) information, it will be valuable to users.

Where would you source this information from?

The current JMX GC instrumentation has access to GarbageCollectionNotificationInfo and GcInfo.

Are you thinking GarbageCollectionNotificationInfo#getGcCause()?

[steverao]

Are you thinking GarbageCollectionNotificationInfo#getGcCause()?

yes, we can get it from above method.