Update handlers in jfr-streaming to match spec

[roberttoyonaga]

Description:
These changes try to update the existing JFR streaming handlers to match the specification here. I think this is needed because it seems as though the handler implementations and the spec have fallen a bit out of sync.

Testing:

Tests were adjusted accordingly to match the updated handler implementations.

Outstanding items and questions:

Tests for specific GC implementations (G1, parallel) have been omitted. I am not sure of a good way to guarantee a specific implementation is used for specific tests.

None of the metrics process.runtime.jvm.memory.* will include theAttribute pair (type,"nonheap"). Question: Doesn't non-heap memory fall under the process.runtime.jvm.buffer.* metrics?

Not all of the pool names of the metrics process.runtime.jvm.memory.* are covered yet. This is in part because we require JDK JFR support to actually emit data for missing pools in JFR events, and partly because more handlers for other GC implementations need to be written in the future.

[breedx-splk]

Thanks for getting these updates in place, much appreciated! Just had a few ideas but looks good overall.

[breedx-splk]

This pattern of checking a field, getting that field, then casting it to RecordedObject is repeated several times here. What if you had a helper method like this:

  private void doIfAvailable(RecordedEvent event, String field, Consumer<RecordedObject> closure){
    if(!event.hasField(field)) {
      return;
    }
    Object value = event.getValue(field);
    if(value instanceof RecordedObject){
      closure.accept((RecordedObject) value);
    }
  }

then you can just invoke a few times like:

doIfAvailable(event, "edenSpace", edenSpace -> {
  if (edenSpace.hasField(USED)) {
    if (before) {
      usageEden = edenSpace.getLong(USED);
    } else {
      usageEdenAfter = edenSpace.getLong(USED);
    }
  }
});
...

I think that would help with some of the boilerplate there without building up too much "infrastructure".

[roberttoyonaga]

That's a good idea! I implemented your suggestion

[breedx-splk]

Thanks again!

[trask]

thx!