ate.actor.crashes, ate.actor.lifecycle.operation.duration and
ate.scheduler.assignment.duration named a WorkerPool by name alone. A
WorkerPool is namespaced, so same-named pools in different namespaces
merged into one series, and the three could not join the instruments
that already carry both keys.
ateattr.WorkerPoolAttributes now builds the pair, and omits both keys
when no pool is assigned, so a crash before the actor reached a worker
no longer reports an empty-string pool. This changes the series identity
of the three instruments.
Fixes#951
> It's a good idea to open an issue first for discussion.
- [x] Tests pass
- [x] Appropriate changes to documentation are included in the PR