v1.1.0 - Router Metrics Improvements and Dropping Akka 2.3 Support

Router Metrics Improvements

This release introduces a few changes related to router metrics:

• Introduced two new metrics:
  • akka.router.pending-messages as a range sampler tracking how many messages are waiting to be processed across all routees of a router.
  • akka.router.members as a range sampler tracking the number of routees in a router.
• All routers now have a routerClass and routeeClass tags.
• The dispatcher tag used on BalancingPool routers has been fixed. For this type of routers the routees would always get a special dispatcher assigned, but the router itself could run on a different dispatcher (usually the default dispatcher). This duplicates the number of metrics created for BalancingDispatchers and leaves half of them alive when removing the router. Since this PR the router actor will have the dispatcher tag value to match the dispatcher name of the routees, which is not 100% accurate, but we can live with that.

Backwards incompatible changes:

The akka.group.mailbox-size metric was renamed to akka.group.pending-messages to stay consistent with the previous change (pending messages is much more close to reality than mailbox size since there is no single mailbox there). The semantics remain the same, only the name was changed.

Dropping Akka 2.3 Support

Starting on this release we are no longer publishing artifacts for Akka 2.3 and completely removed the related project from the codebase. Akka 2.3 reached end-of-life when Akka 2.5 was released, over a year ago, even Akka 2.4 reached EOL as well. For now we are only dropping support for Akka 2.3 and plan to continue supporting Akka 2.4 as long as the maintenance burden remains low.