kamon-io/Kamon — pull request #43 by ivantopo (2014-07-03 03:35:43+00:00)
Title: ! all: refactor the core metric recording instruments and accomodate UserMetrics

This PR is including several changes to the kamon-core, most notably:
- Formalize the interface for Histograms, Counters and MinMaxCounters. Making sure
that the interfaces are as clean as possible.
- Move away from the all Vector[Measurement] based Histogram snapshot to a new approach
in which we use a single long to store both the index in the counts array and the
frequency on that bucket. The leftmost 2 bytes of each long are used for storing the
counts array index and the remaining 6 bytes are used for the actual count, and
everything is put into a simple long array. This way only the buckets that actually
have values will be included in the snapshot with the smallest possible memory
footprint.
- Introduce Gauges.
- Reorganize the instrumentation for Akka and Scala and rewrite most of the tests
of this components to avoid going through the subscription protocol to test.
- Introduce trace tests and fixes on various tests.
- Necessary changes on new relic, datadog and statsd modules to compile with the new
codebase.

Pending:
- Finish the upgrade of the new relic to the current model.
- Introduce proper limit checks for histograms to ensure that we never pass the 2/6 bytes
limits.
- More testing, more testing, more testing.
- Create the KamonStandalone module.

I think that we still have a lot to do over this, but it is time to move it to master and start building on top of it.