class Cabin::Metrics

What type of metrics do we want?

What metrics should come by default? Per-call/transaction/request metrics like:

- hit (count++ type metrics)
- latencies/timings

Per app or generally long-lifetime metrics like:

- "uptime"
- cpu usage
- memory usage
- count of active/in-flight actions/requests/calls/transactions
- peer metrics (number of cluster members, etc)

github.com/codahale/metrics/tree/master/metrics-core/src/main/java/com/yammer/metrics/core Reading what Coda Hale’s “Metrics” stuff has, here’s my summary:

gauges (callback to return a number)
counters (.inc and .dec methods)
meters (.mark to track each 'hit')
  Also exposes 1, 5, 15 minute moving averages
histograms: (.update(value) to record a new value)
  like meter, but takes values more than simply '1'
  as a result, exposes percentiles, median, etc.
timers
  a time-observing interface on top of histogram.

With the exception of gauges, all the other metrics are all active/pushed. Gauges take callbacks, so their values are pulled, not pushed. The active metrics can be represented as events since they the update occurs at the time of the change.

These active/push metrics can therefore be considered events.

All metrics (active/passive) can be queried for ‘current state’, too, making this suitable for serving to interested parties like monitoring and management tools.