* Removed leader commands for Shutdown and Exit
* Member shutdown itself when it sees itself as Exiting
* Singleton cluster with status Exiting will shutdown itself,
in case the Exiting gossip never arrives
* Exiting member not part convergence check
* Exiting member is removed by leader (on convergence) when the
exiting member is in the unreachable set, i.e. sucessfully shutdown
* Reverted the change made for #3266, i.e. Exiting is
detected as unreachable again.
* Adjust ClusterSingletonManager to new Exiting behaviour
* Fix bug in HeartbeatSender, which caused it to continue to
send heartbeats to removed nodes, instead of rebalancing
* Refactoring of leaderActions method
* Leaving section in docs
* Refactoring of standard metrics extractors and data structures
* Removed optional value in Metric, simplified a lot
* Configuration of EWMA by using half-life duration
* Renamed DataStream to EWMA
* Incorporate review feedback
* Use binarySearch for selecting weighted routees
* More metrics selectors for the router
* Removed network metrics, since not supported on linux
* Configuration of router
* Rename to AdaptiveLoadBalancingRouter
* Remove total cores metrics, since it's the same as jmx getAvailableProcessors,
tested on intel 24 core server and amd 48 core server, and MBP
* API cleanup
* Java API additions
* Documentation of metrics and AdaptiveLoadBalancingRouter
* New cluster sample to illustrate metrics in the documentation,
and play around with (factorial)
* MetricsSelector, calculate capacity, weights and allocate weighted
routee refs
* ClusterLoadBalancingRouterSpec
* Optional heap max
* Constants for the metric fields
* Refactoring of Metric and decay
* Rewrite of DataStreamSpec
* Correction of EWMA and removal of BigInt, BigDecimal
* Separation of MetricsCollector into trait and two classes,
SigarMetricsCollector and JmxMetricsCollector
* This will reduce cost when sigar is not installed, such as
avoiding throwing and catching exc for every call
* Improved error handling for loading sigar
* Made MetricsCollector implementation configurable
* Tested with sigar
