ExecutorAllocationManagerSource — Metric Source for Dynamic Allocation

ExecutorAllocationManagerSource is a metric source for dynamic allocation with name ExecutorAllocationManager and the following gauges:

executors/numberExecutorsToAdd which exposes numExecutorsToAdd.
executors/numberExecutorsPendingToRemove which corresponds to the number of elements in executorsPendingToRemove.
executors/numberAllExecutors which corresponds to the number of elements in executorIds.
executors/numberTargetExecutors which is numExecutorsTarget.
executors/numberMaxNeededExecutors which simply calls maxNumExecutorsNeeded.

Note	Spark uses Metrics Java library to expose internal state of its services to measure.

ExecutorAllocationManagerSource