SNAP segment cache metrics

Name Prefix: <app-id>.sparklinedata.executor.segmentcache

Name	Type	Description
SegmentRequest	Timer	Counts and Times for Segment Request calls
SegmentLoad	Timer	Counts and Times for when a Segment is Loaded from Deep Store.
SegmentSizePerRequest	Histogram	Size distribution of Segments being requested from local-cache.
SegmentSizePerLoad	Histogram	Size distribution of Segments being copied from deep store.
numCacheHits	Meter	Count of Requests that are serviced by locally cache segments
cacheHitRatio	Ratio	Ratio of numCacheHits to SegmentRequests
makeSpaceRequest	Timer	Counts and Times when a Segment Request required space to be made in local cache.
cacheTotalSpace	Guage	Total Space of Local Cache
cacheFreeSpace	Guage	Current Free Space in Local Cache