Josh Elser created HBASE-18133:
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             Summary: Low-latency space quota size reports
                 Key: HBASE-18133
                 URL: https://issues.apache.org/jira/browse/HBASE-18133
             Project: HBase
          Issue Type: Improvement
            Reporter: Josh Elser
            Assignee: Josh Elser


Presently space quota enforcement relies on RegionServers sending reports to 
the master about each Region that they host. This is done by periodically, 
reading the cached size of each HFile in each Region (which was ultimately 
computed from HDFS).

This means that the Master is unaware of Region size growth until the the next 
time this chore in a RegionServer fires which is a fair amount of latency (a 
few minutes, by default). Operations like flushes, compactions, and bulk-loads 
are delayed even though the RegionServer is running those operations locally.

Instead, we can create an API which these operations could invoke that would 
automatically update the size of the Region being operated on. For example, a 
successful flush can report that the size of a Region increased by the size of 
the flush. A compaction can subtract the size of the input files of the 
compaction and add in the size of the resulting file.

This de-couples the computation of a Region's size from sending the Region 
sizes to the Master, allowing us to send reports more frequently, increasing 
the responsiveness of the cluster to size changes.



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