[jira] [Created] (HBASE-13472) Polish IN_MEMORY table behavior

["Andrew Purtell (JIRA)" <ji...@apache.org>]

Andrew Purtell created HBASE-13472:
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             Summary: Polish IN_MEMORY table behavior
                 Key: HBASE-13472
                 URL: https://issues.apache.org/jira/browse/HBASE-13472
             Project: HBase
          Issue Type: Task
            Reporter: Andrew Purtell


For a long time we've been able to support a mode of operation that keeps as much table data as possible in memory, so HBase can be used as an 'in-memory' DB with fully durable WAL and write-behind persistence of table data. However:

- There are a set of relevant schema options (IN_MEMORY, CACHE_ON_WRITE, PREFETCH_BLOCKS_ON_OPEN, block encoding), so set up isn't simple. We should have a shortcut that sets all this up in one place. I'm thinking a utility class with static helpers that configure a table descriptor with all of the needed bits. (Other ideas?) 

- We don't have a safety valve. An in-memory table can become too large, where it crowds out all blockcache space for other tables on the cluster, where it falls out of blockcache and performs poorly without warning because it's become too big. Consider table quota support with an option for region size limits as % of total heap consumed by regions for a given table. Warn at soft limit. Refuse writes if over hard limit.

Follow on work can investigate options hooking up to offheap work. That's not in scope here.



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