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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