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HBase >> mail # dev >> Omid: Transactional Support for HBase


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Re: Omid: Transactional Support for HBase
Thanks St.Ack. These are very good questions.

On Nov 4, 2011, at 19:25 , Stack wrote:

2011/11/4 Daniel Gómez Ferro <[EMAIL PROTECTED]<mailto:[EMAIL PROTECTED]>>:
Hi all,

It is my pleasure to announce the open source release of Omid, a project whose goal is to add lock-free transactional support on top of HBase. The current release includes CrSO, a client-replicated status oracle that detects the write-write conflicts to provide Snapshot Isolation. CrSO has the following appealing properties:
Nice addition Daniel.  Thank you for posting the list (FYI, slaves in
HBase are called RegionServers not DataNodes -- you might want to
update your graphic).

The graphic is updated, thanks for noticing.

What does CrSo stand for?

CrSO stands for Client-replicated Status Oracle, which is our current approach to detect conflicts with the least overhead.

  If it fails, all
transactions just abort -- the clients will time them out? (Thats not
bad I'd say).   Thanks for doing the comparison to hbase-trx.  That
helps.

If the CrSO fails it will recover its state from the Write Ahead Log (WAL) that is replicated into multiple remote storage devices via BookKeeper. (Reconstructing memory state from the stored WAL is not implemented yet).  The transactions that were started before the node failure are pessimistically aborted by the new instance of the status oracle.
Good stuff Daniel,
St.Ack