Thanks Maysam. I am trying out Omid to see if it will fit my needs. As I told you I am writing to hbase from a map reduce jobs. If my commit and rollback is around a reducer task then it will be quite straight forward. But if the commit should happen if all tasks of the M/R job succeed(which is what I would want, because if some reducer tasks succeed and some fail, it will not be possible to rerun partial data), it gets tricky. Am I on the wrong track?
Thanks, Deepika On Mon, 2012-03-19 at 11:44 -0700, Maysam Yabandeh wrote: > Hi Deepika, > > Omid provides Snapshot Isolation (SI), which is a well-known isolation > guarantee in database systems such as Oracle. In short, each transaction > reads from a consistent snapshot that does not include partial changes by > concurrent (or failed) transactions. SI also prevents write-write conflicts > between concurrent transactions. The overhead of Omid on HBase is negligible > and does not require any changes into HBase, with the only exception of HBase > garbage collection algorithm that is replaced via a coprocessor. hbase-trx, > on the other hand, does not provide read snapshots and is not safe with > client failures. You can find a more detailed comparison in the Omid wiki > page: > https://github.com/yahoo/omid/wiki > > Cheers > - Maysam Yabandeh > > On Mar 19, 2012, at 6:49 PM, Deepika Khera wrote: > > > Hi, > > > > I have some map reduce jobs that write to Hbase. I am trying to pick a > > library that could provide transactional support for Hbase. I looked at > > Omid and hbase-trx . > > > > Could you please provide me with a comparison between the two so I can > > make the right choice. > > Are there any other ways to do this? > > > > Thanks, > > Deepika > > > > > > > > >
