HBase Write Ahead Log

A new HBase utility from Outerthought, HBase Rowlog library:

If you have an HBase table, and each time a create, update or delete operation happens on a row of this table an index should be updated you’ll need a system to guarantee that this update actually happens even in the case of failing nodes. A Write Ahead Log (WAL) can give you such a guarantee.

The purpose of the WAL is to guarantee the execution of “secondary, subordinate actions” in case a Lily repository node would die in the midst of their execution. These actions are synchronous actions, this means that (1) they should complete before returning execution to the caller, and (2) they should complete before the next update on the record is allowed to happen.

I think Riak solved this using pre-commit and post-commit hooks and CouchDB using the _changes feed (a basic demo of using CouchDB _changes or you can read about a generic CouchDB _changes consumer or streaming notifications about updates).

via: http://lilycms.org/lily/roadmap/sketchbook/hbaserowlog.html