This patch implements hooks inside MySQL/Innodb engine, which can be used to build external replication system for MySQL servers following wsrep API (https://launchpad.net/wsrep). The replication system built on these hooks can be asynchronous or synchronous and have single or multi-master support.

The replication hooks provide management of transaction write sets:

* populating of write sets, in the sending side
* applying of write sets, in the receiving end

The applying happens by high priority transaction(s). Innodb lock manager has been modified to give preference to dedicated high priority MySQL threads.

There are also calls for providing "total order isolated" processing of certain SQL statements. This feature guarantees that each MySQL server in the cluster process the SQL statement in the same order and uninterrupted. .e.g. all DDL statements need to be processed isolated, to maintain data consistency in the cluster.

*** COMPILATION ***
The patch requires certain flags to be (un)set, specifically it DOES NOT COMPILE WITH -DEMBEDDED_LIBRARY. To compile use provided ./BUILD/*-wsrep scripts.

Mailing list: http://groups.google.com/group/codership-team?hl=en

https://launchpad.net/galera implements Galera wsrep replicator for this project.