mysql cluster + get_lock

[komtanoo.pinpimai at livetext.com]

Hello List,

Just want to share an experience of MogileFS with mysqlcluster. Our
system, we have 4 mysqlcluster's ndbd machines, 9 MogileFS machines, each
is running both mogilefsd and mogstored and also mysqld(it connects to
ndbd machines). I have just found out that this setting doesn't work,
because mogilefsd uses GET_LOCK/RELEASE_LOCK to avoid race condition.
However, GET_LOCK/RELEASE_LOCK in the latest mysqlcluster works only in
mysqld process, therefore mogilefsd cannot use multiple mysqld processes.

My point is even we uses mysqlcluster for mogilefs, we still have one
single point of failure which is the single mysqld process. It would be
solved, if mogilefsd uses transaction or other strategies to avoid race
condition, or it gets lock from somewhere else, like lock_cluster_server,
instead of mysql.(I don't know if anyone has ever built it)

-kem