Re: Waiting for commit lock

[Mikael Ronström]

Each MySQL Server has a set of locks to operate on tables.
NDB tables are often accessible even when one MySQL Server
has locked parts.
In principle one can say that NDB allows for higher concurrency
than the MySQL Server is able to handle.
This is one of the reasons why it makes sense to have separate
MySQL Servers for binlogging and to execute metadata statements.

I am not sure exactly what the commit lock is.
So please post the content of a SHOW PROCESSLIST from the problematic
MySQL Server and the error log in this server as well.
These probably have some hints what is happening.

Here is what the manual says about this lock:
Waiting for commit lock

A statement that causes an explicit or implicit commit is waiting for release of a read lock or FLUSH TABLES WITH READ LOCK is waiting for a commit lock.

So it might be that you have locked some table in the problematic
MySQL Server. Table locks are only local to a MySQL Server for NDB tables.