CTDB API

[tridge at samba.org]

Alexander,

 > When speaking of "conditional append" where do the condition function
 > has to be executed?

They are executed on the DMASTER. In many cases the DMASTER will be
the local node (as the record will have migrated), but it could just
as easily be any other node.

A 'conditional append' is very much like a RPC call. Every node in the
cluster registers the same set of functions which are available via
one of these calls. The CTDB infrastructure sends the parameters of
this function to the node that has the record data. It runs the
function on behalf of the caller, possibly updating the record.

I will probably rename 'conditional append' to something like
CTDB_REQ_CALL to make this clearer. I also think that CTDB_REQ_FETCH
can just be an instance of a CTDB_REQ_CALL (so we can remove it).

It might make it easier to follow if I reword the CTDB proposal to use
more RPC style language. It is really just a 'record oriented RPC
system' and maybe thinking of it that way will be easier.

Cheers, Tridge