Announce: mogilefs-server 2.15, aka "fsck, rebalance, drain"

[Brad Fitzpatrick]

> Brad Fitzpatrick wrote:
> > Gearman server/clients are now required
>
> Can you elaborate on what Gearman server/clients are? I've not
> seen any mention of them previously on this mailing list.
>
> I see the modules e.g. Gearman::Server in CPAN, but the documentation
> is rather opaque about what it does. Something about servers, clients,
> and workers but nary a clue about what they all actually do and why you
> would want to use them.

Start with slide 59 of this presentation...

   http://danga.com/words/2007_04_linuxfest_nw/

The way MogileFS is using Gearman, though, isn't over the network with
separate gearmand (Gearman::Server) processes and worker processes, but
rather an embedded Gearman::Server inside the mogstored, and then worker
processes as children, speaking the gearman protocol over a unix
socketpair.

Because of this, you can be totally oblivious to what's going on.... no
extra config/deployment of gearman servers/workers required.

We just do this so we can do RPC between different procesess, including
doing blocking operations in child processes, using an async caller in
another (non-blocking) process.

- Brad