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Re: [linux-lvm] clvmd interface question



Also, there is a package called 'magma' that lives in the cluster tree. This is an abstraction layer to different cluster managers and lock managers. It has the ability to accept plugins for different cluster managers. I wonder if it would be useful for clvm to use magma, then writing plugins is easy and you never have to touch code that makes use of the cluster managers.

Patrick would know if this is a worthwhile goal.

 brassow

On Nov 18, 2005, at 2:14 AM, Patrick Caulfield wrote:

John DeFranco wrote:
Hi, I'm looking for some information. I'm interested in learning more
about the clvmd daemon. I've search and found various pieces of info in
addition to looking at the code. Specifically I looking to for
information (a spec) on how one might be able to add a new cluster
manager plugin if you will (if that is even possible). I know that clvmd interfaces with a couple of different cluster managers now but I'd like
to expland this if possible.

clvmd supports cman and gulm, it has it's own internal function switch that
determines what to do for each cluster manager.

To be honest it's not a good API as it was originally only designed to work with cman and the gulm support was bolted on later - so adding a new cluster manager
might be a bit of work.

Have a look at the bottom of LVM2/daemons/clvmd/clvmd-cman for the function switch.

You'll also need to be aware that CMAN provides its own messaging system, which gulm does not. If your cluster manager provides a messaging system then I recommend you use it - otherwise you should be able to use the tcp-comms.c file
with clvmd (that gulm support uses).

Another way, that might be easier, is to patch clvmd with the libcman patch in head of cluster CVS (cluster/cman/lib/clvmd-libcman.diff) and write a library for your cluster manager that emulates libcman - that one is a nice simple API
and it will be supported by future versions of cman too.

--

patrick

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