[linux-lvm] clvmd interface question

[linux-lvm] clvmd interface question

[John DeFranco]

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.

Thanks

-- 
==========

John DeFranco
Hewlett-Packard Company
Availability Clusters Solution Division
19111 Pruneridge Ave, M/S 4101
Cupertino, CA 95014 
phone: 408-447-7543
mailto: john.defranco@hp.com

Re: [linux-lvm] clvmd interface question

[Patrick Caulfield]

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

Re: [linux-lvm] clvmd interface question

[Jonathan E Brassow]

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
>
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@redhat.com
> https://www.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>

Re: [linux-lvm] clvmd interface question

[Patrick Caulfield]

Jonathan E Brassow wrote:
> 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.

clvmd uses several cluster manager features that magma doesn't provide - off the
top of my head I can't actually remember what these are as it's been ages since
I did it!

Of course, it's quite probable that magma could be extended to provide these
features.  The main reason it is the way it is is that quite a lot of rewriting
of clvmd would have been necessary for it to fit into magma's model due to the
short-sighted way it (clvmd) was written. In effect the abstraction layer (such
as it is) tries to make gulm look like cman/dlm.

I'm sure it could be done...but it's all time...

-- 

patrick

Re: [linux-lvm] clvmd interface question

[John DeFranco]

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.
>
>  
>
Thanks for the info. I'll be looking into this.

-- 
==========
Cheers
   -jdf