[ClusterLabs] Plea for a new DLM release and thoughts on its Pacemaker interface

[wferi at niif.hu]

David Teigland <teigland at redhat.com> writes:

> On Tue, Jan 08, 2019 at 11:56:18AM +0100, wferi at niif.hu wrote:
> 
>> The DLM git repo accumulated a couple of patches over the 4.0.7 tag,
>> would you mind cutting a new release for packaging?
>
> ok

Hi David,

I found the ce1e4cc9 commit bumping the version, but neither a dlm-4.0.8
tag nor a new release tarball at https://releases.pagure.org/dlm/.  Are
you holding those back for a reason, or don't you even plan to provide
them?

>> And once we're at it: the STONITH helper embedding to SONAME of the
>> Pacemaker fencing library is pretty obscure and easy to miss on library
>> transitions.  I guess it's done to avoid unconditionally pulling in
>> Pacemaker libraries and their dependencies.  Don't you think this helper
>> agent had better be a part of the Pacemaker CLI utilities instead?  In
>> my opinion the ABI coupling is stronger than the textual interface
>> dlm_controld uses.  But even if not, it would be possible to dynamically
>> link the agent against the Pacemaker libraries and split it into a
>> separate optional package to make all those dependencies avoidable on
>> systems not using Pacemaker fencing.  If all parties agree, of course.
>
> I wasn't aware of the difficulties.  I'm open to suggestions as long as
> dlm_controld has a fence-agent-style binary to call.

I suggest using the stonith_api_time() and stonith_api_kick() functions
directly and linking against libstonithd explicitly.  Yes, this would
require having the Pacemaker libraries around at install time, too, but
splitting the dlm_stonith binary into a separate package would nicely
counteract that, since dlm_stonith does nothing without those libraries,
so the dependency is already strict in the functional sense.  And
explicit linkage would make this apparent for automatic tools.

Does dlm_controld react differently to dlm_stonith not being around and
it returning -ELIBACC/ENOSYS?
-- 
Regards,
Feri