[ClusterLabs Developers] Impact of changing Pacemaker daemon names on other projects?

[Kristoffer Grönlund]

Ken Gaillot <kgaillot at redhat.com> writes:

> Hi all,
>
> As I'm sure you've seen, there is a strong sentiment on the users list
> to change all the Pacemaker daemon names in Pacemaker 2.0.0, mainly to
> make it easier to read the logs.
>
> This will obviously affect any other scripts and projects that look for
> the old names. I'd like to hear more developer input on how far we
> should go with this, and how much or little of a headache it will
> cause. I'm interested in both the public projects that use pacemaker
> (crmsh, pcs, sbd, dlm, openstack) and one-off scripts that people
> commonly put together.
>
> In order of minimum impact to maximum impact, we could actually do this
> in stages:
>
> 1. Log tags: This hopefully wouldn't affect anyone. For example, from
>
> Mar 12 12:10:49 [11120] node1 pacemakerd:     info:
> crm_log_init:     Changed active directory to /var/lib/pacemaker/cores
>
> to
>
> Mar 12 12:10:49 [11120] node1 pcmk-launchd:     info:
> crm_log_init:     Changed active directory to /var/lib/pacemaker/cores
>

Perhaps surprisingly, this is probably the part which affects crmsh the
most... For the history explorer we do a lot of log scanning and have a
set of regexes to match various interesting outputs from
pacemaker. However, we already handle changes in this format between
versions, so it's just a matter of adding another set of regexes for the
new version.

More details: https://github.com/ClusterLabs/crmsh/blob/master/crmsh/log_patterns.py

There are some other places that have similar things, like
logparser.py.

> 2. Process names: what shows up in "ps". I'm hoping this would affect
> very little outside code, so we can at least get this far.

This will also need some updates in crmsh, but not too many. There is a
list of programs to query for metadata, just adding the new names to
that list should be sufficient for example.

>
> 3. Library names: for example, -lstonithd to -lpcmk-fencing. Other
> projects would need their configure script to auto-detect which is
> available. Not difficult, but it makes all older versions of other
> projects incompatible with Pacemaker 2.0. This is mostly what I want
> feedback on, whether this is a good idea. The only advantage is
> consistency and clarity.

I would just move to the new names and require 2.0 to build the newer
versions.. so it would be a compatibility break both ways.

>
> 4. Public API symbols: for example, crm_meta_name() ->
> pcmk_meta_name(). This would be a huge project with huge impact, and
> will definitely not be done for 2.0.0. We would immediately start using
> the new convention for new API symbols, and more slowly update existing
> ones (with compatibility wrappers for the old names).

Not too much opinion here but seems questionable, not sure how much
benefit it would bring and there are clear downsides to doing it.

Cheers,
Kristoffer

> -- 
> Ken Gaillot <kgaillot at redhat.com>
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-- 
// Kristoffer Grönlund
// kgronlund at suse.com