[ClusterLabs] What are RHCS and LHA fence agents?

Wed Apr 9 07:22:09 UTC 2025

On Wed, Apr 9, 2025 at 12:07 AM Oyvind Albrigtsen <oalbrigt at redhat.com> wrote:
>
> On 08/04/25 22:27 +0900, renayama19661014 at ybb.ne.jp wrote:
> >Hi Reid,
> >Hi All,
> >
> >> > But even going back to those days (late 2012), I don't see any mention
> >> > of "nodeid" in the fence-agents repo, which included the fence_scsi
> >> > agent.
> >
> >I also looked into the nodeid parameter, but found nothing.
> >Since this was a modification made when unfencing was adopted, I thought that it might have been made possible to pass the nodeid to the unfencing STONITH device for key generation, but I could not find any description of this.
> It seems like it's probably nodeid from corosync and not related to
> fence-agents specifically:
> https://github.com/ClusterLabs/fence-agents/issues/270

That would make some sense. But since 2012 the fencer has been looking
for nodeid in the metadata of a fence agent, and reacting accordingly.
I'm not aware of a fence agent that has nodeid in the metadata.

>
> Oyvind Albrigtsen
> >
> >Best Regards,
> >Hideo Yamauchi.
> >
> >> ----- Original Message -----
> >>
> >> From: "ClusterLabs-ML" <users at clusterlabs.org>
> >> To: "Reid Wahl" <nwahl at redhat.com>
> >> Cc: "Yan Gao" <ygao at suse.com>; "ClusterLabs-ML" <users at clusterlabs.org>
> >> Date: 2025/04/08 火 19:24
> >> Subject: Re: [ClusterLabs] What are RHCS and LHA fence agents?
> >>
> >>
> >> On 2025/4/8 10:44, Reid Wahl wrote:
> >> > On Tue, Apr 8, 2025 at 12:15 AM Yan Gao <ygao at suse.com> wrote:
> >> >>
> >> >> Hi Reid,
> >> >>
> >> >> On 2025/4/8 1:52, Reid Wahl wrote:
> >> >>> On Mon, Apr 7, 2025 at 4:30 PM Reid Wahl <nwahl at redhat.com> wrote:
> >> >>>>
> >> >>>> On Mon, Apr 7, 2025 at 4:24 PM Reid Wahl <nwahl at redhat.com> wrote:
> >> >>>>>
> >> >>>>> What are RHCS and LHA fence agents, and what are they used for today?
> >> >>>>>
> >> >>>>> I would have guessed from the names and what commit messages I've found that
> >> >>>>> * RHCS refers to Red Hat Cluster Suite (a.k.a. cman clusters), which
> >> >>>>> has been unsupported since RHEL 7
> >> >>>
> >> >>> Okay, we really ought to rename this stuff soon. Pacemaker uses the
> >> >>> term "rhcs" to mean "standard fence agents" -- the kind that are from
> >> >>> the ClusterLabs/fence-agents repository. Pacemaker actually decides
> >> >>> "this agent is an RHCS-style agent" if it lives in
> >> >>> `PCMK__FENCE_BINDIR` (which is /usr/sbin on my machine) and starts
> >> >>> with "fence_".
> >> >>>
> >> >>> Sigh. Sorry to bother everyone. I'm getting frustrated by unclear and
> >> >>> legacy code :)
> >> >>>
> >> >>>>> * LHA refers to Linux-HA, which... isn't that from Heartbeat clusters
> >> >>>>> or something?
> >> >>
> >> >> Yes, they are originally from heartbeat (the major project by "Linux HA"
> >> >> community back then) and now in cluster-glue. Technically they need a
> >> >> moderator agent "fence_legacy" to be invoked.
> >> >
> >> > Interesting, thanks! Do you know whether there's been any movement to
> >> > get all of these agents (or equivalent agents) into fence-agents? I
> >> > know it's not a trivial task. It just seems odd to me that after this
> >> > much time, we haven't at least deprecated the legacy stuff.
> >>
> >> AFAICS both LHA and RHCS agents might have had a similarly long history
> >> :-) Anyway it indeed has been painful to have two different fashions .
> >>
> >> A good fact is, there are alternatives from fence-agents for the
> >> commonly used fencing mechanisms. We are planning on disabling the
> >> support for LHA agents with pacemaker-3.0 in the next major release of
> >> distribution, meanwhile still need to continue supporting them with
> >> pacemaker-2.1 code base though.
> >>
> >> >
> >> >>
> >> >>>>>
> >> >>>>> All of this is from before my time as a developer for Pacemaker. I'm
> >> >>>>> trying to understand what's still relevant and how.
> >> >>>>>
> >> >>>>> I'm including Yan Gao from SUSE, as they have some commits in the past
> >> >>>>> few years related to both agent types.
> >> >>>>
> >> >>>> Related question: Is anyone aware of ANY fence agent that supports a
> >> >>>> "nodeid" parameter? We seem to have some dead code in Pacemaker
> >> >>>> related to that. I don't see any agent in fence-agents or cluster-glue
> >> >>>> (which is apparently related to LHA fencing) that accepts a nodeid
> >> >>>> parameter.
> >> >>
> >> >> Indeed so.
> >> >>
> >> >> So-called "Stonith scsi agent support" was mentioned in the PR that
> >> >> introduced this:
> >> >> https://github.com/ClusterLabs/pacemaker/pull/186
> >> >
> >> > Also interesting... I didn't find that PR, because when I looked
> >> > through `git log`, I found this commit instead:
> >> > https://github.com/ClusterLabs/pacemaker/commit/c2265a12
> >> >
> >> > It's not attached to any PR. These two commits appear to be identical
> >> > and both part of the main branch. Odd.
> >> >
> >> > But even going back to those days (late 2012), I don't see any mention
> >> > of "nodeid" in the fence-agents repo, which included the fence_scsi
> >> > agent.
> >> >
> >> > I'm inclined to get rid of the fencer code that automatically adds
> >> > this parameter.
> >>
> >> +1
> >>
> >> Regards,
> >>    Yan
> >>
> >> >
> >> >>
> >> >> But not sure whether it had anything to do with fence_scsi agent...
> >> >>
> >> >> Regards,
> >> >>     Yan
> >> >>
> >> >>
> >> >>>
> >> >>> The nodeid question still stands.
> >> >>>
> >> >>>>
> >> >>>> --
> >> >>>> Regards,
> >> >>>>
> >> >>>> Reid Wahl (He/Him)
> >> >>>> Senior Software Engineer, Red Hat
> >> >>>> RHEL High Availability - Pacemaker
> >> >>>
> >> >>>
> >> >>>
> >> >>
> >> >
> >> >
> >>
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-- 
Regards,

Reid Wahl (He/Him)
Senior Software Engineer, Red Hat
RHEL High Availability - Pacemaker