[ClusterLabs] What are RHCS and LHA fence agents?

Tue Apr 8 13:27:04 UTC 2025

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.

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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