[ClusterLabs] What are RHCS and LHA fence agents?

Wed Apr 9 07:06:59 UTC 2025

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

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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