[ClusterLabs] What are RHCS and LHA fence agents?

[Yan Gao]

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.

>>>
>>> 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

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
> 
> 
>