[Openais] cpg join/leave lists

Lars Marowsky-Bree lmb at suse.de
Mon Jul 20 03:17:09 PDT 2009


On 2009-07-13T09:33:50, Steven Dake <sdake at redhat.com> wrote:

> Hmm I don't recall saying they are unreliable or cannot be believed.
> The problem with the join and left list is they don't follow the
> semantics of virtual synchrony, meaning there is no consistent view of
> these join/left lists on each node.  The calculations that generate them
> assume a node-local view instead of a global view.
> 
> So they are not reliable for making distributed decisions because they
> don't follow VS, not because they don't generate proper output.

Can't you just hide the current ones and instead have the new process send a
"I joined" message, which would obey virtual synchrony?

(Node leaves are more difficult, but I wanted to suggest a low hanging
fruit first ;-)

CHAOS (Clustered High Availability Operating Services), SGI's
messaging/membership layer, provide(s|d) virtual synchrony for
join/leave too, by treating the join/leave as a "regular" message
basically. (Of course, leaves would only be virtual synchronous within
a given partition, that is obvious.)


Regards,
    Lars

-- 
Architect Storage/HA, OPS Engineering, Novell, Inc.
SUSE LINUX Products GmbH, GF: Markus Rex, HRB 16746 (AG Nürnberg)
"Experience is the name everyone gives to their mistakes." -- Oscar Wilde



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