[Openais] Re: messages and cluster generation

[Steven Dake]

On Thu, 2004-09-16 at 10:16, Mark Haverkamp wrote:
> Steve,
> 
> When I receive a mcast, is there any way to tell which generation of the
> cluster it came from? During a configuration change, I send a mcast from
> the confchg_fn to start a recovery process to send retained messages.  
> If multiple config changes occur, I don't see how I can tell one config
> change mcast from another, when the last one has arrived, etc.  I see
> that gmi generates a memb_conf_id.  Is this the same value on each of
> the cluster nodes?  If it is, could it be passed to the confchg_fn so I
> can tag my mcasts?
> 
> Thanks,
> Mark.

Mark,

We could add memb_conf_id to the configuration change.  It is the same
on each processor.  In the past I had considered adding it, but couldn't
see an immediate use for it.  I'm not opposed to adding it...

I believe what you want should already be present, though.  When a
configuration change occurs, and then multicasts occurs, all those
multicasts will have been sent in the configuration change that last
occured.  If there is a new configuration change, then the new
multicasts will represent that new configuration change (and will be
delivered after the configuration change).

I think there may be some problems here with queueing.  Ie: you queue a
message in one configuration, and then the message is sent in a new
configuration because a change happens while the message is queued.  Is
that the problem you are seeing?  If so, I think we could/should fix
this problem in gmi.

Does the above help, or do you still think we need the memb_conf_id
passed to the confchg function?

What do you intend to do if the memb_conf_id is invalid in the multicast
message?  Ignore the message?

Thanks
-steve