Christine Caulfield napsal(a):
On 26/03/15 10:36, Christine Caulfield wrote:
On 25/03/15 01:24, Steven Dake wrote:
I think if you dont care about performance, you can have a daemon
process (second process) connect as a cpg service and maintain an
overlay network on top of CPG. Then many other external endpoints could
connect to this server over TCP.
That's an interesting idea that I quite like. And it might be nice and
easy to get a proof-of-concept up and running.
It would probably require a different API to the normal corosync one
(I'm not sure that emulating libcpg etc for a different daemon would be
sensible).
How does that sound to the Pacemaker team?
I've been thinking about Steven Dake's idea most of today and I really
like it. It's clean, doesn't interfere with corosync internals and will
be easier to implement and maintain. Also it won't break the on-wire
protocol.
The one main drawback I see is that the CPG membership will not include
the satellite nodes (unless the parent joins the CPG once for each
parent, which seems excessive). Looking at the pacemaker code this
doesn't seem to be a problem. We can still send node up/down
notifications if needed, even if a satellite joins the cluster, it would
just show the same list of central nodes each time.
I'm less worried about the performance hit for this sort of
implementation though it does need to be borne in mind. I'll forward an
updated document early next week for perusal if David or Andrew chip in
about Pacemaker requirements above.
thoughts?
Looong time ago there was also idea about remote cpg. So basically
application uses special cpg which just forwards request to master node.
So only difference between normal and remote cpg would be IPC layer. In
theory this may be also way to go because it's essentially same idea as
additional daemon but without need for daemon. I can imagine to enrich
CPG so not only nodeid is sent but also IP of sending client so it would
be possible to find out which satellite "nodes" (clients) exists.
What would be probably very hard to achieve (both daemon/remote cpg)
seems to be a possibility to have only ONE configuration file across all
nodes (master/satellite) and ability to promote one of satellite node to
master node when one of master nodes die.
Honza
Chrissie
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