[Pacemaker] network check without ping

[Arnold Krille]

On Thu, 14 Mar 2013 14:06:36 +0000 Owen Le Blanc <LeBlanc at man.ac.uk>
wrote:
> I have a number of pacemaker managed clusters.  We use an independent
> heartbeat network for corosync, and we use another network for the
> managed services.  The heartbeat network is routed using different
> hardware from the service network.  We have two machine rooms, and
> our normal pacemaker clusters have one node in each machine room.
> 
> In the past I've used ocf:pacemaker:ping as part of our
> configurations, but we had problems, since our network is busy, and
> many of the routers (the most reliable things to ping) are configured
> to ignore pings when they have too much to do otherwise.  In this way
> we often had false connectivity failures in the past, and services
> would flop from one side to the other.
> 
> Recently we had a power failure which affected all of the switches on
> our service network in one machine room.  This meant that all
> services in that machine room were unavailable.  Our pacemaker
> clusters unfortunately saw this as no problem, since without a ping
> test, they couldn't tell that the network was down.
> 
> Has anyone done any work to measure network connectivity in
> connection with pacemaker without using ping?  I can see a couple of
> potential ways to avoid it, but I hate to reinvent wheels.

I have seen a commercial (but pacemaker-based) solution that seemed to
use link-detection on the hw-level to suicide the local node when both
links (one to the outside and one to the peer) went down.

But I don't even know if this was done inside pacemaker, nor did I have
time to think about something similar for our cluster.

I just trust that four links using two switches with independant power
will be safe enough...

Have fun,

Arnold
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