Re: Keepalived preempts

On 09/17/2016 12:56 PM, Quentin Armitage wrote:
> I've both looked at the 1.2.16 code, and tested it with your
> configurations, and I cannot reproduce a new instance of keepalived
> taking over as master.

Quentin, thanks for such a thorough testing & response!  Greatly
appreciate you taking a look.

 > Can you try the following:
> 1. Stop keepalived on ip-10-84-129-151, so that ip-10-84-128-202 becomes
> master.
> 2. Start keepalived again on ip-10-84-129-151.
> Does ip-10-84-129-151 take over as master, or does ip-10-84-128-202
> remain as master? I suspect ip-10-84-128-202 will remain as master.
>
> If ip-10-84-128-202 remains as master, then it would suggest that
> keepalived is working as expected.

The prediction is correct, and I agree keepalived is working.  I've
found these boxes have terrible clock problems, and I suspect that's
responsible for a number of issues that I thought were related to
keepalived.

(Details: https://bugs.launchpad.net/ubuntu-on-ec2/+bug/1625193)

> Does ip-10-84-129-151 start keepalived as part of the boot/init process?
> My guess is that when ip-10-84-129-151 boots, it starts keepalived
> before the networking is fully up, and so it doesn't receive any
> advertisements from ip-10-84-128-202, and hence times out and becomes
> master. You then have a split brain situation with both systems thinking
> they are master and are of equal priority.

Yes it is, and I think your assessment is right on.  That means the
issue from Friday was different than previous issues (which turn out to
probably be time-related).

Systemd should be able to help here - sounds like a reason to start
thinking about a move to 16.04.

> I hope that helps,

Yes, quite a lot!  Thanks very much,

Ross

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