Hi Amol, On Sun, Jun 07, 2015 at 11:08:58PM +0000, Amol wrote: > hi Willy,thanks for elaborate explanation on 2 methods, here is my scenario( > i didn't explain much in details earlier) > > I have load balancer 1 which handles all my connections it is a ubuntu 10.04 > LTS machine with haproxy 1.5 running on it, LB1 <public ip> is our DNS for > client applications. having said that. we however are failing a few > compliance scenarios, hence i need to upgrade the VM to 12.04, however in > order to do so this could take us about 2-4 hours and in the mean time the > entire VM has to be rebuild (don't want to do a inplace upgrade). So we only > have http connections and those are also very shortlived 1-2 mins max, and i > have a load balancer 2 configured so that during data center/networking > issues all the connections could still fail over (using keepalived on public > IP of LB1).
That's the first problem, you should never be using one node's IP address but have one IP address dedicated to the service. > so far i tried using keepalived to fail over the public ip to the > LB2, but in that scenario the network connection of LB1 is complete lost and > no updates or packages can be installed making it impractical. Absolutely and that's the reason for what I mentionned above. Now you'll have to assign a new address to LB1 and keep the current address as the public one for the service. You can do that once you've switched the VRRP to LB2. > I have also > tried the IP forwarding approach as i mentioned earlier, but for some reason > connections aren't failing over and keep hanging, I suspect that the masquerade rule doesn't always work and that LB2 responds directly to the net, which cannot work. Anyway since you're planning to reboot the first VM, that cannot work. > so i wanted to check with > the group as to what else could i try to avoid a total downtime and still > keep working on the first LB.I am not too aware of DNS round robin... If you cannot find a 3rd address for LB1, there's another solution which I don't like but which does work when you're short of IP addresses : simply switch LB1 and LB2's addresses during the upgrade. Willy
