Redhat – How to make node join the cluster (Pacemaker, Corosync 2 node setup) automatically after disconnection / unplugging

The best thing to do is test what actually happens under different failure modes, to make sure there is no single failure that could cause both MySQL servers to try to become masters.

Test disabling the internet connection on one server. See what happens on both servers, and watch what happens when you bring it back up.

Do the same for any redundant connections. Then do the same with disabling ALL network connections at once.

One reason for not doing STONITH on a two node cluster is it is fairly easy to end up with both nodes trying to kill the other, and actually succeeding. You need to test your setup to make sure that they don't either both shutdown, or both keep running as masters and get your database out of sync.

One other thing I recommend, while you are testing it, before it goes into production: Intentionally break it. Do something that will cause mysql and drbd to get out of sync, and learn how to fix it. Write down what you needed to do to fix it. Because it's much better to know how to do that BEFORE you really need to.

Okay I found the solution. Basically you add nagios as an "anything" resource

#pcs resource create nagios_test ocf:heartbeat:anything params user="nagios" binfile="/usr/local/nagios/bin/nagios" cmdline_options="-d /usr/local/nagios/etc/nagios.cfg" pidfile="/usr/local/nagios/etc/nagios.pid"