Re: swiftmq HA hangs after switching to standby instance

You had a so-called split brain, see the warning.log/error.log. Here is a description of the problem and how to solve it.

In your case the split brain occurred after you've started the STANDBY instance while the former STANDALONE instance was down. Then you have only 2 minutes to start the other instance, otherwise you will get a negotiation timeout and the STANDBY switches to STANDALONE. See your warning.log. If you now start the other (former STANDALONE) instance, they both detect that they both are in STANDALONE and one of them is shut down. There is administrative action required. See link above.