Not sure if this has been requested yet or not, but right now Logstash can only mirror outputs. Ie if I create two AMQP outputs it will send each log line to both outputs. It would be nice to have the ability to round robin or fail over to a different output.
I know there are plans for reworking the message pipeline, so this may already by considered.
Right now the only way to work with a HA RabbitMQ cluster (that I know of) is to set up a floating VIP, but this can cause problems if the exchange does not exist on the backup server. This would not be problem if the connection was created to that server in the first place.
Redis output accepts an array of hosts for this purpose.
I am going to close this request since AMQP is now unsupported and redis does have this feature.