RabbitMQ HA & Failover - rabbitmq

Question

I've read both the clustering and HA chapters and got a fair understanding on RabbitMQ clustering. One thing I did not understand is, having 2+ nodes on the cluster and a set of HA queues, how connections can be made by the clients so that if one node fails they automatically and seamlessly connect to the remaining node(s). Can this be achieved by a load balancer such as, say, Amazon ELB for deployments made in AWS?

Answer 1

Using a load balancer like Amazon ELB or HAProxy is exactly how you should route traffic to the available nodes in the Rabbit cluster.
I'd recommend HAProxy. Here's a sample HAProxy config:
global
log 127.0.0.1 local1
maxconn 4096
#chroot /usr/share/haproxy
user haproxy
group haproxy
daemon
#debug
#quiet
defaults
log global
mode tcp
option tcplog
retries 3
option redispatch
maxconn 2000
timeout connect 5000
timeout client 50000
timeout server 50000
listen stats :1936
mode http
stats enable
stats hide-version
stats realm Haproxy\ Statistics
stats uri /
listen aqmp_front :5672
mode tcp
balance roundrobin
timeout client 3h
timeout server 3h
option clitcpka
server aqmp-1 rabbitmq1.domain:5672 check inter 5s rise 2 fall 3
server aqmp-2 rabbitmq2.domain:5672 backup check inter 5s rise 2 fall 3
Note the last two lines. You'll need to substitute rabbitmq1.domain and rabbitmq2.domain with the location of your two nodes. Since the second server is setup as backup check HAProxy will balance the request only on the first node, and if this node fails the request will be route to the second node.

Answer 2

I would use simple keepalived deamon on all rabbit nodes. It just adds a virtual IP address shared between nodes which you can use for client access. Configuration is very simple, check this Hollenback's page.
Sample config:
vrrp_instance VI_1 {
state MASTER
interface eth0
virtual_router_id 1
priority 100
virtual_ipaddress {
192.168.1.1/24 brd 192.168.1.255 dev eth0
}
}

Answer 3

You have to configure mirror queue between rabbitmq-servers.
rabbitmqctl set_policy HA '^(?!amq\.).*' '{"ha-mode": "all"}'
In the example rabbitmq will be mirror queue have prefix with amq. When server A fail, those queue unitl exit on server B. You also HA on code(connect to server fail, then connect to server B) or using HA rabbitmq port using keepalive