How to know the broker that is the active controller?

Question

Other than using JMX is there any other way to know, whether a broker is an ActiveController?

I know that the cluster generates a metric kafka.controller:type=KafkaController,name=ActiveControllerCount, but I cannot find which broker is the active controller.

Is it necessary to write a JMX client to know it or is there another (better?) way?

Answer 1

You can find the active controller using the zookeeper-shell tool as follows:

./bin/zookeeper-shell.sh [ZK_IP] get /controller

Answer 2

Perhaps easier way, since you don't need to have kafka and it's zookeeper-shell.sh, is using command line to connect to zookeeper's client port with:

nc [zookeeper_ip] [zookeeper_port]

or

telnet [zookeeper_ip] [zookeeper_port]

and then executing

dump

It will print sessions with ephemeral nodes and one can see which broker is a controller by finding session that contains /controller path

For example, a dump result like this:

Sessions with Ephemerals (3):
0x266542cfaa90000:
    /brokers/ids/1
0x166542cfe670001:
    /brokers/ids/3
0x166542cfe670000:
    /controller
    /brokers/ids/2 

means that controller is a broker whose broker_id is 2.