Brokers are not available - apache-kafka

Question

To /etc/kafka/server.properties the broker is configured using:
############################# Server Basics #############################
# The id of the broker. This must be set to a unique integer for each broker.
broker.id=0
############################# Socket Server Settings #############################
# The address the socket server listens on. It will get the value returned from
# java.net.InetAddress.getCanonicalHostName() if not configured.
# FORMAT:
# listeners = listener_name://host_name:port
# EXAMPLE:
# listeners = PLAINTEXT://your.host.name:9092
listeners=PLAINTEXT://<MY_HOST_NAME>:9092,SASL_SSL://<MY_HOST_NAME>:9093
To check the brokers I run:
/opt/confluent-kafka/v5.5.0/bin/zookeeper-shell localhost:2181 ls /brokers/ids
Which returns:
Connecting to localhost:2181
WATCHER::
WatchedEvent state:SyncConnected type:None path:null
[]
So, it seems that the brokers are not running. As kafka server.properties(above) contains:
listeners=PLAINTEXT://<MY_HOST_NAME>:9092,SASL_SSL://<MY_HOST_NAME>:9093
shouldn't the broker be available ?
My understanding is listeners=PLAINTEXT://<MY_HOST_NAME>:9092,SASL_SSL://<MY_HOST_NAME>:9093 is the config that allows the brokers to be accessible ?

Answer 1

I assume that the connection is within the same host (no advertised listeners nor external clients involved here).
Change the listeners property to make the broker listen to all interfaces:
listeners=PLAINTEXT://0.0.0.0:9092,SASL_SSL://0.0.0.0:9093
If you set your <hostname> as the listener, localhost won't be recognized as a valid binding point: there's no registered "localhost" listener, just the one specified on your config, <hostname>.
By setting 0.0.0.0 as listener, the broker will bind to all interfaces, hence accepting localhost as a valid endpoint. You could find more info regarding this here.