Kubernetes by default inject into each Pod environment variables describing them for service discovery. For example:
MY_CLUSTER_ZOOKEEPER_CLIENT_PORT=tcp://10.105.193.26:2181 MY_CLUSTER_ZOOKEEPER_CLIENT_PORT_2181_TCP=tcp://10.105.193.26:2181 MY_CLUSTER_ZOOKEEPER_CLIENT_PORT_2181_TCP_ADDR=10.105.193.26 MY_CLUSTER_ZOOKEEPER_CLIENT_PORT_2181_TCP_PORT=2181 MY_CLUSTER_ZOOKEEPER_CLIENT_PORT_2181_TCP_PROTO=tcp MY_CLUSTER_ZOOKEEPER_CLIENT_SERVICE_HOST=10.105.193.26 MY_CLUSTER_ZOOKEEPER_CLIENT_SERVICE_PORT=2181 MY_CLUSTER_ZOOKEEPER_CLIENT_SERVICE_PORT_TCP_CLIENTS=2181
In some cases - as described for example in Strimzi#4800 this is not desired.