@Override
    public boolean equals(final Object o) {
        if (this == o) {
            return true;
        }
        if (o == null || getClass() != o.getClass()) {
            return false;
        }

        final HostInfo hostInfo = (HostInfo) o;
        return port == hostInfo.port && host.equals(hostInfo.host);
    }
@return a sentinel for cases where the host metadata is currently unavailable, eg during rebalance operations.
streams/src/main/java/org/apache/kafka/streams/state/HostInfo.java