public String getHostLocality() {
    return getMessageValue(HOST_KEY);
  }
SteContainerToHostMapping is used to set the container to host mapping information.
@param source the source of the message
@param key the key which is used to persist the message
@param hostName the hostname of the container
@param jmxAddress the JMX address of the container
@param jmxTunnelingAddress the JMX tunneling address of the container
samza-core/src/main/java/org/apache/samza/coordinator/stream/messages/SetContainerHostMapping.java