def on_cluster_add(self, cluster):
if cluster.discovery not in self.configurables[Discovery]:<EOL><INDENT>return<EOL><DEDENT>discovery = self.configurables[Discovery][cluster.discovery]<EOL>self.launch_thread(<EOL>cluster.name, discovery.start_watching,<EOL>cluster, self.sync_balancer_files<EOL>)<EOL>
Once a cluster is added we tell its associated discovery method to
start watching for changes to the cluster's child nodes (if the
discovery method is configured and available).