def getInstancesInCluster(self, clusterName):
        """
        Returns List<String>
        Parameters:
            clusterName: String
        @Override


        """
        # String
        memberInstancesPath = HelixUtil.getMemberInstancesPath(clusterName)
        return _zkClient.getChildren(memberInstancesPath)
    def addCluster(self, clusterName, overwritePrevRecord):
        """
        Returns void
        Parameters:
            clusterName: StringoverwritePrevRecord: boolean
        @Override


        """
        # String
        root = "/" + clusterName
        # String
        path = None
        
        if _zkClient.exists(root): 
            logger.warn("Root directory exists.Cleaning the root directory:" + root + " overwritePrevRecord: " + overwritePrevRecord)
            if overwritePrevRecord: 
                _zkClient.deleteRecursive(root)
            else:
                raise HelixException("Cluster " + clusterName + " already exists")



        _zkClient.createPersistent(root)
        _zkClient.createPersistent(HelixUtil.getIdealStatePath(clusterName))
        path = PropertyPathConfig.getPath(PropertyType.CONFIGS, clusterName, ConfigScopeProperty.CLUSTER.toString(), clusterName)
        _zkClient.createPersistent(path, True)
        _zkClient.writeData(path, ZNRecord(clusterName))
        path = PropertyPathConfig.getPath(PropertyType.CONFIGS, clusterName, ConfigScopeProperty.PARTICIPANT.toString())
        _zkClient.createPersistent(path)
        path = PropertyPathConfig.getPath(PropertyType.CONFIGS, clusterName, ConfigScopeProperty.RESOURCE.toString())
        _zkClient.createPersistent(path)
        path = PropertyPathConfig.getPath(PropertyType.PROPERTYSTORE, clusterName)
        _zkClient.createPersistent(path)
        _zkClient.createPersistent(HelixUtil.getLiveInstancesPath(clusterName))
        _zkClient.createPersistent(HelixUtil.getMemberInstancesPath(clusterName))
        _zkClient.createPersistent(HelixUtil.getExternalViewPath(clusterName))
        _zkClient.createPersistent(HelixUtil.getStateModelDefinitionPath(clusterName))
        _zkClient.createPersistent(HelixUtil.getControllerPath(clusterName))
        path = PropertyPathConfig.getPath(PropertyType.HISTORY, clusterName)
        # ZNRecord
        emptyHistory = ZNRecord(PropertyType.HISTORY.toString())
        # List<String>
        emptyList = ArrayList<String>()
        emptyHistory.setListField(clusterName, emptyList)
        _zkClient.createPersistent(path, emptyHistory)
        path = PropertyPathConfig.getPath(PropertyType.MESSAGES_CONTROLLER, clusterName)
        _zkClient.createPersistent(path)
        path = PropertyPathConfig.getPath(PropertyType.STATUSUPDATES_CONTROLLER, clusterName)
        _zkClient.createPersistent(path)
        path = PropertyPathConfig.getPath(PropertyType.ERRORS_CONTROLLER, clusterName)
        _zkClient.createPersistent(path)