| /** |
| * |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.apache.hadoop.hbase.master; |
| |
| import java.util.List; |
| import java.util.Map; |
| |
| import org.apache.hadoop.hbase.classification.InterfaceAudience; |
| import org.apache.hadoop.conf.Configurable; |
| import org.apache.hadoop.hbase.ClusterStatus; |
| import org.apache.hadoop.hbase.HBaseIOException; |
| import org.apache.hadoop.hbase.HRegionInfo; |
| import org.apache.hadoop.hbase.ServerName; |
| import org.apache.hadoop.hbase.Stoppable; |
| |
| /** |
| * Makes decisions about the placement and movement of Regions across |
| * RegionServers. |
| * |
| * <p>Cluster-wide load balancing will occur only when there are no regions in |
| * transition and according to a fixed period of a time using {@link #balanceCluster(Map)}. |
| * |
| * <p>Inline region placement with {@link #immediateAssignment} can be used when |
| * the Master needs to handle closed regions that it currently does not have |
| * a destination set for. This can happen during master failover. |
| * |
| * <p>On cluster startup, bulk assignment can be used to determine |
| * locations for all Regions in a cluster. |
| * |
| * <p>This classes produces plans for the {@link AssignmentManager} to execute. |
| */ |
| @InterfaceAudience.Private |
| public interface LoadBalancer extends Configurable, Stoppable { |
| |
| /** |
| * Set the current cluster status. This allows a LoadBalancer to map host name to a server |
| * @param st |
| */ |
| void setClusterStatus(ClusterStatus st); |
| |
| |
| /** |
| * Set the master service. |
| * @param masterServices |
| */ |
| void setMasterServices(MasterServices masterServices); |
| |
| /** |
| * Perform the major balance operation |
| * @param clusterState |
| * @return List of plans |
| */ |
| List<RegionPlan> balanceCluster(Map<ServerName, |
| List<HRegionInfo>> clusterState) throws HBaseIOException; |
| |
| /** |
| * Perform a Round Robin assignment of regions. |
| * @param regions |
| * @param servers |
| * @return Map of servername to regioninfos |
| */ |
| Map<ServerName, List<HRegionInfo>> roundRobinAssignment( |
| List<HRegionInfo> regions, |
| List<ServerName> servers |
| ) throws HBaseIOException; |
| |
| /** |
| * Assign regions to the previously hosting region server |
| * @param regions |
| * @param servers |
| * @return List of plans |
| */ |
| Map<ServerName, List<HRegionInfo>> retainAssignment( |
| Map<HRegionInfo, ServerName> regions, |
| List<ServerName> servers |
| ) throws HBaseIOException; |
| |
| /** |
| * Sync assign a region |
| * @param regions |
| * @param servers |
| * @return Map regioninfos to servernames |
| */ |
| Map<HRegionInfo, ServerName> immediateAssignment( |
| List<HRegionInfo> regions, |
| List<ServerName> servers |
| ) throws HBaseIOException; |
| |
| /** |
| * Get a random region server from the list |
| * @param regionInfo Region for which this selection is being done. |
| * @param servers |
| * @return Servername |
| */ |
| ServerName randomAssignment( |
| HRegionInfo regionInfo, List<ServerName> servers |
| ) throws HBaseIOException; |
| |
| /** |
| * Initialize the load balancer. Must be called after setters. |
| * @throws HBaseIOException |
| */ |
| void initialize() throws HBaseIOException; |
| |
| /** |
| * Marks the region as online at balancer. |
| * @param regionInfo |
| * @param sn |
| */ |
| void regionOnline(HRegionInfo regionInfo, ServerName sn); |
| |
| /** |
| * Marks the region as offline at balancer. |
| * @param regionInfo |
| */ |
| void regionOffline(HRegionInfo regionInfo); |
| } |