| /** |
| * 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.hdfs.server.namenode.ha; |
| |
| import java.io.IOException; |
| |
| import org.apache.hadoop.classification.InterfaceAudience; |
| import org.apache.hadoop.ha.ServiceFailedException; |
| import org.apache.hadoop.ha.HAServiceProtocol.HAServiceState; |
| import org.apache.hadoop.hdfs.server.namenode.NameNode; |
| import org.apache.hadoop.hdfs.server.namenode.NameNode.OperationCategory; |
| import org.apache.hadoop.ipc.ObserverRetryOnActiveException; |
| import org.apache.hadoop.ipc.StandbyException; |
| |
| /** |
| * Namenode standby state. In this state the namenode acts as warm standby and |
| * keeps the following updated: |
| * <ul> |
| * <li>Namespace by getting the edits.</li> |
| * <li>Block location information by receiving block reports and blocks |
| * received from the datanodes.</li> |
| * </ul> |
| * |
| * It does not handle read/write/checkpoint operations. |
| */ |
| @InterfaceAudience.Private |
| public class StandbyState extends HAState { |
| // TODO: consider implementing a ObserverState instead of using the flag. |
| private final boolean isObserver; |
| |
| public StandbyState() { |
| this(false); |
| } |
| |
| public StandbyState(boolean isObserver) { |
| super(isObserver ? HAServiceState.OBSERVER : HAServiceState.STANDBY); |
| this.isObserver = isObserver; |
| } |
| |
| @Override |
| public void setState(HAContext context, HAState s) throws ServiceFailedException { |
| if (s == NameNode.ACTIVE_STATE || |
| (!isObserver && s == NameNode.OBSERVER_STATE) || |
| (isObserver && s == NameNode.STANDBY_STATE)) { |
| setStateInternal(context, s); |
| return; |
| } |
| super.setState(context, s); |
| } |
| |
| @Override |
| public void enterState(HAContext context) throws ServiceFailedException { |
| try { |
| context.startStandbyServices(); |
| } catch (IOException e) { |
| throw new ServiceFailedException("Failed to start standby services", e); |
| } |
| } |
| |
| @Override |
| public void prepareToExitState(HAContext context) throws ServiceFailedException { |
| context.prepareToStopStandbyServices(); |
| } |
| |
| @Override |
| public void exitState(HAContext context) throws ServiceFailedException { |
| try { |
| context.stopStandbyServices(); |
| } catch (IOException e) { |
| throw new ServiceFailedException("Failed to stop standby services", e); |
| } |
| } |
| |
| @Override |
| public void checkOperation(HAContext context, OperationCategory op) |
| throws StandbyException { |
| if (op == OperationCategory.UNCHECKED || |
| (op == OperationCategory.READ && context.allowStaleReads())) { |
| return; |
| } |
| String faq = ". Visit https://s.apache.org/sbnn-error"; |
| String msg = "Operation category " + op + " is not supported in state " |
| + context.getState() + faq; |
| if (op == OperationCategory.WRITE && isObserver) { |
| // If observer receives a write call, return active retry |
| // exception to inform client to retry on active. |
| // A write should never happen on Observer. Except that, |
| // if access time is enabled. A open call can transition |
| // to a write operation. In this case, Observer |
| // should inform the client to retry this open on Active. |
| throw new ObserverRetryOnActiveException(msg); |
| } else { |
| throw new StandbyException(msg); |
| } |
| } |
| |
| @Override |
| public boolean shouldPopulateReplQueues() { |
| return false; |
| } |
| |
| @Override |
| public String toString() { |
| return isObserver ? "observer" : "standby"; |
| } |
| } |
| |