| /** |
| * 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.protocol.datatransfer; |
| |
| import org.apache.hadoop.HadoopIllegalArgumentException; |
| import org.apache.hadoop.classification.InterfaceAudience; |
| import org.apache.hadoop.classification.InterfaceStability; |
| import org.apache.hadoop.conf.Configuration; |
| import org.apache.hadoop.hdfs.client.HdfsClientConfigKeys; |
| import org.apache.hadoop.hdfs.protocol.DatanodeInfo; |
| |
| /** |
| * The setting of replace-datanode-on-failure feature. |
| */ |
| @InterfaceAudience.Private |
| @InterfaceStability.Evolving |
| public class ReplaceDatanodeOnFailure { |
| /** |
| * DEFAULT condition: |
| * Let r be the replication number. |
| * Let n be the number of existing datanodes. |
| * Add a new datanode only if r >= 3 and either |
| * (1) floor(r/2) >= n or (2) the block is hflushed/appended. |
| */ |
| private static final Condition CONDITION_DEFAULT = new Condition() { |
| @Override |
| public boolean satisfy(final short replication, |
| final DatanodeInfo[] existings, final int n, final boolean isAppend, |
| final boolean isHflushed) { |
| return replication >= 3 && |
| (n <= (replication / 2) || isAppend || isHflushed); |
| } |
| }; |
| /** Return false unconditionally. */ |
| private static final Condition CONDITION_FALSE = new Condition() { |
| @Override |
| public boolean satisfy(short replication, DatanodeInfo[] existings, |
| int nExistings, boolean isAppend, boolean isHflushed) { |
| return false; |
| } |
| }; |
| /** Return true unconditionally. */ |
| private static final Condition CONDITION_TRUE = new Condition() { |
| @Override |
| public boolean satisfy(short replication, DatanodeInfo[] existings, |
| int nExistings, boolean isAppend, boolean isHflushed) { |
| return true; |
| } |
| }; |
| |
| /** The replacement policies */ |
| public enum Policy { |
| /** The feature is disabled in the entire site. */ |
| DISABLE(CONDITION_FALSE), |
| /** Never add a new datanode. */ |
| NEVER(CONDITION_FALSE), |
| /** @see ReplaceDatanodeOnFailure#CONDITION_DEFAULT */ |
| DEFAULT(CONDITION_DEFAULT), |
| /** Always add a new datanode when an existing datanode is removed. */ |
| ALWAYS(CONDITION_TRUE); |
| |
| private final Condition condition; |
| |
| Policy(Condition condition) { |
| this.condition = condition; |
| } |
| |
| Condition getCondition() { |
| return condition; |
| } |
| } |
| |
| /** Datanode replacement condition */ |
| private interface Condition { |
| |
| /** Is the condition satisfied? */ |
| boolean satisfy(short replication, DatanodeInfo[] existings, int nExistings, |
| boolean isAppend, boolean isHflushed); |
| } |
| |
| private final Policy policy; |
| private final boolean bestEffort; |
| |
| public ReplaceDatanodeOnFailure(Policy policy, boolean bestEffort) { |
| this.policy = policy; |
| this.bestEffort = bestEffort; |
| } |
| |
| /** Check if the feature is enabled. */ |
| public void checkEnabled() { |
| if (policy == Policy.DISABLE) { |
| throw new UnsupportedOperationException( |
| "This feature is disabled. Please refer to " |
| + HdfsClientConfigKeys.BlockWrite.ReplaceDatanodeOnFailure.ENABLE_KEY |
| + " configuration property."); |
| } |
| } |
| |
| /** |
| * Best effort means that the client will try to replace the failed datanode |
| * (provided that the policy is satisfied), however, it will continue the |
| * write operation in case that the datanode replacement also fails. |
| * |
| * @return Suppose the datanode replacement fails. |
| * false: An exception should be thrown so that the write will fail. |
| * true : The write should be resumed with the remaining datandoes. |
| */ |
| public boolean isBestEffort() { |
| return bestEffort; |
| } |
| |
| /** Does it need a replacement according to the policy? */ |
| public boolean satisfy( |
| final short replication, final DatanodeInfo[] existings, |
| final boolean isAppend, final boolean isHflushed) { |
| final int n = existings == null ? 0 : existings.length; |
| //don't need to add datanode for any policy. |
| return !(n == 0 || n >= replication) && |
| policy.getCondition().satisfy(replication, existings, n, isAppend, |
| isHflushed); |
| } |
| |
| @Override |
| public String toString() { |
| return policy.toString(); |
| } |
| |
| /** Get the setting from configuration. */ |
| public static ReplaceDatanodeOnFailure get(final Configuration conf) { |
| final Policy policy = getPolicy(conf); |
| final boolean bestEffort = conf.getBoolean( |
| HdfsClientConfigKeys.BlockWrite.ReplaceDatanodeOnFailure.BEST_EFFORT_KEY, |
| HdfsClientConfigKeys.BlockWrite.ReplaceDatanodeOnFailure.BEST_EFFORT_DEFAULT); |
| |
| return new ReplaceDatanodeOnFailure(policy, bestEffort); |
| } |
| |
| private static Policy getPolicy(final Configuration conf) { |
| final boolean enabled = conf.getBoolean( |
| HdfsClientConfigKeys.BlockWrite.ReplaceDatanodeOnFailure.ENABLE_KEY, |
| HdfsClientConfigKeys.BlockWrite.ReplaceDatanodeOnFailure.ENABLE_DEFAULT); |
| if (!enabled) { |
| return Policy.DISABLE; |
| } |
| |
| final String policy = conf.get( |
| HdfsClientConfigKeys.BlockWrite.ReplaceDatanodeOnFailure.POLICY_KEY, |
| HdfsClientConfigKeys.BlockWrite.ReplaceDatanodeOnFailure.POLICY_DEFAULT); |
| for(int i = 1; i < Policy.values().length; i++) { |
| final Policy p = Policy.values()[i]; |
| if (p.name().equalsIgnoreCase(policy)) { |
| return p; |
| } |
| } |
| throw new HadoopIllegalArgumentException("Illegal configuration value for " |
| + HdfsClientConfigKeys.BlockWrite.ReplaceDatanodeOnFailure.POLICY_KEY |
| + ": " + policy); |
| } |
| |
| /** Write the setting to configuration. */ |
| public static void write(final Policy policy, |
| final boolean bestEffort, final Configuration conf) { |
| conf.setBoolean( |
| HdfsClientConfigKeys.BlockWrite.ReplaceDatanodeOnFailure.ENABLE_KEY, |
| policy != Policy.DISABLE); |
| conf.set( |
| HdfsClientConfigKeys.BlockWrite.ReplaceDatanodeOnFailure.POLICY_KEY, |
| policy.name()); |
| conf.setBoolean( |
| HdfsClientConfigKeys.BlockWrite.ReplaceDatanodeOnFailure.BEST_EFFORT_KEY, |
| bestEffort); |
| } |
| } |