Java tutorial
/** * 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; import java.io.IOException; import java.util.List; import org.apache.hadoop.classification.InterfaceAudience; import org.apache.hadoop.classification.InterfaceStability; import org.apache.hadoop.conf.ReconfigurationTaskStatus; import org.apache.hadoop.hdfs.client.BlockReportOptions; import org.apache.hadoop.hdfs.client.HdfsClientConfigKeys; import org.apache.hadoop.hdfs.security.token.block.BlockTokenIdentifier; import org.apache.hadoop.hdfs.security.token.block.BlockTokenSelector; import org.apache.hadoop.security.KerberosInfo; import org.apache.hadoop.security.token.Token; import org.apache.hadoop.security.token.TokenInfo; import org.apache.hadoop.hdfs.server.datanode.DiskBalancerWorkStatus; /** An client-datanode protocol for block recovery */ @InterfaceAudience.Private @InterfaceStability.Evolving @KerberosInfo(serverPrincipal = HdfsClientConfigKeys.DFS_DATANODE_KERBEROS_PRINCIPAL_KEY) @TokenInfo(BlockTokenSelector.class) public interface ClientDatanodeProtocol { /** * Until version 9, this class ClientDatanodeProtocol served as both * the client interface to the DN AND the RPC protocol used to * communicate with the NN. * * This class is used by both the DFSClient and the * DN server side to insulate from the protocol serialization. * * If you are adding/changing DN's interface then you need to * change both this class and ALSO related protocol buffer * wire protocol definition in ClientDatanodeProtocol.proto. * * For more details on protocol buffer wire protocol, please see * .../org/apache/hadoop/hdfs/protocolPB/overview.html * * The log of historical changes can be retrieved from the svn). * 9: Added deleteBlockPool method * * 9 is the last version id when this class was used for protocols * serialization. DO not update this version any further. */ long versionID = 9L; /** Return the visible length of a replica. */ long getReplicaVisibleLength(ExtendedBlock b) throws IOException; /** * Refresh the list of federated namenodes from updated configuration * Adds new namenodes and stops the deleted namenodes. * * @throws IOException on error **/ void refreshNamenodes() throws IOException; /** * Delete the block pool directory. If force is false it is deleted only if * it is empty, otherwise it is deleted along with its contents. * * @param bpid Blockpool id to be deleted. * @param force If false blockpool directory is deleted only if it is empty * i.e. if it doesn't contain any block files, otherwise it is * deleted along with its contents. * @throws IOException */ void deleteBlockPool(String bpid, boolean force) throws IOException; /** * Retrieves the path names of the block file and metadata file stored on the * local file system. * * In order for this method to work, one of the following should be satisfied: * <ul> * <li> * The client user must be configured at the datanode to be able to use this * method.</li> * <li> * When security is enabled, kerberos authentication must be used to connect * to the datanode.</li> * </ul> * * @param block * the specified block on the local datanode * @param token * the block access token. * @return the BlockLocalPathInfo of a block * @throws IOException * on error */ BlockLocalPathInfo getBlockLocalPathInfo(ExtendedBlock block, Token<BlockTokenIdentifier> token) throws IOException; /** * Shuts down a datanode. * * @param forUpgrade If true, data node does extra prep work before shutting * down. The work includes advising clients to wait and saving * certain states for quick restart. This should only be used when * the stored data will remain the same during upgrade/restart. * @throws IOException */ void shutdownDatanode(boolean forUpgrade) throws IOException; /** * Evict clients that are writing to a datanode. * * @throws IOException */ void evictWriters() throws IOException; /** * Obtains datanode info * * @return software/config version and uptime of the datanode */ DatanodeLocalInfo getDatanodeInfo() throws IOException; /** * Asynchronously reload configuration on disk and apply changes. */ void startReconfiguration() throws IOException; /** * Get the status of the previously issued reconfig task. * @see org.apache.hadoop.conf.ReconfigurationTaskStatus */ ReconfigurationTaskStatus getReconfigurationStatus() throws IOException; /** * Get a list of allowed properties for reconfiguration. */ List<String> listReconfigurableProperties() throws IOException; /** * Trigger a new block report. */ void triggerBlockReport(BlockReportOptions options) throws IOException; /** * Get current value of the balancer bandwidth in bytes per second. * * @return balancer bandwidth */ long getBalancerBandwidth() throws IOException; /** * Get volume report of datanode. */ List<DatanodeVolumeInfo> getVolumeReport() throws IOException; /** * Submit a disk balancer plan for execution. */ void submitDiskBalancerPlan(String planID, long planVersion, String planFile, String planData, boolean skipDateCheck) throws IOException; /** * Cancel an executing plan. * * @param planID - A SHA-1 hash of the plan string. */ void cancelDiskBalancePlan(String planID) throws IOException; /** * Gets the status of an executing diskbalancer Plan. */ DiskBalancerWorkStatus queryDiskBalancerPlan() throws IOException; /** * Gets a run-time configuration value from running diskbalancer instance. * For example : Disk Balancer bandwidth of a running instance. * * @param key runtime configuration key * @return value of the key as a string. * @throws IOException - Throws if there is no such key */ String getDiskBalancerSetting(String key) throws IOException; }