001/**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018
019package org.apache.hadoop.yarn.client.api;
020
021
022import java.io.IOException;
023
024import org.apache.hadoop.classification.InterfaceAudience.Private;
025import org.apache.hadoop.classification.InterfaceAudience.Public;
026import org.apache.hadoop.classification.InterfaceStability.Unstable;
027import org.apache.hadoop.fs.Path;
028import org.apache.hadoop.service.AbstractService;
029import org.apache.hadoop.yarn.api.records.ApplicationId;
030import org.apache.hadoop.yarn.client.api.impl.SharedCacheClientImpl;
031import org.apache.hadoop.yarn.exceptions.YarnException;
032
033/**
034 * This is the client for YARN's shared cache.
035 */
036@Public
037@Unstable
038public abstract class SharedCacheClient extends AbstractService {
039
040  @Public
041  public static SharedCacheClient createSharedCacheClient() {
042    SharedCacheClient client = new SharedCacheClientImpl();
043    return client;
044  }
045
046  @Private
047  public SharedCacheClient(String name) {
048    super(name);
049  }
050
051  /**
052   * <p>
053   * The method to claim a resource with the <code>SharedCacheManager.</code>
054   * The client uses a checksum to identify the resource and an
055   * {@link ApplicationId} to identify which application will be using the
056   * resource.
057   * </p>
058   * 
059   * <p>
060   * The <code>SharedCacheManager</code> responds with whether or not the
061   * resource exists in the cache. If the resource exists, a <code>Path</code>
062   * to the resource in the shared cache is returned. If the resource does not
063   * exist, null is returned instead.
064   * </p>
065   * 
066   * @param applicationId ApplicationId of the application using the resource
067   * @param resourceKey the key (i.e. checksum) that identifies the resource
068   * @return Path to the resource, or null if it does not exist
069   */
070  @Public
071  @Unstable
072  public abstract Path use(ApplicationId applicationId, String resourceKey)
073      throws YarnException;
074
075  /**
076   * <p>
077   * The method to release a resource with the <code>SharedCacheManager.</code>
078   * This method is called once an application is no longer using a claimed
079   * resource in the shared cache. The client uses a checksum to identify the
080   * resource and an {@link ApplicationId} to identify which application is
081   * releasing the resource.
082   * </p>
083   * 
084   * <p>
085   * Note: This method is an optimization and the client is not required to call
086   * it for correctness.
087   * </p>
088   * 
089   * @param applicationId ApplicationId of the application releasing the
090   *          resource
091   * @param resourceKey the key (i.e. checksum) that identifies the resource
092   */
093  @Public
094  @Unstable
095  public abstract void release(ApplicationId applicationId, String resourceKey)
096      throws YarnException;
097
098  /**
099   * A convenience method to calculate the checksum of a specified file.
100   * 
101   * @param sourceFile A path to the input file
102   * @return A hex string containing the checksum digest
103   * @throws IOException
104   */
105  @Public
106  @Unstable
107  public abstract String getFileChecksum(Path sourceFile) throws IOException;
108}