shims/src/hadoop2/org/apache/pig/backend/hadoop/executionengine/shims/HadoopShims.java

/*
 * 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.pig.backend.hadoop.executionengine.shims;

import java.io.IOException;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapreduce.ContextFactory;
import org.apache.hadoop.mapreduce.JobContext;
import org.apache.hadoop.mapreduce.JobID;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.hadoop.mapreduce.TaskAttemptID;
import org.apache.hadoop.mapreduce.TaskType;
import org.apache.hadoop.mapreduce.task.JobContextImpl;
import org.apache.hadoop.mapreduce.task.TaskAttemptContextImpl;

public class HadoopShims {

    private static Log LOG = LogFactory.getLog(HadoopShims.class);

    static public JobContext cloneJobContext(JobContext original) throws IOException, InterruptedException {
        JobContext newContext = ContextFactory.cloneContext(original,
                new JobConf(original.getConfiguration()));
        return newContext;
    }

    static public TaskAttemptContext createTaskAttemptContext(Configuration conf,
            TaskAttemptID taskId) {
        if (conf instanceof JobConf) {
            return new TaskAttemptContextImpl(new JobConf(conf), taskId);
        } else {
            return new TaskAttemptContextImpl(conf, taskId);
        }
    }

    static public JobContext createJobContext(Configuration conf,
            JobID jobId) {
        if (conf instanceof JobConf) {
            return new JobContextImpl(new JobConf(conf), jobId);
        } else {
            return new JobContextImpl(conf, jobId);
        }
    }

    static public boolean isMap(TaskAttemptID taskAttemptID) {
        TaskType type = taskAttemptID.getTaskType();
        if (type==TaskType.MAP)
            return true;

        return false;
    }

    static public TaskAttemptID getNewTaskAttemptID() {
        TaskAttemptID taskAttemptID = new TaskAttemptID("", 1, TaskType.MAP,
                1, 1);
        return taskAttemptID;
    }

    static public TaskAttemptID createTaskAttemptID(String jtIdentifier, int jobId, boolean isMap,
            int taskId, int id) {
        if (isMap) {
            return new TaskAttemptID(jtIdentifier, jobId, TaskType.MAP, taskId, id);
        } else {
            return new TaskAttemptID(jtIdentifier, jobId, TaskType.REDUCE, taskId, id);
        }
    }

    /**
     * Returns whether the give path has a FileSystem implementation.
     *
     * @param path path
     * @param conf configuration
     * @return true if the give path's scheme has a FileSystem implementation,
     *         false otherwise
     */
    public static boolean hasFileSystemImpl(Path path, Configuration conf) {
        String scheme = path.toUri().getScheme();
        if (scheme != null) {
            // Hadoop 0.23
            if (conf.get("fs.file.impl") != null) {
                String fsImpl = conf.get("fs." + scheme + ".impl");
                if (fsImpl == null) {
                    return false;
                }
            } else {
                try {
                    Object fs = FileSystem.getFileSystemClass(scheme,conf);
                    return fs == null ? false : true;
                } catch (Exception e) {
                    return false;
                }
            }
        }
        return true;
    }
}