org.apache.hive.hcatalog.mapreduce.TaskCommitContextRegistry.java Source code

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Here is the source code for org.apache.hive.hcatalog.mapreduce.TaskCommitContextRegistry.java

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/**
 * 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.hive.hcatalog.mapreduce;

import org.apache.commons.lang.StringUtils;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.hive.hcatalog.common.HCatConstants;
import org.apache.hive.hcatalog.common.HCatUtil;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.util.HashMap;

/**
 * Singleton Registry to track the commit of TaskAttempts.
 * Used to manage commits for Tasks that create dynamic-partitions.
 */
public class TaskCommitContextRegistry {

    private static final Logger LOG = LoggerFactory.getLogger(TaskCommitContextRegistry.class);

    private static TaskCommitContextRegistry ourInstance = new TaskCommitContextRegistry();

    /**
     * Singleton instance getter.
     */
    public static TaskCommitContextRegistry getInstance() {
        return ourInstance;
    }

    /**
     * Implement this interface to register call-backs for committing TaskAttempts.
     */
    public static interface TaskCommitterProxy {

        /**
         * Call-back for Committer's abortTask().
         */
        public void abortTask(TaskAttemptContext context) throws IOException;

        /**
         * Call-back for Committer's abortTask().
         */
        public void commitTask(TaskAttemptContext context) throws IOException;
    }

    private HashMap<String, TaskCommitterProxy> taskCommitters = new HashMap<String, TaskCommitterProxy>();

    /**
     * Trigger commit for TaskAttempt, as specified by the TaskAttemptContext argument.
     */
    public synchronized void commitTask(TaskAttemptContext context) throws IOException {
        String key = generateKey(context);
        if (!taskCommitters.containsKey(key)) {
            LOG.warn("No callback registered for TaskAttemptID:" + key + ". Skipping.");
            return;
        }

        try {
            LOG.info("Committing TaskAttempt:" + key);
            taskCommitters.get(key).commitTask(context);
        } catch (Throwable t) {
            throw new IOException("Could not clean up TaskAttemptID:" + key, t);
        }

    }

    private String generateKey(TaskAttemptContext context) throws IOException {
        String jobInfoString = context.getConfiguration().get(HCatConstants.HCAT_KEY_OUTPUT_INFO);
        if (StringUtils.isBlank(jobInfoString)) { // Avoid the NPE.
            throw new IOException("Could not retrieve OutputJobInfo for TaskAttempt " + context.getTaskAttemptID());
        }
        OutputJobInfo jobInfo = (OutputJobInfo) HCatUtil.deserialize(jobInfoString);
        return context.getTaskAttemptID().toString() + "@" + jobInfo.getLocation();
    }

    /**
     * Trigger abort for TaskAttempt, as specified by the TaskAttemptContext argument.
     */
    public synchronized void abortTask(TaskAttemptContext context) throws IOException {
        String key = generateKey(context);
        if (!taskCommitters.containsKey(key)) {
            LOG.warn("No callback registered for TaskAttemptID:" + key + ". Skipping.");
            return;
        }

        try {
            LOG.info("Aborting TaskAttempt:" + key);
            taskCommitters.get(key).abortTask(context);
        } catch (Throwable t) {
            throw new IOException("Could not clean up TaskAttemptID:" + key, t);
        }
    }

    /**
     * Method to register call-backs to control commits and aborts of TaskAttempts.
     * @param context The TaskAttemptContext instance for the task-attempt, identifying the output.
     * @param committer Instance of TaskCommitterProxy, to commit/abort a TaskAttempt.
     * @throws java.io.IOException On failure.
     */
    public synchronized void register(TaskAttemptContext context, TaskCommitterProxy committer) throws IOException {
        String key = generateKey(context);
        LOG.info("Registering committer for TaskAttemptID:" + key);
        if (taskCommitters.containsKey(key)) {
            LOG.warn("Replacing previous committer:" + committer);
        }
        taskCommitters.put(key, committer);
    }

    /**
     * Method to discard the committer call-backs for a specified TaskAttemptID.
     * @param context The TaskAttemptContext instance for the task-attempt, identifying the output.
     * @throws java.io.IOException On failure.
     */
    public synchronized void discardCleanupFor(TaskAttemptContext context) throws IOException {
        String key = generateKey(context);
        LOG.info("Discarding all cleanup for TaskAttemptID:" + key);
        if (!taskCommitters.containsKey(key)) {
            LOG.warn("No committer registered for TaskAttemptID:" + key);
        } else {
            taskCommitters.remove(key);
        }
    }

    // Hide constructor, for make benefit glorious Singleton.
    private TaskCommitContextRegistry() {
    }
}