webhcat/svr/src/main/java/org/apache/hcatalog/templeton/CompleteDelegator.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.hcatalog.templeton;

import java.io.IOException;
import java.net.URL;
import java.net.MalformedURLException;
import java.util.Date;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hcatalog.templeton.tool.JobState;
import org.apache.hcatalog.templeton.tool.TempletonUtils;

/**
 * Complete a job.  This will run the callback if
 *
 * - the job is done
 * - there is a callback
 * - the callback has not yet been called
 *
 * There is a small chance for a race condition if two callers run
 * this at the same time.  That should never happen.
 *
 * We use a Hadoop config var to notify this class on the completion
 * of a job.  Hadoop will call use multiple times in the event of
 * failure.  Even if the failure is that the client callback failed.
 *
 * See LauncherDelegator for the HADOOP_END_RETRY* vars that are set.
 */
public class CompleteDelegator extends TempletonDelegator {
    private static final Log LOG = LogFactory.getLog(CompleteDelegator.class);

    public CompleteDelegator(AppConfig appConf) {
        super(appConf);
    }

    public CompleteBean run(String id)
        throws CallbackFailedException, IOException {
        if (id == null)
            acceptWithError("No jobid given");

        JobState state = null;
        try {
            state = new JobState(id, Main.getAppConfigInstance());
            if (state.getCompleteStatus() == null)
                failed("Job not yet complete", null);

            Long notified = state.getNotifiedTime();
            if (notified != null)
                return acceptWithError("Callback already run on "
                    + new Date(notified.longValue()));

            String callback = state.getCallback();
            if (callback == null)
                return new CompleteBean("No callback registered");

            try {
                doCallback(state.getId(), callback);
            } catch (Exception e) {
                failed("Callback failed " + callback + " for " + id, e);
            }

            state.setNotifiedTime(System.currentTimeMillis());
            return new CompleteBean("Callback sent");
        } finally {
            if (state != null)
                state.close();
        }
    }

    /**
     * Call the callback url with the jobid to let them know it's
     * finished.  If the url has the string $jobId in it, it will be
     * replaced with the completed jobid.
     */
    public static void doCallback(String jobid, String url)
        throws MalformedURLException, IOException {
        if (url.contains("$jobId"))
            url = url.replace("$jobId", jobid);
        TempletonUtils.fetchUrl(new URL(url));
    }

    private void failed(String msg, Exception e)
        throws CallbackFailedException {
        if (e != null)
            LOG.error(msg, e);
        else
            LOG.error(msg);
        throw new CallbackFailedException(msg);
    }

    private CompleteBean acceptWithError(String msg) {
        LOG.error(msg);
        return new CompleteBean(msg);
    }
}