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

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.ZooDefs.Ids;
import org.apache.zookeeper.data.Stat;

public class JobStateTracker {
    // The path to the tracking root
    private String job_trackingroot = null;

    // The zookeeper connection to use
    private ZooKeeper zk;

    // The id of the tracking node -- must be a SEQUENTIAL node
    private String trackingnode;

    // The id of the job this tracking node represents
    private String jobid;

    // The logger
    private static final Log LOG = LogFactory.getLog(JobStateTracker.class);

    /**
     * Constructor for a new node -- takes the jobid of an existing job
     *
     */
    public JobStateTracker(String node, ZooKeeper zk, boolean nodeIsTracker,
                           String job_trackingpath) {
        this.zk = zk;
        if (nodeIsTracker) {
            trackingnode = node;
        } else {
            jobid = node;
        }
        job_trackingroot = job_trackingpath;
    }

    /**
     * Create the parent znode for this job state.
     */
    public void create()
        throws IOException {
        String[] paths = ZooKeeperStorage.getPaths(job_trackingroot);
        for (String znode : paths) {
            try {
                zk.create(znode, new byte[0],
                    Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
            } catch (KeeperException.NodeExistsException e) {
            } catch (Exception e) {
                throw new IOException("Unable to create parent nodes");
            }
        }
        try {
            trackingnode = zk.create(makeTrackingZnode(), jobid.getBytes(),
                Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT_SEQUENTIAL);
        } catch (Exception e) {
            throw new IOException("Unable to create " + makeTrackingZnode());
        }
    }

    public void delete()
        throws IOException {
        try {
            zk.delete(makeTrackingJobZnode(trackingnode), -1);
        } catch (Exception e) {
            // Might have been deleted already
            LOG.info("Couldn't delete " + makeTrackingJobZnode(trackingnode));
        }
    }

    /**
     * Get the jobid for this tracking node
     * @throws IOException
     */
    public String getJobID() throws IOException {
        try {
            return new String(zk.getData(makeTrackingJobZnode(trackingnode),
                false, new Stat()));
        } catch (KeeperException e) {
            // It was deleted during the transaction
            throw new IOException("Node already deleted " + trackingnode);
        } catch (InterruptedException e) {
            throw new IOException("Couldn't read node " + trackingnode);
        }
    }

    /**
     * Make a ZK path to a new tracking node
     */
    public String makeTrackingZnode() {
        return job_trackingroot + "/";
    }

    /**
     * Make a ZK path to an existing tracking node
     */
    public String makeTrackingJobZnode(String nodename) {
        return job_trackingroot + "/" + nodename;
    }

    /*
     * Get the list of tracking jobs.  These can be used to determine which jobs have
     * expired.
     */
    public static List<String> getTrackingJobs(Configuration conf, ZooKeeper zk)
        throws IOException {
        ArrayList<String> jobs = new ArrayList<String>();
        try {
            for (String myid : zk.getChildren(
                conf.get(TempletonStorage.STORAGE_ROOT)
                    + ZooKeeperStorage.TRACKINGDIR, false)) {
                jobs.add(myid);
            }
        } catch (Exception e) {
            throw new IOException("Can't get tracking children", e);
        }
        return jobs;
    }
}