org.apache.hadoop.mapred.JobHistoryCopy.java Source code

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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.hadoop.mapred;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.io.UnsupportedEncodingException;
import java.net.URLDecoder;
import java.net.URLEncoder;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.TreeMap;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FSDataOutputStream;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.fs.PathFilter;
import org.apache.hadoop.fs.permission.FsPermission;
import org.apache.hadoop.mapreduce.JobACL;
import org.apache.hadoop.security.authorize.AccessControlList;
import org.apache.hadoop.util.StringUtils;

import com.twitter.hraven.JobHistoryKeys;

/**
 * TODO: ** HACK-ALERT ! **
 * Note that this is a copy of the original JobHistory class.
 * Reason is that the class needs to be modified, yet needs access to
 * package-private methods on the JobTracker class.
 * Hence the same package name.
 * Once this works, we'll submit upstream fixes to this class and
 * port that back to our distro.
 *
 * Changes that we have made:
 * 1) Constructor added with input stream
 * 2) Keys enum refactored in standalone {@link JobHistoryKeys} class
 * as it is needed outside of this context.
 * TODO: ** End of HACK-ALERT **
 *
 * Provides methods for writing to and reading from job history. 
 * Job History works in an append mode, JobHistory and its inner classes provide methods 
 * to log job events. 
 *
 * JobHistory is split into multiple files, format of each file is plain text where each line 
 * is of the format [type (key=value)*], where type identifies the type of the record. 
 * Type maps to UID of one of the inner classes of this class. 
 * 
 * Job history is maintained in a master index which contains star/stop times of all jobs with
 * a few other job level properties. Apart from this each job's history is maintained in a seperate history 
 * file. name of job history files follows the format jobtrackerId_jobid
 *  
 * For parsing the job history it supports a listener based interface where each line is parsed
 * and passed to listener. The listener can create an object model of history or look for specific 
 * events and discard rest of the history.  
 * 
 * CHANGE LOG :
 * Version 0 : The history has the following format : 
 *             TAG KEY1="VALUE1" KEY2="VALUE2" and so on. 
           TAG can be Job, Task, MapAttempt or ReduceAttempt. 
           Note that a '"' is the line delimiter.
 * Version 1 : Changes the line delimiter to '.'
           Values are now escaped for unambiguous parsing. 
           Added the Meta tag to store version info.
 */
public class JobHistoryCopy {

    static final long VERSION = 1L;
    public static final Log LOG = LogFactory.getLog(JobHistoryCopy.class);
    private static final char DELIMITER = ' ';
    static final char LINE_DELIMITER_CHAR = '.';
    static final char[] charsToEscape = new char[] { '"', '=', LINE_DELIMITER_CHAR };
    static final String DIGITS = "[0-9]+";

    static final String KEY = "(\\w+)";
    // value is any character other than quote, but escaped quotes can be there
    static final String VALUE = "[^\"\\\\]*+(?:\\\\.[^\"\\\\]*+)*+";

    static final Pattern pattern = Pattern.compile(KEY + "=" + "\"" + VALUE + "\"");

    public static final int JOB_NAME_TRIM_LENGTH = 50;
    private static String JOBTRACKER_UNIQUE_STRING = null;
    private static String LOG_DIR = null;
    private static final String SECONDARY_FILE_SUFFIX = ".recover";
    private static long jobHistoryBlockSize = 0;
    private static String jobtrackerHostname;
    private static JobHistoryFilesManager fileManager = null;
    final static FsPermission HISTORY_DIR_PERMISSION = FsPermission.createImmutable((short) 0755); // rwxr-xr-x
    final static FsPermission HISTORY_FILE_PERMISSION = FsPermission.createImmutable((short) 0744); // rwxr--r--
    private static FileSystem LOGDIR_FS; // log dir filesystem
    private static FileSystem DONEDIR_FS; // Done dir filesystem
    private static JobConf jtConf;
    private static Path DONE = null; // folder for completed jobs
    private static boolean aclsEnabled = false;
    /**
     * A filter for conf files
     */
    private static final PathFilter CONF_FILTER = new PathFilter() {
        public boolean accept(Path path) {
            return path.getName().endsWith("_conf.xml");
        }
    };

    private static Map<JobID, MovedFileInfo> jobHistoryFileMap = Collections
            .<JobID, MovedFileInfo>synchronizedMap(new LinkedHashMap<JobID, MovedFileInfo>());

    private static class MovedFileInfo {
        private final String historyFile;
        private final long timestamp;

        public MovedFileInfo(String historyFile, long timestamp) {
            this.historyFile = historyFile;
            this.timestamp = timestamp;
        }
    }

    /**
     * Given the job id, return the history file path from the cache
     */
    public static String getHistoryFilePath(JobID jobId) {
        MovedFileInfo info = jobHistoryFileMap.get(jobId);
        if (info == null) {
            return null;
        }
        return info.historyFile;
    }

    /**
     * A class that manages all the files related to a job. For now 
     *   - writers : list of open files
     *   - job history filename
     *   - job conf filename
     */
    private static class JobHistoryFilesManager {
        // a private (virtual) folder for all the files related to a running job
        private static class FilesHolder {
            ArrayList<PrintWriter> writers = new ArrayList<PrintWriter>();
            Path historyFilename; // path of job history file
            Path confFilename; // path of job's conf
        }

        private ThreadPoolExecutor executor = null;
        private final Configuration conf;
        private final JobTracker jobTracker;

        // cache from job-key to files associated with it.
        private Map<JobID, FilesHolder> fileCache = new ConcurrentHashMap<JobID, FilesHolder>();

        JobHistoryFilesManager(Configuration conf, JobTracker jobTracker) throws IOException {
            this.conf = conf;
            this.jobTracker = jobTracker;
        }

        void start() {
            executor = new ThreadPoolExecutor(1, 3, 1, TimeUnit.HOURS, new LinkedBlockingQueue<Runnable>());
        }

        private FilesHolder getFileHolder(JobID id) {
            FilesHolder holder = fileCache.get(id);
            if (holder == null) {
                holder = new FilesHolder();
                fileCache.put(id, holder);
            }
            return holder;
        }

        void addWriter(JobID id, PrintWriter writer) {
            FilesHolder holder = getFileHolder(id);
            holder.writers.add(writer);
        }

        void setHistoryFile(JobID id, Path file) {
            FilesHolder holder = getFileHolder(id);
            holder.historyFilename = file;
        }

        void setConfFile(JobID id, Path file) {
            FilesHolder holder = getFileHolder(id);
            holder.confFilename = file;
        }

        ArrayList<PrintWriter> getWriters(JobID id) {
            FilesHolder holder = fileCache.get(id);
            return holder == null ? null : holder.writers;
        }

        Path getHistoryFile(JobID id) {
            FilesHolder holder = fileCache.get(id);
            return holder == null ? null : holder.historyFilename;
        }

        Path getConfFileWriters(JobID id) {
            FilesHolder holder = fileCache.get(id);
            return holder == null ? null : holder.confFilename;
        }

        void purgeJob(JobID id) {
            fileCache.remove(id);
        }

        void moveToDone(final JobID id) {
            final List<Path> paths = new ArrayList<Path>();
            final Path historyFile = fileManager.getHistoryFile(id);
            if (historyFile == null) {
                LOG.info("No file for job-history with " + id + " found in cache!");
            } else {
                paths.add(historyFile);
            }

            final Path confPath = fileManager.getConfFileWriters(id);
            if (confPath == null) {
                LOG.info("No file for jobconf with " + id + " found in cache!");
            } else {
                paths.add(confPath);
            }

            executor.execute(new Runnable() {

                public void run() {
                    //move the files to DONE folder
                    try {
                        for (Path path : paths) {
                            //check if path exists, in case of retries it may not exist
                            if (LOGDIR_FS.exists(path)) {
                                LOG.info("Moving " + path.toString() + " to " + DONE.toString());
                                DONEDIR_FS.moveFromLocalFile(path, DONE);
                                DONEDIR_FS.setPermission(new Path(DONE, path.getName()),
                                        new FsPermission(HISTORY_FILE_PERMISSION));
                            }
                        }
                    } catch (Throwable e) {
                        LOG.error("Unable to move history file to DONE folder.", e);
                    }
                    String historyFileDonePath = null;
                    if (historyFile != null) {
                        historyFileDonePath = new Path(DONE, historyFile.getName()).toString();
                    }

                    jobHistoryFileMap.put(id, new MovedFileInfo(historyFileDonePath, System.currentTimeMillis()));
                    jobTracker.historyFileCopied(id, historyFileDonePath);

                    //purge the job from the cache
                    fileManager.purgeJob(id);
                }

            });
        }

        void removeWriter(JobID jobId, PrintWriter writer) {
            fileManager.getWriters(jobId).remove(writer);
        }
    }

    /**
     * Record types are identifiers for each line of log in history files. 
     * A record type appears as the first token in a single line of log. 
     */
    public static enum RecordTypes {
        Jobtracker, Job, Task, MapAttempt, ReduceAttempt, Meta
    }

    /**
     * This enum contains some of the values commonly used by history log events. 
     * since values in history can only be strings - Values.name() is used in 
     * most places in history file. 
     */
    public static enum Values {
        SUCCESS, FAILED, KILLED, MAP, REDUCE, CLEANUP, RUNNING, PREP, SETUP
    }

    /**
     * Initialize JobHistory files. 
     * @param conf Jobconf of the job tracker.
     * @param hostname jobtracker's hostname
     * @param jobTrackerStartTime jobtracker's start time
     * @return true if intialized properly
     *         false otherwise
     */
    public static void init(JobTracker jobTracker, JobConf conf, String hostname, long jobTrackerStartTime)
            throws IOException {
        LOG_DIR = conf.get("hadoop.job.history.location", "file:///"
                + new File(System.getProperty("hadoop.log.dir")).getAbsolutePath() + File.separator + "history");
        JOBTRACKER_UNIQUE_STRING = hostname + "_" + String.valueOf(jobTrackerStartTime) + "_";
        jobtrackerHostname = hostname;
        Path logDir = new Path(LOG_DIR);
        LOGDIR_FS = logDir.getFileSystem(conf);
        if (!LOGDIR_FS.exists(logDir)) {
            if (!LOGDIR_FS.mkdirs(logDir, new FsPermission(HISTORY_DIR_PERMISSION))) {
                throw new IOException("Mkdirs failed to create " + logDir.toString());
            }
        }
        conf.set("hadoop.job.history.location", LOG_DIR);
        // set the job history block size (default is 3MB)
        jobHistoryBlockSize = conf.getLong("mapred.jobtracker.job.history.block.size", 3 * 1024 * 1024);
        jtConf = conf;

        // queue and job level security is enabled on the mapreduce cluster or not
        aclsEnabled = conf.getBoolean(JobConf.MR_ACLS_ENABLED, false);

        // initialize the file manager
        fileManager = new JobHistoryFilesManager(conf, jobTracker);
    }

    static void initDone(JobConf conf, FileSystem fs) throws IOException {
        //if completed job history location is set, use that
        String doneLocation = conf.get("mapred.job.tracker.history.completed.location");
        if (doneLocation != null) {
            Path donePath = new Path(doneLocation);
            DONEDIR_FS = donePath.getFileSystem(conf);
            DONE = DONEDIR_FS.makeQualified(donePath);
        } else {
            DONE = new Path(LOG_DIR, "done");
            DONEDIR_FS = LOGDIR_FS;
        }

        //If not already present create the done folder with appropriate 
        //permission
        if (!DONEDIR_FS.exists(DONE)) {
            LOG.info("Creating DONE folder at " + DONE);
            if (!DONEDIR_FS.mkdirs(DONE, new FsPermission(HISTORY_DIR_PERMISSION))) {
                throw new IOException("Mkdirs failed to create " + DONE.toString());
            }
        }
        fileManager.start();
    }

    /**
     * Manages job-history's meta information such as version etc.
     * Helps in logging version information to the job-history and recover
     * version information from the history. 
     */
    static class MetaInfoManager implements Listener {
        private long version = 0L;
        private KeyValuePair pairs = new KeyValuePair();

        // Extract the version of the history that was used to write the history
        public MetaInfoManager(String line) throws IOException {
            if (null != line) {
                // Parse the line
                parseLine(line, this, false);
            }
        }

        // Get the line delimiter
        char getLineDelim() {
            if (version == 0) {
                return '"';
            } else {
                return LINE_DELIMITER_CHAR;
            }
        }

        // Checks if the values are escaped or not
        boolean isValueEscaped() {
            // Note that the values are not escaped in version 0
            return version != 0;
        }

        public void handle(RecordTypes recType, Map<JobHistoryKeys, String> values) throws IOException {
            // Check if the record is of type META
            if (RecordTypes.Meta == recType) {
                pairs.handle(values);
                version = pairs.getLong(JobHistoryKeys.VERSION); // defaults to 0
            }
        }

        /**
         * Logs history meta-info to the history file. This needs to be called once
         * per history file. 
         * @param jobId job id, assigned by jobtracker. 
         */
        static void logMetaInfo(ArrayList<PrintWriter> writers) {
            if (null != writers) {
                JobHistoryCopy.log(writers, RecordTypes.Meta, new JobHistoryKeys[] { JobHistoryKeys.VERSION },
                        new String[] { String.valueOf(VERSION) });
            }
        }
    }

    /** Escapes the string especially for {@link JobHistoryCopy}
     */
    static String escapeString(String data) {
        return StringUtils.escapeString(data, StringUtils.ESCAPE_CHAR, charsToEscape);
    }

    /**
     * Parses history file and invokes Listener.handle() for 
     * each line of history. It can be used for looking through history
     * files for specific items without having to keep whole history in memory. 
     * @param path path to history file
     * @param l Listener for history events 
     * @param fs FileSystem where history file is present
     * @throws IOException
     */
    public static void parseHistoryFromFS(String path, Listener l, FileSystem fs) throws IOException {
        FSDataInputStream in = fs.open(new Path(path));
        parseHistoryFromIS(in, l);
    }

    /**
     * Parses history (file) input stream and invokes Listener.handle() for 
     * each line of history. It can be used for looking through history
     * (file) input streams for specific items without having to keep whole history in memory. 
     * @param in containing history file content
     * @param l Listener for history events
     * @throws IOException
     */
    public static void parseHistoryFromIS(InputStream in, Listener l) throws IOException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(in));
        try {
            String line = null;
            StringBuffer buf = new StringBuffer();

            // Read the meta-info line. Note that this might a jobinfo line for files
            // written with older format
            line = reader.readLine();

            // Check if the file is empty
            if (line == null) {
                return;
            }

            // Get the information required for further processing
            MetaInfoManager mgr = new MetaInfoManager(line);
            boolean isEscaped = mgr.isValueEscaped();
            String lineDelim = String.valueOf(mgr.getLineDelim());
            String escapedLineDelim = StringUtils.escapeString(lineDelim, StringUtils.ESCAPE_CHAR,
                    mgr.getLineDelim());

            do {
                buf.append(line);
                if (!line.trim().endsWith(lineDelim) || line.trim().endsWith(escapedLineDelim)) {
                    buf.append("\n");
                    continue;
                }
                parseLine(buf.toString(), l, isEscaped);
                buf = new StringBuffer();
            } while ((line = reader.readLine()) != null);
        } finally {
            try {
                reader.close();
            } catch (IOException ex) {
            }
        }
    }

    /**
     * Parse a single line of history. 
     * @param line
     * @param l
     * @throws IOException
     */
    private static void parseLine(String line, Listener l, boolean isEscaped) throws IOException {
        // extract the record type 
        int idx = line.indexOf(' ');
        String recType = line.substring(0, idx);
        String data = line.substring(idx + 1, line.length());

        Matcher matcher = pattern.matcher(data);
        Map<JobHistoryKeys, String> parseBuffer = new HashMap<JobHistoryKeys, String>();

        while (matcher.find()) {
            String tuple = matcher.group(0);
            String[] parts = StringUtils.split(tuple, StringUtils.ESCAPE_CHAR, '=');
            String value = parts[1].substring(1, parts[1].length() - 1);
            if (isEscaped) {
                value = StringUtils.unEscapeString(value, StringUtils.ESCAPE_CHAR, charsToEscape);
            }
            parseBuffer.put(JobHistoryKeys.valueOf(parts[0]), value);
        }

        l.handle(RecordTypes.valueOf(recType), parseBuffer);

        parseBuffer.clear();
    }

    /**
     * Log a raw record type with keys and values. This is method is generally not used directly. 
     * @param recordType type of log event
     * @param key key
     * @param value value
     */

    static void log(PrintWriter out, RecordTypes recordType, JobHistoryKeys key, String value) {
        value = escapeString(value);
        out.println(recordType.name() + DELIMITER + key + "=\"" + value + "\"" + DELIMITER + LINE_DELIMITER_CHAR);
    }

    /**
     * Log a number of keys and values with record. the array length of keys and values
     * should be same. 
     * @param recordType type of log event
     * @param keys type of log event
     * @param values type of log event
     */

    /**
     * Log a number of keys and values with record. the array length of keys and values
     * should be same. 
     * @param recordType type of log event
     * @param keys type of log event
     * @param values type of log event
     */

    static void log(ArrayList<PrintWriter> writers, RecordTypes recordType, JobHistoryKeys[] keys,
            String[] values) {
        log(writers, recordType, keys, values, null);
    }

    /**
     * Log a number of keys and values with record. the array length of keys and values
     * should be same. 
     * @param recordType type of log event
     * @param keys type of log event
     * @param values type of log event
     * @param JobID jobid of the job  
     */

    static void log(ArrayList<PrintWriter> writers, RecordTypes recordType, JobHistoryKeys[] keys, String[] values,
            JobID id) {

        // First up calculate the length of buffer, so that we are performant
        // enough.
        int length = recordType.name().length() + keys.length * 4 + 2;
        for (int i = 0; i < keys.length; i++) {
            values[i] = escapeString(values[i]);
            length += values[i].length() + keys[i].toString().length();
        }

        // We have the length of the buffer, now construct it.
        StringBuilder builder = new StringBuilder(length);
        builder.append(recordType.name());
        builder.append(DELIMITER);
        for (int i = 0; i < keys.length; i++) {
            builder.append(keys[i]);
            builder.append("=\"");
            builder.append(values[i]);
            builder.append("\"");
            builder.append(DELIMITER);
        }
        builder.append(LINE_DELIMITER_CHAR);

        for (Iterator<PrintWriter> iter = writers.iterator(); iter.hasNext();) {
            PrintWriter out = iter.next();
            out.println(builder.toString());
            if (out.checkError() && id != null) {
                LOG.info("Logging failed for job " + id + "removing PrintWriter from FileManager");
                iter.remove();
            }
        }
    }

    /**
     * Get the history location
     */
    static Path getJobHistoryLocation() {
        return new Path(LOG_DIR);
    }

    /**
     * Get the history location for completed jobs
     */
    static Path getCompletedJobHistoryLocation() {
        return DONE;
    }

    /**
     * Base class contais utility stuff to manage types key value pairs with enums. 
     */
    static class KeyValuePair {
        private Map<JobHistoryKeys, String> values = new HashMap<JobHistoryKeys, String>();

        /**
         * Get 'String' value for given key. Most of the places use Strings as 
         * values so the default get' method returns 'String'.  This method never returns 
         * null to ease on GUIs. if no value is found it returns empty string ""
         * @param k 
         * @return if null it returns empty string - "" 
         */
        public String get(JobHistoryKeys k) {
            String s = values.get(k);
            return s == null ? "" : s;
        }

        /**
         * Convert value from history to int and return. 
         * if no value is found it returns 0.
         * @param k key 
         */
        public int getInt(JobHistoryKeys k) {
            String s = values.get(k);
            if (null != s) {
                return Integer.parseInt(s);
            }
            return 0;
        }

        /**
         * Convert value from history to int and return. 
         * if no value is found it returns 0.
         * @param k
         */
        public long getLong(JobHistoryKeys k) {
            String s = values.get(k);
            if (null != s) {
                return Long.parseLong(s);
            }
            return 0;
        }

        /**
         * Set value for the key. 
         * @param k
         * @param s
         */
        public void set(JobHistoryKeys k, String s) {
            values.put(k, s);
        }

        /**
         * Adds all values in the Map argument to its own values. 
         * @param m
         */
        public void set(Map<JobHistoryKeys, String> m) {
            values.putAll(m);
        }

        /**
         * Reads values back from the history, input is same Map as passed to Listener by parseHistory().  
         * @param values
         */
        public synchronized void handle(Map<JobHistoryKeys, String> values) {
            set(values);
        }

        /**
         * Returns Map containing all key-values. 
         */
        public Map<JobHistoryKeys, String> getValues() {
            return values;
        }
    }

    /**
     * Helper class for logging or reading back events related to job start, finish or failure. 
     */
    public static class JobInfo extends KeyValuePair {

        private Map<String, Task> allTasks = new TreeMap<String, Task>();
        private Map<JobACL, AccessControlList> jobACLs = new HashMap<JobACL, AccessControlList>();
        private String queueName = null;// queue to which this job was submitted to

        /** Create new JobInfo */
        public JobInfo(String jobId) {
            set(JobHistoryKeys.JOBID, jobId);
        }

        /**
         * Returns all map and reduce tasks <taskid-Task>. 
         */
        public Map<String, Task> getAllTasks() {
            return allTasks;
        }

        /**
         * Get the job acls.
         * 
         * @return a {@link Map} from {@link JobACL} to {@link AccessControlList}
         */
        public Map<JobACL, AccessControlList> getJobACLs() {
            return jobACLs;
        }

        @Override
        public synchronized void handle(Map<JobHistoryKeys, String> values) {
            if (values.containsKey(JobHistoryKeys.SUBMIT_TIME)) {// job submission
                // construct the job ACLs
                String viewJobACL = values.get(JobHistoryKeys.VIEW_JOB);
                String modifyJobACL = values.get(JobHistoryKeys.MODIFY_JOB);
                if (viewJobACL != null) {
                    jobACLs.put(JobACL.VIEW_JOB, new AccessControlList(viewJobACL));
                }
                if (modifyJobACL != null) {
                    jobACLs.put(JobACL.MODIFY_JOB, new AccessControlList(modifyJobACL));
                }
                // get the job queue name
                queueName = values.get(JobHistoryKeys.JOB_QUEUE);
            }
            super.handle(values);
        }

        String getJobQueue() {
            return queueName;
        }

        /**
         * Get the path of the locally stored job file
         * @param jobId id of the job
         * @return the path of the job file on the local file system 
         */
        public static String getLocalJobFilePath(JobID jobId) {
            return System.getProperty("hadoop.log.dir") + File.separator + jobId + "_conf.xml";
        }

        /**
         * Helper function to encode the URL of the path of the job-history
         * log file. 
         * 
         * @param logFile path of the job-history file
         * @return URL encoded path
         * @throws IOException
         */
        public static String encodeJobHistoryFilePath(String logFile) throws IOException {
            Path rawPath = new Path(logFile);
            String encodedFileName = null;
            try {
                encodedFileName = URLEncoder.encode(rawPath.getName(), "UTF-8");
            } catch (UnsupportedEncodingException uee) {
                IOException ioe = new IOException();
                ioe.initCause(uee);
                ioe.setStackTrace(uee.getStackTrace());
                throw ioe;
            }

            Path encodedPath = new Path(rawPath.getParent(), encodedFileName);
            return encodedPath.toString();
        }

        /**
         * Helper function to encode the URL of the filename of the job-history 
         * log file.
         * 
         * @param logFileName file name of the job-history file
         * @return URL encoded filename
         * @throws IOException
         */
        public static String encodeJobHistoryFileName(String logFileName) throws IOException {
            String encodedFileName = null;
            try {
                encodedFileName = URLEncoder.encode(logFileName, "UTF-8");
            } catch (UnsupportedEncodingException uee) {
                IOException ioe = new IOException();
                ioe.initCause(uee);
                ioe.setStackTrace(uee.getStackTrace());
                throw ioe;
            }
            return encodedFileName;
        }

        /**
         * Helper function to decode the URL of the filename of the job-history 
         * log file.
         * 
         * @param logFileName file name of the job-history file
         * @return URL decoded filename
         * @throws IOException
         */
        public static String decodeJobHistoryFileName(String logFileName) throws IOException {
            String decodedFileName = null;
            try {
                decodedFileName = URLDecoder.decode(logFileName, "UTF-8");
            } catch (UnsupportedEncodingException uee) {
                IOException ioe = new IOException();
                ioe.initCause(uee);
                ioe.setStackTrace(uee.getStackTrace());
                throw ioe;
            }
            return decodedFileName;
        }

        /**
         * Get the job name from the job conf
         */
        static String getJobName(JobConf jobConf) {
            String jobName = jobConf.getJobName();
            if (jobName == null || jobName.length() == 0) {
                jobName = "NA";
            }
            return jobName;
        }

        /**
         * Get the user name from the job conf
         */
        public static String getUserName(JobConf jobConf) {
            String user = jobConf.getUser();
            if (user == null || user.length() == 0) {
                user = "NA";
            }
            return user;
        }

        /**
         * Get the job history file path given the history filename
         */
        public static Path getJobHistoryLogLocation(String logFileName) {
            return LOG_DIR == null ? null : new Path(LOG_DIR, logFileName);
        }

        /**
         * Get the user job history file path
         */
        public static Path getJobHistoryLogLocationForUser(String logFileName, JobConf jobConf) {
            // find user log directory 
            Path userLogFile = null;
            Path outputPath = FileOutputFormat.getOutputPath(jobConf);
            String userLogDir = jobConf.get("hadoop.job.history.user.location",
                    outputPath == null ? null : outputPath.toString());
            if ("none".equals(userLogDir)) {
                userLogDir = null;
            }
            if (userLogDir != null) {
                userLogDir = userLogDir + Path.SEPARATOR + "_logs" + Path.SEPARATOR + "history";
                userLogFile = new Path(userLogDir, logFileName);
            }
            return userLogFile;
        }

        /**
         * Generates the job history filename for a new job
         */
        private static String getNewJobHistoryFileName(JobConf jobConf, JobID id) {
            return JOBTRACKER_UNIQUE_STRING + id.toString() + "_" + getUserName(jobConf) + "_"
                    + trimJobName(getJobName(jobConf));
        }

        /**
         * Trims the job-name if required
         */
        private static String trimJobName(String jobName) {
            if (jobName.length() > JOB_NAME_TRIM_LENGTH) {
                jobName = jobName.substring(0, JOB_NAME_TRIM_LENGTH);
            }
            return jobName;
        }

        private static String escapeRegexChars(String string) {
            return "\\Q" + string.replaceAll("\\\\E", "\\\\E\\\\\\\\E\\\\Q") + "\\E";
        }

        /**
         * Recover the job history filename from the history folder. 
         * Uses the following pattern
         *    $jt-hostname_[0-9]*_$job-id_$user-$job-name*
         * @param jobConf the job conf
         * @param id job id
         */
        public static synchronized String getJobHistoryFileName(JobConf jobConf, JobID id) throws IOException {
            return getJobHistoryFileName(jobConf, id, new Path(LOG_DIR), LOGDIR_FS);
        }

        static synchronized String getDoneJobHistoryFileName(JobConf jobConf, JobID id) throws IOException {
            if (DONE == null) {
                return null;
            }
            return getJobHistoryFileName(jobConf, id, DONE, DONEDIR_FS);
        }

        /**
         * @param dir The directory where to search.
         */
        private static synchronized String getJobHistoryFileName(JobConf jobConf, JobID id, Path dir, FileSystem fs)
                throws IOException {
            String user = getUserName(jobConf);
            String jobName = trimJobName(getJobName(jobConf));
            if (LOG_DIR == null) {
                return null;
            }

            // Make the pattern matching the job's history file
            final Pattern historyFilePattern = Pattern.compile(jobtrackerHostname + "_" + DIGITS + "_"
                    + id.toString() + "_" + user + "_" + escapeRegexChars(jobName) + "+");
            // a path filter that matches 4 parts of the filenames namely
            //  - jt-hostname
            //  - job-id
            //  - username
            //  - jobname
            PathFilter filter = new PathFilter() {
                public boolean accept(Path path) {
                    String fileName = path.getName();
                    try {
                        fileName = decodeJobHistoryFileName(fileName);
                    } catch (IOException ioe) {
                        LOG.info("Error while decoding history file " + fileName + "." + " Ignoring file.", ioe);
                        return false;
                    }
                    return historyFilePattern.matcher(fileName).find();
                }
            };

            FileStatus[] statuses = fs.listStatus(dir, filter);
            String filename = null;
            if (statuses.length == 0) {
                LOG.info("Nothing to recover for job " + id);
            } else {
                // return filename considering that fact the name can be a 
                // secondary filename like filename.recover
                filename = getPrimaryFilename(statuses[0].getPath().getName(), jobName);
                LOG.info("Recovered job history filename for job " + id + " is " + filename);
            }
            return filename;
        }

        // removes all extra extensions from a filename and returns the core/primary
        // filename
        private static String getPrimaryFilename(String filename, String jobName) throws IOException {
            filename = decodeJobHistoryFileName(filename);
            // Remove the '.recover' suffix if it exists
            if (filename.endsWith(jobName + SECONDARY_FILE_SUFFIX)) {
                int newLength = filename.length() - SECONDARY_FILE_SUFFIX.length();
                filename = filename.substring(0, newLength);
            }
            return encodeJobHistoryFileName(filename);
        }

        /** Since there was a restart, there should be a master file and 
         * a recovery file. Once the recovery is complete, the master should be 
         * deleted as an indication that the recovery file should be treated as the 
         * master upon completion or next restart.
         * @param fileName the history filename that needs checkpointing
         * @param conf Job conf
         * @throws IOException
         */
        static synchronized void checkpointRecovery(String fileName, JobConf conf) throws IOException {
            Path logPath = JobHistoryCopy.JobInfo.getJobHistoryLogLocation(fileName);
            if (logPath != null) {
                LOG.info("Deleting job history file " + logPath.getName());
                LOGDIR_FS.delete(logPath, false);
            }
            // do the same for the user file too
            logPath = JobHistoryCopy.JobInfo.getJobHistoryLogLocationForUser(fileName, conf);
            if (logPath != null) {
                FileSystem fs = logPath.getFileSystem(conf);
                fs.delete(logPath, false);
            }
        }

        static String getSecondaryJobHistoryFile(String filename) throws IOException {
            return encodeJobHistoryFileName(decodeJobHistoryFileName(filename) + SECONDARY_FILE_SUFFIX);
        }

        /** Selects one of the two files generated as a part of recovery. 
         * The thumb rule is that always select the oldest file. 
         * This call makes sure that only one file is left in the end. 
         * @param conf job conf
         * @param logFilePath Path of the log file
         * @throws IOException 
         */
        public synchronized static Path recoverJobHistoryFile(JobConf conf, Path logFilePath) throws IOException {
            Path ret;
            String logFileName = logFilePath.getName();
            String tmpFilename = getSecondaryJobHistoryFile(logFileName);
            Path logDir = logFilePath.getParent();
            Path tmpFilePath = new Path(logDir, tmpFilename);
            if (LOGDIR_FS.exists(logFilePath)) {
                LOG.info(logFileName + " exists!");
                if (LOGDIR_FS.exists(tmpFilePath)) {
                    LOG.info("Deleting " + tmpFilename + "  and using " + logFileName + " for recovery.");
                    LOGDIR_FS.delete(tmpFilePath, false);
                }
                ret = tmpFilePath;
            } else {
                LOG.info(logFileName + " doesnt exist! Using " + tmpFilename + " for recovery.");
                if (LOGDIR_FS.exists(tmpFilePath)) {
                    LOG.info("Renaming " + tmpFilename + " to " + logFileName);
                    LOGDIR_FS.rename(tmpFilePath, logFilePath);
                    ret = tmpFilePath;
                } else {
                    ret = logFilePath;
                }
            }

            // do the same for the user files too
            logFilePath = getJobHistoryLogLocationForUser(logFileName, conf);
            if (logFilePath != null) {
                FileSystem fs = logFilePath.getFileSystem(conf);
                logDir = logFilePath.getParent();
                tmpFilePath = new Path(logDir, tmpFilename);
                if (fs.exists(logFilePath)) {
                    LOG.info(logFileName + " exists!");
                    if (fs.exists(tmpFilePath)) {
                        LOG.info("Deleting " + tmpFilename + "  and making " + logFileName
                                + " as the master history file for user.");
                        fs.delete(tmpFilePath, false);
                    }
                } else {
                    LOG.info(logFileName + " doesnt exist! Using " + tmpFilename
                            + " as the master history file for user.");
                    if (fs.exists(tmpFilePath)) {
                        LOG.info("Renaming " + tmpFilename + " to " + logFileName + " in user directory");
                        fs.rename(tmpFilePath, logFilePath);
                    }
                }
            }

            return ret;
        }

        /** Finalize the recovery and make one file in the end. 
         * This invloves renaming the recover file to the master file.
         * Note that this api should be invoked only if recovery is involved.
         * @param id Job id  
         * @param conf the job conf
         * @throws IOException
         */
        static synchronized void finalizeRecovery(JobID id, JobConf conf) throws IOException {
            Path tmpLogPath = fileManager.getHistoryFile(id);
            if (tmpLogPath == null) {
                if (LOG.isDebugEnabled()) {
                    LOG.debug("No file for job with " + id + " found in cache!");
                }
                return;
            }
            String tmpLogFileName = tmpLogPath.getName();

            // get the primary filename from the cached filename
            String masterLogFileName = getPrimaryFilename(tmpLogFileName, getJobName(conf));
            Path masterLogPath = new Path(tmpLogPath.getParent(), masterLogFileName);

            // rename the tmp file to the master file. Note that this should be 
            // done only when the file is closed and handles are released.
            LOG.info("Renaming " + tmpLogFileName + " to " + masterLogFileName);
            LOGDIR_FS.rename(tmpLogPath, masterLogPath);
            // update the cache
            fileManager.setHistoryFile(id, masterLogPath);

            // do the same for the user file too
            masterLogPath = JobHistoryCopy.JobInfo.getJobHistoryLogLocationForUser(masterLogFileName, conf);
            tmpLogPath = JobHistoryCopy.JobInfo.getJobHistoryLogLocationForUser(tmpLogFileName, conf);
            if (masterLogPath != null) {
                FileSystem fs = masterLogPath.getFileSystem(conf);
                if (fs.exists(tmpLogPath)) {
                    LOG.info("Renaming " + tmpLogFileName + " to " + masterLogFileName + " in user directory");
                    fs.rename(tmpLogPath, masterLogPath);
                }
            }
        }

        /**
         * Deletes job data from the local disk.
         * For now just deletes the localized copy of job conf
         */
        static void cleanupJob(JobID id) {
            String localJobFilePath = JobInfo.getLocalJobFilePath(id);
            File f = new File(localJobFilePath);
            LOG.info("Deleting localized job conf at " + f);
            if (!f.delete()) {
                if (LOG.isDebugEnabled()) {
                    LOG.debug("Failed to delete file " + f);
                }
            }
        }

        /**
         * Delete job conf from the history folder.
         */
        static void deleteConfFiles() throws IOException {
            LOG.info("Cleaning up config files from the job history folder");
            FileSystem fs = new Path(LOG_DIR).getFileSystem(jtConf);
            FileStatus[] status = fs.listStatus(new Path(LOG_DIR), CONF_FILTER);
            for (FileStatus s : status) {
                LOG.info("Deleting conf file " + s.getPath());
                fs.delete(s.getPath(), false);
            }
        }

        /**
         * Move the completed job into the completed folder.
         * This assumes that the jobhistory file is closed and all operations on the
         * jobhistory file is complete.
         * This *should* be the last call to jobhistory for a given job.
         */
        static void markCompleted(JobID id) throws IOException {
            fileManager.moveToDone(id);
        }

        /**
        * Log job submitted event to history. Creates a new file in history 
        * for the job. if history file creation fails, it disables history 
        * for all other events. 
        * @param jobId job id assigned by job tracker.
        * @param jobConf job conf of the job
        * @param jobConfPath path to job conf xml file in HDFS.
        * @param submitTime time when job tracker received the job
        * @throws IOException
        * @deprecated Use 
        *     {@link #logSubmitted(JobID, JobConf, String, long, boolean)} instead.
        */
        @Deprecated
        public static void logSubmitted(JobID jobId, JobConf jobConf, String jobConfPath, long submitTime)
                throws IOException {
            logSubmitted(jobId, jobConf, jobConfPath, submitTime, true);
        }

        public static void logSubmitted(JobID jobId, JobConf jobConf, String jobConfPath, long submitTime,
                boolean restarted) throws IOException {
            FileSystem fs = null;
            String userLogDir = null;
            String jobUniqueString = JOBTRACKER_UNIQUE_STRING + jobId;

            // Get the username and job name to be used in the actual log filename;
            // sanity check them too        
            String jobName = getJobName(jobConf);
            String user = getUserName(jobConf);

            // get the history filename
            String logFileName = null;
            if (restarted) {
                logFileName = getJobHistoryFileName(jobConf, jobId);
                if (logFileName == null) {
                    logFileName = encodeJobHistoryFileName(getNewJobHistoryFileName(jobConf, jobId));
                } else {
                    String parts[] = logFileName.split("_");
                    //TODO this is a hack :(
                    // jobtracker-hostname_jobtracker-identifier_
                    String jtUniqueString = parts[0] + "_" + parts[1] + "_";
                    jobUniqueString = jtUniqueString + jobId.toString();
                }
            } else {
                logFileName = encodeJobHistoryFileName(getNewJobHistoryFileName(jobConf, jobId));
            }

            // setup the history log file for this job
            Path logFile = getJobHistoryLogLocation(logFileName);

            // find user log directory
            Path userLogFile = getJobHistoryLogLocationForUser(logFileName, jobConf);
            PrintWriter writer = null;
            try {
                FSDataOutputStream out = null;
                if (LOG_DIR != null) {
                    // create output stream for logging in hadoop.job.history.location
                    if (restarted) {
                        logFile = recoverJobHistoryFile(jobConf, logFile);
                        logFileName = logFile.getName();
                    }

                    int defaultBufferSize = LOGDIR_FS.getConf().getInt("io.file.buffer.size", 4096);
                    out = LOGDIR_FS.create(logFile, new FsPermission(HISTORY_FILE_PERMISSION), true,
                            defaultBufferSize, LOGDIR_FS.getDefaultReplication(), jobHistoryBlockSize, null);
                    writer = new PrintWriter(out);
                    fileManager.addWriter(jobId, writer);

                    // cache it ...
                    fileManager.setHistoryFile(jobId, logFile);
                }
                if (userLogFile != null) {
                    // Get the actual filename as recoverJobHistoryFile() might return
                    // a different filename
                    userLogDir = userLogFile.getParent().toString();
                    userLogFile = new Path(userLogDir, logFileName);

                    // create output stream for logging 
                    // in hadoop.job.history.user.location
                    fs = userLogFile.getFileSystem(jobConf);

                    out = fs.create(userLogFile, true, 4096);
                    writer = new PrintWriter(out);
                    fileManager.addWriter(jobId, writer);
                }

                ArrayList<PrintWriter> writers = fileManager.getWriters(jobId);
                // Log the history meta info
                JobHistoryCopy.MetaInfoManager.logMetaInfo(writers);

                String viewJobACL = "*";
                String modifyJobACL = "*";
                if (aclsEnabled) {
                    viewJobACL = jobConf.get(JobACL.VIEW_JOB.getAclName(), " ");
                    modifyJobACL = jobConf.get(JobACL.MODIFY_JOB.getAclName(), " ");
                }
                //add to writer as well 
                JobHistoryCopy.log(writers, RecordTypes.Job,
                        new JobHistoryKeys[] { JobHistoryKeys.JOBID, JobHistoryKeys.JOBNAME, JobHistoryKeys.USER,
                                JobHistoryKeys.SUBMIT_TIME, JobHistoryKeys.JOBCONF, JobHistoryKeys.VIEW_JOB,
                                JobHistoryKeys.MODIFY_JOB, JobHistoryKeys.JOB_QUEUE },
                        new String[] { jobId.toString(), jobName, user, String.valueOf(submitTime), jobConfPath,
                                viewJobACL, modifyJobACL, jobConf.getQueueName() },
                        jobId);

            } catch (IOException e) {
                LOG.error("Failed creating job history log file for job " + jobId, e);
                if (writer != null) {
                    fileManager.removeWriter(jobId, writer);
                }
            }
            // Always store job conf on local file system 
            String localJobFilePath = JobInfo.getLocalJobFilePath(jobId);
            File localJobFile = new File(localJobFilePath);
            FileOutputStream jobOut = null;
            try {
                jobOut = new FileOutputStream(localJobFile);
                jobConf.writeXml(jobOut);
                if (LOG.isDebugEnabled()) {
                    LOG.debug("Job conf for " + jobId + " stored at " + localJobFile.getAbsolutePath());
                }
            } catch (IOException ioe) {
                LOG.error("Failed to store job conf on the local filesystem ", ioe);
            } finally {
                if (jobOut != null) {
                    try {
                        jobOut.close();
                    } catch (IOException ie) {
                        LOG.info(
                                "Failed to close the job configuration file " + StringUtils.stringifyException(ie));
                    }
                }
            }

            /* Storing the job conf on the log dir */
            Path jobFilePath = null;
            if (LOG_DIR != null) {
                jobFilePath = new Path(LOG_DIR + File.separator + jobUniqueString + "_conf.xml");
                fileManager.setConfFile(jobId, jobFilePath);
            }
            Path userJobFilePath = null;
            if (userLogDir != null) {
                userJobFilePath = new Path(userLogDir + File.separator + jobUniqueString + "_conf.xml");
            }
            FSDataOutputStream jobFileOut = null;
            try {
                if (LOG_DIR != null) {
                    int defaultBufferSize = LOGDIR_FS.getConf().getInt("io.file.buffer.size", 4096);
                    if (!LOGDIR_FS.exists(jobFilePath)) {
                        jobFileOut = LOGDIR_FS.create(jobFilePath, new FsPermission(HISTORY_FILE_PERMISSION), true,
                                defaultBufferSize, LOGDIR_FS.getDefaultReplication(),
                                LOGDIR_FS.getDefaultBlockSize(), null);
                        jobConf.writeXml(jobFileOut);
                        jobFileOut.close();
                    }
                }
                if (userLogDir != null) {
                    fs = new Path(userLogDir).getFileSystem(jobConf);
                    jobFileOut = fs.create(userJobFilePath);
                    jobConf.writeXml(jobFileOut);
                }
                if (LOG.isDebugEnabled()) {
                    LOG.debug("Job conf for " + jobId + " stored at " + jobFilePath + "and" + userJobFilePath);
                }
            } catch (IOException ioe) {
                LOG.error("Failed to store job conf in the log dir", ioe);
            } finally {
                if (jobFileOut != null) {
                    try {
                        jobFileOut.close();
                    } catch (IOException ie) {
                        LOG.info(
                                "Failed to close the job configuration file " + StringUtils.stringifyException(ie));
                    }
                }
            }
        }

        /**
         * Logs launch time of job. 
         * 
         * @param jobId job id, assigned by jobtracker. 
         * @param startTime start time of job. 
         * @param totalMaps total maps assigned by jobtracker. 
         * @param totalReduces total reduces. 
         */
        public static void logInited(JobID jobId, long startTime, int totalMaps, int totalReduces) {
            ArrayList<PrintWriter> writer = fileManager.getWriters(jobId);

            if (null != writer) {
                JobHistoryCopy.log(writer, RecordTypes.Job,
                        new JobHistoryKeys[] { JobHistoryKeys.JOBID, JobHistoryKeys.LAUNCH_TIME,
                                JobHistoryKeys.TOTAL_MAPS, JobHistoryKeys.TOTAL_REDUCES,
                                JobHistoryKeys.JOB_STATUS },
                        new String[] { jobId.toString(), String.valueOf(startTime), String.valueOf(totalMaps),
                                String.valueOf(totalReduces), Values.PREP.name() },
                        jobId);
            }
        }

        /**
          * Logs the job as RUNNING. 
          *
          * @param jobId job id, assigned by jobtracker. 
          * @param startTime start time of job. 
          * @param totalMaps total maps assigned by jobtracker. 
          * @param totalReduces total reduces. 
          * @deprecated Use {@link #logInited(JobID, long, int, int)} and 
          * {@link #logStarted(JobID)}
          */
        @Deprecated
        public static void logStarted(JobID jobId, long startTime, int totalMaps, int totalReduces) {
            logStarted(jobId);
        }

        /**
         * Logs job as running 
         * @param jobId job id, assigned by jobtracker. 
         */
        public static void logStarted(JobID jobId) {
            ArrayList<PrintWriter> writer = fileManager.getWriters(jobId);

            if (null != writer) {
                JobHistoryCopy.log(writer, RecordTypes.Job,
                        new JobHistoryKeys[] { JobHistoryKeys.JOBID, JobHistoryKeys.JOB_STATUS },
                        new String[] { jobId.toString(), Values.RUNNING.name() }, jobId);
            }
        }

        /**
         * Log job finished. closes the job file in history. 
         * @param jobId job id, assigned by jobtracker. 
         * @param finishTime finish time of job in ms. 
         * @param finishedMaps no of maps successfully finished. 
         * @param finishedReduces no of reduces finished sucessfully. 
         * @param failedMaps no of failed map tasks. 
         * @param failedReduces no of failed reduce tasks. 
         * @param counters the counters from the job
         */
        public static void logFinished(JobID jobId, long finishTime, int finishedMaps, int finishedReduces,
                int failedMaps, int failedReduces, Counters mapCounters, Counters reduceCounters,
                Counters counters) {
            // close job file for this job
            ArrayList<PrintWriter> writer = fileManager.getWriters(jobId);

            if (null != writer) {
                JobHistoryCopy.log(writer, RecordTypes.Job, new JobHistoryKeys[] { JobHistoryKeys.JOBID,
                        JobHistoryKeys.FINISH_TIME, JobHistoryKeys.JOB_STATUS, JobHistoryKeys.FINISHED_MAPS,
                        JobHistoryKeys.FINISHED_REDUCES, JobHistoryKeys.FAILED_MAPS, JobHistoryKeys.FAILED_REDUCES,
                        JobHistoryKeys.MAP_COUNTERS, JobHistoryKeys.REDUCE_COUNTERS, JobHistoryKeys.COUNTERS },
                        new String[] { jobId.toString(), Long.toString(finishTime), Values.SUCCESS.name(),
                                String.valueOf(finishedMaps), String.valueOf(finishedReduces),
                                String.valueOf(failedMaps), String.valueOf(failedReduces),
                                mapCounters.makeEscapedCompactString(), reduceCounters.makeEscapedCompactString(),
                                counters.makeEscapedCompactString() },
                        jobId);
                for (PrintWriter out : writer) {
                    out.close();
                }
            }
            Thread historyCleaner = new Thread(new HistoryCleaner());
            historyCleaner.start();
        }

        /**
         * Logs job failed event. Closes the job history log file. 
         * @param jobid job id
         * @param timestamp time when job failure was detected in ms.  
         * @param finishedMaps no finished map tasks. 
         * @param finishedReduces no of finished reduce tasks. 
         */
        public static void logFailed(JobID jobid, long timestamp, int finishedMaps, int finishedReduces) {
            ArrayList<PrintWriter> writer = fileManager.getWriters(jobid);

            if (null != writer) {
                JobHistoryCopy.log(writer, RecordTypes.Job,
                        new JobHistoryKeys[] { JobHistoryKeys.JOBID, JobHistoryKeys.FINISH_TIME,
                                JobHistoryKeys.JOB_STATUS, JobHistoryKeys.FINISHED_MAPS,
                                JobHistoryKeys.FINISHED_REDUCES },
                        new String[] { jobid.toString(), String.valueOf(timestamp), Values.FAILED.name(),
                                String.valueOf(finishedMaps), String.valueOf(finishedReduces) },
                        jobid);
                for (PrintWriter out : writer) {
                    out.close();
                }
            }
        }

        /**
         * Logs job killed event. Closes the job history log file.
         * 
         * @param jobid
         *          job id
         * @param timestamp
         *          time when job killed was issued in ms.
         * @param finishedMaps
         *          no finished map tasks.
         * @param finishedReduces
         *          no of finished reduce tasks.
         */
        public static void logKilled(JobID jobid, long timestamp, int finishedMaps, int finishedReduces) {
            ArrayList<PrintWriter> writer = fileManager.getWriters(jobid);

            if (null != writer) {
                JobHistoryCopy.log(writer, RecordTypes.Job,
                        new JobHistoryKeys[] { JobHistoryKeys.JOBID, JobHistoryKeys.FINISH_TIME,
                                JobHistoryKeys.JOB_STATUS, JobHistoryKeys.FINISHED_MAPS,
                                JobHistoryKeys.FINISHED_REDUCES },
                        new String[] { jobid.toString(), String.valueOf(timestamp), Values.KILLED.name(),
                                String.valueOf(finishedMaps), String.valueOf(finishedReduces) },
                        jobid);
                for (PrintWriter out : writer) {
                    out.close();
                }
            }
        }

        /**
         * Log job's priority. 
         * @param jobid job id
         * @param priority Jobs priority 
         */
        public static void logJobPriority(JobID jobid, JobPriority priority) {
            ArrayList<PrintWriter> writer = fileManager.getWriters(jobid);

            if (null != writer) {
                JobHistoryCopy.log(writer, RecordTypes.Job,
                        new JobHistoryKeys[] { JobHistoryKeys.JOBID, JobHistoryKeys.JOB_PRIORITY },
                        new String[] { jobid.toString(), priority.toString() }, jobid);
            }
        }

        /**
         * Log job's submit-time/launch-time 
         * @param jobid job id
         * @param submitTime job's submit time
         * @param launchTime job's launch time
         * @param restartCount number of times the job got restarted
         * @deprecated Use {@link #logJobInfo(JobID, long, long)} instead.
         */
        @Deprecated
        public static void logJobInfo(JobID jobid, long submitTime, long launchTime, int restartCount) {
            logJobInfo(jobid, submitTime, launchTime);
        }

        public static void logJobInfo(JobID jobid, long submitTime, long launchTime) {
            ArrayList<PrintWriter> writer = fileManager.getWriters(jobid);

            if (null != writer) {
                JobHistoryCopy.log(writer, RecordTypes.Job,
                        new JobHistoryKeys[] { JobHistoryKeys.JOBID, JobHistoryKeys.SUBMIT_TIME,
                                JobHistoryKeys.LAUNCH_TIME },
                        new String[] { jobid.toString(), String.valueOf(submitTime), String.valueOf(launchTime) },
                        jobid);
            }
        }
    }

    /**
     * Helper class for logging or reading back events related to Task's start, finish or failure. 
     * All events logged by this class are logged in a separate file per job in 
     * job tracker history. These events map to TIPs in jobtracker. 
     */
    public static class Task extends KeyValuePair {
        private Map<String, TaskAttempt> taskAttempts = new TreeMap<String, TaskAttempt>();

        /**
         * Log start time of task (TIP).
         * @param taskId task id
         * @param taskType MAP or REDUCE
         * @param startTime startTime of tip. 
         */
        public static void logStarted(TaskID taskId, String taskType, long startTime, String splitLocations) {
            JobID id = taskId.getJobID();
            ArrayList<PrintWriter> writer = fileManager.getWriters(id);

            if (null != writer) {
                JobHistoryCopy.log(writer, RecordTypes.Task,
                        new JobHistoryKeys[] { JobHistoryKeys.TASKID, JobHistoryKeys.TASK_TYPE,
                                JobHistoryKeys.START_TIME, JobHistoryKeys.SPLITS },
                        new String[] { taskId.toString(), taskType, String.valueOf(startTime), splitLocations },
                        id);
            }
        }

        /**
         * Log finish time of task. 
         * @param taskId task id
         * @param taskType MAP or REDUCE
         * @param finishTime finish timeof task in ms
         */
        public static void logFinished(TaskID taskId, String taskType, long finishTime, Counters counters) {
            JobID id = taskId.getJobID();
            ArrayList<PrintWriter> writer = fileManager.getWriters(id);

            if (null != writer) {
                JobHistoryCopy.log(writer, RecordTypes.Task,
                        new JobHistoryKeys[] { JobHistoryKeys.TASKID, JobHistoryKeys.TASK_TYPE,
                                JobHistoryKeys.TASK_STATUS, JobHistoryKeys.FINISH_TIME, JobHistoryKeys.COUNTERS },
                        new String[] { taskId.toString(), taskType, Values.SUCCESS.name(),
                                String.valueOf(finishTime), counters.makeEscapedCompactString() },
                        id);
            }
        }

        /**
         * Update the finish time of task. 
         * @param taskId task id
         * @param finishTime finish time of task in ms
         */
        public static void logUpdates(TaskID taskId, long finishTime) {
            JobID id = taskId.getJobID();
            ArrayList<PrintWriter> writer = fileManager.getWriters(id);

            if (null != writer) {
                JobHistoryCopy.log(writer, RecordTypes.Task,
                        new JobHistoryKeys[] { JobHistoryKeys.TASKID, JobHistoryKeys.FINISH_TIME },
                        new String[] { taskId.toString(), String.valueOf(finishTime) }, id);
            }
        }

        /**
         * Log job failed event.
         * @param taskId task id
         * @param taskType MAP or REDUCE.
         * @param time timestamp when job failed detected. 
         * @param error error message for failure. 
         */
        public static void logFailed(TaskID taskId, String taskType, long time, String error) {
            logFailed(taskId, taskType, time, error, null);
        }

        /**
         * @param failedDueToAttempt The attempt that caused the failure, if any
         */
        public static void logFailed(TaskID taskId, String taskType, long time, String error,
                TaskAttemptID failedDueToAttempt) {
            JobID id = taskId.getJobID();
            ArrayList<PrintWriter> writer = fileManager.getWriters(id);

            if (null != writer) {
                String failedAttempt = failedDueToAttempt == null ? "" : failedDueToAttempt.toString();
                JobHistoryCopy.log(writer, RecordTypes.Task,
                        new JobHistoryKeys[] { JobHistoryKeys.TASKID, JobHistoryKeys.TASK_TYPE,
                                JobHistoryKeys.TASK_STATUS, JobHistoryKeys.FINISH_TIME, JobHistoryKeys.ERROR,
                                JobHistoryKeys.TASK_ATTEMPT_ID },
                        new String[] { taskId.toString(), taskType, Values.FAILED.name(), String.valueOf(time),
                                error, failedAttempt },
                        id);
            }
        }

        /**
         * Returns all task attempts for this task. <task attempt id - TaskAttempt>
         */
        public Map<String, TaskAttempt> getTaskAttempts() {
            return this.taskAttempts;
        }
    }

    /**
     * Base class for Map and Reduce TaskAttempts. 
     */
    public static class TaskAttempt extends Task {
    }

    /**
     * Helper class for logging or reading back events related to start, finish or failure of 
     * a Map Attempt on a node.
     */
    public static class MapAttempt extends TaskAttempt {
        /**
         * Log start time of this map task attempt. 
         * @param taskAttemptId task attempt id
         * @param startTime start time of task attempt as reported by task tracker. 
         * @param hostName host name of the task attempt. 
         * @deprecated Use 
         *             {@link #logStarted(TaskAttemptID, long, String, int, String)}
         */
        @Deprecated
        public static void logStarted(TaskAttemptID taskAttemptId, long startTime, String hostName) {
            logStarted(taskAttemptId, startTime, hostName, -1, Values.MAP.name());
        }

        /**
         * Log start time of this map task attempt.
         *  
         * @param taskAttemptId task attempt id
         * @param startTime start time of task attempt as reported by task tracker. 
         * @param trackerName name of the tracker executing the task attempt.
         * @param httpPort http port of the task tracker executing the task attempt
         * @param taskType Whether the attempt is cleanup or setup or map 
         */
        public static void logStarted(TaskAttemptID taskAttemptId, long startTime, String trackerName, int httpPort,
                String taskType) {
            JobID id = taskAttemptId.getJobID();
            ArrayList<PrintWriter> writer = fileManager.getWriters(id);

            if (null != writer) {
                JobHistoryCopy.log(writer, RecordTypes.MapAttempt,
                        new JobHistoryKeys[] { JobHistoryKeys.TASK_TYPE, JobHistoryKeys.TASKID,
                                JobHistoryKeys.TASK_ATTEMPT_ID, JobHistoryKeys.START_TIME,
                                JobHistoryKeys.TRACKER_NAME, JobHistoryKeys.HTTP_PORT },
                        new String[] { taskType, taskAttemptId.getTaskID().toString(), taskAttemptId.toString(),
                                String.valueOf(startTime), trackerName,
                                httpPort == -1 ? "" : String.valueOf(httpPort) },
                        id);
            }
        }

        /**
         * Log finish time of map task attempt. 
         * @param taskAttemptId task attempt id 
         * @param finishTime finish time
         * @param hostName host name 
         * @deprecated Use 
         * {@link #logFinished(TaskAttemptID, long, String, String, String, Counters)}
         */
        @Deprecated
        public static void logFinished(TaskAttemptID taskAttemptId, long finishTime, String hostName) {
            logFinished(taskAttemptId, finishTime, hostName, Values.MAP.name(), "", new Counters());
        }

        /**
         * Log finish time of map task attempt. 
         * 
         * @param taskAttemptId task attempt id 
         * @param finishTime finish time
         * @param hostName host name 
         * @param taskType Whether the attempt is cleanup or setup or map 
         * @param stateString state string of the task attempt
         * @param counter counters of the task attempt
         */
        public static void logFinished(TaskAttemptID taskAttemptId, long finishTime, String hostName,
                String taskType, String stateString, Counters counter) {
            JobID id = taskAttemptId.getJobID();
            ArrayList<PrintWriter> writer = fileManager.getWriters(id);

            if (null != writer) {
                JobHistoryCopy.log(writer, RecordTypes.MapAttempt,
                        new JobHistoryKeys[] { JobHistoryKeys.TASK_TYPE, JobHistoryKeys.TASKID,
                                JobHistoryKeys.TASK_ATTEMPT_ID, JobHistoryKeys.TASK_STATUS,
                                JobHistoryKeys.FINISH_TIME, JobHistoryKeys.HOSTNAME, JobHistoryKeys.STATE_STRING,
                                JobHistoryKeys.COUNTERS },
                        new String[] { taskType, taskAttemptId.getTaskID().toString(), taskAttemptId.toString(),
                                Values.SUCCESS.name(), String.valueOf(finishTime), hostName, stateString,
                                counter.makeEscapedCompactString() },
                        id);
            }
        }

        /**
         * Log task attempt failed event.  
         * @param taskAttemptId task attempt id
         * @param timestamp timestamp
         * @param hostName hostname of this task attempt.
         * @param error error message if any for this task attempt.
         * @deprecated Use
         * {@link #logFailed(TaskAttemptID, long, String, String, String)} 
         */
        @Deprecated
        public static void logFailed(TaskAttemptID taskAttemptId, long timestamp, String hostName, String error) {
            logFailed(taskAttemptId, timestamp, hostName, error, Values.MAP.name());
        }

        /**
         * Log task attempt failed event. 
         *  
         * @param taskAttemptId task attempt id
         * @param timestamp timestamp
         * @param hostName hostname of this task attempt.
         * @param error error message if any for this task attempt. 
         * @param taskType Whether the attempt is cleanup or setup or map 
         */
        public static void logFailed(TaskAttemptID taskAttemptId, long timestamp, String hostName, String error,
                String taskType) {
            JobID id = taskAttemptId.getJobID();
            ArrayList<PrintWriter> writer = fileManager.getWriters(id);

            if (null != writer) {
                JobHistoryCopy.log(writer, RecordTypes.MapAttempt,
                        new JobHistoryKeys[] { JobHistoryKeys.TASK_TYPE, JobHistoryKeys.TASKID,
                                JobHistoryKeys.TASK_ATTEMPT_ID, JobHistoryKeys.TASK_STATUS,
                                JobHistoryKeys.FINISH_TIME, JobHistoryKeys.HOSTNAME, JobHistoryKeys.ERROR },
                        new String[] { taskType, taskAttemptId.getTaskID().toString(), taskAttemptId.toString(),
                                Values.FAILED.name(), String.valueOf(timestamp), hostName, error },
                        id);
            }
        }

        /**
         * Log task attempt killed event.  
         * @param taskAttemptId task attempt id
         * @param timestamp timestamp
         * @param hostName hostname of this task attempt.
         * @param error error message if any for this task attempt. 
         * @deprecated Use 
         * {@link #logKilled(TaskAttemptID, long, String, String, String)}
         */
        @Deprecated
        public static void logKilled(TaskAttemptID taskAttemptId, long timestamp, String hostName, String error) {
            logKilled(taskAttemptId, timestamp, hostName, error, Values.MAP.name());
        }

        /**
         * Log task attempt killed event.  
         * 
         * @param taskAttemptId task attempt id
         * @param timestamp timestamp
         * @param hostName hostname of this task attempt.
         * @param error error message if any for this task attempt. 
         * @param taskType Whether the attempt is cleanup or setup or map 
         */
        public static void logKilled(TaskAttemptID taskAttemptId, long timestamp, String hostName, String error,
                String taskType) {
            JobID id = taskAttemptId.getJobID();
            ArrayList<PrintWriter> writer = fileManager.getWriters(id);

            if (null != writer) {
                JobHistoryCopy.log(writer, RecordTypes.MapAttempt,
                        new JobHistoryKeys[] { JobHistoryKeys.TASK_TYPE, JobHistoryKeys.TASKID,
                                JobHistoryKeys.TASK_ATTEMPT_ID, JobHistoryKeys.TASK_STATUS,
                                JobHistoryKeys.FINISH_TIME, JobHistoryKeys.HOSTNAME, JobHistoryKeys.ERROR },
                        new String[] { taskType, taskAttemptId.getTaskID().toString(), taskAttemptId.toString(),
                                Values.KILLED.name(), String.valueOf(timestamp), hostName, error },
                        id);
            }
        }
    }

    /**
     * Helper class for logging or reading back events related to start, finish or failure of 
     * a Map Attempt on a node.
     */
    public static class ReduceAttempt extends TaskAttempt {
        /**
         * Log start time of  Reduce task attempt. 
         * @param taskAttemptId task attempt id
         * @param startTime start time
         * @param hostName host name 
         * @deprecated Use 
         * {@link #logStarted(TaskAttemptID, long, String, int, String)}
         */
        @Deprecated
        public static void logStarted(TaskAttemptID taskAttemptId, long startTime, String hostName) {
            logStarted(taskAttemptId, startTime, hostName, -1, Values.REDUCE.name());
        }

        /**
         * Log start time of  Reduce task attempt. 
         * 
         * @param taskAttemptId task attempt id
         * @param startTime start time
         * @param trackerName tracker name 
         * @param httpPort the http port of the tracker executing the task attempt
         * @param taskType Whether the attempt is cleanup or setup or reduce 
         */
        public static void logStarted(TaskAttemptID taskAttemptId, long startTime, String trackerName, int httpPort,
                String taskType) {
            JobID id = taskAttemptId.getJobID();
            ArrayList<PrintWriter> writer = fileManager.getWriters(id);

            if (null != writer) {
                JobHistoryCopy.log(writer, RecordTypes.ReduceAttempt,
                        new JobHistoryKeys[] { JobHistoryKeys.TASK_TYPE, JobHistoryKeys.TASKID,
                                JobHistoryKeys.TASK_ATTEMPT_ID, JobHistoryKeys.START_TIME,
                                JobHistoryKeys.TRACKER_NAME, JobHistoryKeys.HTTP_PORT },
                        new String[] { taskType, taskAttemptId.getTaskID().toString(), taskAttemptId.toString(),
                                String.valueOf(startTime), trackerName,
                                httpPort == -1 ? "" : String.valueOf(httpPort) },
                        id);
            }
        }

        /**
         * Log finished event of this task. 
         * @param taskAttemptId task attempt id
         * @param shuffleFinished shuffle finish time
         * @param sortFinished sort finish time
         * @param finishTime finish time of task
         * @param hostName host name where task attempt executed
         * @deprecated Use 
         * {@link #logFinished(TaskAttemptID, long, long, long, String, String, String, Counters)}
         */
        @Deprecated
        public static void logFinished(TaskAttemptID taskAttemptId, long shuffleFinished, long sortFinished,
                long finishTime, String hostName) {
            logFinished(taskAttemptId, shuffleFinished, sortFinished, finishTime, hostName, Values.REDUCE.name(),
                    "", new Counters());
        }

        /**
         * Log finished event of this task. 
         * 
         * @param taskAttemptId task attempt id
         * @param shuffleFinished shuffle finish time
         * @param sortFinished sort finish time
         * @param finishTime finish time of task
         * @param hostName host name where task attempt executed
         * @param taskType Whether the attempt is cleanup or setup or reduce 
         * @param stateString the state string of the attempt
         * @param counter counters of the attempt
         */
        public static void logFinished(TaskAttemptID taskAttemptId, long shuffleFinished, long sortFinished,
                long finishTime, String hostName, String taskType, String stateString, Counters counter) {
            JobID id = taskAttemptId.getJobID();
            ArrayList<PrintWriter> writer = fileManager.getWriters(id);

            if (null != writer) {
                JobHistoryCopy.log(writer, RecordTypes.ReduceAttempt,
                        new JobHistoryKeys[] { JobHistoryKeys.TASK_TYPE, JobHistoryKeys.TASKID,
                                JobHistoryKeys.TASK_ATTEMPT_ID, JobHistoryKeys.TASK_STATUS,
                                JobHistoryKeys.SHUFFLE_FINISHED, JobHistoryKeys.SORT_FINISHED,
                                JobHistoryKeys.FINISH_TIME, JobHistoryKeys.HOSTNAME, JobHistoryKeys.STATE_STRING,
                                JobHistoryKeys.COUNTERS },
                        new String[] { taskType, taskAttemptId.getTaskID().toString(), taskAttemptId.toString(),
                                Values.SUCCESS.name(), String.valueOf(shuffleFinished),
                                String.valueOf(sortFinished), String.valueOf(finishTime), hostName, stateString,
                                counter.makeEscapedCompactString() },
                        id);
            }
        }

        /**
         * Log failed reduce task attempt. 
         * @param taskAttemptId task attempt id
         * @param timestamp time stamp when task failed
         * @param hostName host name of the task attempt.  
         * @param error error message of the task.
         * @deprecated Use 
         * {@link #logFailed(TaskAttemptID, long, String, String, String)} 
         */
        @Deprecated
        public static void logFailed(TaskAttemptID taskAttemptId, long timestamp, String hostName, String error) {
            logFailed(taskAttemptId, timestamp, hostName, error, Values.REDUCE.name());
        }

        /**
         * Log failed reduce task attempt.
         *  
         * @param taskAttemptId task attempt id
         * @param timestamp time stamp when task failed
         * @param hostName host name of the task attempt.  
         * @param error error message of the task. 
         * @param taskType Whether the attempt is cleanup or setup or reduce 
         */
        public static void logFailed(TaskAttemptID taskAttemptId, long timestamp, String hostName, String error,
                String taskType) {
            JobID id = taskAttemptId.getJobID();
            ArrayList<PrintWriter> writer = fileManager.getWriters(id);

            if (null != writer) {
                JobHistoryCopy.log(writer, RecordTypes.ReduceAttempt,
                        new JobHistoryKeys[] { JobHistoryKeys.TASK_TYPE, JobHistoryKeys.TASKID,
                                JobHistoryKeys.TASK_ATTEMPT_ID, JobHistoryKeys.TASK_STATUS,
                                JobHistoryKeys.FINISH_TIME, JobHistoryKeys.HOSTNAME, JobHistoryKeys.ERROR },
                        new String[] { taskType, taskAttemptId.getTaskID().toString(), taskAttemptId.toString(),
                                Values.FAILED.name(), String.valueOf(timestamp), hostName, error },
                        id);
            }
        }

        /**
         * Log killed reduce task attempt. 
         * @param taskAttemptId task attempt id
         * @param timestamp time stamp when task failed
         * @param hostName host name of the task attempt.  
         * @param error error message of the task.
         * @deprecated Use 
         * {@link #logKilled(TaskAttemptID, long, String, String, String)} 
         */
        @Deprecated
        public static void logKilled(TaskAttemptID taskAttemptId, long timestamp, String hostName, String error) {
            logKilled(taskAttemptId, timestamp, hostName, error, Values.REDUCE.name());
        }

        /**
         * Log killed reduce task attempt. 
         * 
         * @param taskAttemptId task attempt id
         * @param timestamp time stamp when task failed
         * @param hostName host name of the task attempt.  
         * @param error error message of the task. 
         * @param taskType Whether the attempt is cleanup or setup or reduce 
        */
        public static void logKilled(TaskAttemptID taskAttemptId, long timestamp, String hostName, String error,
                String taskType) {
            JobID id = taskAttemptId.getJobID();
            ArrayList<PrintWriter> writer = fileManager.getWriters(id);

            if (null != writer) {
                JobHistoryCopy.log(writer, RecordTypes.ReduceAttempt,
                        new JobHistoryKeys[] { JobHistoryKeys.TASK_TYPE, JobHistoryKeys.TASKID,
                                JobHistoryKeys.TASK_ATTEMPT_ID, JobHistoryKeys.TASK_STATUS,
                                JobHistoryKeys.FINISH_TIME, JobHistoryKeys.HOSTNAME, JobHistoryKeys.ERROR },
                        new String[] { taskType, taskAttemptId.getTaskID().toString(), taskAttemptId.toString(),
                                Values.KILLED.name(), String.valueOf(timestamp), hostName, error },
                        id);
            }
        }
    }

    /**
     * Callback interface for reading back log events from JobHistory. This interface 
     * should be implemented and passed to JobHistory.parseHistory() 
     *
     */
    public static interface Listener {
        /**
         * Callback method for history parser. 
         * @param recType type of record, which is the first entry in the line.
         * @param values a map of key-value pairs as thry appear in history.
         * @throws IOException
         */
        public void handle(RecordTypes recType, Map<JobHistoryKeys, String> values) throws IOException;
    }

    /**
     * Delete history files older than one month. Update master index and remove all 
     * jobs older than one month. Also if a job tracker has no jobs in last one month
     * remove reference to the job tracker. 
     *
     */
    public static class HistoryCleaner implements Runnable {
        static final long ONE_DAY_IN_MS = 24 * 60 * 60 * 1000L;
        static final long THIRTY_DAYS_IN_MS = 30 * ONE_DAY_IN_MS;
        private long now;
        private static boolean isRunning = false;
        private static long lastRan = 0;

        /**
         * Cleans up history data. 
         */
        public void run() {
            if (isRunning) {
                return;
            }
            now = System.currentTimeMillis();
            // clean history only once a day at max
            if (lastRan != 0 && (now - lastRan) < ONE_DAY_IN_MS) {
                return;
            }
            lastRan = now;
            isRunning = true;
            try {
                FileStatus[] historyFiles = DONEDIR_FS.listStatus(DONE);
                // delete if older than 30 days
                if (historyFiles != null) {
                    for (FileStatus f : historyFiles) {
                        if (now - f.getModificationTime() > THIRTY_DAYS_IN_MS) {
                            DONEDIR_FS.delete(f.getPath(), true);
                            LOG.info("Deleting old history file : " + f.getPath());
                        }
                    }
                }

                //walking over the map to purge entries from jobHistoryFileMap
                synchronized (jobHistoryFileMap) {
                    Iterator<Entry<JobID, MovedFileInfo>> it = jobHistoryFileMap.entrySet().iterator();
                    while (it.hasNext()) {
                        MovedFileInfo info = it.next().getValue();
                        if (now - info.timestamp > THIRTY_DAYS_IN_MS) {
                            it.remove();
                        } else {
                            //since entries are in sorted timestamp order, no more entries
                            //are required to be checked
                            break;
                        }
                    }
                }
            } catch (IOException ie) {
                LOG.info("Error cleaning up history directory" + StringUtils.stringifyException(ie));
            }
            isRunning = false;
        }

        static long getLastRan() {
            return lastRan;
        }
    }

    /**
     * Return the TaskLogsUrl of a particular TaskAttempt
     * 
     * @param attempt
     * @return the taskLogsUrl. null if http-port or tracker-name or
     *         task-attempt-id are unavailable.
     */
    public static String getTaskLogsUrl(JobHistoryCopy.TaskAttempt attempt) {
        if (attempt.get(JobHistoryKeys.HTTP_PORT).equals("") || attempt.get(JobHistoryKeys.TRACKER_NAME).equals("")
                || attempt.get(JobHistoryKeys.TASK_ATTEMPT_ID).equals("")) {
            return null;
        }

        String taskTrackerName = JobInProgress
                .convertTrackerNameToHostName(attempt.get(JobHistoryKeys.TRACKER_NAME));
        return TaskLogServlet.getTaskLogUrl(taskTrackerName, attempt.get(JobHistoryKeys.HTTP_PORT),
                attempt.get(JobHistoryKeys.TASK_ATTEMPT_ID));
    }
}