hadoop/CHANGES.txt

Hadoop Change Log


Trunk (unreleased changes)

 1. HADOOP-655.  Remove most deprecated code.  A few deprecated things
    remain, notably UTF8 and some methods that are still required.
    Also cleaned up constructors for SequenceFile, MapFile, SetFile,
    and ArrayFile a bit.  (cutting)

 2. HADOOP-565.  Upgrade to Jetty version 6. (Sanjay Dahiya via cutting)

 3. HADOOP-682.  Fix DFS format command to work correctly when
    configured with a non-existent directory. (Sanjay Dahiya via cutting)

 4. HADOOP-645.  Fix a bug in contrib/streaming when -reducer is NONE.
    (Dhruba Borthakur via cutting) 

 5. HADOOP-687.  Fix a classpath bug in bin/hadoop that blocked the
    servers from starting. (Sameer Paranjpye via omalley)

 6. HADOOP-683.  Remove a script dependency on bash, so it works with
    dash, the new default for /bin/sh on Ubuntu.  (James Todd via cutting)

 7. HADOOP-382.  Extend unit tests to run multiple datanodes.
    (Milind Bhandarkar via cutting)


Release 0.8.0 - 2006-11-03

 1. HADOOP-477.  Extend contrib/streaming to scan the PATH environment
    variables when resolving executable program names.
    (Dhruba Borthakur via cutting) 

 2. HADOOP-583.  In DFSClient, reduce the log level of re-connect
    attempts from 'info' to 'debug', so they are not normally shown.
    (Konstantin Shvachko via cutting)

 3. HADOOP-498.  Re-implement DFS integrity checker to run server-side,
    for much improved performance.  (Milind Bhandarkar via cutting)

 4. HADOOP-586.  Use the jar name for otherwise un-named jobs.
    (Sanjay Dahiya via cutting)

 5. HADOOP-514.  Make DFS heartbeat interval configurable.
    (Milind Bhandarkar via cutting)

 6. HADOOP-588.  Fix logging and accounting of failed tasks.
    (Sanjay Dahiya via cutting)

 7. HADOOP-462.  Improve command line parsing in DFSShell, so that
    incorrect numbers of arguments result in informative errors rather
    than ArrayOutOfBoundsException.  (Dhruba Borthakur via cutting) 

 8. HADOOP-561.  Fix DFS so that one replica of each block is written
    locally, if possible.  This was the intent, but there as a bug.
    (Dhruba Borthakur via cutting) 

 9. HADOOP-610.  Fix TaskTracker to survive more exceptions, keeping
    tasks from becoming lost.  (omalley via cutting)

10. HADOOP-625.  Add a servlet to all http daemons that displays a
    stack dump, useful for debugging.  (omalley via cutting)

11. HADOOP-554.  Fix DFSShell to return -1 for errors.
    (Dhruba Borthakur via cutting) 

12. HADOOP-626.  Correct the documentation in the NNBench example
    code, and also remove a mistaken call there.
    (Nigel Daley via cutting)

13. HADOOP-634.  Add missing license to many files.
    (Nigel Daley via cutting)

14. HADOOP-627.  Fix some synchronization problems in MiniMRCluster
    that sometimes caused unit tests to fail.  (Nigel Daley via cutting)

15. HADOOP-563.  Improve the NameNode's lease policy so that leases
    are held for one hour without renewal (instead of one minute).
    However another attempt to create the same file will still succeed
    if the lease has not been renewed within a minute.  This prevents
    communication or scheduling problems from causing a write to fail
    for up to an hour, barring some other process trying to create the
    same file.  (Dhruba Borthakur via cutting)

16. HADOOP-635.  In DFSShell, permit specification of multiple files
    as the source for file copy and move commands.
    (Dhruba Borthakur via cutting)

17. HADOOP-641.  Change NameNode to request a fresh block report from
    a re-discovered DataNode, so that no-longer-needed replications
    are stopped promptly.  (Konstantin Shvachko via cutting)

18. HADOOP-642.  Change IPC client to specify an explicit connect
    timeout.  (Konstantin Shvachko via cutting)

19. HADOOP-638.  Fix an unsynchronized access to TaskTracker's
    internal state.  (Nigel Daley via cutting)

20. HADOOP-624.  Fix servlet path to stop a Jetty warning on startup.
    (omalley via cutting)

21. HADOOP-578.  Failed tasks are no longer placed at the end of the
    task queue.  This was originally done to work around other
    problems that have now been fixed.  Re-executing failed tasks
    sooner causes buggy jobs to fail faster.  (Sanjay Dahiya via cutting)

22. HADOOP-658.  Update source file headers per Apache policy.  (cutting)

23. HADOOP-636.  Add MapFile & ArrayFile constructors which accept a
    Progressable, and pass it down to SequenceFile.  This permits
    reduce tasks which use MapFile to still report progress while
    writing blocks to the filesystem.  (cutting)

24. HADOOP-576.  Enable contrib/streaming to use the file cache.  Also
    extend the cache to permit symbolic links to cached items, rather
    than local file copies.  (Mahadev Konar via cutting)

25. HADOOP-482.  Fix unit tests to work when a cluster is running on
    the same machine, removing port conflicts.  (Wendy Chien via cutting)

26. HADOOP-90.  Permit dfs.name.dir to list multiple directories,
    where namenode data is to be replicated. (Milind Bhandarkar via cutting)

27. HADOOP-651.  Fix DFSCk to correctly pass parameters to the servlet
    on the namenode.  (Milind Bhandarkar via cutting)

28. HADOOP-553.  Change main() routines of DataNode and NameNode to
    log exceptions rather than letting the JVM print them to standard
    error.  Also, change the hadoop-daemon.sh script to rotate
    standard i/o log files.  (Raghu Angadi via cutting)

29. HADOOP-399.  Fix javadoc warnings.  (Nigel Daley via cutting)

30. HADOOP-599.  Fix web ui and command line to correctly report DFS
    filesystem size statistics.  Also improve web layout.
    (Raghu Angadi via cutting)

31. HADOOP-660.  Permit specification of junit test output format.
    (Nigel Daley via cutting)

32. HADOOP-663.  Fix a few unit test issues.  (Mahadev Konar via cutting)

33. HADOOP-664.  Cause entire build to fail if libhdfs tests fail.
    (Nigel Daley via cutting)

34. HADOOP-633.  Keep jobtracker from dying when job initialization
    throws exceptions.  Also improve exception handling in a few other
    places and add more informative thread names.
    (omalley via cutting)

35. HADOOP-669.  Fix a problem introduced by HADOOP-90 that can cause
    DFS to lose files.  (Milind Bhandarkar via cutting)

36. HADOOP-373.  Consistently check the value returned by
    FileSystem.mkdirs().  (Wendy Chien via cutting)

37. HADOOP-670.  Code cleanups in some DFS internals: use generic
    types, replace Vector with ArrayList, etc.
    (Konstantin Shvachko via cutting)

38. HADOOP-647.  Permit map outputs to use a different compression
    type than the job output.  (omalley via cutting)

39. HADOOP-671.  Fix file cache to check for pre-existence before
    creating .  (Mahadev Konar via cutting)

40. HADOOP-665.  Extend many DFSShell commands to accept multiple
    arguments.  Now commands like "ls", "rm", etc. will operate on
    multiple files.  (Dhruba Borthakur via cutting)


Release 0.7.2 - 2006-10-18

 1. HADOOP-607.  Fix a bug where classes included in job jars were not
    found by tasks.  (Mahadev Konar via cutting)

 2. HADOOP-609.  Add a unit test that checks that classes in job jars
    can be found by tasks.  Also modify unit tests to specify multiple
    local directories.  (Mahadev Konar via cutting)


Release 0.7.1 - 2006-10-11

 1. HADOOP-593.  Fix a NullPointerException in the JobTracker.
    (omalley via cutting)

 2. HADOOP-592.  Fix a NullPointerException in the IPC Server.  Also
    consistently log when stale calls are discarded.  (omalley via cutting)

 3. HADOOP-594.  Increase the DFS safe-mode threshold from .95 to
    .999, so that nearly all blocks must be reported before filesystem
    modifications are permitted.  (Konstantin Shvachko via cutting)

 4. HADOOP-598.  Fix tasks to retry when reporting completion, so that
    a single RPC timeout won't fail a task.  (omalley via cutting)

 5. HADOOP-597.  Fix TaskTracker to not discard map outputs for errors
    in transmitting them to reduce nodes.  (omalley via cutting)


Release 0.7.0 - 2006-10-06

 1. HADOOP-243.  Fix rounding in the display of task and job progress
    so that things are not shown to be 100% complete until they are in
    fact finished.  (omalley via cutting) 

 2. HADOOP-438.  Limit the length of absolute paths in DFS, since the
    file format used to store pathnames has some limitations.
    (Wendy Chien via cutting)

 3. HADOOP-530.  Improve error messages in SequenceFile when keys or
    values are of the wrong type.  (Hairong Kuang via cutting)

 4. HADOOP-288.  Add a file caching system and use it in MapReduce to
    cache job jar files on slave nodes.  (Mahadev Konar via cutting)

 5. HADOOP-533.  Fix unit test to not modify conf directory.
   (Hairong Kuang via cutting)

 6. HADOOP-527.  Permit specification of the local address that various
    Hadoop daemons should bind to.  (Philippe Gassmann via cutting)

 7. HADOOP-542.  Updates to contrib/streaming: reformatted source code,
    on-the-fly merge sort, a fix for HADOOP-540, etc.
    (Michel Tourn via cutting)

 8. HADOOP-545.  Remove an unused config file parameter.
    (Philippe Gassmann via cutting)

 9. HADOOP-548.  Add an Ant property "test.output" to build.xml that
    causes test output to be logged to the console.  (omalley via cutting)

10. HADOOP-261.  Record an error message when map output is lost.
    (omalley via cutting)

11. HADOOP-293.  Report the full list of task error messages in the
    web ui, not just the most recent.  (omalley via cutting)

12. HADOOP-551.  Restore JobClient's console printouts to only include
    a maximum of one update per one percent of progress.
    (omalley via cutting)

13. HADOOP-306.  Add a "safe" mode to DFS.  The name node enters this
    when less than a specified percentage of file data is complete.
    Currently safe mode is only used on startup, but eventually it
    will also be entered when datanodes disconnect and file data
    becomes incomplete.  While in safe mode no filesystem
    modifications are permitted and block replication is inhibited.
    (Konstantin Shvachko via cutting)

14. HADOOP-431.  Change 'dfs -rm' to not operate recursively and add a
    new command, 'dfs -rmr' which operates recursively.
    (Sameer Paranjpye via cutting)

15. HADOOP-263.  Include timestamps for job transitions.  The web
    interface now displays the start and end times of tasks and the
    start times of sorting and reducing for reduce tasks.  Also,
    extend ObjectWritable to handle enums, so that they can be passed
    as RPC parameters.  (Sanjay Dahiya via cutting)

16. HADOOP-556.  Contrib/streaming: send keep-alive reports to task
    tracker every 10 seconds rather than every 100 records, to avoid
    task timeouts.  (Michel Tourn via cutting)

17. HADOOP-547.  Fix reduce tasks to ping tasktracker while copying
    data, rather than only between copies, avoiding task timeouts.
    (Sanjay Dahiya via cutting)

18. HADOOP-537.  Fix src/c++/libhdfs build process to create files in
    build/, no longer modifying the source tree.
    (Arun C Murthy via cutting)

19. HADOOP-487.  Throw a more informative exception for unknown RPC
    hosts.  (Sameer Paranjpye via cutting)

20. HADOOP-559.  Add file name globbing (pattern matching) support to
    the FileSystem API, and use it in DFSShell ('bin/hadoop dfs')
    commands.  (Hairong Kuang via cutting)

21. HADOOP-508.  Fix a bug in FSDataInputStream.  Incorrect data was
    returned after seeking to a random location.
    (Milind Bhandarkar via cutting)

22. HADOOP-560.  Add a "killed" task state.  This can be used to
    distinguish kills from other failures.  Task state has also been
    converted to use an enum type instead of an int, uncovering a bug
    elsewhere.  The web interface is also updated to display killed
    tasks.  (omalley via cutting)

23. HADOOP-423.  Normalize Paths containing directories named "." and
    "..", using the standard, unix interpretation.  Also add checks in
    DFS, prohibiting the use of "." or ".." as directory or file
    names.  (Wendy Chien via cutting)

24. HADOOP-513.  Replace map output handling with a servlet, rather
    than a JSP page.  This fixes an issue where
    IllegalStateException's were logged, sets content-length
    correctly, and better handles some errors.  (omalley via cutting)

25. HADOOP-552.  Improved error checking when copying map output files
    to reduce nodes.  (omalley via cutting)

26. HADOOP-566.  Fix scripts to work correctly when accessed through
    relative symbolic links.  (Lee Faris via cutting)

27. HADOOP-519.  Add positioned read methods to FSInputStream.  These
    permit one to read from a stream without moving its position, and
    can hence be performed by multiple threads at once on a single
    stream. Implement an optimized version for DFS and local FS.
    (Milind Bhandarkar via cutting)

28. HADOOP-522. Permit block compression with MapFile and SetFile.
    Since these formats are always sorted, block compression can
    provide a big advantage.  (cutting)

29. HADOOP-567. Record version and revision information in builds.  A
    package manifest is added to the generated jar file containing
    version information, and a VersionInfo utility is added that
    includes further information, including the build date and user,
    and the subversion revision and repository.  A 'bin/hadoop
    version' comand is added to show this information, and it is also
    added to various web interfaces.  (omalley via cutting)

30. HADOOP-568.  Fix so that errors while initializing tasks on a
    tasktracker correctly report the task as failed to the jobtracker,
    so that it will be rescheduled.  (omalley via cutting)

31. HADOOP-550.  Disable automatic UTF-8 validation in Text.  This
    permits, e.g., TextInputFormat to again operate on non-UTF-8 data.
    (Hairong and Mahadev via cutting)

32. HADOOP-343.  Fix mapred copying so that a failed tasktracker
    doesn't cause other copies to slow.  (Sameer Paranjpye via cutting)

33. HADOOP-239.  Add a persistent job history mechanism, so that basic
    job statistics are not lost after 24 hours and/or when the
    jobtracker is restarted.  (Sanjay Dahiya via cutting)

34. HADOOP-506.  Ignore heartbeats from stale task trackers.
   (Sanjay Dahiya via cutting)

35. HADOOP-255.  Discard stale, queued IPC calls.  Do not process
    calls whose clients will likely time out before they receive a
    response.  When the queue is full, new calls are now received and
    queued, and the oldest calls are discarded, so that, when servers
    get bogged down, they no longer develop a backlog on the socket.
    This should improve some DFS namenode failure modes.
    (omalley via cutting)

36. HADOOP-581.  Fix datanode to not reset itself on communications
    errors with the namenode.  If a request to the namenode fails, the
    datanode should retry, not restart.  This reduces the load on the
    namenode, since restarts cause a resend of the block report.
    (omalley via cutting)


Release 0.6.2 - 2006-09-18

1. HADOOP-532.  Fix a bug reading value-compressed sequence files,
   where an exception was thrown reporting that the full value had not
   been read.  (omalley via cutting)

2. HADOOP-534.  Change the default value class in JobConf to be Text
   instead of the now-deprecated UTF8.  This fixes the Grep example
   program, which was updated to use Text, but relies on this
   default.  (Hairong Kuang via cutting)


Release 0.6.1 - 2006-09-13

 1. HADOOP-520.  Fix a bug in libhdfs, where write failures were not
    correctly returning error codes.  (Arun C Murthy via cutting)

 2. HADOOP-523.  Fix a NullPointerException when TextInputFormat is
    explicitly specified.  Also add a test case for this.
    (omalley via cutting)

 3. HADOOP-521.  Fix another NullPointerException finding the
    ClassLoader when using libhdfs.  (omalley via cutting)

 4. HADOOP-526.  Fix a NullPointerException when attempting to start
    two datanodes in the same directory.  (Milind Bhandarkar via cutting)

 5. HADOOP-529.  Fix a NullPointerException when opening
    value-compressed sequence files generated by pre-0.6.0 Hadoop.
    (omalley via cutting)


Release 0.6.0 - 2006-09-08

 1. HADOOP-427.  Replace some uses of DatanodeDescriptor in the DFS
    web UI code with DatanodeInfo, the preferred public class.
    (Devaraj Das via cutting)

 2. HADOOP-426.  Fix streaming contrib module to work correctly on
    Solaris.  This was causing nightly builds to fail.
    (Michel Tourn via cutting)

 3. HADOOP-400.  Improvements to task assignment.  Tasks are no longer
    re-run on nodes where they have failed (unless no other node is
    available).  Also, tasks are better load-balanced among nodes.
    (omalley via cutting)

 4. HADOOP-324.  Fix datanode to not exit when a disk is full, but
    rather simply to fail writes.  (Wendy Chien via cutting)

 5. HADOOP-434.  Change smallJobsBenchmark to use standard Hadoop
    scripts.  (Sanjay Dahiya via cutting)

 6. HADOOP-453.  Fix a bug in Text.setCapacity().  (siren via cutting)


 7. HADOOP-450.  Change so that input types are determined by the
    RecordReader rather than specified directly in the JobConf.  This
    facilitates jobs with a variety of input types.

    WARNING: This contains incompatible API changes!  The RecordReader
    interface has two new methods that all user-defined InputFormats
    must now define.  Also, the values returned by TextInputFormat are
    no longer of class UTF8, but now of class Text.

 8. HADOOP-436.  Fix an error-handling bug in the web ui.
    (Devaraj Das via cutting)

 9. HADOOP-455.  Fix a bug in Text, where DEL was not permitted.
    (Hairong Kuang via cutting)

10. HADOOP-456.  Change the DFS namenode to keep a persistent record
    of the set of known datanodes.  This will be used to implement a
    "safe mode" where filesystem changes are prohibited when a
    critical percentage of the datanodes are unavailable.
    (Konstantin Shvachko via cutting)

11. HADOOP-322.  Add a job control utility.  This permits one to
    specify job interdependencies.  Each job is submitted only after
    the jobs it depends on have successfully completed.
    (Runping Qi via cutting)

12. HADOOP-176.  Fix a bug in IntWritable.Comparator.
    (Dick King via cutting)

13. HADOOP-421.  Replace uses of String in recordio package with Text
    class, for improved handling of UTF-8 data.
    (Milind Bhandarkar via cutting)

14. HADOOP-464.  Improved error message when job jar not found.
    (Michel Tourn via cutting)

15. HADOOP-469.  Fix /bin/bash specifics that have crept into our
    /bin/sh scripts since HADOOP-352.
    (Jean-Baptiste Quenot via cutting)

16. HADOOP-468.  Add HADOOP_NICENESS environment variable to set
    scheduling priority for daemons.  (Vetle Roeim via cutting)

17. HADOOP-473.  Fix TextInputFormat to correctly handle more EOL
    formats.  Things now work correctly with CR, LF or CRLF.
    (Dennis Kubes & James White via cutting)

18. HADOOP-461.  Make Java 1.5 an explicit requirement.  (cutting)

19. HADOOP-54.  Add block compression to SequenceFile.  One may now
    specify that blocks of keys and values are compressed together,
    improving compression for small keys and values.
    SequenceFile.Writer's constructor is now deprecated and replaced
    with a factory method.  (Arun C Murthy via cutting)

20. HADOOP-281.  Prohibit DFS files that are also directories.
    (Wendy Chien via cutting)

21. HADOOP-486.  Add the job username to JobStatus instances returned
    by JobClient.  (Mahadev Konar via cutting)

22. HADOOP-437.  contrib/streaming: Add support for gzipped inputs.
    (Michel Tourn via cutting)

23. HADOOP-463.  Add variable expansion to config files.
    Configuration property values may now contain variable
    expressions.  A variable is referenced with the syntax
    '${variable}'.  Variables values are found first in the
    configuration, and then in Java system properties.  The default
    configuration is modified so that temporary directories are now
    under ${hadoop.tmp.dir}, which is, by default,
    /tmp/hadoop-${user.name}.  (Michel Tourn via cutting)

24. HADOOP-419. Fix a NullPointerException finding the ClassLoader
    when using libhdfs.  (omalley via cutting)

25. HADOOP-460. Fix contrib/smallJobsBenchmark to use Text instead of
    UTF8.  (Sanjay Dahiya via cutting)

26. HADOOP-196.  Fix Configuration(Configuration) constructor to work
    correctly.  (Sami Siren via cutting)

27. HADOOP-501.  Fix Configuration.toString() to handle URL resources.
    (Thomas Friol via cutting)

28. HADOOP-499.  Reduce the use of Strings in contrib/streaming,
    replacing them with Text for better performance.
    (Hairong Kuang via cutting)

29. HADOOP-64.  Manage multiple volumes with a single DataNode.
    Previously DataNode would create a separate daemon per configured
    volume, each with its own connection to the NameNode.  Now all
    volumes are handled by a single DataNode daemon, reducing the load
    on the NameNode.  (Milind Bhandarkar via cutting)

30. HADOOP-424.  Fix MapReduce so that jobs which generate zero splits
    do not fail.  (Frédéric Bertin via cutting)

31. HADOOP-408.  Adjust some timeouts and remove some others so that
    unit tests run faster.  (cutting)

32. HADOOP-507.  Fix an IllegalAccessException in DFS.
    (omalley via cutting)

33. HADOOP-320.  Fix so that checksum files are correctly copied when
    the destination of a file copy is a directory.
    (Hairong Kuang via cutting)

34. HADOOP-286.  In DFSClient, avoid pinging the NameNode with
    renewLease() calls when no files are being written.
    (Konstantin Shvachko via cutting)

35. HADOOP-312.  Close idle IPC connections.  All IPC connections were
    cached forever.  Now, after a connection has been idle for more
    than a configurable amount of time (one second by default), the
    connection is closed, conserving resources on both client and
    server. (Devaraj Das via cutting)

36. HADOOP-497.  Permit the specification of the network interface and
    nameserver to be used when determining the local hostname
    advertised by datanodes and tasktrackers.
    (Lorenzo Thione via cutting)

37. HADOOP-441.  Add a compression codec API and extend SequenceFile
    to use it.  This will permit the use of alternate compression
    codecs in SequenceFile.  (Arun C Murthy via cutting)

38. HADOOP-483. Improvements to libhdfs build and documentation.
    (Arun C Murthy via cutting)

39. HADOOP-458.  Fix a memory corruption bug in libhdfs.
    (Arun C Murthy via cutting)

40. HADOOP-517.  Fix a contrib/streaming bug in end-of-line detection.
    (Hairong Kuang via cutting)

41. HADOOP-474.  Add CompressionCodecFactory, and use it in
    TextInputFormat and TextOutputFormat.  Compressed input files are
    automatically decompressed when they have the correct extension.
    Output files will, when output compression is specified, be
    generated with an approprate extension.  Also add a gzip codec and
    fix problems with UTF8 text inputs.  (omalley via cutting)


Release 0.5.0 - 2006-08-04

 1. HADOOP-352.  Fix shell scripts to use /bin/sh instead of
    /bin/bash, for better portability.
    (Jean-Baptiste Quenot via cutting)

 2. HADOOP-313.  Permit task state to be saved so that single tasks
    may be manually re-executed when debugging.  (omalley via cutting)

 3. HADOOP-339.  Add method to JobClient API listing jobs that are
    not yet complete, i.e., that are queued or running.
    (Mahadev Konar via cutting)

 4. HADOOP-355.  Updates to the streaming contrib module, including
    API fixes, making reduce optional, and adding an input type for
    StreamSequenceRecordReader.  (Michel Tourn via cutting)

 5. HADOOP-358.  Fix a NPE bug in Path.equals().
    (Frédéric Bertin via cutting)

 6. HADOOP-327.  Fix ToolBase to not call System.exit() when
    exceptions are thrown.  (Hairong Kuang via cutting)

 7. HADOOP-359.  Permit map output to be compressed.
    (omalley via cutting)

 8. HADOOP-341.  Permit input URI to CopyFiles to use the HTTP
    protocol.  This lets one, e.g., more easily copy log files into
    DFS.  (Arun C Murthy via cutting)

 9. HADOOP-361.  Remove unix dependencies from streaming contrib
    module tests, making them pure java. (Michel Tourn via cutting)

10. HADOOP-354.  Make public methods to stop DFS daemons.
    (Barry Kaplan via cutting)

11. HADOOP-252.  Add versioning to RPC protocols.
    (Milind Bhandarkar via cutting)

12. HADOOP-356.  Add contrib to "compile" and "test" build targets, so
    that this code is better maintained. (Michel Tourn via cutting)

13. HADOOP-307.  Add smallJobsBenchmark contrib module.  This runs
    lots of small jobs, in order to determine per-task overheads.
    (Sanjay Dahiya via cutting)

14. HADOOP-342.  Add a tool for log analysis: Logalyzer.
    (Arun C Murthy via cutting)

15. HADOOP-347.  Add web-based browsing of DFS content.  The namenode
    redirects browsing requests to datanodes.  Content requests are
    redirected to datanodes where the data is local when possible.
    (Devaraj Das via cutting)

16. HADOOP-351.  Make Hadoop IPC kernel independent of Jetty.
    (Devaraj Das via cutting)

17. HADOOP-237.  Add metric reporting to DFS and MapReduce.  With only
    minor configuration changes, one can now monitor many Hadoop
    system statistics using Ganglia or other monitoring systems.
    (Milind Bhandarkar via cutting)

18. HADOOP-376.  Fix datanode's HTTP server to scan for a free port.
    (omalley via cutting)

19. HADOOP-260.  Add --config option to shell scripts, specifying an
    alternate configuration directory. (Milind Bhandarkar via cutting)

20. HADOOP-381.  Permit developers to save the temporary files for
    tasks whose names match a regular expression, to facilliate
    debugging.  (omalley via cutting)

21. HADOOP-344.  Fix some Windows-related problems with DF.
    (Konstantin Shvachko via cutting)

22. HADOOP-380.  Fix reduce tasks to poll less frequently for map
    outputs. (Mahadev Konar via cutting)

23. HADOOP-321.  Refactor DatanodeInfo, in preparation for
    HADOOP-306.  (Konstantin Shvachko & omalley via cutting)

24. HADOOP-385.  Fix some bugs in record io code generation.
    (Milind Bhandarkar via cutting)

25. HADOOP-302.  Add new Text class to replace UTF8, removing
    limitations of that class.  Also refactor utility methods for
    writing zero-compressed integers (VInts and VLongs).
    (Hairong Kuang via cutting)

26. HADOOP-335.  Refactor DFS namespace/transaction logging in
    namenode.   (Konstantin Shvachko via cutting)

27. HADOOP-375.  Fix handling of the datanode HTTP daemon's port so
    that multiple datanode's can be run on a single host.
    (Devaraj Das via cutting)

28. HADOOP-386.  When removing excess DFS block replicas, remove those
    on nodes with the least free space first.
    (Johan Oskarson via cutting)

29. HADOOP-389.  Fix intermittent failures of mapreduce unit tests.
    Also fix some build dependencies.
    (Mahadev & Konstantin via cutting)

30. HADOOP-362.  Fix a problem where jobs hang when status messages
    are recieved out-of-order.  (omalley via cutting)

31. HADOOP-394.  Change order of DFS shutdown in unit tests to
    minimize errors logged.  (Konstantin Shvachko via cutting)

32. HADOOP-396.  Make DatanodeID implement Writable.
    (Konstantin Shvachko via cutting)

33. HADOOP-377.  Permit one to add URL resources to a Configuration.
    (Jean-Baptiste Quenot via cutting)

34. HADOOP-345.  Permit iteration over Configuration key/value pairs.
    (Michel Tourn via cutting)

35. HADOOP-409.  Streaming contrib module: make configuration
    properties available to commands as environment variables.
    (Michel Tourn via cutting)

36. HADOOP-369.  Add -getmerge option to dfs command that appends all
    files in a directory into a single local file.
    (Johan Oskarson via cutting)

37. HADOOP-410.  Replace some TreeMaps with HashMaps in DFS, for
    a 17% performance improvement. (Milind Bhandarkar via cutting)

38. HADOOP-411.  Add unit tests for command line parser.
    (Hairong Kuang via cutting)

39. HADOOP-412.  Add MapReduce input formats that support filtering
    of SequenceFile data, including sampling and regex matching.
    Also, move JobConf.newInstance() to a new utility class.
    (Hairong Kuang via cutting)

40. HADOOP-226.  Fix fsck command to properly consider replication
    counts, now that these can vary per file.  (Bryan Pendleton via cutting)

41. HADOOP-425.  Add a Python MapReduce example, using Jython.
    (omalley via cutting)


Release 0.4.0 - 2006-06-28

 1. HADOOP-298.  Improved progress reports for CopyFiles utility, the
    distributed file copier.  (omalley via cutting)

 2. HADOOP-299.  Fix the task tracker, permitting multiple jobs to
    more easily execute at the same time.  (omalley via cutting)

 3. HADOOP-250.  Add an HTTP user interface to the namenode, running
    on port 50070. (Devaraj Das via cutting)

 4. HADOOP-123.  Add MapReduce unit tests that run a jobtracker and
    tasktracker, greatly increasing code coverage.
    (Milind Bhandarkar via cutting)

 5. HADOOP-271.  Add links from jobtracker's web ui to tasktracker's
    web ui.  Also attempt to log a thread dump of child processes
    before they're killed.  (omalley via cutting)

 6. HADOOP-210.  Change RPC server to use a selector instead of a
    thread per connection.  This should make it easier to scale to
    larger clusters.  Note that this incompatibly changes the RPC
    protocol: clients and servers must both be upgraded to the new
    version to ensure correct operation.  (Devaraj Das via cutting)

 7. HADOOP-311.  Change DFS client to retry failed reads, so that a
    single read failure will not alone cause failure of a task.
    (omalley via cutting)

 8. HADOOP-314.  Remove the "append" phase when reducing.  Map output
    files are now directly passed to the sorter, without first
    appending them into a single file.  Now, the first third of reduce
    progress is "copy" (transferring map output to reduce nodes), the
    middle third is "sort" (sorting map output) and the last third is
    "reduce" (generating output).  Long-term, the "sort" phase will
    also be removed.  (omalley via cutting)

 9. HADOOP-316.  Fix a potential deadlock in the jobtracker.
    (omalley via cutting)

10. HADOOP-319.  Fix FileSystem.close() to remove the FileSystem
    instance from the cache.  (Hairong Kuang via cutting)

11. HADOOP-135.  Fix potential deadlock in JobTracker by acquiring
    locks in a consistent order.  (omalley via cutting)

12. HADOOP-278.  Check for existence of input directories before
    starting MapReduce jobs, making it easier to debug this common
    error.  (omalley via cutting)

13. HADOOP-304.  Improve error message for
    UnregisterdDatanodeException to include expected node name.
   (Konstantin Shvachko via cutting)

14. HADOOP-305.  Fix TaskTracker to ask for new tasks as soon as a
    task is finished, rather than waiting for the next heartbeat.
    This improves performance when tasks are short.
    (Mahadev Konar via cutting)

15. HADOOP-59.  Add support for generic command line options.  One may
    now specify the filesystem (-fs), the MapReduce jobtracker (-jt),
    a config file (-conf) or any configuration property (-D).  The
    "dfs", "fsck", "job", and "distcp" commands currently support
    this, with more to be added.  (Hairong Kuang via cutting)

16. HADOOP-296.  Permit specification of the amount of reserved space
    on a DFS datanode.  One may specify both the percentage free and
    the number of bytes.  (Johan Oskarson via cutting)

17. HADOOP-325.  Fix a problem initializing RPC parameter classes, and
    remove the workaround used to initialize classes.
    (omalley via cutting)

18. HADOOP-328.  Add an option to the "distcp" command to ignore read
    errors while copying.  (omalley via cutting)

19. HADOOP-27.  Don't allocate tasks to trackers whose local free
    space is too low.  (Johan Oskarson via cutting)

20. HADOOP-318.  Keep slow DFS output from causing task timeouts.
    This incompatibly changes some public interfaces, adding a
    parameter to OutputFormat.getRecordWriter() and the new method
    Reporter.progress(), but it makes lots of tasks succeed that were
    previously failing.  (Milind Bhandarkar via cutting)


Release 0.3.2 - 2006-06-09

 1. HADOOP-275.  Update the streaming contrib module to use log4j for
    its logging.  (Michel Tourn via cutting)

 2. HADOOP-279.  Provide defaults for log4j logging parameters, so
    that things still work reasonably when Hadoop-specific system
    properties are not provided.  (omalley via cutting)

 3. HADOOP-280.  Fix a typo in AllTestDriver which caused the wrong
    test to be run when "DistributedFSCheck" was specified.
   (Konstantin Shvachko via cutting)

 4. HADOOP-240.  DFS's mkdirs() implementation no longer logs a warning
    when the directory already exists. (Hairong Kuang via cutting)

 5. HADOOP-285.  Fix DFS datanodes to be able to re-join the cluster
    after the connection to the namenode is lost.  (omalley via cutting)

 6. HADOOP-277.  Fix a race condition when creating directories.
   (Sameer Paranjpye via cutting)

 7. HADOOP-289.  Improved exception handling in DFS datanode.
    (Konstantin Shvachko via cutting)

 8. HADOOP-292.  Fix client-side logging to go to standard error
    rather than standard output, so that it can be distinguished from
    application output.  (omalley via cutting)

 9. HADOOP-294.  Fixed bug where conditions for retrying after errors
    in the DFS client were reversed.  (omalley via cutting)


Release 0.3.1 - 2006-06-05

 1. HADOOP-272.  Fix a bug in bin/hadoop setting log
    parameters. (omalley & cutting)

 2. HADOOP-274.  Change applications to log to standard output rather
    than to a rolling log file like daemons.  (omalley via cutting)

 3. HADOOP-262.  Fix reduce tasks to report progress while they're
    waiting for map outputs, so that they do not time out.
    (Mahadev Konar via cutting)

 4. HADOOP-245 and HADOOP-246.  Improvements to record io package.  
    (Mahadev Konar via cutting)

 5. HADOOP-276.  Add logging config files to jar file so that they're
    always found.  (omalley via cutting)


Release 0.3.0 - 2006-06-02

 1. HADOOP-208.  Enhance MapReduce web interface, adding new pages
    for failed tasks, and tasktrackers.  (omalley via cutting)

 2. HADOOP-204.  Tweaks to metrics package.  (David Bowen via cutting)

 3. HADOOP-209.  Add a MapReduce-based file copier.  This will
    copy files within or between file systems in parallel.
    (Milind Bhandarkar via cutting)

 4. HADOOP-146.  Fix DFS to check when randomly generating a new block
    id that no existing blocks already have that id.
    (Milind Bhandarkar via cutting)

 5. HADOOP-180. Make a daemon thread that does the actual task clean ups, so
    that the main offerService thread in the taskTracker doesn't get stuck
    and miss his heartbeat window. This was killing many task trackers as
    big jobs finished (300+ tasks / node). (omalley via cutting)

 6. HADOOP-200. Avoid transmitting entire list of map task names to
    reduce tasks.  Instead just transmit the number of map tasks and
    henceforth refer to them by number when collecting map output.
    (omalley via cutting)

 7. HADOOP-219. Fix a NullPointerException when handling a checksum
    exception under SequenceFile.Sorter.sort().  (cutting & stack)

 8. HADOOP-212. Permit alteration of the file block size in DFS.  The
    default block size for new files may now be specified in the
    configuration with the dfs.block.size property.  The block size
    may also be specified when files are opened.
    (omalley via cutting)

 9. HADOOP-218. Avoid accessing configuration while looping through
    tasks in JobTracker.  (Mahadev Konar via cutting)

10. HADOOP-161. Add hashCode() method to DFS's Block.
    (Milind Bhandarkar via cutting)

11. HADOOP-115. Map output types may now be specified.  These are also
    used as reduce input types, thus permitting reduce input types to
    differ from reduce output types.  (Runping Qi via cutting)

12. HADOOP-216. Add task progress to task status page.
    (Bryan Pendelton via cutting)

13. HADOOP-233.  Add web server to task tracker that shows running
    tasks and logs.  Also add log access to job tracker web interface.
    (omalley via cutting)

14. HADOOP-205.  Incorporate pending tasks into tasktracker load
    calculations.  (Mahadev Konar via cutting)

15. HADOOP-247.  Fix sort progress to better handle exceptions.
    (Mahadev Konar via cutting)

16. HADOOP-195.  Improve performance of the transfer of map outputs to
    reduce nodes by performing multiple transfers in parallel, each on
    a separate socket.  (Sameer Paranjpye via cutting)

17. HADOOP-251.  Fix task processes to be tolerant of failed progress
    reports to their parent process.  (omalley via cutting)

18. HADOOP-325.  Improve the FileNotFound exceptions thrown by
    LocalFileSystem to include the name of the file.
    (Benjamin Reed via cutting)

19. HADOOP-254.  Use HTTP to transfer map output data to reduce
    nodes.  This, together with HADOOP-195, greatly improves the
    performance of these transfers.  (omalley via cutting)

20. HADOOP-163.  Cause datanodes that\ are unable to either read or
    write data to exit, so that the namenode will no longer target
    them for new blocks and will replicate their data on other nodes.
    (Hairong Kuang via cutting)

21. HADOOP-222.  Add a -setrep option to the dfs commands that alters
    file replication levels.  (Johan Oskarson via cutting)

22. HADOOP-75.  In DFS, only check for a complete file when the file
    is closed, rather than as each block is written.
    (Milind Bhandarkar via cutting)

23. HADOOP-124. Change DFS so that datanodes are identified by a
    persistent ID rather than by host and port.  This solves a number
    of filesystem integrity problems, when, e.g., datanodes are
    restarted.  (Konstantin Shvachko via cutting)

24. HADOOP-256.  Add a C API for DFS.  (Arun C Murthy via cutting)

25. HADOOP-211.  Switch to use the Jakarta Commons logging internally,
    configured to use log4j by default.  (Arun C Murthy and cutting)

26. HADOOP-265.  Tasktracker now fails to start if it does not have a
    writable local directory for temporary files.  In this case, it
    logs a message to the JobTracker and exits. (Hairong Kuang via cutting)

27. HADOOP-270.  Fix potential deadlock in datanode shutdown.
    (Hairong Kuang via cutting)

Release 0.2.1 - 2006-05-12

 1. HADOOP-199.  Fix reduce progress (broken by HADOOP-182).
    (omalley via cutting)

 2. HADOOP-201.  Fix 'bin/hadoop dfs -report'.  (cutting)

 3. HADOOP-207.  Fix JDK 1.4 incompatibility introduced by HADOOP-96.
    System.getenv() does not work in JDK 1.4.  (Hairong Kuang via cutting)


Release 0.2.0 - 2006-05-05

 1. Fix HADOOP-126. 'bin/hadoop dfs -cp' now correctly copies .crc
    files.  (Konstantin Shvachko via cutting)

 2. Fix HADOOP-51. Change DFS to support per-file replication counts.
    (Konstantin Shvachko via cutting)

 3. Fix HADOOP-131.  Add scripts to start/stop dfs and mapred daemons.
    Use these in start/stop-all scripts.  (Chris Mattmann via cutting)

 4. Stop using ssh options by default that are not yet in widely used
    versions of ssh.  Folks can still enable their use by uncommenting
    a line in conf/hadoop-env.sh. (cutting)

 5. Fix HADOOP-92.  Show information about all attempts to run each
    task in the web ui.  (Mahadev konar via cutting)

 6. Fix HADOOP-128.  Improved DFS error handling. (Owen O'Malley via cutting)

 7. Fix HADOOP-129.  Replace uses of java.io.File with new class named
    Path.  This fixes bugs where java.io.File methods were called
    directly when FileSystem methods were desired, and reduces the
    likelihood of such bugs in the future.  It also makes the handling
    of pathnames more consistent between local and dfs FileSystems and
    between Windows and Unix. java.io.File-based methods are still
    available for back-compatibility, but are deprecated and will be
    removed once 0.2 is released. (cutting)

 8. Change dfs.data.dir and mapred.local.dir to be comma-separated
    lists of directories, no longer be space-separated. This fixes
    several bugs on Windows. (cutting)

 9. Fix HADOOP-144.  Use mapred task id for dfs client id, to
    facilitate debugging.  (omalley via cutting)

10. Fix HADOOP-143.  Do not line-wrap stack-traces in web ui.
    (omalley via cutting)

11. Fix HADOOP-118.  In DFS, improve clean up of abandoned file
    creations.  (omalley via cutting)

12. Fix HADOOP-138.  Stop multiple tasks in a single heartbeat, rather
    than one per heartbeat.  (Stefan via cutting)

13. Fix HADOOP-139.  Remove a potential deadlock in
    LocalFileSystem.lock().  (Igor Bolotin via cutting)

14. Fix HADOOP-134.  Don't hang jobs when the tasktracker is
    misconfigured to use an un-writable local directory.  (omalley via cutting)

15. Fix HADOOP-115.  Correct an error message.  (Stack via cutting)

16. Fix HADOOP-133.  Retry pings from child to parent, in case of
    (local) communcation problems.  Also log exit status, so that one
    can distinguish patricide from other deaths.  (omalley via cutting)

17. Fix HADOOP-142.  Avoid re-running a task on a host where it has
    previously failed.  (omalley via cutting)

18. Fix HADOOP-148.  Maintain a task failure count for each
    tasktracker and display it in the web ui.  (omalley via cutting)

19. Fix HADOOP-151.  Close a potential socket leak, where new IPC
    connection pools were created per configuration instance that RPCs
    use.  Now a global RPC connection pool is used again, as
    originally intended.  (cutting)

20. Fix HADOOP-69.  Don't throw a NullPointerException when getting
    hints for non-existing file split.  (Bryan Pendelton via cutting)

21. Fix HADOOP-157.  When a task that writes dfs files (e.g., a reduce
    task) failed and was retried, it would fail again and again,
    eventually failing the job.  The problem was that dfs did not yet
    know that the failed task had abandoned the files, and would not
    yet let another task create files with the same names.  Dfs now
    retries when creating a file long enough for locks on abandoned
    files to expire.  (omalley via cutting)

22. Fix HADOOP-150.  Improved task names that include job
    names. (omalley via cutting)

23. Fix HADOOP-162.  Fix ConcurrentModificationException when
    releasing file locks. (omalley via cutting)

24. Fix HADOOP-132.  Initial check-in of new Metrics API, including 
    implementations for writing metric data to a file and for sending
    it to Ganglia.  (David Bowen via cutting)

25. Fix HADOOP-160.  Remove some uneeded synchronization around
    time-consuming operations in the TaskTracker.  (omalley via cutting)

26. Fix HADOOP-166.  RPCs failed when passed subclasses of a declared
    parameter type.  This is fixed by changing ObjectWritable to store
    both the declared type and the instance type for Writables.  Note
    that this incompatibly changes the format of ObjectWritable and
    will render unreadable any ObjectWritables stored in files.
    Nutch only uses ObjectWritable in intermediate files, so this
    should not be a problem for Nutch.  (Stefan & cutting)

27. Fix HADOOP-168.  MapReduce RPC protocol methods should all declare
    IOException, so that timeouts are handled appropriately.
    (omalley via cutting)

28. Fix HADOOP-169.  Don't fail a reduce task if a call to the
    jobtracker to locate map outputs fails.  (omalley via cutting)

29. Fix HADOOP-170.  Permit FileSystem clients to examine and modify
    the replication count of individual files.  Also fix a few
    replication-related bugs. (Konstantin Shvachko via cutting)

30. Permit specification of a higher replication levels for job
    submission files (job.xml and job.jar).  This helps with large
    clusters, since these files are read by every node.  (cutting)

31. HADOOP-173.  Optimize allocation of tasks with local data.  (cutting)

32. HADOOP-167.  Reduce number of Configurations and JobConf's
    created.  (omalley via cutting)

33. NUTCH-256.  Change FileSystem#createNewFile() to create a .crc
    file.  The lack of a .crc file was causing warnings.  (cutting)

34. HADOOP-174.  Change JobClient to not abort job until it has failed
    to contact the job tracker for five attempts, not just one as
    before.  (omalley via cutting)

35. HADOOP-177.  Change MapReduce web interface to page through tasks.
    Previously, when jobs had more than a few thousand tasks they
    could crash web browsers.  (Mahadev Konar via cutting)

36. HADOOP-178.  In DFS, piggyback blockwork requests from datanodes
    on heartbeat responses from namenode.  This reduces the volume of
    RPC traffic.  Also move startup delay in blockwork from datanode
    to namenode.  This fixes a problem where restarting the namenode
    triggered a lot of uneeded replication. (Hairong Kuang via cutting)

37. HADOOP-183.  If the DFS namenode is restarted with different
    minimum and/or maximum replication counts, existing files'
    replication counts are now automatically adjusted to be within the
    newly configured bounds. (Hairong Kuang via cutting)

38. HADOOP-186.  Better error handling in TaskTracker's top-level
    loop.  Also improve calculation of time to send next heartbeat.
    (omalley via cutting)

39. HADOOP-187.  Add two MapReduce examples/benchmarks.  One creates
    files containing random data.  The second sorts the output of the
    first.  (omalley via cutting)

40. HADOOP-185.  Fix so that, when a task tracker times out making the
    RPC asking for a new task to run, the job tracker does not think
    that it is actually running the task returned.  (omalley via cutting)

41. HADOOP-190.  If a child process hangs after it has reported
    completion, its output should not be lost.  (Stack via cutting)

42. HADOOP-184. Re-structure some test code to better support testing
    on a cluster.  (Mahadev Konar via cutting)

43. HADOOP-191  Add streaming package, Hadoop's first contrib module.
    This permits folks to easily submit MapReduce jobs whose map and
    reduce functions are implemented by shell commands.  Use
    'bin/hadoop jar build/hadoop-streaming.jar' to get details.
    (Michel Tourn via cutting)

44. HADOOP-189.  Fix MapReduce in standalone configuration to
    correctly handle job jar files that contain a lib directory with
    nested jar files.  (cutting)

45. HADOOP-65.  Initial version of record I/O framework that enables
    the specification of record types and generates marshalling code
    in both Java and C++.  Generated Java code implements
    WritableComparable, but is not yet otherwise used by
    Hadoop. (Milind Bhandarkar via cutting)

46. HADOOP-193.  Add a MapReduce-based FileSystem benchmark.
    (Konstantin Shvachko via cutting)

47. HADOOP-194.  Add a MapReduce-based FileSystem checker.  This reads
    every block in every file in the filesystem.  (Konstantin Shvachko
    via cutting)

48. HADOOP-182.  Fix so that lost task trackers to not change the
    status of reduce tasks or completed jobs.  Also fixes the progress
    meter so that failed tasks are subtracted. (omalley via cutting)

49. HADOOP-96.  Logging improvements.  Log files are now separate from
    standard output and standard error files.  Logs are now rolled.
    Logging of all DFS state changes can be enabled, to facilitate
    debugging.  (Hairong Kuang via cutting)


Release 0.1.1 - 2006-04-08

 1. Added CHANGES.txt, logging all significant changes to Hadoop.  (cutting)

 2. Fix MapReduceBase.close() to throw IOException, as declared in the
    Closeable interface.  This permits subclasses which override this
    method to throw that exception. (cutting)

 3. Fix HADOOP-117.  Pathnames were mistakenly transposed in
    JobConf.getLocalFile() causing many mapred temporary files to not
    be removed.  (Raghavendra Prabhu via cutting)
 
 4. Fix HADOOP-116. Clean up job submission files when jobs complete.
    (cutting)

 5. Fix HADOOP-125. Fix handling of absolute paths on Windows (cutting)

Release 0.1.0 - 2006-04-01

 1. The first release of Hadoop.