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Release notes

Disco 0.4.1 (Sep 23rd 2011)

The official Disco repository is now at http://github.com/discoproject/disco

New features

  • DiscoDB: ddb_cursor_count() added. iterator.count() is now faster.
  • DiscoDB: Value lists are now stored in deltalists instead of lists during discodb construction, resulting to 50-75% smaller memory footprint in the many-values-per-key case.

Bugfixes

  • Fix GC timeout issue (#268).
  • Fix regression in Temp GC (09a1debb). Thanks to Jamie Brandon.
  • Improved and fixed documentation. Thanks to Jens Rantil, stillinbeta and Luke Hoersten.
  • Fix chunking. Thanks to Daniel Grana.
  • Minor fixes in DiscoDB.
  • Fix a bug in job pack extraction (e7b3b6).

Disco 0.4 (May 4th 2011)

New features

Bugfixes

  • DDFS:
    • important Recreating a previously deleted tag with a token did not work correctly. The call returned without an error but the tag was not created.
    • Under some circumstances DDFS garbage collector deleted .partial files, causing PUT operations to fail (6deef33f).
  • Redundant inputs using the http:// scheme were not handled correctly (disco:// scheme worked ok) (9fcc740d).
  • Fix eaddrinuse errors caused by already running nodes (1eed58d08).
  • Fix newlines in error messages in the web UI.
  • The web UI no longer loses the filter when the events are refreshed.
  • Several fixes in node_mon. It should handle unavailable nodes now more robustly.
  • The OOB issue (#227) highlighted below became a non-issue as GC takes care of removing OOB results when the job is garbage collected.
  • Fix the issue with the job starting even when the client got an error when submitting a new job.

Deprecated

Disco 0.3.2 (Dec 6th 2010)

Note

In contrast to earlier releases, in 0.3.2 purging a job does not delete OOB results of the job automatically. This is listed as issue #227 and will be fixed in the next release together with other changes in OOB handling. Meanwhile, you can use :meth:`disco.ddfs.DDFS.delete` to delete OOB results if needed.

New features

Bugfixes

  • Several bugfixes in DDFS garbage collection.
  • Tasks may be marked successful before results are persisted to disk (#208).
  • Improved error handling for badly dying tasks (#162).
  • Allow dots in DDFS paths (#196).
  • Improved handling of out of memory conditions (#168, #200).
  • Fix blocking net_adm:names in node_mon (#216).
  • Fix a badmatch error on unknown jobname (#81).
  • Fixed error handling if sort fails.
  • Tutorial example fixed.
  • HTTP error message made more informative.

Disco 0.3.1 (Sep 1st 2010)

Note

This release fixes a serious bug in how partition files are handled under certain error conditions. The bug has existed since Disco 0.1.

If a node becomes unavailable, for instance due to network congestion, master restarts the tasks that were running on the failed node on other nodes. However, it is possible that old tasks continue running on the failed node, producing results as usual. This can lead to duplicate entries being written to result files.

Note that not all task failures are suspectible to this bug. If the task itself fails, which is the most typical error scenario, Disco ensures that results are still valid. Only if your job events have contained messages like Node unavailable or Connection lost to the node, it is possible that results are invalid and you should re-run the suspected jobs with Disco 0.3.1 or newer.

This bug also revealed a similar issue with jobs that save their results to DDFS with save=True (available since Disco 0.3). It is possible that duplicate tasks create duplicate entries in the result tag. This is easy to detect and fix afterwards by listing urls in the tag and ensuring that there are no duplicates. A script is provided at util/fix-jobtag that can be used to check and fix suspected tags.

New features

  • Improved robustness and scalability:
    • Jobs are now immortal by default; they should never fail due to temporary errors unless a user-defined limit is reached.
    • New shuffle phase to optimize intermediate results for reduce.
    • Support for Varnish for DISCO_PROXY. In some cases, Varnish can be over three times faster than Lighttpd.
  • :ref:`ddfs`:
    • Improved blob placement policy.
    • Atomic set updates (update=1).
    • Delayed commits (delayed=1), which gives a major performance boost without sacrificing data consistency.
    • Garbage collection is now scheme-agnostic (#189).
  • Major :mod:`discodb` enhancements:
    • Values are now compressed without sacrificing performance.
    • Constructor accepts unsorted key-value pairs.
    • Option (unique_items=True) to remove duplicates from inputs automatically.
    • unique_values() iterator.
  • Alternative signature for reduce: Reduce can now yield key-value pairs (or return an iterator) instead of calling out.add() (see :func:`disco.func.reduce2`).
  • Enhanced Java support added as a Git submodule under contrib/java-ext (Thanks to Ryan Maus).
  • Disk space monitoring for DDFS added to the Web UI.
  • Lots of enhancements to :mod:`discodex <discodexcli>` and :mod:`disco <discocli>` command line utilities.
  • New setting DISCO_SORT_BUFFER_SIZE to control memory usage of the external sort (see :mod:`disco.settings`).
  • :func:`disco.func.gzip_reader` for reading gzipped inputs.
  • Easier single-node installation with default localhost configuration.

Deprecated

  • Important! The default reader function, :func:`disco.func.map_line_reader`, will be deprecated. The new default is to iterate over the object returned by map_reader. In practice, the default map_reader will still return an object that iterates over lines. However, it will not strip newline characters from the end of lines as the old :func:`disco.func.map_line_reader` does.

    Make sure that your jobs that rely on the default map_reader will handle newline characters correctly. You can do this easily by calling string.strip() for each line.

Backwards incompatible changes

  • Installation script for Amazon EC2 removed (aws/setup-instances.py) and documentation updated accordingly (see :ref:`ec2`). Disco still works in Amazon EC2 and other similar environments flawlessly but a more modern mechanism for easy deployments is needed.

Bugfixes

  • Critical bug fixes to fix partition file handling and save=True behavior under temporary node failures (see a separate note above).
  • Delayed commits in DDFS fix OOB slowness (#155)
  • Fix unicode handling (#185, #190)
  • In-memory sort disabled as it doesn't work well compressed inputs (#145)
  • Fixed/improved replica handling (#170, #178, #176)
  • Three bugfixes in :mod:`discodb` querying and iterators (#181)
  • Don't rate limit internal messages, to prevent bursts of messages crashing the job (#169)
  • Random bytes in a message should not make json encoding fail (#161)
  • :meth:`disco.core.Disco.wait` should not throw an exception if master doesn't respond immediately (#183)
  • Connections should not fail immediately if creating a connection fails (#179)
  • Fixed an upload issue in comm_pycurl.py (#156)
  • Disable HTTP keep-alive on master.
  • Sort failing is not a fatal error.
  • Partitioned only-reduce did not check the number of input partitions correctly.
  • DISCO_PROXY did not work correctly if disco was run with a non-standard port.
  • node_mon didn't handle all messages from nodes correctly, which lead its message queue to grow, leading to spurious Node unavailable messages.
  • Fix mouse-over for showing active cores in the status page.

Disco 0.3 (May 26th 2010)

New features

  • :ref:`ddfs` - distributed and replicated data storage for Disco.
  • :ref:`discodex` - distributed indices for efficient querying of data.
  • :mod:`discodb` - lightning fast and scalable mapping data structure.
  • New internal data format, supporting compression and pickling of Python objects by default.
  • Clarified the partitioning logic in Disco, see :ref:`dataflow`.
  • Integrated web server (Mochiweb) replaces Lighttpd, making installation easier and allows more fine-grained data flow control.
  • Chunked data transfer and improved handling of network congestion.
  • Support for partial job functions (Thanks to Jarno Seppänen)
  • Unified interface for readers and input streams, writers deprecated. See :meth:`disco.core.Disco.new_job`.
  • New save=True parameter for :meth:`disco.core.Disco.new_job` which persists job results in DDFS.
  • New garbage collector deletes job data DISCO_GC_AFTER seconds after the job has finished (see :mod:`disco.settings`). Defaults to 100 years. Use save=True, if you want to keep the results permanently.
  • Support for Out-of-band (OOB) results implemented using DDFS.
  • disco-worker checks that there is enough disk space before it starts up.
  • :mod:`discocli` - Command line interface for Disco
  • :mod:`ddfscli` - Command line interface for DDFS
  • Improved load balancing in scheduler.
  • Integrated Disco proxy based on Lighttpd.
  • Debian packaging: disco-master and disco-node do not conflict anymore, making it possible to run Disco locally from Debian packages.

Deprecated

These features will be removed in the coming releases:
  • object_reader and object_writer - Disco supports now pickling by default.
  • map_writer and reduce_writer (use output streams instead).
  • nr_reduces (use partitions)
  • fun_map and input_files (use map and input)

Backwards incompatible changes

  • Experimental support for GlusterFS removed
  • homedisco removed - use a local Disco instead
  • Deprecated chunked parameter removed from :meth:`disco.core.Disco.new_job`.
  • If you have been using a custom output stream with the default writer, you need to specify the writer now explictly, or upgrade your output stream to support the .out(k, v)` method which replaces writers in 0.3.

Bugfixes

  • Jobs should disappear from list immediately after deleted (bug #43)
  • Running jobs with empty input gives "Jobs status dead" (bug #92)
  • Full disk may crash a job in _safe_fileop() (bug #120)
  • Eventmonitor shows each job multiple times when tracking multiple jobs (bug #94)
  • Change eventmonitor default output handle to sys.stderr (bug #83)
  • Tell user what the spawn command was if the task fails right away (bug #113)
  • Normalize pathnames on PYTHONPATH (bug #134)
  • Timeouts were handled incorrectly in wait() (bug #96)
  • Cast unicode urls to strings in comm_curl (bug #52)
  • External sort handles objects in values correctly. Thanks to Tomaž Šolc for the patch!
  • Scheduler didn't handle node changes correctly - this solves the hanging jobs issue
  • Several bug fixes in comm_*.py
  • Duplicate nodes on the node config table crashed master
  • Handle timeout correctly in fair_scheduler_job (if system is under heavy load)

Disco 0.2.4 (February 8th 2010)

New features

Bugfixes

  • Set LC_ALL=C for disco worker to ensure that external sort produces consistent results (bug #36, 7635c9a)
  • Apply rate limit to all messages on stdout / stderr. (bug #21, db76c80)
  • Fixed flock error handing for OS X (b06757e4)
  • Documentation fixes (bug #34, #42 9cd9b6f1)

Disco 0.2.3 (September 9th 2009)

New features

  • The :mod:`disco.settings` control script makes setting up and running Disco much easier than before.
  • Console output of job events (screenshot). You can now follow progress of a job on the console instead of the web UI by setting DISCO_EVENTS=1. See :meth:`disco.core.Disco.events` and :meth:`disco.core.Disco.wait`.
  • Automatic inference and distribution of dependent modules. See :mod:`disco.modutil`.
  • required_files parameter added to :meth:`disco.core.Disco.new_job`.
  • Combining the previous two features, a new easier way to use external C libraries is provided, see :ref:`discoext`.
  • Support for Python 2.6 and 2.7.
  • Easier installation of a simple single-server cluster. Just run disco master start on the disco directory. The DISCO_MASTER_PORT setting is deprecated.
  • Improved support for OS X. The DISCO_SLAVE_OS setting is deprecated.
  • Debian packages upgraded to use Erlang 13B.
  • Several improvements related to fault-tolerance of the system
  • Serialize job parameters using more efficient and compact binary format.
  • Improved support for GlusterFS (2.0.6 and newer).
  • Support for the pre-0.1 disco module, disco.job call etc., removed.

Bugfixes

  • critical External sort didn't work correctly with non-numeric keys (5ef88ad4)
  • External sort didn't handle newlines correctly (61d6a597f)
  • Regression fixed in :meth:`disco.core.Disco.jobspec`; the function works now again (e5c20bbfec4)
  • Filter fixed on the web UI (bug #4, e9c265b)
  • Tracebacks are now shown correctly on the web UI (bug #3, ea26802ce)
  • Fixed negative number of maps on the web UI (bug #28, 5b23327 and 3e079b7)
  • The comm_curl module might return an insufficient number of bytes (761c28c4a)
  • Temporary node failure (noconnection) shouldn't be a fatal error (bug #22, ad95935)
  • nr_maps and nr_reduces limits were off by one (873d90a7)
  • Fixed a Javascript bug on the config table (11bb933)
  • Timeouts in starting a new worker shouldn't be fatal (f8dfcb94)
  • The connection pool in comm_httplib didn't work correctly (bug #30, 5c9d7a88e9)
  • Added timeouts to comm_curl to fix occasional issues with the connection getting stuck (2f79c698)
  • All IOErrors and CommExceptions are now non-fatal (f1d4a127c)

Disco 0.2.2 (July 26th 2009)

New features

  • Experimental support for POSIX-compatible distributed filesystems, in particular GlusterFS. Two modes are available: Disco can read input data from a distributed filesystem while preserving data locality (aka inputfs). Disco can also use a DFS for internal communication, replacing the need for node-specific web servers (aka resultfs).

Bugfixes

  • DISCO_PROXY handles now out-of-band results correctly (commit b1c0f9911)
  • make-lighttpd-proxyconf.py now ignores commented out lines in /etc/hosts (bug #14, commit a1a93045d)
  • Fixed missing PID file in the disco-master script. The /etc/init.d/disco-master script in Debian packages now works correctly (commit 223c2eb01)
  • Fixed a regression in Makefile. Config files were not copied to /etc/disco (bug #13, commit c058e5d6)
  • Increased server.max-write-idle setting in Lighttpd config. This prevents the http connection from disconnecting with long running, cpu-intensive reduce tasks (bug #12, commit 956617b0)

Disco 0.2.1 (May 26th 2009)

New features

  • Support for redundant inputs: You can now specify many redundant addresses for an input file. Scheduler chooses the address which points at the node with the lowest load. If the address fails, other addresses are tried one by one until the task succeeds. See inputs in :meth:`disco.core.Disco.new_job` for more information.
  • Task profiling: See :ref:`profiling`
  • Implemented an efficient way to poll for results of many concurrent jobs. See :meth:`disco.core.Disco.results`.
  • Support for the Curl HTTP client library added. Curl is used by default if the pycurl module is available.
  • Improved storing of intermediate results: Results are now spread to a directory hierarchy based on the md5 checkum of the job name.

Bugfixes

  • Check for ionice before using it. (commit dacbbbf785)
  • required_modules didn't handle submodules (PIL.Image etc.) correctly (commit a5b9fcd970)
  • Missing file balls.png added. (bug #7, commit d5617a788)
  • Missing and crashed nodes don't cause the job to fail (bug #2, commit 6a5e7f754b)
  • Default value for nr_reduces now never exceeds 100 (bug #9, commit 5b9e6924)
  • Fixed homedisco regression in 0.2. (bugs #5, #10, commit caf78f77356)

Disco 0.2 (April 7th 2009)

New features

Bugfixes

(NB: bug IDs in 0.2 refer to the old bug tracking system)

  • chunked = false mode produced incorrect input files for the reduce phase (commit db718eb6)
  • Shell enabled for the disco master process (bug #7, commit 7944e4c8)
  • Added warning about unknown parameters in new_job() (bug #8, commit db707e7d)
  • Fix for sending invalid configuration data (bug #1, commit bea70dd4)
  • Fixed missing msg, err and data_err functions (commit e99a406d)