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Roberto Tyley 5dcc8693d7 Fix concurrent creation of fan-out object directories 
If multiple threads attempted to insert loose objects into the same new
fan-out directory, the creation of that directory was subject to a race
condition that could lead to an unnecessary IOException being thrown -
because an inserter could not 'create' a directory that had just been
generated by a different thread. All we require is that the directory
does indeed *exist*, so not being able to _create_ it is not actually a
fatal problem. Setting 'skipExisting' to 'true' on the call to mkdir()
fixes the issue.

I found this issue as a real world occurrence while working on The BFG
Repo Cleaner (https://github.com/rtyley/bfg-repo-cleaner), a tool which
concurrently performs a lot of object creation.

In order to demonstrate the problem here I've added a small test case
which reliably reproduces the issue on the few different hardware
systems I've tried. The error thrown when the race-condition arises is
this:

java.io.IOException: Creating directory /home/roberto/repo.git/objects/e6 failed
at org.eclipse.jgit.util.FileUtils.mkdir(FileUtils.java:182)
at org.eclipse.jgit.storage.file.ObjectDirectory.insertUnpackedObject(ObjectDirectory.java:590)
at org.eclipse.jgit.storage.file.ObjectDirectoryInserter.insertOneObject(ObjectDirectoryInserter.java:113)
at org.eclipse.jgit.storage.file.ObjectDirectoryInserter.insert(ObjectDirectoryInserter.java:91)
at org.eclipse.jgit.lib.ObjectInserter.insert(ObjectInserter.java:329)

Change-Id: I88eac49bc600c56ba9ad290e6133d8a7113125ab
 		2013-01-13 18:59:59 -05:00
org.eclipse.jgit Fix concurrent creation of fan-out object directories 2013-01-13 18:59:59 -05:00
org.eclipse.jgit.ant Prepare 2.3.0 builds 2012-12-21 00:48:45 +01:00
org.eclipse.jgit.ant.test Prepare 2.3.0 builds 2012-12-21 00:48:45 +01:00
org.eclipse.jgit.console Mark non-externalizable strings as such 2012-12-27 16:57:38 +01:00
org.eclipse.jgit.http.server Declare essentially static methods as static 2012-12-27 12:08:06 -05:00
org.eclipse.jgit.http.test Declare essentially static methods as static 2012-12-27 12:08:06 -05:00
org.eclipse.jgit.junit Remove packIndex field from FileObjDatabase openPack method. 2013-01-10 14:02:28 -08:00
org.eclipse.jgit.junit.http Prepare 2.3.0 builds 2012-12-21 00:48:45 +01:00
org.eclipse.jgit.packaging Delete the iplog generator 2013-01-09 14:21:40 +01:00
org.eclipse.jgit.pgm Delete the iplog generator 2013-01-09 14:21:40 +01:00
org.eclipse.jgit.pgm.test Prepare 2.3.0 builds 2012-12-21 00:48:45 +01:00
org.eclipse.jgit.test Fix concurrent creation of fan-out object directories 2013-01-13 18:59:59 -05:00
org.eclipse.jgit.ui Declare essentially static methods as static 2012-12-27 12:08:06 -05:00
tools Fix version.sh 2011-12-10 01:03:33 +01:00
.eclipse_iplog Update Eclipse IP log for 1.0 2011-05-25 20:14:35 +02:00
.gitattributes Initial JGit contribution to eclipse.org 2009-09-29 16:47:03 -07:00
.gitignore Ignore /target 2012-03-05 21:11:57 -08:00
LICENSE Clean up LICENSE file 2010-07-02 14:52:49 -07:00
README.md Update README 2012-09-28 23:21:22 +02:00
SUBMITTING_PATCHES Correcting explanation of EDL 2009-10-28 14:12:07 +01:00
pom.xml Delete the iplog generator 2013-01-09 14:21:40 +01:00

README.md

Java Git

An implementation of the Git version control system in pure Java.

This package is licensed under the EDL (Eclipse Distribution License).

  • org.eclipse.jgit

    A pure Java library capable of being run standalone, with no additional support libraries. It provides classes to read and write a Git repository and operate on a working directory.

    All portions of jgit are covered by the EDL. Absolutely no GPL, LGPL or EPL contributions are accepted within this package.

  • org.eclipse.jgit.ant

    Ant tasks based on JGit.

  • org.eclipse.jgit.http.server

    Server for the smart and dumb Git HTTP protocol.

  • org.eclipse.jgit.pgm

    Command-line interface Git commands implemented using JGit ("pgm" stands for program).

  • org.eclipse.jgit.test

    Unit tests for org.eclipse.jgit and the same licensing rules.

Warnings/Caveats

  • Symbolic links are not supported because java does not support it. Such links could be damaged.

  • Only the timestamp of the index is used by jgit check if the index is dirty.

  • Don't try the library with a JDK other than 1.6 (Java 6) unless you are prepared to investigate problems yourself. JDK 1.5.0_11 and later Java 5 versions may work. Earlier versions do not. JDK 1.4 is not supported. Apple's Java 1.5.0_07 is reported to work acceptably. We have no information about other vendors. Please report your findings if you try.

  • CRLF conversion is performed depending on the core.autocrlf setting, however Git for Windows by default stores that setting during installation in the "system wide" configuration file. If Git is not installed, use the global or repository configuration for the core.autocrlf setting.

  • The system wide configuration file is located relative to where C Git is installed. Make sure Git can be found via the PATH environment variable. When installing Git for Windows check the "Run Git from the Windows Command Prompt" option. There are other options like the jgit.gitprefix system propety or Eclipse settings that can be used for pointing out where C Git is installed. Modifying PATH is the recommended option if C Git is installed.

  • We try to use the same notation of $HOME as C Git does. On Windows this is often not same value as the user.home system property.

Package Features

  • org.eclipse.jgit/

    • Read loose and packed commits, trees, blobs, including deltafied objects.

    • Read objects from shared repositories

    • Write loose commits, trees, blobs.

    • Write blobs from local files or Java InputStreams.

    • Read blobs as Java InputStreams.

    • Copy trees to local directory, or local directory to a tree.

    • Lazily loads objects as necessary.

    • Read and write .git/config files.

    • Create a new repository.

    • Read and write refs, including walking through symrefs.

    • Read, update and write the Git index.

    • Checkout in dirty working directory if trivial.

    • Walk the history from a given set of commits looking for commits introducing changes in files under a specified path.

    • Object transport Fetch via ssh, git, http, Amazon S3 and bundles. Push via ssh, git and Amazon S3. JGit does not yet deltify the pushed packs so they may be a lot larger than C Git packs.

  • org.eclipse.jgit.pgm/

    • Assorted set of command line utilities. Mostly for ad-hoc testing of jgit log, glog, fetch etc.

Missing Features

There are some missing features:

  • gitattributes support

  • Recursive merge strategy

Support

Post question, comments or patches to the jgit-dev@eclipse.org mailing list. You need to be subscribed to post, see here:

https://dev.eclipse.org/mailman/listinfo/jgit-dev

Contributing

See the EGit Contributor Guide:

http://wiki.eclipse.org/EGit/Contributor_Guide

About Git

More information about Git, its repository format, and the canonical C based implementation can be obtained from the Git website:

http://git-scm.com/