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Git index locking problem [message #1727357]

Tue, 22 March 2016 12:05

Radek Jakubowski

Messages: 6
Registered: October 2015

Junior Member

Hi!
My scenario in my java program is the following:
1. Two users in parallel commit a file and doing a push.
2. Method is synchronized.
3. Code:

synchronized(getSynchroForRepo(rootRepoDir)) {
            File file = new File(rootRepoDir, listDefinitionName);
            writeFile(file, xmlDef.getBytes());
    		try {
    			git.add().addFilepattern(listDefinitionName).call();
    			CommitCommand commit = git.commit();
    			commit.setMessage("Commit file: "+listDefinitionName).call();
    			GitPush();
    		}

Unfortunately I get the exception (addFilepattern line above):
org.eclipse.jgit.api.errors.JGitInternalException: Exception caught during execution of add command
at org.eclipse.jgit.api.AddCommand.call(AddCommand.java:242)
...
Caused by: org.eclipse.jgit.errors.LockFailedException: Cannot lock C:\RepoGit\.git\index
at org.eclipse.jgit.dircache.DirCache.lock(DirCache.java:250)
at org.eclipse.jgit.dircache.DirCache.lock(DirCache.java:327)
at org.eclipse.jgit.dircache.DirCache.lock(DirCache.java:293)
at org.eclipse.jgit.lib.Repository.lockDirCache(Repository.java:1158)
at org.eclipse.jgit.api.AddCommand.call(AddCommand.java:147)
... 30 more

If anybody had any idea what I'm doing wrong I'd appreciate it!

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Re: Git index locking problem [message #1727505 is a reply to message #1727357]

Wed, 23 March 2016 11:58

Radek Jakubowski

Messages: 6
Registered: October 2015

Junior Member

I think I found a solution. I had different methods for repo access like storeFile(), removeFile(), getFile() etc.
Each method was synchronized with different key. After changing so all store/remove methods use the same synchronization key, so far my tests don't show any problems.

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Re: Git index locking problem [message #1729407 is a reply to message #1727505]

Wed, 13 April 2016 22:00

Matthias Sohn

Messages: 1095
Registered: July 2009

Senior Member

The DirCache (aka git index) can only be locked once.
So all operations working on a working tree needing a locked index can't run concurrently.
The straight forward solution is to use one clone per user, as soon as support for git worktree is available in jgit
this could also help. With that each user would need a separate worktree (sharing the same .git object database) and git index.
Unfortunately worktree support isn't yet available in jgit.

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