concurrent access problems

[ExtraHop Networks]

There appear to be problems with bzr-svn and concurrent access. If another checkin occurs while the user is typing a commit message in the editor, bzr-svn will overwrite the other checkin rather than fail with an out-of-date error. The out-of-date check seems to occur before the editor is invoked, but not again afterwards.

Repro:

* Create a test svn repository and project:
  $ svnadmin create /var/tmp/svn
  $ mkdir test
  $ echo "test file" > test/test.txt
  $ svn import -m "test project" test file:///var/tmp/svn/test

* Check out the svn project to a working directory:
  $ svn co file:///var/tmp/svn/test

* Create a bazaar repository and checkout the test project:
  $ bzr init-repo --rich-root-pack /var/tmp/bzr
  $ bzr co file:///var/tmp/svn/test /var/tmp/bzr/test

* Checkin a change from bazaar but remain in the editor:
  $ cd /var/tmp/bzr/test
  $ echo "change from bazaar" >> test.txt
  $ bzr commit

* Sneak in a change to the test project from another shell:
  $ echo "change from subversion" >> test.txt
  $ svn commit -m "change from subversion" test.txt

* Return to the editor in the bazaar session and complete the commit. Notice
  that there are no out-of-date complaints. The change from subversion is
  no longer present on HEAD and revision 2 is missing in the svn log.

We are using bzr 1.5 and bzr-svn 0.4.10 with the stock packages for
python and python-subversion from Ubuntu 8.04.

[nicholas a. evans (nevans)]

I've also been experiencing this issue. I hadn't noticed it until just recently, and when I looked back through the logs, it first occurred for me six months ago (01/23/08), and it's also occured with bzr 1.5 and bzr-svn 0.4.10.

[Jelmer Vernooij (jelmer)]

The unfortunate thing is that subversion doesn't allow locking of directories; it does allow locking of files.

[Jelmer Vernooij (jelmer)]

This requires a fix in bzr first. In bzrlib.commit it should call something less generic than repository.fetch() followed by master_branch.set_last_revision() to pull the revision into the master branch.

[CodyC (cody-casterline)]

First, a note: Reproducing this bug is currently blocked by https://bugs.launchpad.net/bzr/+bug/293440

Second:
Instead of acquiring a lock on a directory while a user writes a commit message (since SVN doesn't allow it), what about just moving the out-of-date check to happen after the user supplies the commit message? It's not foolproof, but it reduces the time between check & push, and the likelyhood of the above issue arising.

[Jelmer Vernooij (jelmer)]

That would require changes in bzrlib as well. It also doesn't help with push.

[Jelmer Vernooij (jelmer)]

I've submitted the required changes for bzr to the mailing list:

http://bundlebuggy.aaronbentley.com/project/bzr/request/%3C20090211150929.D9B03574FA%40charis.vernstok.nl.vernstok.nl%3E

[Jelmer Vernooij (jelmer)]

merged now