Mercurial > public > mercurial-scm > hg-stable
diff mercurial/hg.py @ 28289:d493d64757eb stable 3.7.2
hg: obtain lock when creating share from pooled repo (issue5104)
There are race conditions between clients performing a shared clone
to pooled storage:
1) Clients race to create the new shared repo in the pool directory
2) 1 client is seeding the repo in the pool directory and another goes
to share it before it is fully cloned
We prevent these race conditions by obtaining a lock in the pool
directory that is derived from the name of the repo we will be
accessing.
To test this, a simple generic "lockdelay" extension has been added.
The extension inserts an optional, configurable delay before or after
lock acquisition. In the test, we delay 2 seconds after lock acquisition
in the first process and 1 second before lock acquisition in the 2nd
process. This means the first process has 1s to obtain the lock. There
is a race condition here. If we encounter it in the wild, we could
change the dummy extension to wait on the lock file to appear instead
of relying on timing. But that's more complicated. Let's see what
happens first.
| author | Gregory Szorc <gregory.szorc@gmail.com> |
|---|---|
| date | Sat, 27 Feb 2016 18:22:49 -0800 |
| parents | b502138f5faa |
| children | 549ff28a345f a2c2dd399f3b |
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--- a/mercurial/hg.py Tue Mar 01 03:28:46 2016 +0900 +++ b/mercurial/hg.py Sat Feb 27 18:22:49 2016 -0800 @@ -335,17 +335,30 @@ "support clone by revision")) revs = [srcpeer.lookup(r) for r in rev] + # Obtain a lock before checking for or cloning the pooled repo otherwise + # 2 clients may race creating or populating it. + pooldir = os.path.dirname(sharepath) + # lock class requires the directory to exist. + try: + util.makedir(pooldir, False) + except OSError as e: + if e.errno != errno.EEXIST: + raise + + poolvfs = scmutil.vfs(pooldir) basename = os.path.basename(sharepath) - if os.path.exists(sharepath): - ui.status(_('(sharing from existing pooled repository %s)\n') % - basename) - else: - ui.status(_('(sharing from new pooled repository %s)\n') % basename) - # Always use pull mode because hardlinks in share mode don't work well. - # Never update because working copies aren't necessary in share mode. - clone(ui, peeropts, source, dest=sharepath, pull=True, - rev=rev, update=False, stream=stream) + with lock.lock(poolvfs, '%s.lock' % basename): + if os.path.exists(sharepath): + ui.status(_('(sharing from existing pooled repository %s)\n') % + basename) + else: + ui.status(_('(sharing from new pooled repository %s)\n') % basename) + # Always use pull mode because hardlinks in share mode don't work + # well. Never update because working copies aren't necessary in + # share mode. + clone(ui, peeropts, source, dest=sharepath, pull=True, + rev=rev, update=False, stream=stream) sharerepo = repository(ui, path=sharepath) share(ui, sharerepo, dest=dest, update=update, bookmarks=False)