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.
#require darcs
$ echo "[extensions]" >> $HGRCPATH
$ echo "convert=" >> $HGRCPATH
$ DARCS_EMAIL='test@example.org'; export DARCS_EMAIL
initialize darcs repo
$ mkdir darcs-repo
$ cd darcs-repo
$ darcs init
$ echo a > a
$ darcs record -a -l -m p0
Finished recording patch 'p0'
$ cd ..
branch and update
$ darcs get -q darcs-repo darcs-clone >/dev/null
$ cd darcs-clone
$ echo c >> a
$ echo c > c
$ darcs record -a -l -m p1.1
Finished recording patch 'p1.1'
$ cd ..
skip if we can't import elementtree
$ if hg convert darcs-repo darcs-dummy 2>&1 | grep ElementTree > /dev/null; then
> echo 'skipped: missing feature: elementtree module'
> exit 80
> fi
update source
$ cd darcs-repo
$ echo b >> a
$ echo b > b
$ darcs record -a -l -m p1.2
Finished recording patch 'p1.2'
$ darcs pull -q -a --no-set-default ../darcs-clone
Backing up ./a(*) (glob)
We have conflicts in the following files:
./a
$ sleep 1
$ echo e > a
$ echo f > f
$ mkdir dir
$ echo d > dir/d
$ echo d > dir/d2
$ darcs record -a -l -m p2
Finished recording patch 'p2'
test file and directory move
$ darcs mv f ff
Test remove + move
$ darcs remove dir/d2
$ rm dir/d2
$ darcs mv dir dir2
$ darcs record -a -l -m p3
Finished recording patch 'p3'
The converter does not currently handle patch conflicts very well.
When they occur, it reverts *all* changes and moves forward,
letting the conflict resolving patch fix collisions.
Unfortunately, non-conflicting changes, like the addition of the
"c" file in p1.1 patch are reverted too.
Just to say that manifest not listing "c" here is a bug.
$ cd ..
$ hg convert darcs-repo darcs-repo-hg
initializing destination darcs-repo-hg repository
scanning source...
sorting...
converting...
4 p0
3 p1.2
2 p1.1
1 p2
0 p3
$ hg log -R darcs-repo-hg -g --template '{rev} "{desc|firstline}" ({author}) files: {files}\n' "$@"
4 "p3" (test@example.org) files: dir/d dir/d2 dir2/d f ff
3 "p2" (test@example.org) files: a dir/d dir/d2 f
2 "p1.1" (test@example.org) files:
1 "p1.2" (test@example.org) files: a b
0 "p0" (test@example.org) files: a
$ hg up -q -R darcs-repo-hg
$ hg -R darcs-repo-hg manifest --debug
7225b30cdf38257d5cc7780772c051b6f33e6d6b 644 a
1e88685f5ddec574a34c70af492f95b6debc8741 644 b
37406831adc447ec2385014019599dfec953c806 644 dir2/d
b783a337463792a5c7d548ad85a7d3253c16ba8c 644 ff
#if no-outer-repo
try converting darcs1 repository
$ hg clone -q "$TESTDIR/bundles/darcs1.hg" darcs
$ hg convert -s darcs darcs/darcs1 2>&1 | grep darcs-1.0
darcs-1.0 repository format is unsupported, please upgrade
#endif