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 killdaemons
Preparing the subrepository 'sub'
$ hg init sub
$ echo sub > sub/sub
$ hg add -R sub
adding sub/sub (glob)
$ hg commit -R sub -m "sub import"
Preparing the 'main' repo which depends on the subrepo 'sub'
$ hg init main
$ echo main > main/main
$ echo "sub = ../sub" > main/.hgsub
$ hg clone sub main/sub
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg add -R main
adding main/.hgsub (glob)
adding main/main (glob)
$ hg commit -R main -m "main import"
Cleaning both repositories, just as a clone -U
$ hg up -C -R sub null
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ hg up -C -R main null
0 files updated, 0 files merged, 3 files removed, 0 files unresolved
$ rm -rf main/sub
hide outer repo
$ hg init
Serving them both using hgweb
$ printf '[paths]\n/main = main\nsub = sub\n' > webdir.conf
$ hg serve --webdir-conf webdir.conf -a localhost -p $HGPORT \
> -A /dev/null -E /dev/null --pid-file hg.pid -d
$ cat hg.pid >> $DAEMON_PIDS
Clone main from hgweb
$ hg clone "http://localhost:$HGPORT/main" cloned
requesting all changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 3 changes to 3 files
updating to branch default
cloning subrepo sub from http://localhost:$HGPORT/sub
requesting all changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
3 files updated, 0 files merged, 0 files removed, 0 files unresolved
Checking cloned repo ids
$ hg id -R cloned
fdfeeb3e979e tip
$ hg id -R cloned/sub
863c1745b441 tip
subrepo debug for 'main' clone
$ hg debugsub -R cloned
path sub
source ../sub
revision 863c1745b441bd97a8c4a096e87793073f4fb215
$ killdaemons.py
subrepo paths with ssh urls
$ hg clone -e "python \"$TESTDIR/dummyssh\"" ssh://user@dummy/cloned sshclone
requesting all changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 3 changes to 3 files
updating to branch default
cloning subrepo sub from ssh://user@dummy/sub
requesting all changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
3 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg -R sshclone push -e "python \"$TESTDIR/dummyssh\"" ssh://user@dummy/`pwd`/cloned
pushing to ssh://user@dummy/$TESTTMP/cloned
pushing subrepo sub to ssh://user@dummy/$TESTTMP/sub
searching for changes
no changes found
searching for changes
no changes found
[1]
$ cat dummylog
Got arguments 1:user@dummy 2:hg -R cloned serve --stdio
Got arguments 1:user@dummy 2:hg -R sub serve --stdio
Got arguments 1:user@dummy 2:hg -R $TESTTMP/cloned serve --stdio
Got arguments 1:user@dummy 2:hg -R $TESTTMP/sub serve --stdio