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.
$ hg init t
$ cd t
$ echo 1 > a
$ hg ci -qAm "first"
$ hg cp a b
$ hg mv a c
$ echo 2 >> b
$ echo 2 >> c
$ hg ci -qAm "second"
$ hg co -C 0
1 files updated, 0 files merged, 2 files removed, 0 files unresolved
$ echo 0 > a
$ echo 1 >> a
$ hg ci -qAm "other"
$ hg merge --debug
searching for copies back to rev 1
unmatched files in other:
b
c
all copies found (* = to merge, ! = divergent, % = renamed and deleted):
src: 'a' -> dst: 'b' *
src: 'a' -> dst: 'c' *
checking for directory renames
resolving manifests
branchmerge: True, force: False, partial: False
ancestor: b8bf91eeebbc, local: add3f11052fa+, remote: 17c05bb7fcb6
preserving a for resolve of b
preserving a for resolve of c
removing a
b: remote moved from a -> m (premerge)
picked tool ':merge' for b (binary False symlink False changedelete False)
merging a and b to b
my b@add3f11052fa+ other b@17c05bb7fcb6 ancestor a@b8bf91eeebbc
premerge successful
c: remote moved from a -> m (premerge)
picked tool ':merge' for c (binary False symlink False changedelete False)
merging a and c to c
my c@add3f11052fa+ other c@17c05bb7fcb6 ancestor a@b8bf91eeebbc
premerge successful
0 files updated, 2 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
file b
$ cat b
0
1
2
file c
$ cat c
0
1
2
Test disabling copy tracing
- first verify copy metadata was kept
$ hg up -qC 2
$ hg rebase --keep -d 1 -b 2 --config extensions.rebase=
rebasing 2:add3f11052fa "other" (tip)
merging b and a to b
merging c and a to c
$ cat b
0
1
2
- next verify copy metadata is lost when disabled
$ hg strip -r . --config extensions.strip=
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
saved backup bundle to $TESTTMP/t/.hg/strip-backup/550bd84c0cd3-fc575957-backup.hg (glob)
$ hg up -qC 2
$ hg rebase --keep -d 1 -b 2 --config extensions.rebase= --config experimental.disablecopytrace=True --config ui.interactive=True << EOF
> c
> EOF
rebasing 2:add3f11052fa "other" (tip)
remote changed a which local deleted
use (c)hanged version, leave (d)eleted, or leave (u)nresolved? c
$ cat b
1
2
$ cd ..
Verify disabling copy tracing still keeps copies from rebase source
$ hg init copydisable
$ cd copydisable
$ touch a
$ hg ci -Aqm 'add a'
$ touch b
$ hg ci -Aqm 'add b, c'
$ hg cp b x
$ echo x >> x
$ hg ci -qm 'copy b->x'
$ hg up -q 1
$ touch z
$ hg ci -Aqm 'add z'
$ hg log -G -T '{rev} {desc}\n'
@ 3 add z
|
| o 2 copy b->x
|/
o 1 add b, c
|
o 0 add a
$ hg rebase -d . -b 2 --config extensions.rebase= --config experimental.disablecopytrace=True
rebasing 2:6adcf8c12e7d "copy b->x"
saved backup bundle to $TESTTMP/copydisable/.hg/strip-backup/6adcf8c12e7d-ce4b3e75-backup.hg (glob)
$ hg up -q 3
$ hg log -f x -T '{rev} {desc}\n'
3 copy b->x
1 add b, c
$ cd ../
Verify we duplicate existing copies, instead of detecting them
$ hg init copydisable3
$ cd copydisable3
$ touch a
$ hg ci -Aqm 'add a'
$ hg cp a b
$ hg ci -Aqm 'copy a->b'
$ hg mv b c
$ hg ci -Aqm 'move b->c'
$ hg up -q 0
$ hg cp a b
$ echo b >> b
$ hg ci -Aqm 'copy a->b (2)'
$ hg log -G -T '{rev} {desc}\n'
@ 3 copy a->b (2)
|
| o 2 move b->c
| |
| o 1 copy a->b
|/
o 0 add a
$ hg rebase -d 2 -s 3 --config extensions.rebase= --config experimental.disablecopytrace=True
rebasing 3:47e1a9e6273b "copy a->b (2)" (tip)
saved backup bundle to $TESTTMP/copydisable3/.hg/strip-backup/47e1a9e6273b-2d099c59-backup.hg (glob)
$ hg log -G -f b
@ changeset: 3:76024fb4b05b
| tag: tip
| user: test
| date: Thu Jan 01 00:00:00 1970 +0000
| summary: copy a->b (2)
|
o changeset: 0:ac82d8b1f7c4
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: add a