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.
setup
$ cat >> $HGRCPATH <<EOF
> [extensions]
> blackbox=
> mock=$TESTDIR/mockblackbox.py
> mq=
> EOF
$ hg init blackboxtest
$ cd blackboxtest
command, exit codes, and duration
$ echo a > a
$ hg add a
$ hg blackbox
1970/01/01 00:00:00 bob (*)> add a (glob)
1970/01/01 00:00:00 bob (*)> add a exited 0 after * seconds (glob)
incoming change tracking
create two heads to verify that we only see one change in the log later
$ hg commit -ma
$ hg up null
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ echo b > b
$ hg commit -Amb
adding b
created new head
clone, commit, pull
$ hg clone . ../blackboxtest2
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ echo c > c
$ hg commit -Amc
adding c
$ cd ../blackboxtest2
$ hg pull
pulling from $TESTTMP/blackboxtest (glob)
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
(run 'hg update' to get a working copy)
$ hg blackbox -l 5
1970/01/01 00:00:00 bob (*)> pull (glob)
1970/01/01 00:00:00 bob (*)> updated served branch cache in ?.???? seconds (glob)
1970/01/01 00:00:00 bob (*)> wrote served branch cache with 1 labels and 2 nodes (glob)
1970/01/01 00:00:00 bob (*)> 1 incoming changes - new heads: d02f48003e62 (glob)
1970/01/01 00:00:00 bob (*)> pull exited 0 after * seconds (glob)
we must not cause a failure if we cannot write to the log
$ hg rollback
repository tip rolled back to revision 1 (undo pull)
#if unix-permissions no-root
$ chmod 000 .hg/blackbox.log
$ hg --debug incoming
warning: cannot write to blackbox.log: Permission denied
comparing with $TESTTMP/blackboxtest (glob)
query 1; heads
searching for changes
all local heads known remotely
changeset: 2:d02f48003e62c24e2659d97d30f2a83abe5d5d51
tag: tip
phase: draft
parent: 1:6563da9dcf87b1949716e38ff3e3dfaa3198eb06
parent: -1:0000000000000000000000000000000000000000
manifest: 2:ab9d46b053ebf45b7996f2922b9893ff4b63d892
user: test
date: Thu Jan 01 00:00:00 1970 +0000
files+: c
extra: branch=default
description:
c
#endif
$ hg pull
pulling from $TESTTMP/blackboxtest (glob)
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
(run 'hg update' to get a working copy)
a failure reading from the log is fine
#if unix-permissions no-root
$ hg blackbox -l 3
abort: Permission denied: $TESTTMP/blackboxtest2/.hg/blackbox.log
[255]
$ chmod 600 .hg/blackbox.log
#endif
backup bundles get logged
$ touch d
$ hg commit -Amd
adding d
created new head
$ hg strip tip
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
saved backup bundle to $TESTTMP/blackboxtest2/.hg/strip-backup/*-backup.hg (glob)
$ hg blackbox -l 5
1970/01/01 00:00:00 bob (*)> strip tip (glob)
1970/01/01 00:00:00 bob (*)> saved backup bundle to $TESTTMP/blackboxtest2/.hg/strip-backup/*-backup.hg (glob)
1970/01/01 00:00:00 bob (*)> updated base branch cache in ?.???? seconds (glob)
1970/01/01 00:00:00 bob (*)> wrote base branch cache with 1 labels and 2 nodes (glob)
1970/01/01 00:00:00 bob (*)> strip tip exited 0 after * seconds (glob)
extension and python hooks - use the eol extension for a pythonhook
$ echo '[extensions]' >> .hg/hgrc
$ echo 'eol=' >> .hg/hgrc
$ echo '[hooks]' >> .hg/hgrc
$ echo 'update = echo hooked' >> .hg/hgrc
$ hg update
hooked
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg blackbox -l 5
1970/01/01 00:00:00 bob (*)> update (glob)
1970/01/01 00:00:00 bob (*)> writing .hg/cache/tags2-visible with 0 tags (glob)
1970/01/01 00:00:00 bob (*)> pythonhook-preupdate: hgext.eol.preupdate finished in * seconds (glob)
1970/01/01 00:00:00 bob (*)> exthook-update: echo hooked finished in * seconds (glob)
1970/01/01 00:00:00 bob (*)> update exited 0 after * seconds (glob)
log rotation
$ echo '[blackbox]' >> .hg/hgrc
$ echo 'maxsize = 20 b' >> .hg/hgrc
$ echo 'maxfiles = 3' >> .hg/hgrc
$ hg status
$ hg status
$ hg status
$ hg tip -q
2:d02f48003e62
$ ls .hg/blackbox.log*
.hg/blackbox.log
.hg/blackbox.log.1
.hg/blackbox.log.2
cleanup
$ cd ..