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.
Test adding .hgeol
$ cat >> $HGRCPATH <<EOF
> [diff]
> git = 1
> EOF
$ seteol () {
> if [ $1 = "LF" ]; then
> EOL='\n'
> else
> EOL='\r\n'
> fi
> }
$ makerepo () {
> echo
> echo "# ==== setup repository ===="
> echo '% hg init'
> hg init repo
> cd repo
> printf "first\nsecond\nthird\n" > a.txt
> hg commit -d '100 0' --addremove -m 'LF commit'
> cd ..
> }
$ dotest () {
> seteol $1
> echo
> echo "% hg clone repo repo-$1"
> hg clone repo repo-$1
> cd repo-$1
> cat > .hg/hgrc <<EOF
> [extensions]
> eol =
> [eol]
> native = LF
> EOF
> cat > .hgeol <<EOF
> [patterns]
> **.txt = native
> [repository]
> native = $1
> EOF
> echo '% hg add .hgeol'
> hg add .hgeol
> echo '% hg status'
> hg status
> echo '% hg commit'
> hg commit -d '200 0' -m 'Added .hgeol file'
> echo '% hg status'
> hg status
> echo '% hg tip -p'
> hg tip -p
> cd ..
> rm -r repo-$1
> }
$ makerepo
# ==== setup repository ====
% hg init
adding a.txt
$ dotest LF
% hg clone repo repo-LF
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
% hg add .hgeol
% hg status
A .hgeol
% hg commit
% hg status
% hg tip -p
changeset: 1:33503edb53b0
tag: tip
user: test
date: Thu Jan 01 00:03:20 1970 +0000
summary: Added .hgeol file
diff --git a/.hgeol b/.hgeol
new file mode 100644
--- /dev/null
+++ b/.hgeol
@@ -0,0 +1,4 @@
+[patterns]
+**.txt = native
+[repository]
+native = LF
$ dotest CRLF
% hg clone repo repo-CRLF
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
% hg add .hgeol
% hg status
M a.txt
A .hgeol
% hg commit
% hg status
% hg tip -p
changeset: 1:6e64eaa9eb23
tag: tip
user: test
date: Thu Jan 01 00:03:20 1970 +0000
summary: Added .hgeol file
diff --git a/.hgeol b/.hgeol
new file mode 100644
--- /dev/null
+++ b/.hgeol
@@ -0,0 +1,4 @@
+[patterns]
+**.txt = native
+[repository]
+native = CRLF
diff --git a/a.txt b/a.txt
--- a/a.txt
+++ b/a.txt
@@ -1,3 +1,3 @@
-first
-second
-third
+first\r (esc)
+second\r (esc)
+third\r (esc)
$ rm -r repo