branchcache: skip entries that are topological heads in the on disk file
In the majority of cases, topological heads are also branch heads. We have
efficient way to get the topological heads and efficient way to retrieve
their branch information. So there is little value in putting them in the branch
cache file explicitly. On the contrary, writing them explicitly tend to create
very large cache file that are inefficient to read and update.
So the branch cache v3 format is no longer including them. This changeset focus
on the format aspect and have no focus on the performance aspect. We will cover
that later.
#testcases skip-detection fail-if-detected
Test situations that "should" only be reproducible:
- on networked filesystems, or
- user using `hg debuglocks` to eliminate the lock file, or
- something (that doesn't respect the lock file) writing to the .hg directory
while we're running
Initial setup
-------------
$ hg init base-repo
$ cd base-repo
$ cat > "$TESTTMP_FORWARD_SLASH/waitlock_editor.sh" <<EOF
> [ -n "\${WAITLOCK_ANNOUNCE:-}" ] && touch "\${WAITLOCK_ANNOUNCE}"
> f="\${WAITLOCK_FILE}"
> start=\`date +%s\`
> timeout=5
> "$RUNTESTDIR_FORWARD_SLASH/testlib/wait-on-file" "\$timeout" "\$f"
> if [ \$# -gt 1 ]; then
> cat "\$@"
> fi
> EOF
Things behave differently if we don't already have a 00changelog.i file when
this all starts, so let's make one.
$ echo r0 > r0
$ hg commit -qAm 'r0'
$ cd ..
$ cp -R base-repo main-client
$ cp -R base-repo racing-client
$ mkdir sync
$ EDITOR_STARTED="$TESTTMP_FORWARD_SLASH/sync/.editor_started"
$ MISCHIEF_MANAGED="$TESTTMP_FORWARD_SLASH/sync/.mischief_managed"
$ JOBS_FINISHED="$TESTTMP_FORWARD_SLASH/sync/.jobs_finished"
Actual test
-----------
Start an hg commit that will take a while
$ cd main-client
#if fail-if-detected
$ cat >> $HGRCPATH << EOF
> [debug]
> revlog.verifyposition.changelog = fail
> EOF
#endif
$ echo foo > foo
$ (
> unset HGEDITOR;
> WAITLOCK_ANNOUNCE="${EDITOR_STARTED}" \
> WAITLOCK_FILE="${MISCHIEF_MANAGED}" \
> hg commit -qAm 'r1 (foo)' --edit foo \
> --config ui.editor="sh $TESTTMP_FORWARD_SLASH/waitlock_editor.sh" \
> > .foo_commit_out 2>&1 ;\
> touch "${JOBS_FINISHED}"
> ) &
Wait for the "editor" to actually start
$ sh "$RUNTESTDIR_FORWARD_SLASH/testlib/wait-on-file" 5 "${EDITOR_STARTED}"
Do a concurrent edition
$ cd ../racing-client
$ touch ../pre-race
$ sleep 1
$ echo bar > bar
$ hg --repository ../racing-client commit -qAm 'r2 (bar)' bar
$ hg --repository ../racing-client debugrevlogindex -c
rev linkrev nodeid p1 p2
0 0 222799e2f90b 000000000000 000000000000
1 1 6f124f6007a0 222799e2f90b 000000000000
We simulate an network FS race by overwriting raced repo content with the new
content of the files changed in the racing repository
$ for x in `find . -type f -newer ../pre-race`; do
> cp $x ../main-client/$x
> done
$ cd ../main-client
Awaken the editor from that first commit
$ touch "${MISCHIEF_MANAGED}"
And wait for it to finish
$ WAITLOCK_FILE="${JOBS_FINISHED}" sh "$TESTTMP_FORWARD_SLASH/waitlock_editor.sh"
#if skip-detection
(Ensure there was no output)
$ cat .foo_commit_out
And observe a corrupted repository -- rev 2's linkrev is 1, which should never
happen for the changelog (the linkrev should always refer to itself).
$ hg debugrevlogindex -c
rev linkrev nodeid p1 p2
0 0 222799e2f90b 000000000000 000000000000
1 1 6f124f6007a0 222799e2f90b 000000000000
2 1 ac80e6205bb2 222799e2f90b 000000000000
#endif
#if fail-if-detected
$ cat .foo_commit_out
note: commit message saved in .hg/last-message.txt
note: use 'hg commit --logfile .hg/last-message.txt --edit' to reuse it
transaction abort!
rollback completed
abort: 00changelog.i: file cursor at position 128, expected 64
And no corruption in the changelog.
$ hg debugrevlogindex -c
rev linkrev nodeid p1 p2
0 0 222799e2f90b 000000000000 000000000000
1 1 6f124f6007a0 222799e2f90b 000000000000 (missing-correct-output !)
And, because of transactions, there's none in the manifestlog either.
$ hg debugrevlogindex -m
rev linkrev nodeid p1 p2
0 0 7b7020262a56 000000000000 000000000000
1 1 ad3fe36d86d9 7b7020262a56 000000000000
#endif