Mercurial > hg
view tests/test-mq-qpush-fail.t @ 26623:5a95fe44121d
clonebundles: support for seeding clones from pre-generated bundles
Cloning can be an expensive operation for servers because the server
generates a bundle from existing repository data at request time. For
a large repository like mozilla-central, this consumes 4+ minutes
of CPU time on the server. It also results in significant network
utilization. Multiplied by hundreds or even thousands of clients and
the ensuing load can result in difficulties scaling the Mercurial server.
Despite generation of bundles being deterministic until the next
changeset is added, the generation of bundles to service a clone request
is not cached. Each clone thus performs redundant work. This is
wasteful.
This patch introduces the "clonebundles" extension and related
client-side functionality to help alleviate this deficiency. The
client-side feature is behind an experimental flag and is not enabled by
default.
It works as follows:
1) Server operator generates a bundle and makes it available on a
server (likely HTTP).
2) Server operator defines the URL of a bundle file in a
.hg/clonebundles.manifest file.
3) Client `hg clone`ing sees the server is advertising bundle URLs.
4) Client fetches and applies the advertised bundle.
5) Client performs equivalent of `hg pull` to fetch changes made since
the bundle was created.
Essentially, the server performs the expensive work of generating a
bundle once and all subsequent clones fetch a static file from
somewhere. Scaling static file serving is a much more manageable
problem than scaling a Python application like Mercurial. Assuming your
repository grows less than 1% per day, the end result is 99+% of CPU
and network load from clones is eliminated, allowing Mercurial servers
to scale more easily. Serving static files also means data can be
transferred to clients as fast as they can consume it, rather than as
fast as servers can generate it. This makes clones faster.
Mozilla has implemented similar functionality of this patch on
hg.mozilla.org using a custom extension. We are hosting bundle files in
Amazon S3 and CloudFront (a CDN) and have successfully offloaded
>1 TB/day in data transfer from hg.mozilla.org, freeing up significant
bandwidth and CPU resources. The positive impact has been stellar and
I believe it has proved its value to be included in Mercurial core. I
feel it is important for the client-side support to be enabled in core
by default because it means that clients will get faster, more reliable
clones and will enable server operators to reduce load without
requiring any client-side configuration changes (assuming clients are
up to date, of course).
The scope of this feature is narrowly and specifically tailored to
cloning, despite "serve pulls from pre-generated bundles" being a valid
and useful feature. I would eventually like for Mercurial servers to
support transferring *all* repository data via statically hosted files.
You could imagine a server that siphons all pushed data to bundle files
and instructs clients to apply a stream of bundles to reconstruct all
repository data. This feature, while useful and powerful, is
significantly more work to implement because it requires the server
component have awareness of discovery and a mapping of which changesets
are in which files. Full, clone bundles, by contrast, are much simpler.
The wire protocol command is named "clonebundles" instead of something
more generic like "staticbundles" to leave the door open for a new, more
powerful and more generic server-side component with minimal backwards
compatibility implications. The name "bundleclone" is used by Mozilla's
extension and would cause problems since there are subtle differences
in Mozilla's extension.
Mozilla's experience with this idea has taught us that some form of
"content negotiation" is required. Not all clients will support all
bundle formats or even URLs (advanced TLS requirements, etc). To ensure
the highest uptake possible, a server needs to advertise multiple
versions of bundles and clients need to be able to choose the most
appropriate from that list one. The "attributes" in each
server-advertised entry facilitate this filtering and sorting. Their
use will become apparent in subsequent patches.
Initial inspiration and credit for the idea of cloning from static files
belongs to Augie Fackler and his "lookaside clone" extension proof of
concept.
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Fri, 09 Oct 2015 11:22:01 -0700 |
parents | 7df090c9c9fe |
children | 30657909b2ba |
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Test that qpush cleans things up if it doesn't complete $ echo "[extensions]" >> $HGRCPATH $ echo "mq=" >> $HGRCPATH $ hg init repo $ cd repo $ echo foo > foo $ hg ci -Am 'add foo' adding foo $ touch untracked-file $ echo 'syntax: glob' > .hgignore $ echo '.hgignore' >> .hgignore $ hg qinit test qpush on empty series $ hg qpush no patches in series $ hg qnew patch1 $ echo >> foo $ hg qrefresh -m 'patch 1' $ hg qnew patch2 $ echo bar > bar $ hg add bar $ hg qrefresh -m 'patch 2' $ hg qnew --config 'mq.plain=true' -U bad-patch $ echo >> foo $ hg qrefresh $ hg qpop -a popping bad-patch popping patch2 popping patch1 patch queue now empty $ $PYTHON -c 'print "\xe9"' > message $ cat .hg/patches/bad-patch >> message $ mv message .hg/patches/bad-patch $ cat > $TESTTMP/wrapplayback.py <<EOF > import os > from mercurial import extensions, transaction > def wrapplayback(orig, > journal, report, opener, vfsmap, entries, backupentries, > unlink=True): > orig(journal, report, opener, vfsmap, entries, backupentries, unlink) > # Touching files truncated at "transaction.abort" causes > # forcible re-loading invalidated filecache properties > # (including repo.changelog) > for f, o, _ignore in entries: > if o or not unlink: > os.utime(opener.join(f), (0.0, 0.0)) > def extsetup(ui): > extensions.wrapfunction(transaction, '_playback', wrapplayback) > EOF $ hg qpush -a --config extensions.wrapplayback=$TESTTMP/wrapplayback.py && echo 'qpush succeeded?!' applying patch1 applying patch2 applying bad-patch transaction abort! rollback completed cleaning up working directory...done abort: decoding near '\xe9': 'ascii' codec can't decode byte 0xe9 in position 0: ordinal not in range(128)! (esc) [255] $ hg parents changeset: 0:bbd179dfa0a7 tag: tip user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: add foo test corrupt status file $ hg qpush applying patch1 now at: patch1 $ cp .hg/patches/status .hg/patches/status.orig $ hg qpop popping patch1 patch queue now empty $ cp .hg/patches/status.orig .hg/patches/status $ hg qpush abort: working directory revision is not qtip [255] $ rm .hg/patches/status .hg/patches/status.orig bar should be gone; other unknown/ignored files should still be around $ hg status -A ? untracked-file I .hgignore C foo preparing qpush of a missing patch $ hg qpop -a no patches applied $ hg qpush applying patch1 now at: patch1 $ rm .hg/patches/patch2 now we expect the push to fail, but it should NOT complain about patch1 $ hg qpush applying patch2 unable to read patch2 now at: patch1 [1] preparing qpush of missing patch with no patch applied $ hg qpop -a popping patch1 patch queue now empty $ rm .hg/patches/patch1 qpush should fail the same way as below $ hg qpush applying patch1 unable to read patch1 [1] Test qpush to a patch below the currently applied patch. $ hg qq -c guardedseriesorder $ hg qnew a $ hg qguard +block $ hg qnew b $ hg qnew c $ hg qpop -a popping c popping b popping a patch queue now empty try to push and pop while a is guarded $ hg qpush a cannot push 'a' - guarded by '+block' [1] $ hg qpush -a applying b patch b is empty applying c patch c is empty now at: c now try it when a is unguarded, and we're at the top of the queue $ hg qapplied -v 0 G a 1 A b 2 A c $ hg qsel block $ hg qpush b abort: cannot push to a previous patch: b [255] $ hg qpush a abort: cannot push to a previous patch: a [255] and now we try it one more time with a unguarded, while we're not at the top of the queue $ hg qpop b popping c now at: b $ hg qpush a abort: cannot push to a previous patch: a [255] test qpop --force and backup files $ hg qpop -a popping b patch queue now empty $ hg qq --create force $ echo a > a $ echo b > b $ echo c > c $ hg ci -Am add a b c $ echo a >> a $ hg rm b $ hg rm c $ hg qnew p1 $ echo a >> a $ echo bb > b $ hg add b $ echo cc > c $ hg add c $ hg qpop --force --verbose saving current version of a as a.orig saving current version of b as b.orig saving current version of c as c.orig popping p1 patch queue now empty $ hg st ? a.orig ? b.orig ? c.orig ? untracked-file $ cat a.orig a a a $ cat b.orig bb $ cat c.orig cc test qpop --force --no-backup $ hg qpush applying p1 now at: p1 $ rm a.orig $ echo a >> a $ hg qpop --force --no-backup --verbose popping p1 patch queue now empty $ test -f a.orig && echo 'error: backup with --no-backup' [1] test qpop --keep-changes $ hg qpush applying p1 now at: p1 $ hg qpop --keep-changes --force abort: cannot use both --force and --keep-changes [255] $ echo a >> a $ hg qpop --keep-changes abort: local changes found, refresh first [255] $ hg revert -qa a $ rm a $ hg qpop --keep-changes abort: local changes found, refresh first [255] $ hg rm -A a $ hg qpop --keep-changes abort: local changes found, refresh first [255] $ hg revert -qa a $ echo b > b $ hg add b $ hg qpop --keep-changes abort: local changes found, refresh first [255] $ hg forget b $ echo d > d $ hg add d $ hg qpop --keep-changes popping p1 patch queue now empty $ hg forget d $ rm d test qpush --force and backup files $ echo a >> a $ hg qnew p2 $ echo b >> b $ echo d > d $ echo e > e $ hg add d e $ hg rm c $ hg qnew p3 $ hg qpop -a popping p3 popping p2 patch queue now empty $ echo a >> a $ echo b1 >> b $ echo d1 > d $ hg add d $ echo e1 > e $ hg qpush -a --force --verbose applying p2 saving current version of a as a.orig patching file a committing files: a committing manifest committing changelog applying p3 saving current version of b as b.orig saving current version of d as d.orig patching file b patching file c patching file d file d already exists 1 out of 1 hunks FAILED -- saving rejects to file d.rej patching file e file e already exists 1 out of 1 hunks FAILED -- saving rejects to file e.rej patch failed to apply committing files: b committing manifest committing changelog patch failed, rejects left in working directory errors during apply, please fix and refresh p3 [2] $ cat a.orig a a $ cat b.orig b b1 $ cat d.orig d1 test qpush --force --no-backup $ hg revert -qa $ hg qpop -a popping p3 popping p2 patch queue now empty $ echo a >> a $ rm a.orig $ hg qpush --force --no-backup --verbose applying p2 patching file a committing files: a committing manifest committing changelog now at: p2 $ test -f a.orig && echo 'error: backup with --no-backup' [1] test qgoto --force --no-backup $ hg qpop popping p2 patch queue now empty $ echo a >> a $ hg qgoto --force --no-backup p2 --verbose applying p2 patching file a committing files: a committing manifest committing changelog now at: p2 $ test -f a.orig && echo 'error: backup with --no-backup' [1] test qpush --keep-changes $ hg qpush --keep-changes --force abort: cannot use both --force and --keep-changes [255] $ hg qpush --keep-changes --exact abort: cannot use --exact and --keep-changes together [255] $ echo b >> b $ hg qpush --keep-changes applying p3 abort: conflicting local changes found (did you forget to qrefresh?) [255] $ rm b $ hg qpush --keep-changes applying p3 abort: conflicting local changes found (did you forget to qrefresh?) [255] $ hg rm -A b $ hg qpush --keep-changes applying p3 abort: conflicting local changes found (did you forget to qrefresh?) [255] $ hg revert -aq b $ echo d > d $ hg add d $ hg qpush --keep-changes applying p3 abort: conflicting local changes found (did you forget to qrefresh?) [255] $ hg forget d $ rm d $ hg qpop popping p2 patch queue now empty $ echo b >> b $ hg qpush -a --keep-changes applying p2 applying p3 abort: conflicting local changes found (did you forget to qrefresh?) [255] $ hg qtop p2 $ hg parents --template "{rev} {desc}\n" 2 imported patch p2 $ hg st b M b $ cat b b b test qgoto --keep-changes $ hg revert -aq b $ rm e $ hg qgoto --keep-changes --force p3 abort: cannot use both --force and --keep-changes [255] $ echo a >> a $ hg qgoto --keep-changes p3 applying p3 now at: p3 $ hg st a M a $ hg qgoto --keep-changes p2 popping p3 now at: p2 $ hg st a M a test mq.keepchanges setting $ hg --config mq.keepchanges=1 qpush applying p3 now at: p3 $ hg st a M a $ hg --config mq.keepchanges=1 qpop popping p3 now at: p2 $ hg st a M a $ hg --config mq.keepchanges=1 qgoto p3 applying p3 now at: p3 $ hg st a M a $ echo b >> b $ hg --config mq.keepchanges=1 qpop --force popping p3 now at: p2 $ hg st b $ hg --config mq.keepchanges=1 qpush --exact abort: local changes found, refresh first [255] $ hg revert -qa a $ hg qpop popping p2 patch queue now empty $ echo a >> a $ hg --config mq.keepchanges=1 qpush --force applying p2 now at: p2 $ hg st a $ cd ..