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.

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 ..