view tests/test-backout.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.

  $ hg init basic
  $ cd basic

should complain

  $ hg backout
  abort: please specify a revision to backout
  [255]
  $ hg backout -r 0 0
  abort: please specify just one revision
  [255]

basic operation
(this also tests that editor is invoked if the commit message is not
specified explicitly)

  $ echo a > a
  $ hg commit -d '0 0' -A -m a
  adding a
  $ echo b >> a
  $ hg commit -d '1 0' -m b

  $ hg status --rev tip --rev "tip^1"
  M a
  $ HGEDITOR=cat hg backout -d '2 0' tip --tool=true
  reverting a
  Backed out changeset a820f4f40a57
  
  
  HG: Enter commit message.  Lines beginning with 'HG:' are removed.
  HG: Leave message empty to abort commit.
  HG: --
  HG: user: test
  HG: branch 'default'
  HG: changed a
  changeset 2:2929462c3dff backs out changeset 1:a820f4f40a57
  $ cat a
  a
  $ hg summary
  parent: 2:2929462c3dff tip
   Backed out changeset a820f4f40a57
  branch: default
  commit: (clean)
  update: (current)
  phases: 3 draft

commit option

  $ cd ..
  $ hg init commit
  $ cd commit

  $ echo tomatoes > a
  $ hg add a
  $ hg commit -d '0 0' -m tomatoes

  $ echo chair > b
  $ hg add b
  $ hg commit -d '1 0' -m chair

  $ echo grapes >> a
  $ hg commit -d '2 0' -m grapes

  $ hg backout --commit -d '4 0' 1 --tool=:fail
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  changeset 3:1c2161e97c0a backs out changeset 1:22cb4f70d813
  $ hg summary
  parent: 3:1c2161e97c0a tip
   Backed out changeset 22cb4f70d813
  branch: default
  commit: (clean)
  update: (current)
  phases: 4 draft

  $ echo ypples > a
  $ hg commit -d '5 0' -m ypples

  $ hg backout --commit -d '6 0' 2 --tool=:fail
  0 files updated, 0 files merged, 0 files removed, 1 files unresolved
  use 'hg resolve' to retry unresolved file merges
  [1]
  $ hg summary
  parent: 4:ed99997b793d tip
   ypples
  branch: default
  commit: 1 unresolved (clean)
  update: (current)
  phases: 5 draft

file that was removed is recreated
(this also tests that editor is not invoked if the commit message is
specified explicitly)

  $ cd ..
  $ hg init remove
  $ cd remove

  $ echo content > a
  $ hg commit -d '0 0' -A -m a
  adding a

  $ hg rm a
  $ hg commit -d '1 0' -m b

  $ HGEDITOR=cat hg backout -d '2 0' tip --tool=true -m "Backed out changeset 76862dcce372"
  adding a
  changeset 2:de31bdc76c0d backs out changeset 1:76862dcce372
  $ cat a
  content
  $ hg summary
  parent: 2:de31bdc76c0d tip
   Backed out changeset 76862dcce372
  branch: default
  commit: (clean)
  update: (current)
  phases: 3 draft

backout of backout is as if nothing happened

  $ hg backout -d '3 0' --merge tip --tool=true
  removing a
  changeset 3:7f6d0f120113 backs out changeset 2:de31bdc76c0d
  $ test -f a
  [1]
  $ hg summary
  parent: 3:7f6d0f120113 tip
   Backed out changeset de31bdc76c0d
  branch: default
  commit: (clean)
  update: (current)
  phases: 4 draft

Test that 'hg rollback' restores dirstate just before opening
transaction: in-memory dirstate changes should be written into
'.hg/journal.dirstate' as expected.

  $ echo 'removed soon' > b
  $ hg commit -A -d '4 0' -m 'prepare for subsequent removing'
  adding b
  $ echo 'newly added' > c
  $ hg add c
  $ hg remove b
  $ hg commit -d '5 0' -m 'prepare for subsequent backout'
  $ touch -t 200001010000 c
  $ hg status -A
  C c
  $ hg debugstate --nodates
  n 644         12 set                 c
  $ hg backout -d '6 0' -m 'to be rollback-ed soon' -r .
  adding b
  removing c
  changeset 6:4bfec048029d backs out changeset 5:fac0b729a654
  $ hg rollback -q
  $ hg status -A
  A b
  R c
  $ hg debugstate --nodates
  a   0         -1 unset               b
  r   0          0 set                 c

across branch

  $ cd ..
  $ hg init branch
  $ cd branch
  $ echo a > a
  $ hg ci -Am0
  adding a
  $ echo b > b
  $ hg ci -Am1
  adding b
  $ hg co -C 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ hg summary
  parent: 0:f7b1eb17ad24 
   0
  branch: default
  commit: (clean)
  update: 1 new changesets (update)
  phases: 2 draft

should fail

  $ hg backout 1
  abort: cannot backout change that is not an ancestor
  [255]
  $ echo c > c
  $ hg ci -Am2
  adding c
  created new head
  $ hg summary
  parent: 2:db815d6d32e6 tip
   2
  branch: default
  commit: (clean)
  update: 1 new changesets, 2 branch heads (merge)
  phases: 3 draft

should fail

  $ hg backout 1
  abort: cannot backout change that is not an ancestor
  [255]
  $ hg summary
  parent: 2:db815d6d32e6 tip
   2
  branch: default
  commit: (clean)
  update: 1 new changesets, 2 branch heads (merge)
  phases: 3 draft

backout with merge

  $ cd ..
  $ hg init merge
  $ cd merge

  $ echo line 1 > a
  $ echo line 2 >> a
  $ hg commit -d '0 0' -A -m a
  adding a
  $ hg summary
  parent: 0:59395513a13a tip
   a
  branch: default
  commit: (clean)
  update: (current)
  phases: 1 draft

remove line 1

  $ echo line 2 > a
  $ hg commit -d '1 0' -m b

  $ echo line 3 >> a
  $ hg commit -d '2 0' -m c

  $ hg backout --merge -d '3 0' 1 --tool=true
  reverting a
  created new head
  changeset 3:26b8ccb9ad91 backs out changeset 1:5a50a024c182
  merging with changeset 3:26b8ccb9ad91
  merging a
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg commit -d '4 0' -m d
  $ hg summary
  parent: 4:c7df5e0b9c09 tip
   d
  branch: default
  commit: (clean)
  update: (current)
  phases: 5 draft

check line 1 is back

  $ cat a
  line 1
  line 2
  line 3

  $ cd ..

backout should not back out subsequent changesets

  $ hg init onecs
  $ cd onecs
  $ echo 1 > a
  $ hg commit -d '0 0' -A -m a
  adding a
  $ echo 2 >> a
  $ hg commit -d '1 0' -m b
  $ echo 1 > b
  $ hg commit -d '2 0' -A -m c
  adding b
  $ hg summary
  parent: 2:882396649954 tip
   c
  branch: default
  commit: (clean)
  update: (current)
  phases: 3 draft

without --merge
  $ hg backout -d '3 0' 1 --tool=true
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  changeset 22bca4c721e5 backed out, don't forget to commit.
  $ hg locate b
  b
  $ hg update -C tip
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg locate b
  b
  $ hg summary
  parent: 2:882396649954 tip
   c
  branch: default
  commit: (clean)
  update: (current)
  phases: 3 draft

with --merge
  $ hg backout --merge -d '3 0' 1 --tool=true
  reverting a
  created new head
  changeset 3:3202beb76721 backs out changeset 1:22bca4c721e5
  merging with changeset 3:3202beb76721
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg locate b
  b
  $ hg update -C tip
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ hg locate b
  [1]

  $ cd ..
  $ hg init m
  $ cd m
  $ echo a > a
  $ hg commit -d '0 0' -A -m a
  adding a
  $ echo b > b
  $ hg commit -d '1 0' -A -m b
  adding b
  $ echo c > c
  $ hg commit -d '2 0' -A -m b
  adding c
  $ hg update 1
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ echo d > d
  $ hg commit -d '3 0' -A -m c
  adding d
  created new head
  $ hg merge 2
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg commit -d '4 0' -A -m d
  $ hg summary
  parent: 4:b2f3bb92043e tip
   d
  branch: default
  commit: (clean)
  update: (current)
  phases: 5 draft

backout of merge should fail

  $ hg backout 4
  abort: cannot backout a merge changeset
  [255]

backout of merge with bad parent should fail

  $ hg backout --parent 0 4
  abort: cb9a9f314b8b is not a parent of b2f3bb92043e
  [255]

backout of non-merge with parent should fail

  $ hg backout --parent 0 3
  abort: cannot use --parent on non-merge changeset
  [255]

backout with valid parent should be ok

  $ hg backout -d '5 0' --parent 2 4 --tool=true
  removing d
  changeset 5:10e5328c8435 backs out changeset 4:b2f3bb92043e
  $ hg summary
  parent: 5:10e5328c8435 tip
   Backed out changeset b2f3bb92043e
  branch: default
  commit: (clean)
  update: (current)
  phases: 6 draft

  $ hg rollback
  repository tip rolled back to revision 4 (undo commit)
  working directory now based on revision 4
  $ hg update -C
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg summary
  parent: 4:b2f3bb92043e tip
   d
  branch: default
  commit: (clean)
  update: (current)
  phases: 5 draft

  $ hg backout -d '6 0' --parent 3 4 --tool=true
  removing c
  changeset 5:033590168430 backs out changeset 4:b2f3bb92043e
  $ hg summary
  parent: 5:033590168430 tip
   Backed out changeset b2f3bb92043e
  branch: default
  commit: (clean)
  update: (current)
  phases: 6 draft

  $ cd ..

named branches

  $ hg init named_branches
  $ cd named_branches

  $ echo default > default
  $ hg ci -d '0 0' -Am default
  adding default
  $ hg branch branch1
  marked working directory as branch branch1
  (branches are permanent and global, did you want a bookmark?)
  $ echo branch1 > file1
  $ hg ci -d '1 0' -Am file1
  adding file1
  $ hg branch branch2
  marked working directory as branch branch2
  $ echo branch2 > file2
  $ hg ci -d '2 0' -Am file2
  adding file2

without --merge
  $ hg backout -r 1 --tool=true
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  changeset bf1602f437f3 backed out, don't forget to commit.
  $ hg branch
  branch2
  $ hg status -A
  R file1
  C default
  C file2
  $ hg summary
  parent: 2:45bbcd363bf0 tip
   file2
  branch: branch2
  commit: 1 removed
  update: (current)
  phases: 3 draft

with --merge
(this also tests that editor is invoked if '--edit' is specified
explicitly regardless of '--message')

  $ hg update -qC
  $ HGEDITOR=cat hg backout --merge -d '3 0' -r 1 -m 'backout on branch1' --tool=true --edit
  removing file1
  backout on branch1
  
  
  HG: Enter commit message.  Lines beginning with 'HG:' are removed.
  HG: Leave message empty to abort commit.
  HG: --
  HG: user: test
  HG: branch 'branch2'
  HG: removed file1
  created new head
  changeset 3:d4e8f6db59fb backs out changeset 1:bf1602f437f3
  merging with changeset 3:d4e8f6db59fb
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg summary
  parent: 2:45bbcd363bf0 
   file2
  parent: 3:d4e8f6db59fb tip
   backout on branch1
  branch: branch2
  commit: 1 removed (merge)
  update: (current)
  phases: 4 draft
  $ hg update -q -C 2

on branch2 with branch1 not merged, so file1 should still exist:

  $ hg id
  45bbcd363bf0 (branch2)
  $ hg st -A
  C default
  C file1
  C file2
  $ hg summary
  parent: 2:45bbcd363bf0 
   file2
  branch: branch2
  commit: (clean)
  update: 1 new changesets, 2 branch heads (merge)
  phases: 4 draft

on branch2 with branch1 merged, so file1 should be gone:

  $ hg merge
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg ci -d '4 0' -m 'merge backout of branch1'
  $ hg id
  22149cdde76d (branch2) tip
  $ hg st -A
  C default
  C file2
  $ hg summary
  parent: 4:22149cdde76d tip
   merge backout of branch1
  branch: branch2
  commit: (clean)
  update: (current)
  phases: 5 draft

on branch1, so no file1 and file2:

  $ hg co -C branch1
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ hg id
  bf1602f437f3 (branch1)
  $ hg st -A
  C default
  C file1
  $ hg summary
  parent: 1:bf1602f437f3 
   file1
  branch: branch1
  commit: (clean)
  update: (current)
  phases: 5 draft

  $ cd ..

backout of empty changeset (issue4190)

  $ hg init emptycommit
  $ cd emptycommit

  $ touch file1
  $ hg ci -Aqm file1
  $ hg branch -q branch1
  $ hg ci -qm branch1
  $ hg backout -v 1
  resolving manifests
  nothing changed
  [1]

  $ cd ..


Test usage of `hg resolve` in case of conflict
(issue4163)

  $ hg init issue4163
  $ cd issue4163
  $ touch foo
  $ hg add foo
  $ cat > foo << EOF
  > one
  > two
  > three
  > four
  > five
  > six
  > seven
  > height
  > nine
  > ten
  > EOF
  $ hg ci -m 'initial'
  $ cat > foo << EOF
  > one
  > two
  > THREE
  > four
  > five
  > six
  > seven
  > height
  > nine
  > ten
  > EOF
  $ hg ci -m 'capital three'
  $ cat > foo << EOF
  > one
  > two
  > THREE
  > four
  > five
  > six
  > seven
  > height
  > nine
  > TEN
  > EOF
  $ hg ci -m 'capital ten'
  $ hg backout -r 'desc("capital three")' --tool internal:fail
  0 files updated, 0 files merged, 0 files removed, 1 files unresolved
  use 'hg resolve' to retry unresolved file merges
  [1]
  $ hg status
  $ hg debugmergestate
  * version 2 records
  local: b71750c4b0fdf719734971e3ef90dbeab5919a2d
  other: a30dd8addae3ce71b8667868478542bc417439e6
  file: foo (state "u", hash 0beec7b5ea3f0fdbc95d0dd47f3c5bc275da8a33)
    local path: foo (flags "")
    ancestor path: foo (node f89532f44c247a0e993d63e3a734dd781ab04708)
    other path: foo (node f50039b486d6fa1a90ae51778388cad161f425ee)
  $ mv .hg/merge/state2 .hg/merge/state2-moved
  $ hg debugmergestate
  * version 1 records
  local: b71750c4b0fdf719734971e3ef90dbeab5919a2d
  file: foo (state "u", hash 0beec7b5ea3f0fdbc95d0dd47f3c5bc275da8a33)
    local path: foo (flags "")
    ancestor path: foo (node f89532f44c247a0e993d63e3a734dd781ab04708)
    other path: foo (node not stored in v1 format)
  $ mv .hg/merge/state2-moved .hg/merge/state2
  $ hg resolve -l  # still unresolved
  U foo
  $ hg summary
  parent: 2:b71750c4b0fd tip
   capital ten
  branch: default
  commit: 1 unresolved (clean)
  update: (current)
  phases: 3 draft
  $ hg resolve --all --debug
  picked tool ':merge' for foo (binary False symlink False)
  merging foo
  my foo@b71750c4b0fd+ other foo@a30dd8addae3 ancestor foo@913609522437
   premerge successful
  (no more unresolved files)
  $ hg status
  M foo
  ? foo.orig
  $ hg resolve -l
  R foo
  $ hg summary
  parent: 2:b71750c4b0fd tip
   capital ten
  branch: default
  commit: 1 modified, 1 unknown
  update: (current)
  phases: 3 draft
  $ cat foo
  one
  two
  three
  four
  five
  six
  seven
  height
  nine
  TEN