view tests/test-backout.t @ 40021:c537144fdbef

wireprotov2: support response caching

One of the things I've learned from managing VCS servers over the
years is that they are hard to scale. It is well known that some
companies have very beefy (read: very expensive) servers to power
their VCS needs. It is also known that specialized servers for
various VCS exist in order to facilitate scaling servers. (Mercurial
is in this boat.)

One of the aspects that make a VCS server hard to scale is the
high CPU load incurred by constant client clone/pull operations.

To alleviate the scaling pain associated with data retrieval
operations, I want to integrate caching into the Mercurial wire
protocol server as robustly as possible such that servers can
aggressively cache responses and defer as much server load as
possible.

This commit represents the initial implementation of a general
caching layer in wire protocol version 2.

We define a new interface and behavior for a wire protocol cacher
in repository.py. (This is probably where a reviewer should look
first to understand what is going on.)

The bulk of the added code is in wireprotov2server.py, where we
define how a command can opt in to being cached and integrate
caching into command dispatching.

From a very high-level:

* A command can declare itself as cacheable by providing a callable
  that can be used to derive a cache key.
* At dispatch time, if a command is cacheable, we attempt to
  construct a cacher and use it for serving the request and/or
  caching the request.
* The dispatch layer handles the bulk of the business logic for
  caching, making cachers mostly "dumb content stores."
* The mechanism for invalidating cached entries (one of the harder
  parts about caching in general) is by varying the cache key when
  state changes. As such, cachers don't need to be concerned with
  cache invalidation.

Initially, we've hooked up support for caching "manifestdata" and
"filedata" commands. These are the simplest to cache, as they should
be immutable over time. Caching of commands related to changeset
data is a bit harder (because cache validation is impacted by
changes to bookmarks, phases, etc). This will be implemented later.
(Strictly speaking, censoring a file should invalidate caches. I've
added an inline TODO to track this edge case.)

To prove it works, this commit implements a test-only extension
providing in-memory caching backed by an lrucachedict. A new test
showing this extension behaving properly is added. FWIW, the
cacher is ~50 lines of code, demonstrating the relative ease with
which a cache can be added to a server.

While the test cacher is not suitable for production workloads, just
for kicks I performed a clone of just the changeset and manifest data
for the mozilla-unified repository. With a fully warmed cache (of just
the manifest data since changeset data is not cached), server-side
CPU usage dropped from ~73s to ~28s. That's pretty significant and
demonstrates the potential that response caching has on server
scalability!

Differential Revision: https://phab.mercurial-scm.org/D4773

  $ 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 -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 -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 --no-dates
  n 644         12 set                 c
  $ hg backout -d '6 0' -m 'to be rollback-ed soon' -r .
  removing c
  adding b
  changeset 6:4bfec048029d backs out changeset 5:fac0b729a654
  $ hg rollback -q
  $ hg status -A
  A b
  R c
  $ hg debugstate --no-dates
  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

Test visibility of in-memory dirstate changes outside transaction to
external hook process

  $ cat > $TESTTMP/checkvisibility.sh <<EOF
  > echo "==== \$1:"
  > hg parents --template "{rev}:{node|short}\n"
  > echo "===="
  > EOF

"hg backout --merge REV1" at REV2 below implies steps below:

(1) update to REV1 (REV2 => REV1)
(2) revert by REV1^1
(3) commit backing out revision (REV3)
(4) update to REV2 (REV3 => REV2)
(5) merge with REV3 (REV2 => REV2, REV3)

== test visibility to external preupdate hook

  $ hg update -q -C 2
  $ hg --config extensions.strip= strip 3
  saved backup bundle to * (glob)

  $ cat >> .hg/hgrc <<EOF
  > [hooks]
  > preupdate.visibility = sh $TESTTMP/checkvisibility.sh preupdate
  > EOF

("-m" is needed to avoid writing dirstate changes out at other than
invocation of the hook to be examined)

  $ hg backout --merge -d '3 0' 1 --tool=true -m 'fixed comment'
  ==== preupdate:
  2:6ea3f2a197a2
  ====
  reverting a
  created new head
  changeset 3:d92a3f57f067 backs out changeset 1:5a50a024c182
  ==== preupdate:
  3:d92a3f57f067
  ====
  merging with changeset 3:d92a3f57f067
  ==== preupdate:
  2:6ea3f2a197a2
  ====
  merging a
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

  $ cat >> .hg/hgrc <<EOF
  > [hooks]
  > preupdate.visibility =
  > EOF

== test visibility to external update hook

  $ hg update -q -C 2
  $ hg --config extensions.strip= strip 3
  saved backup bundle to * (glob)

  $ cat >> .hg/hgrc <<EOF
  > [hooks]
  > update.visibility = sh $TESTTMP/checkvisibility.sh update
  > EOF

  $ hg backout --merge -d '3 0' 1 --tool=true -m 'fixed comment'
  ==== update:
  1:5a50a024c182
  ====
  reverting a
  created new head
  changeset 3:d92a3f57f067 backs out changeset 1:5a50a024c182
  ==== update:
  2:6ea3f2a197a2
  ====
  merging with changeset 3:d92a3f57f067
  merging a
  ==== update:
  2:6ea3f2a197a2
  3:d92a3f57f067
  ====
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

  $ cat >> .hg/hgrc <<EOF
  > [hooks]
  > update.visibility =
  > EOF

  $ 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 --no-commit -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 --no-commit -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 extras: foo (ancestorlinknode = 91360952243723bd5b1138d5f26bd8c8564cb553)
  file: foo (record type "F", 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 (record type "F", 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 changedelete False)
  merging foo
  my foo@b71750c4b0fd+ other foo@a30dd8addae3 ancestor foo@913609522437
   premerge successful
  (no more unresolved files)
  continue: hg commit
  $ 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

--no-commit shouldn't commit

  $ hg init a
  $ cd a
  $ for i in 1 2 3; do
  >   touch $i
  >   hg ci -Am $i
  > done
  adding 1
  adding 2
  adding 3
  $ hg backout --no-commit .
  removing 3
  changeset cccc23d9d68f backed out, don't forget to commit.
  $ hg revert -aq

--no-commit can't be used with --merge

  $ hg backout --merge --no-commit 2
  abort: cannot use --merge with --no-commit
  [255]