view tests/test-rebase-collapse.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.

  $ cat >> $HGRCPATH <<EOF
  > [extensions]
  > rebase=
  > mq=
  > 
  > [phases]
  > publish=False
  > 
  > [alias]
  > tglog = log -G --template "{rev}: '{desc}' {branches}\n"
  > tglogp = log -G --template "{rev}:{phase} '{desc}' {branches}\n"
  > EOF

Create repo a:

  $ hg init a
  $ cd a
  $ hg unbundle "$TESTDIR/bundles/rebase.hg"
  adding changesets
  adding manifests
  adding file changes
  added 8 changesets with 7 changes to 7 files (+2 heads)
  (run 'hg heads' to see heads, 'hg merge' to merge)
  $ hg up tip
  3 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ hg tglog
  @  7: 'H'
  |
  | o  6: 'G'
  |/|
  o |  5: 'F'
  | |
  | o  4: 'E'
  |/
  | o  3: 'D'
  | |
  | o  2: 'C'
  | |
  | o  1: 'B'
  |/
  o  0: 'A'
  
  $ cd ..


Rebasing B onto H and collapsing changesets with different phases:


  $ hg clone -q -u 3 a a1
  $ cd a1

  $ hg phase --force --secret 3

  $ cat > $TESTTMP/editor.sh <<EOF
  > echo "==== before editing"
  > cat \$1
  > echo "===="
  > echo "edited manually" >> \$1
  > EOF
  $ HGEDITOR="sh $TESTTMP/editor.sh" hg rebase --collapse --keepbranches -e
  rebasing 1:42ccdea3bb16 "B"
  note: rebase of 1:42ccdea3bb16 created no changes to commit
  rebasing 2:5fddd98957c8 "C"
  note: rebase of 2:5fddd98957c8 created no changes to commit
  rebasing 3:32af7686d403 "D"
  note: rebase of 3:32af7686d403 created no changes to commit
  ==== before editing
  Collapsed revision
  * B
  * C
  * D
  
  
  HG: Enter commit message.  Lines beginning with 'HG:' are removed.
  HG: Leave message empty to abort commit.
  HG: --
  HG: user: Nicolas Dumazet <[e-mail]>
  HG: branch 'default'
  HG: added B
  HG: added C
  HG: added D
  ====
  saved backup bundle to $TESTTMP/a1/.hg/strip-backup/42ccdea3bb16-3cb021d3-backup.hg (glob)

  $ hg tglogp
  @  5:secret 'Collapsed revision
  |  * B
  |  * C
  |  * D
  |
  |
  |  edited manually'
  o  4:draft 'H'
  |
  | o  3:draft 'G'
  |/|
  o |  2:draft 'F'
  | |
  | o  1:draft 'E'
  |/
  o  0:draft 'A'
  
  $ hg manifest --rev tip
  A
  B
  C
  D
  F
  H

  $ cd ..


Rebasing E onto H:

  $ hg clone -q -u . a a2
  $ cd a2

  $ hg phase --force --secret 6
  $ hg rebase --source 4 --collapse
  rebasing 4:9520eea781bc "E"
  note: rebase of 4:9520eea781bc created no changes to commit
  rebasing 6:eea13746799a "G"
  note: rebase of 6:eea13746799a created no changes to commit
  saved backup bundle to $TESTTMP/a2/.hg/strip-backup/9520eea781bc-fcd8edd4-backup.hg (glob)

  $ hg tglog
  o  6: 'Collapsed revision
  |  * E
  |  * G'
  @  5: 'H'
  |
  o  4: 'F'
  |
  | o  3: 'D'
  | |
  | o  2: 'C'
  | |
  | o  1: 'B'
  |/
  o  0: 'A'
  
  $ hg manifest --rev tip
  A
  E
  F
  H

  $ cd ..

Rebasing G onto H with custom message:

  $ hg clone -q -u . a a3
  $ cd a3

  $ hg rebase --base 6 -m 'custom message'
  abort: message can only be specified with collapse
  [255]

  $ cat > $TESTTMP/checkeditform.sh <<EOF
  > env | grep HGEDITFORM
  > true
  > EOF
  $ HGEDITOR="sh $TESTTMP/checkeditform.sh" hg rebase --source 4 --collapse -m 'custom message' -e
  rebasing 4:9520eea781bc "E"
  note: rebase of 4:9520eea781bc created no changes to commit
  rebasing 6:eea13746799a "G"
  note: rebase of 6:eea13746799a created no changes to commit
  HGEDITFORM=rebase.collapse
  saved backup bundle to $TESTTMP/a3/.hg/strip-backup/9520eea781bc-fcd8edd4-backup.hg (glob)

  $ hg tglog
  o  6: 'custom message'
  |
  @  5: 'H'
  |
  o  4: 'F'
  |
  | o  3: 'D'
  | |
  | o  2: 'C'
  | |
  | o  1: 'B'
  |/
  o  0: 'A'
  
  $ hg manifest --rev tip
  A
  E
  F
  H

  $ cd ..

Create repo b:

  $ hg init b
  $ cd b

  $ echo A > A
  $ hg ci -Am A
  adding A
  $ echo B > B
  $ hg ci -Am B
  adding B

  $ hg up -q 0

  $ echo C > C
  $ hg ci -Am C
  adding C
  created new head

  $ hg merge
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

  $ echo D > D
  $ hg ci -Am D
  adding D

  $ hg up -q 1

  $ echo E > E
  $ hg ci -Am E
  adding E
  created new head

  $ echo F > F
  $ hg ci -Am F
  adding F

  $ hg merge
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg ci -m G

  $ hg up -q 0

  $ echo H > H
  $ hg ci -Am H
  adding H
  created new head

  $ hg tglog
  @  7: 'H'
  |
  | o    6: 'G'
  | |\
  | | o  5: 'F'
  | | |
  | | o  4: 'E'
  | | |
  | o |  3: 'D'
  | |\|
  | o |  2: 'C'
  |/ /
  | o  1: 'B'
  |/
  o  0: 'A'
  
  $ cd ..


Rebase and collapse - more than one external (fail):

  $ hg clone -q -u . b b1
  $ cd b1

  $ hg rebase -s 2 --collapse
  abort: unable to collapse on top of 7, there is more than one external parent: 1, 5
  [255]

Rebase and collapse - E onto H:

  $ hg rebase -s 4 --collapse # root (4) is not a merge
  rebasing 4:8a5212ebc852 "E"
  note: rebase of 4:8a5212ebc852 created no changes to commit
  rebasing 5:7f219660301f "F"
  note: rebase of 5:7f219660301f created no changes to commit
  rebasing 6:c772a8b2dc17 "G"
  note: rebase of 6:c772a8b2dc17 created no changes to commit
  saved backup bundle to $TESTTMP/b1/.hg/strip-backup/8a5212ebc852-75046b61-backup.hg (glob)

  $ hg tglog
  o    5: 'Collapsed revision
  |\   * E
  | |  * F
  | |  * G'
  | @  4: 'H'
  | |
  o |    3: 'D'
  |\ \
  | o |  2: 'C'
  | |/
  o /  1: 'B'
  |/
  o  0: 'A'
  
  $ hg manifest --rev tip
  A
  C
  D
  E
  F
  H

  $ cd ..




Test that branchheads cache is updated correctly when doing a strip in which
the parent of the ancestor node to be stripped does not become a head and also,
the parent of a node that is a child of the node stripped becomes a head (node
3). The code is now much simpler and we could just test a simpler scenario
We keep it the test this way in case new complexity is injected.

  $ hg clone -q -u . b b2
  $ cd b2

  $ hg heads --template="{rev}:{node} {branch}\n"
  7:c65502d4178782309ce0574c5ae6ee9485a9bafa default
  6:c772a8b2dc17629cec88a19d09c926c4814b12c7 default

  $ cat $TESTTMP/b2/.hg/cache/branch2-served
  c65502d4178782309ce0574c5ae6ee9485a9bafa 7
  c772a8b2dc17629cec88a19d09c926c4814b12c7 o default
  c65502d4178782309ce0574c5ae6ee9485a9bafa o default

  $ hg strip 4
  saved backup bundle to $TESTTMP/b2/.hg/strip-backup/8a5212ebc852-75046b61-backup.hg (glob)

  $ cat $TESTTMP/b2/.hg/cache/branch2-served
  c65502d4178782309ce0574c5ae6ee9485a9bafa 4
  2870ad076e541e714f3c2bc32826b5c6a6e5b040 o default
  c65502d4178782309ce0574c5ae6ee9485a9bafa o default

  $ hg heads --template="{rev}:{node} {branch}\n"
  4:c65502d4178782309ce0574c5ae6ee9485a9bafa default
  3:2870ad076e541e714f3c2bc32826b5c6a6e5b040 default

  $ cd ..






Create repo c:

  $ hg init c
  $ cd c

  $ echo A > A
  $ hg ci -Am A
  adding A
  $ echo B > B
  $ hg ci -Am B
  adding B

  $ hg up -q 0

  $ echo C > C
  $ hg ci -Am C
  adding C
  created new head

  $ hg merge
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

  $ echo D > D
  $ hg ci -Am D
  adding D

  $ hg up -q 1

  $ echo E > E
  $ hg ci -Am E
  adding E
  created new head
  $ echo F > E
  $ hg ci -m 'F'

  $ echo G > G
  $ hg ci -Am G
  adding G

  $ hg merge
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

  $ hg ci -m H

  $ hg up -q 0

  $ echo I > I
  $ hg ci -Am I
  adding I
  created new head

  $ hg tglog
  @  8: 'I'
  |
  | o    7: 'H'
  | |\
  | | o  6: 'G'
  | | |
  | | o  5: 'F'
  | | |
  | | o  4: 'E'
  | | |
  | o |  3: 'D'
  | |\|
  | o |  2: 'C'
  |/ /
  | o  1: 'B'
  |/
  o  0: 'A'
  
  $ cd ..


Rebase and collapse - E onto I:

  $ hg clone -q -u . c c1
  $ cd c1

  $ hg rebase -s 4 --collapse # root (4) is not a merge
  rebasing 4:8a5212ebc852 "E"
  note: rebase of 4:8a5212ebc852 created no changes to commit
  rebasing 5:dca5924bb570 "F"
  merging E
  note: rebase of 5:dca5924bb570 created no changes to commit
  rebasing 6:55a44ad28289 "G"
  note: rebase of 6:55a44ad28289 created no changes to commit
  rebasing 7:417d3b648079 "H"
  note: rebase of 7:417d3b648079 created no changes to commit
  saved backup bundle to $TESTTMP/c1/.hg/strip-backup/8a5212ebc852-f95d0879-backup.hg (glob)

  $ hg tglog
  o    5: 'Collapsed revision
  |\   * E
  | |  * F
  | |  * G
  | |  * H'
  | @  4: 'I'
  | |
  o |    3: 'D'
  |\ \
  | o |  2: 'C'
  | |/
  o /  1: 'B'
  |/
  o  0: 'A'
  
  $ hg manifest --rev tip
  A
  C
  D
  E
  G
  I

  $ hg up tip -q
  $ cat E
  F

  $ cd ..


Create repo d:

  $ hg init d
  $ cd d

  $ echo A > A
  $ hg ci -Am A
  adding A
  $ echo B > B
  $ hg ci -Am B
  adding B
  $ echo C > C
  $ hg ci -Am C
  adding C

  $ hg up -q 1

  $ echo D > D
  $ hg ci -Am D
  adding D
  created new head
  $ hg merge
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

  $ hg ci -m E

  $ hg up -q 0

  $ echo F > F
  $ hg ci -Am F
  adding F
  created new head

  $ hg tglog
  @  5: 'F'
  |
  | o    4: 'E'
  | |\
  | | o  3: 'D'
  | | |
  | o |  2: 'C'
  | |/
  | o  1: 'B'
  |/
  o  0: 'A'
  
  $ cd ..


Rebase and collapse - B onto F:

  $ hg clone -q -u . d d1
  $ cd d1

  $ hg rebase -s 1 --collapse
  rebasing 1:27547f69f254 "B"
  note: rebase of 1:27547f69f254 created no changes to commit
  rebasing 2:f838bfaca5c7 "C"
  note: rebase of 2:f838bfaca5c7 created no changes to commit
  rebasing 3:7bbcd6078bcc "D"
  note: rebase of 3:7bbcd6078bcc created no changes to commit
  rebasing 4:0a42590ed746 "E"
  note: rebase of 4:0a42590ed746 created no changes to commit
  saved backup bundle to $TESTTMP/d1/.hg/strip-backup/27547f69f254-9a3f7d92-backup.hg (glob)

  $ hg tglog
  o  2: 'Collapsed revision
  |  * B
  |  * C
  |  * D
  |  * E'
  @  1: 'F'
  |
  o  0: 'A'
  
  $ hg manifest --rev tip
  A
  B
  C
  D
  F

Interactions between collapse and keepbranches
  $ cd ..
  $ hg init e
  $ cd e
  $ echo 'a' > a
  $ hg ci -Am 'A'
  adding a

  $ hg branch 'one'
  marked working directory as branch one
  (branches are permanent and global, did you want a bookmark?)
  $ echo 'b' > b
  $ hg ci -Am 'B'
  adding b

  $ hg branch 'two'
  marked working directory as branch two
  $ echo 'c' > c
  $ hg ci -Am 'C'
  adding c

  $ hg up -q 0
  $ echo 'd' > d
  $ hg ci -Am 'D'
  adding d

  $ hg tglog
  @  3: 'D'
  |
  | o  2: 'C' two
  | |
  | o  1: 'B' one
  |/
  o  0: 'A'
  
  $ hg rebase --keepbranches --collapse -s 1 -d 3
  abort: cannot collapse multiple named branches
  [255]

  $ repeatchange() {
  >   hg checkout $1
  >   hg cp d z
  >   echo blah >> z
  >   hg commit -Am "$2" --user "$3"
  > }
  $ repeatchange 3 "E" "user1"
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ repeatchange 3 "E" "user2"
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  created new head
  $ hg tglog
  @  5: 'E'
  |
  | o  4: 'E'
  |/
  o  3: 'D'
  |
  | o  2: 'C' two
  | |
  | o  1: 'B' one
  |/
  o  0: 'A'
  
  $ hg rebase -s 5 -d 4
  rebasing 5:fbfb97b1089a "E" (tip)
  note: rebase of 5:fbfb97b1089a created no changes to commit
  saved backup bundle to $TESTTMP/e/.hg/strip-backup/fbfb97b1089a-553e1d85-backup.hg (glob)
  $ hg tglog
  @  4: 'E'
  |
  o  3: 'D'
  |
  | o  2: 'C' two
  | |
  | o  1: 'B' one
  |/
  o  0: 'A'
  
  $ hg export tip
  # HG changeset patch
  # User user1
  # Date 0 0
  #      Thu Jan 01 00:00:00 1970 +0000
  # Node ID f338eb3c2c7cc5b5915676a2376ba7ac558c5213
  # Parent  41acb9dca9eb976e84cd21fcb756b4afa5a35c09
  E
  
  diff -r 41acb9dca9eb -r f338eb3c2c7c z
  --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
  +++ b/z	Thu Jan 01 00:00:00 1970 +0000
  @@ -0,0 +1,2 @@
  +d
  +blah

  $ cd ..

Rebase, collapse and copies

  $ hg init copies
  $ cd copies
  $ hg unbundle "$TESTDIR/bundles/renames.hg"
  adding changesets
  adding manifests
  adding file changes
  added 4 changesets with 11 changes to 7 files (+1 heads)
  (run 'hg heads' to see heads, 'hg merge' to merge)
  $ hg up -q tip
  $ hg tglog
  @  3: 'move2'
  |
  o  2: 'move1'
  |
  | o  1: 'change'
  |/
  o  0: 'add'
  
  $ hg rebase --collapse -d 1
  rebasing 2:6e7340ee38c0 "move1"
  merging a and d to d
  merging b and e to e
  merging c and f to f
  note: rebase of 2:6e7340ee38c0 created no changes to commit
  rebasing 3:338e84e2e558 "move2" (tip)
  merging f and c to c
  merging e and g to g
  note: rebase of 3:338e84e2e558 created no changes to commit
  saved backup bundle to $TESTTMP/copies/.hg/strip-backup/6e7340ee38c0-ef8ef003-backup.hg (glob)
  $ hg st
  $ hg st --copies --change tip
  A d
    a
  A g
    b
  R b
  $ hg up tip -q
  $ cat c
  c
  c
  $ cat d
  a
  a
  $ cat g
  b
  b
  $ hg log -r . --template "{file_copies}\n"
  d (a)g (b)

Test collapsing a middle revision in-place

  $ hg tglog
  @  2: 'Collapsed revision
  |  * move1
  |  * move2'
  o  1: 'change'
  |
  o  0: 'add'
  
  $ hg rebase --collapse -r 1 -d 0
  abort: can't remove original changesets with unrebased descendants
  (use --keep to keep original changesets)
  [255]

Test collapsing in place

  $ hg rebase --collapse -b . -d 0
  rebasing 1:1352765a01d4 "change"
  note: rebase of 1:1352765a01d4 created no changes to commit
  rebasing 2:64b456429f67 "Collapsed revision" (tip)
  note: rebase of 2:64b456429f67 created no changes to commit
  saved backup bundle to $TESTTMP/copies/.hg/strip-backup/1352765a01d4-45a352ea-backup.hg (glob)
  $ hg st --change tip --copies
  M a
  M c
  A d
    a
  A g
    b
  R b
  $ hg up tip -q
  $ cat a
  a
  a
  $ cat c
  c
  c
  $ cat d
  a
  a
  $ cat g
  b
  b
  $ cd ..


Test stripping a revision with another child

  $ hg init f
  $ cd f

  $ echo A > A
  $ hg ci -Am A
  adding A
  $ echo B > B
  $ hg ci -Am B
  adding B

  $ hg up -q 0

  $ echo C > C
  $ hg ci -Am C
  adding C
  created new head

  $ hg tglog
  @  2: 'C'
  |
  | o  1: 'B'
  |/
  o  0: 'A'
  


  $ hg heads --template="{rev}:{node} {branch}: {desc}\n"
  2:c5cefa58fd557f84b72b87f970135984337acbc5 default: C
  1:27547f69f25460a52fff66ad004e58da7ad3fb56 default: B

  $ hg strip 2
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  saved backup bundle to $TESTTMP/f/.hg/strip-backup/c5cefa58fd55-629429f4-backup.hg (glob)

  $ hg tglog
  o  1: 'B'
  |
  @  0: 'A'
  


  $ hg heads --template="{rev}:{node} {branch}: {desc}\n"
  1:27547f69f25460a52fff66ad004e58da7ad3fb56 default: B

  $ cd ..

Test collapsing changes that add then remove a file

  $ hg init collapseaddremove
  $ cd collapseaddremove

  $ touch base
  $ hg commit -Am base
  adding base
  $ touch a
  $ hg commit -Am a
  adding a
  $ hg rm a
  $ touch b
  $ hg commit -Am b
  adding b
  $ hg book foo
  $ hg rebase -d 0 -r "1::2" --collapse -m collapsed
  rebasing 1:6d8d9f24eec3 "a"
  note: rebase of 1:6d8d9f24eec3 created no changes to commit
  rebasing 2:1cc73eca5ecc "b" (tip foo)
  note: rebase of 2:1cc73eca5ecc created no changes to commit
  saved backup bundle to $TESTTMP/collapseaddremove/.hg/strip-backup/6d8d9f24eec3-77d3b6e2-backup.hg (glob)
  $ hg log -G --template "{rev}: '{desc}' {bookmarks}"
  @  1: 'collapsed' foo
  |
  o  0: 'base'
  
  $ hg manifest --rev tip
  b
  base

  $ cd ..