view tests/test-transaction-safety.t @ 49777:e1953a34c110

bundle: emit full snapshot as is, without doing a redelta

With the new `forced` delta-reused policy, it become important to be able to
send full snapshot where full snapshot are needed. Otherwise, the fallback delta
will simply be used on the client side… creating monstrous delta chain, since
revision that are meant as a reset of delta-chain chain becoming too complex are
simply adding a new full delta-tree on the leaf of another one.

In the `non-forced` cases, client process full snapshot from the bundle
differently from deltas, so client will still try to convert the full snapshot
into a delta if possible. So this will no lead to pathological storage
explosion.

I have considered making this configurable, but the impact seems limited enough
that it does not seems to be worth it. Especially with the current
sparse-revlog format that use "delta-tree" with multiple level snapshots, full
snapshot are much less frequent and not that different from other intermediate
snapshot that we are already sending over the wire anyway.

CPU wise, this will help the bundling side a little as it will not need to
reconstruct revisions and compute deltas. The unbundling side might save a tiny
amount of CPU as it won't need to reconstruct the delta-base to reconstruct the
revision full text. This only slightly visible in some of the benchmarks. And
have no real impact on most of them.

### data-env-vars.name      = pypy-2018-08-01-zstd-sparse-revlog
  # benchmark.name          = perf-bundle
  # benchmark.variants.revs = last-40000
before:          11.467186 seconds
just-emit-full:  11.190576 seconds   (-2.41%)
with-pull-force: 11.041091 seconds   (-3.72%)
  # benchmark.name          = perf-unbundle
  # benchmark.variants.revs = last-40000
before:     16.744862
just-emit-full:: 16.561036 seconds   (-1.10%)
with-pull-force: 16.389344 seconds   (-2.12%)
  # benchmark.name          = pull
  # benchmark.variants.revs = last-40000
before:     26.870569
just-emit-full:  26.391188 seconds   (-1.78%)
with-pull-force: 25.633184 seconds   (-4.60%)


Space wise (so network-wise) the impact is fairly small. When taking compression into
account.

Below are tests the size of `hg bundle --all` for a handful of benchmark repositories
(with bzip, zstd compression and without it)

This show a small increase in the bundle size, but nothing really significant
except maybe for mozilla-try (+12%) that nobody really pulls large chunk of anyway.
Mozilla-try is also the repository that benefit the most for not having to
recompute deltas client size.

### mercurial:
bzip-before:     26 406 342 bytes
bzip-after:      26 691 543 bytes  +1.08%

zstd-before:     27 918 645 bytes
zstd-after:      28 075 896 bytes  +0.56%

none-before:     98 675 601 bytes
none-after:     100 411 237 bytes  +1.76%


### pypy
bzip-before:    201 295 752 bytes
bzip-after:     209 780 282 bytes  +4.21%

zstd-before:    202 974 795 bytes
zstd-after:     205 165 780 bytes  +1.08%

none-before:    871 070 261 bytes
none-after:     993 595 057 bytes +14.07%


### netbeans
bzip-before:    601 314 330 bytes
bzip-after:     614 246 241 bytes  +2.15%

zstd-before:    604 745 136 bytes
zstd-after:     615 497 705 bytes  +1.78%

none-before:  3 338 238 571 bytes
none-after:   3 439 422 535 bytes  +3.03%


### mozilla-central
bzip-before:  1 493 006 921 bytes
bzip-after:   1 549 650 570 bytes  +3.79%

zstd-before:  1 481 910 102 bytes
zstd-after:   1 513 052 415 bytes  +2.10%

none-before:  6 535 929 910 bytes
none-after:   7 010 191 342 bytes  +7.26%


### mozilla-try
bzip-before:  6 583 425 999 bytes
bzip-after:   7 423 536 928 bytes +12.76%

zstd-before:  6 021 009 212 bytes
zstd-after:   6 674 922 420 bytes +10.86%

none-before: 22 954 739 558 bytes
none-after:  26 013 854 771 bytes +13.32%

Test transaction safety
=======================

#testcases revlogv1 revlogv2 changelogv2

#if revlogv1

  $ cat << EOF >> $HGRCPATH
  > [experimental]
  > revlogv2=no
  > EOF

#endif

#if revlogv2

  $ cat << EOF >> $HGRCPATH
  > [experimental]
  > revlogv2=enable-unstable-format-and-corrupt-my-data
  > EOF

#endif

#if changelogv2

  $ cat << EOF >> $HGRCPATH
  > [format]
  > exp-use-changelog-v2=enable-unstable-format-and-corrupt-my-data
  > EOF

#endif

This test basic case to make sure external process do not see transaction
content until it is committed.

# TODO: also add an external reader accessing revlog files while they are written
#       (instead of during transaction finalisation)

# TODO: also add stream clone and hardlink clone happening during these transaction.

setup
-----

synchronisation+output script using the following schedule:

[A1] "external"       is started
[A2] "external"       waits on EXT_UNLOCK
[A2] "external"       + creates EXT_WAITING → unlocks [C1]
[B1] "hg commit/pull" is started
[B2] "hg commit/pull" is ready to be committed
[B3] "hg commit/pull" spawn "internal" using a pretxnclose hook (need [C4])
[C1] "internal"       waits on EXT_WAITING (need [A2])
[C2] "internal"       creates EXT_UNLOCK → unlocks [A2]
[C3] "internal"       show the tipmost revision (inside of the transaction)
[C4] "internal"       waits on EXT_DONE (need [A4])
[A3] "external"       show the tipmost revision (outside of the transaction)
[A4] "external"       creates EXT_DONE → unlocks [C4]
[C5] "internal"       end of execution -> unlock [B3]
[B4] "hg commit/pull" transaction is committed on disk


  $ mkdir sync
  $ mkdir output
  $ mkdir script
  $ HG_TEST_FILE_EXT_WAITING=$TESTTMP/sync/ext_waiting
  $ export HG_TEST_FILE_EXT_WAITING
  $ HG_TEST_FILE_EXT_UNLOCK=$TESTTMP/sync/ext_unlock
  $ export HG_TEST_FILE_EXT_UNLOCK
  $ HG_TEST_FILE_EXT_DONE=$TESTTMP/sync/ext_done
  $ export HG_TEST_FILE_EXT_DONE
  $ cat << EOF > script/external.sh
  > #!/bin/sh
  > "$RUNTESTDIR/testlib/wait-on-file" 5 "$HG_TEST_FILE_EXT_UNLOCK" "$HG_TEST_FILE_EXT_WAITING"
  > hg log --rev 'tip' -T 'external: {rev} {desc}\n' > "$TESTTMP/output/external.out"
  > touch "$HG_TEST_FILE_EXT_DONE"
  > EOF
  $ cat << EOF > script/internal.sh
  > #!/bin/sh
  > "$RUNTESTDIR/testlib/wait-on-file" 5 "$HG_TEST_FILE_EXT_WAITING"
  > touch "$HG_TEST_FILE_EXT_UNLOCK"
  > hg log --rev 'tip' -T 'internal: {rev} {desc}\n' > "$TESTTMP/output/internal.out"
  > "$RUNTESTDIR/testlib/wait-on-file" 5 "$HG_TEST_FILE_EXT_DONE"
  > EOF


Automated commands:

  $ make_one_commit() {
  > rm -f $TESTTMP/sync/*
  > rm -f $TESTTMP/output/*
  > hg log --rev 'tip' -T 'pre-commit: {rev} {desc}\n'
  > echo x >> a
  > sh $TESTTMP/script/external.sh & hg commit -m "$1"
  > cat $TESTTMP/output/external.out
  > cat $TESTTMP/output/internal.out
  > hg log --rev 'tip' -T 'post-tr:  {rev} {desc}\n'
  > }


  $ make_one_pull() {
  > rm -f $TESTTMP/sync/*
  > rm -f $TESTTMP/output/*
  > hg log --rev 'tip' -T 'pre-commit: {rev} {desc}\n'
  > echo x >> a
  > sh $TESTTMP/script/external.sh & hg pull ../other-repo/ --rev "$1" --force --quiet
  > cat $TESTTMP/output/external.out
  > cat $TESTTMP/output/internal.out
  > hg log --rev 'tip' -T 'post-tr:  {rev} {desc}\n'
  > }

prepare a large source to which to pull from:

The source is large to unsure we don't use inline more after the pull

  $ hg init other-repo
  $ hg -R other-repo debugbuilddag .+500


prepare an empty repository where to make test:

  $ hg init repo
  $ cd repo
  $ touch a
  $ hg add a

prepare a small extension to controll inline size

  $ mkdir $TESTTMP/ext
  $ cat << EOF > $TESTTMP/ext/small_inline.py
  > from mercurial import revlog
  > revlog._maxinline = 64 * 100
  > EOF




  $ cat << EOF >> $HGRCPATH
  > [extensions]
  > small_inline=$TESTTMP/ext/small_inline.py
  > [hooks]
  > pretxnclose = sh $TESTTMP/script/internal.sh
  > EOF

check this is true for the initial commit (inline → inline)
-----------------------------------------------------------

the repository should still be inline (for relevant format)

  $ make_one_commit first
  pre-commit: -1 
  external: -1 
  internal: 0 first
  post-tr:  0 first

#if revlogv1

  $ hg debugrevlog -c | grep inline
  flags  : inline

#endif

check this is true for extra commit (inline → inline)
-----------------------------------------------------

the repository should still be inline (for relevant format)

#if revlogv1

  $ hg debugrevlog -c | grep inline
  flags  : inline

#endif

  $ make_one_commit second
  pre-commit: 0 first
  external: 0 first
  internal: 1 second
  post-tr:  1 second

#if revlogv1

  $ hg debugrevlog -c | grep inline
  flags  : inline

#endif

check this is true for a small pull (inline → inline)
-----------------------------------------------------

the repository should still be inline (for relevant format)

#if revlogv1

  $ hg debugrevlog -c | grep inline
  flags  : inline

#endif

  $ make_one_pull 3
  pre-commit: 1 second
  warning: repository is unrelated
  external: 1 second
  internal: 5 r3
  post-tr:  5 r3

#if revlogv1

  $ hg debugrevlog -c | grep inline
  flags  : inline

#endif

Make a large pull (inline → no-inline)
---------------------------------------

the repository should no longer be inline (for relevant format)

#if revlogv1

  $ hg debugrevlog -c | grep inline
  flags  : inline

#endif

  $ make_one_pull 400
  pre-commit: 5 r3
  external: 5 r3
  internal: 402 r400
  post-tr:  402 r400

#if revlogv1

  $ hg debugrevlog -c | grep inline
  [1]

#endif

check this is true for extra commit (no-inline → no-inline)
-----------------------------------------------------------

the repository should no longer be inline (for relevant format)

#if revlogv1

  $ hg debugrevlog -c | grep inline
  [1]

#endif

  $ make_one_commit third
  pre-commit: 402 r400
  external: 402 r400
  internal: 403 third
  post-tr:  403 third

#if revlogv1

  $ hg debugrevlog -c | grep inline
  [1]

#endif


Make a  pull (not-inline → no-inline)
-------------------------------------

the repository should no longer be inline (for relevant format)

#if revlogv1

  $ hg debugrevlog -c | grep inline
  [1]

#endif

  $ make_one_pull tip
  pre-commit: 403 third
  external: 403 third
  internal: 503 r500
  post-tr:  503 r500

#if revlogv1

  $ hg debugrevlog -c | grep inline
  [1]

#endif