comparison tests/test-tags.t @ 24735:07200e3332a1

tags: extract .hgtags filenodes cache to a standalone file

Resolution of .hgtags filenodes values has historically been a
performance pain point for large repositories, where reading individual
manifests can take over 100ms. Multiplied by hundreds or even thousands
of heads and resolving .hgtags filenodes becomes a performance issue.

This patch establishes a standalone cache file holding the .hgtags
filenodes for each changeset. After this patch, the .hgtags filenode
for any particular changeset should only have to be computed once
during the lifetime of the repository.

The introduced hgtagsfnodes1 cache file is modeled after the rev branch
cache: the cache is effectively an array of entries consisting of a
changeset fragment and the filenode for a revision. The file grows in
proportion to the length of the repository (24 bytes per changeset) and
is truncated when the repository is stripped. The file is not written
unless tag info is requested and tags have changed since last time.

This patch partially addresses issue4550. Future patches will split the
"tags" cache file into per-filter files and will refactor the cache
format to not capture the .hgtags fnodes, as these are now stored in
the hgtagsfnodes1 cache. This patch is capable of standing alone. We
should not have to wait on the tags cache filter split and format
refactor for this patch to land.

24734:fb6cb1b82f4f

  $ cacheexists() {
  >   [ -f .hg/cache/tags ] && echo "tag cache exists" || echo "no tag cache"
  > }

  $ dumptags() {
  >     rev=$1
  >     echo "rev $rev: .hgtags:"
  >     hg cat -r$rev .hgtags
  > }

  $ hg init t
  $ cd t
  $ cacheexists
  no tag cache
  $ hg id
  000000000000 tip
  $ cacheexists
  no tag cache
  $ echo a > a
  $ hg add a
  $ hg commit -m "test"
  $ hg co
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg identify
  acb14030fe0a tip
  $ cacheexists
  tag cache exists

Try corrupting the cache

  $ printf 'a b' > .hg/cache/tags
  $ hg identify
  acb14030fe0a tip
  $ cacheexists
  tag cache exists
  $ hg identify
  acb14030fe0a tip

Create local tag with long name:

  tip                                1:b9154636be93
  first                              0:acb14030fe0a
  $ hg identify
  b9154636be93 tip

Repeat with cold tag cache:

  $ rm -f .hg/cache/tags
  $ hg identify
  b9154636be93 tip

And again, but now unable to write tag cache:

#if unix-permissions
  $ rm -f .hg/cache/tags
  $ chmod 555 .hg
  $ hg identify
  b9154636be93 tip
  $ chmod 755 .hg
#endif

Tag cache debug info written to blackbox log

  $ rm -f .hg/cache/tags
  $ hg identify
  b9154636be93 tip
  $ hg blackbox -l 4
  1970/01/01 00:00:00 bob> identify
  1970/01/01 00:00:00 bob> resolved 1 tags cache entries from 1 manifests in ?.???? seconds (glob)
  1970/01/01 00:00:00 bob> writing tags cache file with 1 heads and 1 tags
  1970/01/01 00:00:00 bob> identify exited 0 after ?.?? seconds (glob)


Create a branch:

  $ echo bb > a
  $ hg status

  M a
  $ echo 1 > b
  $ hg add b
  $ hg commit -m "branch"
  created new head
  $ hg id
  c8edf04160c7 tip

Merge the two heads:

  $ hg merge 1
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  2 7a94127795a33c10a370c93f731fd9fea0b79af6 0c04f2a8af31de17fab7422878ee5a2dadbc943d
  
  bbd179dfa0a71671c253b3ae0aa1513b60d199fa bar
  bbd179dfa0a71671c253b3ae0aa1513b60d199fa bar
  78391a272241d70354aa14c874552cad6b51bb42 bar

Test tag removal:

  $ hg tag --remove bar     # rev 5
  $ hg tip -vp

24735:07200e3332a1

  $ cacheexists() {
  >   [ -f .hg/cache/tags ] && echo "tag cache exists" || echo "no tag cache"
  > }

  $ fnodescacheexists() {
  >   [ -f .hg/cache/hgtagsfnodes1 ] && echo "fnodes cache exists" || echo "no fnodes cache"
  > }

  $ dumptags() {
  >     rev=$1
  >     echo "rev $rev: .hgtags:"
  >     hg cat -r$rev .hgtags
  > }

  $ hg init t
  $ cd t
  $ cacheexists
  no tag cache
  $ fnodescacheexists
  no fnodes cache
  $ hg id
  000000000000 tip
  $ cacheexists
  no tag cache
  $ fnodescacheexists
  no fnodes cache
  $ echo a > a
  $ hg add a
  $ hg commit -m "test"
  $ hg co
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg identify
  acb14030fe0a tip
  $ cacheexists
  tag cache exists
No fnodes cache because .hgtags file doesn't exist
(this is an implementation detail)
  $ fnodescacheexists
  no fnodes cache

Try corrupting the cache

  $ printf 'a b' > .hg/cache/tags
  $ hg identify
  acb14030fe0a tip
  $ cacheexists
  tag cache exists
  $ fnodescacheexists
  no fnodes cache
  $ hg identify
  acb14030fe0a tip

Create local tag with long name:

  tip                                1:b9154636be93
  first                              0:acb14030fe0a
  $ hg identify
  b9154636be93 tip

We should have a fnodes cache now that we have a real tag
The cache should have an empty entry for rev 0 and a valid entry for rev 1.


  $ fnodescacheexists
  fnodes cache exists
  $ f --size --hexdump .hg/cache/hgtagsfnodes1
  .hg/cache/hgtagsfnodes1: size=48
  0000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff |................|
  0010: ff ff ff ff ff ff ff ff b9 15 46 36 26 b7 b4 a7 |..........F6&...|
  0020: 73 e0 9e e3 c5 2f 51 0e 19 e0 5e 1f f9 66 d8 59 |s..../Q...^..f.Y|

Repeat with cold tag cache:

  $ rm -f .hg/cache/tags .hg/cache/hgtagsfnodes1
  $ hg identify
  b9154636be93 tip

  $ fnodescacheexists
  fnodes cache exists
  $ f --size --hexdump .hg/cache/hgtagsfnodes1
  .hg/cache/hgtagsfnodes1: size=48
  0000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff |................|
  0010: ff ff ff ff ff ff ff ff b9 15 46 36 26 b7 b4 a7 |..........F6&...|
  0020: 73 e0 9e e3 c5 2f 51 0e 19 e0 5e 1f f9 66 d8 59 |s..../Q...^..f.Y|

And again, but now unable to write tag cache:

#if unix-permissions
  $ rm -f .hg/cache/tags .hg/cache/hgtagsfnodes1
  $ chmod 555 .hg/cache
  $ hg identify
  b9154636be93 tip
  $ chmod 755 .hg/cache
#endif

Tag cache debug info written to blackbox log

  $ rm -f .hg/cache/tags .hg/cache/hgtagsfnodes1
  $ hg identify
  b9154636be93 tip
  $ hg blackbox -l 5
  1970/01/01 00:00:00 bob> identify
  1970/01/01 00:00:00 bob> writing 48 bytes to cache/hgtagsfnodes1
  1970/01/01 00:00:00 bob> 0/1 cache hits/lookups in * seconds (glob)
  1970/01/01 00:00:00 bob> writing tags cache file with 1 heads and 1 tags
  1970/01/01 00:00:00 bob> identify exited 0 after ?.?? seconds (glob)

Failure to acquire lock results in no write

  $ rm -f .hg/cache/tags .hg/cache/hgtagsfnodes1
  $ echo 'foo:1' > .hg/wlock
  $ hg identify
  b9154636be93 tip
  $ hg blackbox -l 5
  1970/01/01 00:00:00 bob> identify
  1970/01/01 00:00:00 bob> not writing .hg/cache/hgtagsfnodes1 because lock held
  1970/01/01 00:00:00 bob> 0/1 cache hits/lookups in * seconds (glob)
  1970/01/01 00:00:00 bob> writing tags cache file with 1 heads and 1 tags
  1970/01/01 00:00:00 bob> identify exited 0 after * seconds (glob)

  $ fnodescacheexists
  no fnodes cache

  $ rm .hg/wlock

  $ rm -f .hg/cache/tags .hg/cache/hgtagsfnodes1
  $ hg identify
  b9154636be93 tip

Create a branch:

  $ echo bb > a
  $ hg status

  M a
  $ echo 1 > b
  $ hg add b
  $ hg commit -m "branch"
  created new head

Creating a new commit shouldn't append the .hgtags fnodes cache until
tags info is accessed

  $ f --size --hexdump .hg/cache/hgtagsfnodes1
  .hg/cache/hgtagsfnodes1: size=48
  0000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff |................|
  0010: ff ff ff ff ff ff ff ff b9 15 46 36 26 b7 b4 a7 |..........F6&...|
  0020: 73 e0 9e e3 c5 2f 51 0e 19 e0 5e 1f f9 66 d8 59 |s..../Q...^..f.Y|

  $ hg id
  c8edf04160c7 tip

First 4 bytes of record 3 are changeset fragment

  $ f --size --hexdump .hg/cache/hgtagsfnodes1
  .hg/cache/hgtagsfnodes1: size=72
  0000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff |................|
  0010: ff ff ff ff ff ff ff ff b9 15 46 36 26 b7 b4 a7 |..........F6&...|
  0020: 73 e0 9e e3 c5 2f 51 0e 19 e0 5e 1f f9 66 d8 59 |s..../Q...^..f.Y|
  0030: c8 ed f0 41 00 00 00 00 00 00 00 00 00 00 00 00 |...A............|
  0040: 00 00 00 00 00 00 00 00                         |........|

Merge the two heads:

  $ hg merge 1
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  2 7a94127795a33c10a370c93f731fd9fea0b79af6 0c04f2a8af31de17fab7422878ee5a2dadbc943d
  
  bbd179dfa0a71671c253b3ae0aa1513b60d199fa bar
  bbd179dfa0a71671c253b3ae0aa1513b60d199fa bar
  78391a272241d70354aa14c874552cad6b51bb42 bar

  $ f --size --hexdump .hg/cache/hgtagsfnodes1
  .hg/cache/hgtagsfnodes1: size=120
  0000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff |................|
  0010: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff |................|
  0020: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff |................|
  0030: 7a 94 12 77 0c 04 f2 a8 af 31 de 17 fa b7 42 28 |z..w.....1....B(|
  0040: 78 ee 5a 2d ad bc 94 3d 6f a4 50 21 7d 3b 71 8c |x.Z-...=o.P!};q.|
  0050: 96 4e f3 7b 89 e5 50 eb da fd 57 89 e7 6c e1 b0 |.N.{..P...W..l..|
  0060: 0c 19 2d 7d 0c 04 f2 a8 af 31 de 17 fa b7 42 28 |..-}.....1....B(|
  0070: 78 ee 5a 2d ad bc 94 3d                         |x.Z-...=|

Corrupt the .hgtags fnodes cache
Extra junk data at the end should get overwritten on next cache update

  $ echo extra >> .hg/cache/hgtagsfnodes1
  $ echo dummy1 > foo
  $ hg commit -m throwaway1

  $ hg tags
  tip                                5:8dbfe60eff30
  bar                                1:78391a272241

  $ hg blackbox -l 5
  1970/01/01 00:00:00 bob> tags
  1970/01/01 00:00:00 bob> writing 24 bytes to cache/hgtagsfnodes1
  1970/01/01 00:00:00 bob> 0/1 cache hits/lookups in * seconds (glob)
  1970/01/01 00:00:00 bob> writing tags cache file with 3 heads and 1 tags
  1970/01/01 00:00:00 bob> tags exited 0 after * seconds (glob)

#if unix-permissions no-root
Errors writing to .hgtags fnodes cache are silently ignored

  $ echo dummy2 > foo
  $ hg commit -m throwaway2

  $ chmod a-w .hg/cache/hgtagsfnodes1
  $ rm -f .hg/cache/tags

  $ hg tags
  tip                                6:b968051b5cf3
  bar                                1:78391a272241

  $ hg blackbox -l 5
  1970/01/01 00:00:00 bob> tags
  1970/01/01 00:00:00 bob> couldn't write cache/hgtagsfnodes1: [Errno 13] Permission denied: '$TESTTMP/t2/.hg/cache/hgtagsfnodes1'
  1970/01/01 00:00:00 bob> 2/3 cache hits/lookups in * seconds (glob)
  1970/01/01 00:00:00 bob> writing tags cache file with 3 heads and 1 tags
  1970/01/01 00:00:00 bob> tags exited 0 after * seconds (glob)

  $ chmod a+w .hg/cache/hgtagsfnodes1
#endif

  $ rm -f .hg/cache/tags
  $ hg tags
  tip                                6:b968051b5cf3
  bar                                1:78391a272241

  $ hg blackbox -l 5
  1970/01/01 00:00:00 bob> tags
  1970/01/01 00:00:00 bob> writing 24 bytes to cache/hgtagsfnodes1
  1970/01/01 00:00:00 bob> 2/3 cache hits/lookups in * seconds (glob)
  1970/01/01 00:00:00 bob> writing tags cache file with 3 heads and 1 tags
  1970/01/01 00:00:00 bob> tags exited 0 after * seconds (glob)

  $ f --size .hg/cache/hgtagsfnodes1
  .hg/cache/hgtagsfnodes1: size=168

Stripping doesn't truncate the tags cache until new data is available

  $ hg -q --config extensions.strip= strip -r 5 --no-backup
  $ hg tags
  tip                                4:0c192d7d5e6b
  bar                                1:78391a272241

  $ hg blackbox -l 4
  1970/01/01 00:00:00 bob> tags
  1970/01/01 00:00:00 bob> 1/1 cache hits/lookups in * seconds (glob)
  1970/01/01 00:00:00 bob> writing tags cache file with 3 heads and 1 tags
  1970/01/01 00:00:00 bob> tags exited 0 after * seconds (glob)

  $ f --size .hg/cache/hgtagsfnodes1
  .hg/cache/hgtagsfnodes1: size=168

  $ echo dummy > foo
  $ hg commit -m throwaway3

  $ hg tags
  tip                                5:035f65efb448
  bar                                1:78391a272241

  $ hg blackbox -l 5
  1970/01/01 00:00:00 bob> tags
  1970/01/01 00:00:00 bob> writing 24 bytes to cache/hgtagsfnodes1
  1970/01/01 00:00:00 bob> 0/1 cache hits/lookups in * seconds (glob)
  1970/01/01 00:00:00 bob> writing tags cache file with 3 heads and 1 tags
  1970/01/01 00:00:00 bob> tags exited 0 after * seconds (glob)
  $ f --size .hg/cache/hgtagsfnodes1
  .hg/cache/hgtagsfnodes1: size=144

  $ hg -q --config extensions.strip= strip -r 5 --no-backup

Test tag removal:

  $ hg tag --remove bar     # rev 5
  $ hg tip -vp