diff 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.

--- a/tests/test-tags.t	Wed Apr 15 12:18:05 2015 -0400
+++ b/tests/test-tags.t	Wed Apr 15 17:42:38 2015 -0400
@@ -12,6 +12,10 @@
   >   [ -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:"
@@ -28,10 +32,14 @@
   $ 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"
@@ -41,6 +49,10 @@
   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
 
@@ -49,6 +61,8 @@
   acb14030fe0a tip
   $ cacheexists
   tag cache exists
+  $ fnodescacheexists
+  no fnodes cache
   $ hg identify
   acb14030fe0a tip
 
@@ -74,33 +88,75 @@
   $ 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
+  $ 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
-  $ chmod 555 .hg
+  $ rm -f .hg/cache/tags .hg/cache/hgtagsfnodes1
+  $ chmod 555 .hg/cache
   $ hg identify
   b9154636be93 tip
-  $ chmod 755 .hg
+  $ chmod 755 .hg/cache
 #endif
 
 Tag cache debug info written to blackbox log
 
-  $ rm -f .hg/cache/tags
+  $ rm -f .hg/cache/tags .hg/cache/hgtagsfnodes1
   $ hg identify
   b9154636be93 tip
-  $ hg blackbox -l 4
+  $ hg blackbox -l 5
   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 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:
 
@@ -121,9 +177,29 @@
   $ 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
@@ -244,6 +320,107 @@
   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