view tests/test-symlinks.t @ 47010:76ae43d5b1db stable

repoview: fix memory leak of filtered repo classes

The leak occurs in long-running server processes with
extensions, and is measured at 110kB per request.

Before this change, the contents of the `_filteredrepotypes`
cache are not properly garbage collected, despite it begin
a `WeakKeyDictionary`.

Extensions have a tendency to generate a new repository class
for each `localrepo` instantiation. Server processes based
on `hgwebdir_mod` will instantiate a new `localrepo` for each
HTTP request that involves a repository.

As a result, with a testing process that repeatedly opens a
repository with several extensions activated
(`topic` notably among them), we see a steady increase in
resident memory of 110kB per repository instantiation before this
change. This is also true, if we call `gc.collect()` at each
instantiation, like `hgwebdir_mod` does, or not.

The cause of the leak is that the *values* aren't weak references.
This change uses `weakref.ref` for the values, and this makes
in our measurements the resident size increase drop to 5kB per
repository instantiation, with no explicit call of `gc.collect()`
at all.
There is currently no reason to believe that this remaining leak
of 5kB is related to or even due to Mercurial core.

We've also seen evidence that `ui.ui` instances weren't properly
garbage collected before the change (with the change, they are).
This could explain why the figures are relatively high.

In theory, the collection of weak references could lead to
much more misses in the cache, so we measured the impact on
the original case that was motivation for introducing that cache
in 7e89bd0cfb86 (see also issue5043): `hg convert` of the
mozilla-central repository. The bad news here is that there is a
major memory leak there, both with and without the present changeset.
There were no more cache misses, and we could see no
more memory leak with this change: the resident size after importing
roughly 100000 changesets was at 12.4GB before, and 12.5GB after.
The small increase is mentioned for completeness only, and we
believe that it should be ignored, at least as long as the main
leak isn't fixed. At less than 1% of the main leak, even finding out
whether it is merely noise would be wasteful.

Original context where this was spotted and first mitigated:
  https://foss.heptapod.net/heptapod/heptapod/-/issues/466

The leak reduction was also obtained in Heptapod inner HTTP server,
which amounts to the same as `hgwebdir_mod` for these questions.

The measurements done with Python 3.9, similar figures seen with 3.8.
More work on our side would be needed to give measurements with 2.7,
because of testing server process does not support it.

#require symlink

== tests added in 0.7 ==

  $ hg init test-symlinks-0.7; cd test-symlinks-0.7;
  $ touch foo; ln -s foo bar; ln -s nonexistent baz

import with add and addremove -- symlink walking should _not_ screwup.

  $ hg add
  adding bar
  adding baz
  adding foo
  $ hg forget bar baz foo
  $ hg addremove
  adding bar
  adding baz
  adding foo

commit -- the symlink should _not_ appear added to dir state

  $ hg commit -m 'initial'

  $ touch bomb

again, symlink should _not_ show up on dir state

  $ hg addremove
  adding bomb

Assert screamed here before, should go by without consequence

  $ hg commit -m 'is there a bug?'
  $ cd ..


== fifo & ignore ==

  $ hg init test; cd test;

  $ mkdir dir
  $ touch a.c dir/a.o dir/b.o

test what happens if we want to trick hg

  $ hg commit -A -m 0
  adding a.c
  adding dir/a.o
  adding dir/b.o
  $ echo "relglob:*.o" > .hgignore
  $ rm a.c
  $ rm dir/a.o
  $ rm dir/b.o
  $ mkdir dir/a.o
  $ ln -s nonexistent dir/b.o
  $ mkfifo a.c

it should show a.c, dir/a.o and dir/b.o deleted

  $ hg status
  M dir/b.o
  ! a.c
  ! dir/a.o
  ? .hgignore
  $ hg status a.c
  a.c: unsupported file type (type is fifo)
  ! a.c
  $ cd ..


== symlinks from outside the tree ==

test absolute path through symlink outside repo

  $ p=`pwd`
  $ hg init x
  $ ln -s x y
  $ cd x
  $ touch f
  $ hg add f
  $ hg status "$p"/y/f
  A f

try symlink outside repo to file inside

  $ ln -s x/f ../z

this should fail

  $ hg status ../z && { echo hg mistakenly exited with status 0; exit 1; } || :
  abort: ../z not under root '$TESTTMP/x'
  $ cd ..


== cloning symlinks ==
  $ hg init clone; cd clone;

try cloning symlink in a subdir
1. commit a symlink

  $ mkdir -p a/b/c
  $ cd a/b/c
  $ ln -s /path/to/symlink/source demo
  $ cd ../../..
  $ hg stat
  ? a/b/c/demo
  $ hg commit -A -m 'add symlink in a/b/c subdir'
  adding a/b/c/demo

2. clone it

  $ cd ..
  $ hg clone clone clonedest
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved


== symlink and git diffs ==

git symlink diff

  $ cd clonedest
  $ hg diff --git -r null:tip
  diff --git a/a/b/c/demo b/a/b/c/demo
  new file mode 120000
  --- /dev/null
  +++ b/a/b/c/demo
  @@ -0,0 +1,1 @@
  +/path/to/symlink/source
  \ No newline at end of file
  $ hg export --git tip > ../sl.diff

import git symlink diff

  $ hg rm a/b/c/demo
  $ hg commit -m'remove link'
  $ hg import ../sl.diff
  applying ../sl.diff
  $ hg diff --git -r 1:tip
  diff --git a/a/b/c/demo b/a/b/c/demo
  new file mode 120000
  --- /dev/null
  +++ b/a/b/c/demo
  @@ -0,0 +1,1 @@
  +/path/to/symlink/source
  \ No newline at end of file

== symlinks and addremove ==

directory moved and symlinked

  $ mkdir foo
  $ touch foo/a
  $ hg ci -Ama
  adding foo/a
  $ mv foo bar
  $ ln -s bar foo
  $ hg status
  ! foo/a
  ? bar/a
  ? foo

now addremove should remove old files

  $ hg addremove
  adding bar/a
  adding foo
  removing foo/a

commit and update back

  $ hg ci -mb
  $ hg up '.^'
  1 files updated, 0 files merged, 2 files removed, 0 files unresolved
  $ hg up tip
  2 files updated, 0 files merged, 1 files removed, 0 files unresolved

  $ cd ..

== root of repository is symlinked ==

  $ hg init root
  $ ln -s root link
  $ cd root
  $ echo foo > foo
  $ hg status
  ? foo
  $ hg status ../link
  ? foo
  $ hg add foo
  $ hg cp foo "$TESTTMP/link/bar"
  foo has not been committed yet, so no copy data will be stored for bar.
  $ cd ..


  $ hg init b
  $ cd b
  $ ln -s nothing dangling
  $ hg commit -m 'commit symlink without adding' dangling
  abort: dangling: file not tracked!
  [10]
  $ hg add dangling
  $ hg commit -m 'add symlink'

  $ hg tip -v
  changeset:   0:cabd88b706fc
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  files:       dangling
  description:
  add symlink
  
  
  $ hg manifest --debug
  2564acbe54bbbedfbf608479340b359f04597f80 644 @ dangling
  $ readlink.py dangling
  dangling -> nothing

  $ rm dangling
  $ ln -s void dangling
  $ hg commit -m 'change symlink'
  $ readlink.py dangling
  dangling -> void


modifying link

  $ rm dangling
  $ ln -s empty dangling
  $ readlink.py dangling
  dangling -> empty


reverting to rev 0:

  $ hg revert -r 0 -a
  reverting dangling
  $ readlink.py dangling
  dangling -> nothing


backups:

  $ readlink.py *.orig
  dangling.orig -> empty
  $ rm *.orig
  $ hg up -C
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

copies

  $ hg cp -v dangling dangling2
  copying dangling to dangling2
  $ hg st -Cmard
  A dangling2
    dangling
  $ readlink.py dangling dangling2
  dangling -> void
  dangling2 -> void


Issue995: hg copy -A incorrectly handles symbolic links

  $ hg up -C
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ mkdir dir
  $ ln -s dir dirlink
  $ hg ci -qAm 'add dirlink'
  $ mkdir newdir
  $ mv dir newdir/dir
  $ mv dirlink newdir/dirlink
  $ hg mv -A dirlink newdir/dirlink

  $ cd ..