view tests/test-hardlinks.t @ 39764:e4e881572382

localrepo: iteratively derive local repository type

This commit implements the dynamic local repository type derivation
that was explained in the recent commit
bfeab472e3c0 "localrepo: create new function for instantiating a local
repo object."

Instead of a static localrepository class/type which must be customized
after construction, we now dynamically construct a type by building up
base classes/types to represent specific repository interfaces.

Conceptually, the end state is similar to what was happening when
various extensions would monkeypatch the __class__ of newly-constructed
repo instances. However, the approach is inverted. Instead of making
the instance then customizing it, we do the customization up front
by influencing the behavior of the type then we instantiate that
custom type.

This approach gives us much more flexibility. For example, we can
use completely separate classes for implementing different aspects
of the repository. For example, we could have one class representing
revlog-based file storage and another representing non-revlog based
file storage. When then choose which implementation to use based on
the presence of repo requirements.

A concern with this approach is that it creates a lot more types
and complexity and that complexity adds overhead. Yes, it is true that
this approach will result in more types being created. Yes, this is
more complicated than traditional "instantiate a static type." However,
I believe the alternatives to supporting alternate storage backends
are just as complicated. (Before I arrived at this solution, I had
patches storing factory functions on local repo instances for e.g.
constructing a file storage instance. We ended up having a handful
of these. And this was logically identical to assigning custom
methods. Since we were logically changing the type of the instance,
I figured it would be better to just use specialized types instead
of introducing levels of abstraction at run-time.)

On the performance front, I don't believe that having N base classes
has any significant performance overhead compared to just a single base
class. Intuition says that Python will need to iterate the base classes
to find an attribute. However, CPython caches method lookups: as long as
the __class__ or MRO isn't changing, method attribute lookup should be
constant time after first access. And non-method attributes are stored
in __dict__, of which there is only 1 per object, so the number of
base classes for __dict__ is irrelevant.

Anyway, this commit splits up the monolithic completelocalrepository
interface into sub-interfaces: 1 for file storage and 1 representing
everything else.

We've taught ``makelocalrepository()`` to call a series of factory
functions which will produce types implementing specific interfaces.
It then calls type() to create a new type from the built-up list of
base types.

This commit should be considered a start and not the end state. I
suspect we'll hit a number of problems as we start to implement
alternate storage backends:

* Passing custom arguments to __init__ and setting custom attributes
  on __dict__.
* Customizing the set of interfaces that are needed. e.g. the
  "readonly" intent could translate to not requesting an interface
  providing methods related to writing.
* More ergonomic way for extensions to insert themselves so their
  callbacks aren't unconditionally called.
* Wanting to modify vfs instances, other arguments passed to __init__.

That being said, this code is usable in its current state and I'm
convinced future commits will demonstrate the value in this approach.

Differential Revision: https://phab.mercurial-scm.org/D4642

#require hardlink reporevlogstore

  $ cat > nlinks.py <<EOF
  > from __future__ import print_function
  > import sys
  > from mercurial import util
  > for f in sorted(sys.stdin.readlines()):
  >     f = f[:-1]
  >     print(util.nlinks(f), f)
  > EOF

  $ nlinksdir()
  > {
  >     find "$@" -type f | "$PYTHON" $TESTTMP/nlinks.py
  > }

Some implementations of cp can't create hardlinks (replaces 'cp -al' on Linux):

  $ cat > linkcp.py <<EOF
  > from __future__ import absolute_import
  > import sys
  > from mercurial import util
  > util.copyfiles(sys.argv[1], sys.argv[2], hardlink=True)
  > EOF

  $ linkcp()
  > {
  >     "$PYTHON" $TESTTMP/linkcp.py $1 $2
  > }

Prepare repo r1:

  $ hg init r1
  $ cd r1

  $ echo c1 > f1
  $ hg add f1
  $ hg ci -m0

  $ mkdir d1
  $ cd d1
  $ echo c2 > f2
  $ hg add f2
  $ hg ci -m1
  $ cd ../..

  $ nlinksdir r1/.hg/store
  1 r1/.hg/store/00changelog.i
  1 r1/.hg/store/00manifest.i
  1 r1/.hg/store/data/d1/f2.i
  1 r1/.hg/store/data/f1.i
  1 r1/.hg/store/fncache (repofncache !)
  1 r1/.hg/store/phaseroots
  1 r1/.hg/store/undo
  1 r1/.hg/store/undo.backup.fncache (repofncache !)
  1 r1/.hg/store/undo.backupfiles
  1 r1/.hg/store/undo.phaseroots


Create hardlinked clone r2:

  $ hg clone -U --debug r1 r2 --config progress.debug=true
  linking: 1
  linking: 2
  linking: 3
  linking: 4
  linking: 5
  linking: 6
  linking: 7
  linked 7 files

Create non-hardlinked clone r3:

  $ hg clone --pull r1 r3
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 2 changesets with 2 changes to 2 files
  new changesets 40d85e9847f2:7069c422939c
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved


Repos r1 and r2 should now contain hardlinked files:

  $ nlinksdir r1/.hg/store
  2 r1/.hg/store/00changelog.i
  2 r1/.hg/store/00manifest.i
  2 r1/.hg/store/data/d1/f2.i
  2 r1/.hg/store/data/f1.i
  2 r1/.hg/store/fncache (repofncache !)
  1 r1/.hg/store/phaseroots
  1 r1/.hg/store/undo
  1 r1/.hg/store/undo.backup.fncache (repofncache !)
  1 r1/.hg/store/undo.backupfiles
  1 r1/.hg/store/undo.phaseroots

  $ nlinksdir r2/.hg/store
  2 r2/.hg/store/00changelog.i
  2 r2/.hg/store/00manifest.i
  2 r2/.hg/store/data/d1/f2.i
  2 r2/.hg/store/data/f1.i
  2 r2/.hg/store/fncache (repofncache !)

Repo r3 should not be hardlinked:

  $ nlinksdir r3/.hg/store
  1 r3/.hg/store/00changelog.i
  1 r3/.hg/store/00manifest.i
  1 r3/.hg/store/data/d1/f2.i
  1 r3/.hg/store/data/f1.i
  1 r3/.hg/store/fncache (repofncache !)
  1 r3/.hg/store/phaseroots
  1 r3/.hg/store/undo
  1 r3/.hg/store/undo.backupfiles
  1 r3/.hg/store/undo.phaseroots


Create a non-inlined filelog in r3:

  $ cd r3/d1
  >>> f = open('data1', 'wb')
  >>> for x in range(10000):
  ...     f.write(b"%d\n" % x) and None
  >>> f.close()
  $ for j in 0 1 2 3 4 5 6 7 8 9; do
  >   cat data1 >> f2
  >   hg commit -m$j
  > done
  $ cd ../..

  $ nlinksdir r3/.hg/store
  1 r3/.hg/store/00changelog.i
  1 r3/.hg/store/00manifest.i
  1 r3/.hg/store/data/d1/f2.d
  1 r3/.hg/store/data/d1/f2.i
  1 r3/.hg/store/data/f1.i
  1 r3/.hg/store/fncache (repofncache !)
  1 r3/.hg/store/phaseroots
  1 r3/.hg/store/undo
  1 r3/.hg/store/undo.backup.fncache (repofncache !)
  1 r3/.hg/store/undo.backup.phaseroots
  1 r3/.hg/store/undo.backupfiles
  1 r3/.hg/store/undo.phaseroots

Push to repo r1 should break up most hardlinks in r2:

  $ hg -R r2 verify
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  checked 2 changesets with 2 changes to 2 files

  $ cd r3
  $ hg push
  pushing to $TESTTMP/r1
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 10 changesets with 10 changes to 1 files

  $ cd ..

  $ nlinksdir r2/.hg/store
  1 r2/.hg/store/00changelog.i
  1 r2/.hg/store/00manifest.i
  1 r2/.hg/store/data/d1/f2.i
  2 r2/.hg/store/data/f1.i
  [12] r2/\.hg/store/fncache (re) (repofncache !)

#if hardlink-whitelisted repofncache
  $ nlinksdir r2/.hg/store/fncache
  2 r2/.hg/store/fncache
#endif

  $ hg -R r2 verify
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  checked 2 changesets with 2 changes to 2 files


  $ cd r1
  $ hg up
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

Committing a change to f1 in r1 must break up hardlink f1.i in r2:

  $ echo c1c1 >> f1
  $ hg ci -m00
  $ cd ..

  $ nlinksdir r2/.hg/store
  1 r2/.hg/store/00changelog.i
  1 r2/.hg/store/00manifest.i
  1 r2/.hg/store/data/d1/f2.i
  1 r2/.hg/store/data/f1.i
  [12] r2/\.hg/store/fncache (re) (repofncache !)

#if hardlink-whitelisted repofncache
  $ nlinksdir r2/.hg/store/fncache
  2 r2/.hg/store/fncache
#endif

Create a file which exec permissions we will change
  $ cd r3
  $ echo "echo hello world" > f3
  $ hg add f3
  $ hg ci -mf3
  $ cd ..

  $ cd r3
  $ hg tip --template '{rev}:{node|short}\n'
  12:d3b77733a28a
  $ echo bla > f1
  $ chmod +x f3
  $ hg ci -m1
  $ cd ..

Create hardlinked copy r4 of r3 (on Linux, we would call 'cp -al'):

  $ linkcp r3 r4

'checklink' is produced by hardlinking a symlink, which is undefined whether
the symlink should be followed or not. It does behave differently on Linux and
BSD. Just remove it so the test pass on both platforms.

  $ rm -f r4/.hg/cache/checklink

r4 has hardlinks in the working dir (not just inside .hg):

  $ nlinksdir r4
  2 r4/.hg/00changelog.i
  2 r4/.hg/branch
  2 r4/.hg/cache/branch2-base
  2 r4/.hg/cache/branch2-served
  2 r4/.hg/cache/checkisexec (execbit !)
  ? r4/.hg/cache/checklink-target (glob) (symlink !)
  2 r4/.hg/cache/checknoexec (execbit !)
  2 r4/.hg/cache/manifestfulltextcache (reporevlogstore !)
  2 r4/.hg/cache/rbc-names-v1
  2 r4/.hg/cache/rbc-revs-v1
  2 r4/.hg/dirstate
  2 r4/.hg/fsmonitor.state (fsmonitor !)
  2 r4/.hg/hgrc
  2 r4/.hg/last-message.txt
  2 r4/.hg/requires
  2 r4/.hg/store/00changelog.i
  2 r4/.hg/store/00manifest.i
  2 r4/.hg/store/data/d1/f2.d
  2 r4/.hg/store/data/d1/f2.i
  2 r4/.hg/store/data/f1.i
  2 r4/.hg/store/data/f3.i
  2 r4/.hg/store/fncache (repofncache !)
  2 r4/.hg/store/phaseroots
  2 r4/.hg/store/undo
  2 r4/.hg/store/undo.backup.fncache (repofncache !)
  2 r4/.hg/store/undo.backup.phaseroots
  2 r4/.hg/store/undo.backupfiles
  2 r4/.hg/store/undo.phaseroots
  [24] r4/\.hg/undo\.backup\.dirstate (re)
  2 r4/.hg/undo.bookmarks
  2 r4/.hg/undo.branch
  2 r4/.hg/undo.desc
  [24] r4/\.hg/undo\.dirstate (re)
  2 r4/d1/data1
  2 r4/d1/f2
  2 r4/f1
  2 r4/f3

Update back to revision 12 in r4 should break hardlink of file f1 and f3:
#if hardlink-whitelisted
  $ nlinksdir r4/.hg/undo.backup.dirstate r4/.hg/undo.dirstate
  4 r4/.hg/undo.backup.dirstate
  4 r4/.hg/undo.dirstate
#endif


  $ hg -R r4 up 12
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved (execbit !)
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved (no-execbit !)

  $ nlinksdir r4
  2 r4/.hg/00changelog.i
  1 r4/.hg/branch
  2 r4/.hg/cache/branch2-base
  2 r4/.hg/cache/branch2-served
  2 r4/.hg/cache/checkisexec (execbit !)
  2 r4/.hg/cache/checklink-target (symlink !)
  2 r4/.hg/cache/checknoexec (execbit !)
  2 r4/.hg/cache/manifestfulltextcache (reporevlogstore !)
  2 r4/.hg/cache/rbc-names-v1
  2 r4/.hg/cache/rbc-revs-v1
  1 r4/.hg/dirstate
  1 r4/.hg/fsmonitor.state (fsmonitor !)
  2 r4/.hg/hgrc
  2 r4/.hg/last-message.txt
  2 r4/.hg/requires
  2 r4/.hg/store/00changelog.i
  2 r4/.hg/store/00manifest.i
  2 r4/.hg/store/data/d1/f2.d
  2 r4/.hg/store/data/d1/f2.i
  2 r4/.hg/store/data/f1.i
  2 r4/.hg/store/data/f3.i
  2 r4/.hg/store/fncache
  2 r4/.hg/store/phaseroots
  2 r4/.hg/store/undo
  2 r4/.hg/store/undo.backup.fncache (repofncache !)
  2 r4/.hg/store/undo.backup.phaseroots
  2 r4/.hg/store/undo.backupfiles
  2 r4/.hg/store/undo.phaseroots
  [24] r4/\.hg/undo\.backup\.dirstate (re)
  2 r4/.hg/undo.bookmarks
  2 r4/.hg/undo.branch
  2 r4/.hg/undo.desc
  [24] r4/\.hg/undo\.dirstate (re)
  2 r4/d1/data1
  2 r4/d1/f2
  1 r4/f1
  1 r4/f3 (execbit !)
  2 r4/f3 (no-execbit !)

#if hardlink-whitelisted
  $ nlinksdir r4/.hg/undo.backup.dirstate r4/.hg/undo.dirstate
  4 r4/.hg/undo.backup.dirstate
  4 r4/.hg/undo.dirstate
#endif

Test hardlinking outside hg:

  $ mkdir x
  $ echo foo > x/a

  $ linkcp x y
  $ echo bar >> y/a

No diff if hardlink:

  $ diff x/a y/a

Test mq hardlinking:

  $ echo "[extensions]" >> $HGRCPATH
  $ echo "mq=" >> $HGRCPATH

  $ hg init a
  $ cd a

  $ hg qimport -n foo - << EOF
  > # HG changeset patch
  > # Date 1 0
  > diff -r 2588a8b53d66 a
  > --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
  > +++ b/a	Wed Jul 23 15:54:29 2008 +0200
  > @@ -0,0 +1,1 @@
  > +a
  > EOF
  adding foo to series file

  $ hg qpush
  applying foo
  now at: foo

  $ cd ..
  $ linkcp a b
  $ cd b

  $ hg qimport -n bar - << EOF
  > # HG changeset patch
  > # Date 2 0
  > diff -r 2588a8b53d66 a
  > --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
  > +++ b/b	Wed Jul 23 15:54:29 2008 +0200
  > @@ -0,0 +1,1 @@
  > +b
  > EOF
  adding bar to series file

  $ hg qpush
  applying bar
  now at: bar

  $ cat .hg/patches/status
  430ed4828a74fa4047bc816a25500f7472ab4bfe:foo
  4e7abb4840c46a910f6d7b4d3c3fc7e5209e684c:bar

  $ cat .hg/patches/series
  foo
  bar

  $ cat ../a/.hg/patches/status
  430ed4828a74fa4047bc816a25500f7472ab4bfe:foo

  $ cat ../a/.hg/patches/series
  foo

Test tags hardlinking:

  $ hg qdel -r qbase:qtip
  patch foo finalized without changeset message
  patch bar finalized without changeset message

  $ hg tag -l lfoo
  $ hg tag foo

  $ cd ..
  $ linkcp b c
  $ cd c

  $ hg tag -l -r 0 lbar
  $ hg tag -r 0 bar

  $ cat .hgtags
  4e7abb4840c46a910f6d7b4d3c3fc7e5209e684c foo
  430ed4828a74fa4047bc816a25500f7472ab4bfe bar

  $ cat .hg/localtags
  4e7abb4840c46a910f6d7b4d3c3fc7e5209e684c lfoo
  430ed4828a74fa4047bc816a25500f7472ab4bfe lbar

  $ cat ../b/.hgtags
  4e7abb4840c46a910f6d7b4d3c3fc7e5209e684c foo

  $ cat ../b/.hg/localtags
  4e7abb4840c46a910f6d7b4d3c3fc7e5209e684c lfoo

  $ cd ..