view tests/test-pull-bundle.t @ 44118:f81c17ec303c

hgdemandimport: apply lazy module loading to sys.meta_path finders

Python's `sys.meta_path` finders are the primary objects whose job it
is to find a module at import time. When `import` is called, Python
iterates objects in this list and calls `o.find_spec(...)` to find
a `ModuleSpec` (or None if the module couldn't be found by that
finder). If no meta path finder can find a module, import fails.

One of the default meta path finders is `PathFinder`. Its job is to
import modules from the filesystem and is probably the most important
importer. This finder looks at `sys.path` and `sys.path_hooks` to do
its job.

The `ModuleSpec` returned by `MetaPathImporter.find_spec()` has a
`loader` attribute, which defines the concrete module loader to use.
`sys.path_hooks` is a hook point for teaching `PathFinder` to
instantiate custom loader types.

Previously, we injected a custom `sys.path_hook` that told `PathFinder`
to wrap the default loaders with a loader that creates a module object
that is lazy.

This approach worked. But its main limitation was that it only applied
to the `PathFinder` meta path importer. There are other meta path
importers that are registered. And in the case of PyOxidizer loading
modules from memory, `PathFinder` doesn't come into play since
PyOxidizer's own meta path importer was handling all imports.

This commit changes our approach to lazy module loading by proxying
all meta path importers. Specifically, we overload the `find_spec()`
method to swap in a wrapped loader on the `ModuleSpec` before it
is returned. The end result of this is all meta path importers should
be lazy.

As much as I would have loved to utilize .__class__ manipulation to
achieve this, some meta path importers are implemented in C/Rust
in such a way that they cannot be monkeypatched. This is why we
use __getattribute__ to define a proxy.

Also, this change could theoretically open us up to regressions in
meta path importers whose loader is creating module objects which
can't be monkeypatched. But I'm not aware of any of these in the
wild. So I think we'll be safe.

According to hyperfine, this change yields a decent startup time win of
5-6ms:

```
Benchmark #1: ~/.pyenv/versions/3.6.10/bin/python ./hg version
  Time (mean ± σ):      86.8 ms ±   0.5 ms    [User: 78.0 ms, System: 8.7 ms]
  Range (min … max):    86.0 ms …  89.1 ms    50 runs

  Time (mean ± σ):      81.1 ms ±   2.7 ms    [User: 74.5 ms, System: 6.5 ms]
  Range (min … max):    77.8 ms …  90.5 ms    50 runs

Benchmark #2: ~/.pyenv/versions/3.7.6/bin/python ./hg version
  Time (mean ± σ):      78.9 ms ±   0.6 ms    [User: 70.2 ms, System: 8.7 ms]
  Range (min … max):    78.1 ms …  81.2 ms    50 runs

  Time (mean ± σ):      73.4 ms ±   0.6 ms    [User: 65.3 ms, System: 8.0 ms]
  Range (min … max):    72.4 ms …  75.7 ms    50 runs

Benchmark #3: ~/.pyenv/versions/3.8.1/bin/python ./hg version
  Time (mean ± σ):      78.1 ms ±   0.6 ms    [User: 70.2 ms, System: 7.9 ms]
  Range (min … max):    77.4 ms …  80.9 ms    50 runs

  Time (mean ± σ):      72.1 ms ±   0.4 ms    [User: 64.4 ms, System: 7.6 ms]
  Range (min … max):    71.4 ms …  74.1 ms    50 runs
```

Differential Revision: https://phab.mercurial-scm.org/D7954

#require no-chg

  $ hg init repo
  $ cd repo
  $ echo foo > foo
  $ hg ci -qAm 'add foo'
  $ echo >> foo
  $ hg ci -m 'change foo'
  $ hg up -qC 0
  $ echo bar > bar
  $ hg ci -qAm 'add bar'

  $ hg log
  changeset:   2:effea6de0384
  tag:         tip
  parent:      0:bbd179dfa0a7
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     add bar
  
  changeset:   1:ed1b79f46b9a
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     change foo
  
  changeset:   0:bbd179dfa0a7
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     add foo
  
  $ cd ..

Test pullbundle functionality

  $ cd repo
  $ cat <<EOF > .hg/hgrc
  > [server]
  > pullbundle = True
  > [extensions]
  > blackbox =
  > EOF
  $ hg bundle --base null -r 0 .hg/0.hg
  1 changesets found
  $ hg bundle --base 0 -r 1 .hg/1.hg
  1 changesets found
  $ hg bundle --base 1 -r 2 .hg/2.hg
  1 changesets found
  $ cat <<EOF > .hg/pullbundles.manifest
  > 2.hg BUNDLESPEC=none-v2 heads=effea6de0384e684f44435651cb7bd70b8735bd4 bases=bbd179dfa0a71671c253b3ae0aa1513b60d199fa
  > 1.hg BUNDLESPEC=bzip2-v2 heads=ed1b79f46b9a29f5a6efa59cf12fcfca43bead5a bases=bbd179dfa0a71671c253b3ae0aa1513b60d199fa
  > 0.hg BUNDLESPEC=gzip-v2 heads=bbd179dfa0a71671c253b3ae0aa1513b60d199fa
  > EOF
  $ hg --config blackbox.track=debug --debug serve -p $HGPORT2 -d --pid-file=../repo.pid
  listening at http://*:$HGPORT2/ (bound to $LOCALIP:$HGPORT2) (glob) (?)
  $ cat ../repo.pid >> $DAEMON_PIDS
  $ cd ..
  $ hg clone -r 0 http://localhost:$HGPORT2/ repo.pullbundle
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  new changesets bbd179dfa0a7 (1 drafts)
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd repo.pullbundle
  $ hg pull -r 1
  pulling from http://localhost:$HGPORT2/
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  new changesets ed1b79f46b9a (1 drafts)
  (run 'hg update' to get a working copy)
  $ hg pull -r 2
  pulling from http://localhost:$HGPORT2/
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files (+1 heads)
  new changesets effea6de0384 (1 drafts)
  (run 'hg heads' to see heads, 'hg merge' to merge)
  $ cd ..
  $ killdaemons.py
  $ grep 'sending pullbundle ' repo/.hg/blackbox.log
  * sending pullbundle "0.hg" (glob)
  * sending pullbundle "1.hg" (glob)
  * sending pullbundle "2.hg" (glob)
  $ rm repo/.hg/blackbox.log

Test pullbundle functionality for incremental pulls

  $ cd repo
  $ hg --config blackbox.track=debug --debug serve -p $HGPORT2 -d --pid-file=../repo.pid
  listening at http://*:$HGPORT2/ (bound to $LOCALIP:$HGPORT2) (glob) (?)
  $ cat ../repo.pid >> $DAEMON_PIDS
  $ cd ..
  $ hg clone http://localhost:$HGPORT2/ repo.pullbundle2
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  adding changesets
  adding manifests
  adding file changes
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 3 changes to 3 files (+1 heads)
  new changesets bbd179dfa0a7:ed1b79f46b9a (3 drafts)
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ killdaemons.py
  $ grep 'sending pullbundle ' repo/.hg/blackbox.log
  * sending pullbundle "0.hg" (glob)
  * sending pullbundle "2.hg" (glob)
  * sending pullbundle "1.hg" (glob)
  $ rm repo/.hg/blackbox.log

Test pullbundle functionality for incoming

  $ cd repo
  $ hg --config blackbox.track=debug --debug serve -p $HGPORT2 -d --pid-file=../repo.pid
  listening at http://*:$HGPORT2/ (bound to $LOCALIP:$HGPORT2) (glob) (?)
  $ cat ../repo.pid >> $DAEMON_PIDS
  $ cd ..
  $ hg clone http://localhost:$HGPORT2/ repo.pullbundle2a -r 0
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  new changesets bbd179dfa0a7 (1 drafts)
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd repo.pullbundle2a
  $ hg incoming -r ed1b79f46b9a
  comparing with http://localhost:$HGPORT2/
  searching for changes
  changeset:   1:ed1b79f46b9a
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     change foo
  
  $ cd ..
  $ killdaemons.py
  $ grep 'sending pullbundle ' repo/.hg/blackbox.log
  * sending pullbundle "0.hg" (glob)
  * sending pullbundle "1.hg" (glob)
  $ rm repo/.hg/blackbox.log

Test recovery from misconfigured server sending no new data

  $ cd repo
  $ cat <<EOF > .hg/pullbundles.manifest
  > 0.hg heads=ed1b79f46b9a29f5a6efa59cf12fcfca43bead5a bases=bbd179dfa0a71671c253b3ae0aa1513b60d199fa
  > 0.hg heads=bbd179dfa0a71671c253b3ae0aa1513b60d199fa
  > EOF
  $ hg --config blackbox.track=debug --debug serve -p $HGPORT2 -d --pid-file=../repo.pid
  listening at http://*:$HGPORT2/ (bound to $LOCALIP:$HGPORT2) (glob) (?)
  $ cat ../repo.pid >> $DAEMON_PIDS
  $ cd ..
  $ hg clone -r 0 http://localhost:$HGPORT2/ repo.pullbundle3
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  new changesets bbd179dfa0a7 (1 drafts)
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd repo.pullbundle3
  $ hg pull -r 1
  pulling from http://localhost:$HGPORT2/
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 0 changesets with 0 changes to 1 files
  abort: 00changelog.i@ed1b79f46b9a: no node!
  [255]
  $ cd ..
  $ killdaemons.py
  $ grep 'sending pullbundle ' repo/.hg/blackbox.log
  * sending pullbundle "0.hg" (glob)
  * sending pullbundle "0.hg" (glob)
  $ rm repo/.hg/blackbox.log