tests/test-hgrc.t

localrepo: experimental support for non-zlib revlog compression

The final part of integrating the compression manager APIs into
revlog storage is the plumbing for repositories to advertise they
are using non-zlib storage and for revlogs to instantiate a non-zlib
compression engine.

The main intent of the compression manager work was to zstd all
of the things. Adding zstd to revlogs has proved to be more involved
than other places because revlogs are... special. Very small inputs
and the use of delta chains (which are themselves a form of
compression) are a completely different use case from streaming
compression, which bundles and the wire protocol employ. I've
conducted numerous experiments with zstd in revlogs and have yet
to formalize compression settings and a storage architecture that
I'm confident I won't regret later. In other words, I'm not yet
ready to commit to a new mechanism for using zstd - or any other
compression format - in revlogs.

That being said, having some support for zstd (and other compression
formats) in revlogs in core is beneficial. It can allow others to
conduct experiments.

This patch introduces *highly experimental* support for non-zlib
compression formats in revlogs. Introduced is a config option to
control which compression engine to use. Also introduced is a namespace
of "exp-compression-*" requirements to denote support for non-zlib
compression in revlogs. I've prefixed the namespace with "exp-"
(short for "experimental") because I'm not confident of the
requirements "schema" and in no way want to give the illusion of
supporting these requirements in the future. I fully intend to drop
support for these requirements once we figure out what we're doing
with zstd in revlogs.

A good portion of the patch is teaching the requirements system
about registered compression engines and passing the requested
compression engine as an opener option so revlogs can instantiate
the proper compression engine for new operations.

That's a verbose way of saying "we can now use zstd in revlogs!"

On an `hg pull` conversion of the mozilla-unified repo with no extra
redelta settings (like aggressivemergedeltas), we can see the impact
of zstd vs zlib in revlogs:

$ hg perfrevlogchunks -c
! chunk
! wall 2.032052 comb 2.040000 user 1.990000 sys 0.050000 (best of 5)
! wall 1.866360 comb 1.860000 user 1.820000 sys 0.040000 (best of 6)

! chunk batch
! wall 1.877261 comb 1.870000 user 1.860000 sys 0.010000 (best of 6)
! wall 1.705410 comb 1.710000 user 1.690000 sys 0.020000 (best of 6)

$ hg perfrevlogchunks -m
! chunk
! wall 2.721427 comb 2.720000 user 2.640000 sys 0.080000 (best of 4)
! wall 2.035076 comb 2.030000 user 1.950000 sys 0.080000 (best of 5)

! chunk batch
! wall 2.614561 comb 2.620000 user 2.580000 sys 0.040000 (best of 4)
! wall 1.910252 comb 1.910000 user 1.880000 sys 0.030000 (best of 6)

$ hg perfrevlog -c -d 1
! wall 4.812885 comb 4.820000 user 4.800000 sys 0.020000 (best of 3)
! wall 4.699621 comb 4.710000 user 4.700000 sys 0.010000 (best of 3)

$ hg perfrevlog -m -d 1000
! wall 34.252800 comb 34.250000 user 33.730000 sys 0.520000 (best of 3)
! wall 24.094999 comb 24.090000 user 23.320000 sys 0.770000 (best of 3)

Only modest wins for the changelog. But manifest reading is
significantly faster. What's going on?

One reason might be data volume. zstd decompresses faster. So given
more bytes, it will put more distance between it and zlib.

Another reason is size. In the current design, zstd revlogs are
*larger*:

debugcreatestreamclonebundle (size in bytes)
zlib: 1,638,852,492
zstd: 1,680,601,332

I haven't investigated this fully, but I reckon a significant cause of
larger revlogs is that the zstd frame/header has more bytes than
zlib's. For very small inputs or data that doesn't compress well, we'll
tend to store more uncompressed chunks than with zlib (because the
compressed size isn't smaller than original). This will make revlog
reading faster because it is doing less decompression.

Moving on to bundle performance:

$ hg bundle -a -t none-v2 (total CPU time)
zlib: 102.79s
zstd:  97.75s

So, marginal CPU decrease for reading all chunks in all revlogs
(this is somewhat disappointing).

$ hg bundle -a -t <engine>-v2 (total CPU time)
zlib: 191.59s
zstd: 115.36s

This last test effectively measures the difference between zlib->zlib
and zstd->zstd for revlogs to bundle. This is a rough approximation of
what a server does during `hg clone`.

There are some promising results for zstd. But not enough for me to
feel comfortable advertising it to users. We'll get there...

hide outer repo
  $ hg init

Use hgrc within $TESTTMP

  $ HGRCPATH=`pwd`/hgrc
  $ export HGRCPATH

Use an alternate var for scribbling on hgrc to keep check-code from
complaining about the important settings we may be overwriting:

  $ HGRC=`pwd`/hgrc
  $ export HGRC

Basic syntax error

  $ echo "invalid" > $HGRC
  $ hg version
  hg: parse error at $TESTTMP/hgrc:1: invalid
  [255]
  $ echo "" > $HGRC

Issue1199: Can't use '%' in hgrc (eg url encoded username)

  $ hg init "foo%bar"
  $ hg clone "foo%bar" foobar
  updating to branch default
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd foobar
  $ cat .hg/hgrc
  # example repository config (see 'hg help config' for more info)
  [paths]
  default = $TESTTMP/foo%bar (glob)
  
  # path aliases to other clones of this repo in URLs or filesystem paths
  # (see 'hg help config.paths' for more info)
  #
  # default-push = ssh://[e-mail]/hg/jdoes-fork
  # my-fork      = ssh://[e-mail]/hg/jdoes-fork
  # my-clone     = /home/jdoe/jdoes-clone
  
  [ui]
  # name and email (local to this repository, optional), e.g.
  # username = Jane Doe <[e-mail]>
  $ hg paths
  default = $TESTTMP/foo%bar (glob)
  $ hg showconfig
  bundle.mainreporoot=$TESTTMP/foobar (glob)
  paths.default=$TESTTMP/foo%bar (glob)
  $ cd ..

issue1829: wrong indentation

  $ echo '[foo]' > $HGRC
  $ echo '  x = y' >> $HGRC
  $ hg version
  hg: parse error at $TESTTMP/hgrc:2:   x = y
  unexpected leading whitespace
  [255]

  $ $PYTHON -c "print '[foo]\nbar = a\n b\n c \n  de\n fg \nbaz = bif cb \n'" \
  > > $HGRC
  $ hg showconfig foo
  foo.bar=a\nb\nc\nde\nfg
  foo.baz=bif cb

  $ FAKEPATH=/path/to/nowhere
  $ export FAKEPATH
  $ echo '%include $FAKEPATH/no-such-file' > $HGRC
  $ hg version
  Mercurial Distributed SCM (version *) (glob)
  (see https://mercurial-scm.org for more information)
  
  Copyright (C) 2005-2016 Matt Mackall and others
  This is free software; see the source for copying conditions. There is NO
  warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  $ unset FAKEPATH

make sure global options given on the cmdline take precedence

  $ hg showconfig --config ui.verbose=True --quiet
  bundle.mainreporoot=$TESTTMP
  ui.verbose=False
  ui.debug=False
  ui.quiet=True

  $ touch foobar/untracked
  $ cat >> foobar/.hg/hgrc <<EOF
  > [ui]
  > verbose=True
  > EOF
  $ hg -R foobar st -q

username expansion

  $ olduser=$HGUSER
  $ unset HGUSER

  $ FAKEUSER='John Doe'
  $ export FAKEUSER
  $ echo '[ui]' > $HGRC
  $ echo 'username = $FAKEUSER' >> $HGRC

  $ hg init usertest
  $ cd usertest
  $ touch bar
  $ hg commit --addremove --quiet -m "added bar"
  $ hg log --template "{author}\n"
  John Doe
  $ cd ..

  $ hg showconfig
  bundle.mainreporoot=$TESTTMP
  ui.username=$FAKEUSER

  $ unset FAKEUSER
  $ HGUSER=$olduser
  $ export HGUSER

showconfig with multiple arguments

  $ echo "[alias]" > $HGRC
  $ echo "log = log -g" >> $HGRC
  $ echo "[defaults]" >> $HGRC
  $ echo "identify = -n" >> $HGRC
  $ hg showconfig alias defaults
  alias.log=log -g
  defaults.identify=-n
  $ hg showconfig alias defaults.identify
  abort: only one config item permitted
  [255]
  $ hg showconfig alias.log defaults.identify
  abort: only one config item permitted
  [255]

HGPLAIN

  $ echo "[ui]" > $HGRC
  $ echo "debug=true" >> $HGRC
  $ echo "fallbackencoding=ASCII" >> $HGRC
  $ echo "quiet=true" >> $HGRC
  $ echo "slash=true" >> $HGRC
  $ echo "traceback=true" >> $HGRC
  $ echo "verbose=true" >> $HGRC
  $ echo "style=~/.hgstyle" >> $HGRC
  $ echo "logtemplate={node}" >> $HGRC
  $ echo "[defaults]" >> $HGRC
  $ echo "identify=-n" >> $HGRC
  $ echo "[alias]" >> $HGRC
  $ echo "log=log -g" >> $HGRC

customized hgrc

  $ hg showconfig
  read config from: $TESTTMP/hgrc
  $TESTTMP/hgrc:13: alias.log=log -g
  repo: bundle.mainreporoot=$TESTTMP
  $TESTTMP/hgrc:11: defaults.identify=-n
  $TESTTMP/hgrc:2: ui.debug=true
  $TESTTMP/hgrc:3: ui.fallbackencoding=ASCII
  $TESTTMP/hgrc:4: ui.quiet=true
  $TESTTMP/hgrc:5: ui.slash=true
  $TESTTMP/hgrc:6: ui.traceback=true
  $TESTTMP/hgrc:7: ui.verbose=true
  $TESTTMP/hgrc:8: ui.style=~/.hgstyle
  $TESTTMP/hgrc:9: ui.logtemplate={node}

plain hgrc

  $ HGPLAIN=; export HGPLAIN
  $ hg showconfig --config ui.traceback=True --debug
  read config from: $TESTTMP/hgrc
  repo: bundle.mainreporoot=$TESTTMP
  --config: ui.traceback=True
  --verbose: ui.verbose=False
  --debug: ui.debug=True
  --quiet: ui.quiet=False

plain mode with exceptions

  $ cat > plain.py <<EOF
  > from mercurial import commands, extensions
  > def _config(orig, ui, repo, *values, **opts):
  >     ui.write('plain: %r\n' % ui.plain())
  >     return orig(ui, repo, *values, **opts)
  > def uisetup(ui):
  >     extensions.wrapcommand(commands.table, 'config', _config)
  > EOF
  $ echo "[extensions]" >> $HGRC
  $ echo "plain=./plain.py" >> $HGRC
  $ HGPLAINEXCEPT=; export HGPLAINEXCEPT
  $ hg showconfig --config ui.traceback=True --debug
  plain: True
  read config from: $TESTTMP/hgrc
  repo: bundle.mainreporoot=$TESTTMP
  $TESTTMP/hgrc:15: extensions.plain=./plain.py
  --config: ui.traceback=True
  --verbose: ui.verbose=False
  --debug: ui.debug=True
  --quiet: ui.quiet=False
  $ unset HGPLAIN
  $ hg showconfig --config ui.traceback=True --debug
  plain: True
  read config from: $TESTTMP/hgrc
  repo: bundle.mainreporoot=$TESTTMP
  $TESTTMP/hgrc:15: extensions.plain=./plain.py
  --config: ui.traceback=True
  --verbose: ui.verbose=False
  --debug: ui.debug=True
  --quiet: ui.quiet=False
  $ HGPLAINEXCEPT=i18n; export HGPLAINEXCEPT
  $ hg showconfig --config ui.traceback=True --debug
  plain: True
  read config from: $TESTTMP/hgrc
  repo: bundle.mainreporoot=$TESTTMP
  $TESTTMP/hgrc:15: extensions.plain=./plain.py
  --config: ui.traceback=True
  --verbose: ui.verbose=False
  --debug: ui.debug=True
  --quiet: ui.quiet=False

source of paths is not mangled

  $ cat >> $HGRCPATH <<EOF
  > [paths]
  > foo = bar
  > EOF
  $ hg showconfig --debug paths
  plain: True
  read config from: $TESTTMP/hgrc
  $TESTTMP/hgrc:17: paths.foo=$TESTTMP/bar (glob)