view tests/test-remotefilelog-bgprefetch.t @ 46667:93e9f448273c

rhg: Add support for automatic fallback to Python

`rhg` is a command-line application that can do a small subset of what
`hg` can. It is written entirely in Rust, which avoids the cost of starting
a Python interpreter and importing many Python modules.
In a script that runs many `hg` commands, this cost can add up.

However making users decide when to use `rhg` instead of `hg` is
not practical as we want the subset of supported functionality
to grow over time.

Instead we introduce "fallback" behavior where, when `rhg` encounters
something (a sub-command, a repository format, …) that is not implemented
in Rust-only, it does nothing but silently start a subprocess of
Python-based `hg` running the same command.
That way `rhg` becomes a drop-in replacement for `hg` that sometimes
goes faster. Whether Python is used should be an implementation detail
not apparent to users (other than through speed).

A new `fallback` value is added to the previously introduced
`rhg.on-unsupported` configuration key. When in this mode, the new
`rhg.fallback-executable` config is determine what command to use
to run a Python-based `hg`.

The previous `rhg.on-unsupported = abort-silent` configuration was designed
to let a wrapper script call `rhg` and then fall back to `hg` based on the
exit code. This is still available, but having fallback behavior built-in
in rhg might be easier for users instead of leaving that script "as an
exercise for the reader".

Using a subprocess like this is not idea, especially when `rhg` is to be
installed in `$PATH` as `hg`, since the other `hg.py` executable needs
to still be available… somewhere. Eventually this could be replaced
by using PyOxidizer to a have a single executable that embeds a Python
interpreter, but only starts it when needed.

Differential Revision: https://phab.mercurial-scm.org/D10093

#require no-windows

  $ . "$TESTDIR/remotefilelog-library.sh"
  $ cat >> $HGRCPATH <<EOF
  > [devel]
  > remotefilelog.bg-wait=True
  > EOF

  $ hg init master
  $ cd master
  $ cat >> .hg/hgrc <<EOF
  > [remotefilelog]
  > server=True
  > EOF
  $ echo x > x
  $ echo z > z
  $ hg commit -qAm x
  $ echo x2 > x
  $ echo y > y
  $ hg commit -qAm y
  $ echo w > w
  $ rm z
  $ hg commit -qAm w
  $ hg bookmark foo

  $ cd ..

# clone the repo

  $ hgcloneshallow ssh://user@dummy/master shallow --noupdate
  streaming all changes
  2 files to transfer, 776 bytes of data
  transferred 776 bytes in * seconds (*/sec) (glob)
  searching for changes
  no changes found

# Set the prefetchdays config to zero so that all commits are prefetched
# no matter what their creation date is. Also set prefetchdelay config
# to zero so that there is no delay between prefetches.
  $ cd shallow
  $ cat >> .hg/hgrc <<EOF
  > [remotefilelog]
  > prefetchdays=0
  > prefetchdelay=0
  > EOF
  $ cd ..

# prefetch a revision
  $ cd shallow

  $ hg prefetch -r 0
  2 files fetched over 1 fetches - (2 misses, 0.00% hit ratio) over *s (glob)

  $ hg cat -r 0 x
  x

# background prefetch on pull when configured

  $ cat >> .hg/hgrc <<EOF
  > [remotefilelog]
  > pullprefetch=bookmark()
  > backgroundprefetch=True
  > EOF
  $ hg strip tip
  saved backup bundle to $TESTTMP/shallow/.hg/strip-backup/6b4b6f66ef8c-b4b8bdaf-backup.hg (glob)

  $ clearcache
  $ hg pull
  pulling from ssh://user@dummy/master
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  updating bookmark foo
  added 1 changesets with 0 changes to 0 files
  new changesets 6b4b6f66ef8c
  (run 'hg update' to get a working copy)
  prefetching file contents
  $ find $CACHEDIR -type f | sort
  $TESTTMP/hgcache/master/11/f6ad8ec52a2984abaafd7c3b516503785c2072/ef95c5376f34698742fe34f315fd82136f8f68c0
  $TESTTMP/hgcache/master/95/cb0bfd2977c761298d9624e4b4d4c72a39974a/076f5e2225b3ff0400b98c92aa6cdf403ee24cca
  $TESTTMP/hgcache/master/af/f024fe4ab0fece4091de044c58c9ae4233383a/bb6ccd5dceaa5e9dc220e0dad65e051b94f69a2c
  $TESTTMP/hgcache/repos

# background prefetch with repack on pull when configured

  $ cat >> .hg/hgrc <<EOF
  > [remotefilelog]
  > backgroundrepack=True
  > EOF
  $ hg strip tip
  saved backup bundle to $TESTTMP/shallow/.hg/strip-backup/6b4b6f66ef8c-b4b8bdaf-backup.hg (glob)

  $ clearcache
  $ hg pull
  pulling from ssh://user@dummy/master
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  updating bookmark foo
  added 1 changesets with 0 changes to 0 files
  new changesets 6b4b6f66ef8c
  (run 'hg update' to get a working copy)
  prefetching file contents
  $ find $CACHEDIR -type f | sort
  $TESTTMP/hgcache/master/packs/6e8633deba6e544e5f8edbd7b996d6e31a2c42ae.histidx
  $TESTTMP/hgcache/master/packs/6e8633deba6e544e5f8edbd7b996d6e31a2c42ae.histpack
  $TESTTMP/hgcache/master/packs/8ce5ab3745465ab83bba30a7b9c295e0c8404652.dataidx
  $TESTTMP/hgcache/master/packs/8ce5ab3745465ab83bba30a7b9c295e0c8404652.datapack
  $TESTTMP/hgcache/repos

# background prefetch with repack on update when wcprevset configured

  $ clearcache
  $ hg up -r 0
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  2 files fetched over 1 fetches - (2 misses, 0.00% hit ratio) over *s (glob)
  $ find $CACHEDIR -type f | sort
  $TESTTMP/hgcache/master/11/f6ad8ec52a2984abaafd7c3b516503785c2072/1406e74118627694268417491f018a4a883152f0
  $TESTTMP/hgcache/master/39/5df8f7c51f007019cb30201c49e884b46b92fa/69a1b67522704ec122181c0890bd16e9d3e7516a
  $TESTTMP/hgcache/repos

  $ hg up -r 1
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  2 files fetched over 2 fetches - (2 misses, 0.00% hit ratio) over *s (glob)

  $ cat >> .hg/hgrc <<EOF
  > [remotefilelog]
  > bgprefetchrevs=.::
  > EOF

  $ clearcache
  $ hg up -r 0
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  * files fetched over * fetches - (* misses, 0.00% hit ratio) over *s (glob)
  $ find $CACHEDIR -type f | sort
  $TESTTMP/hgcache/master/packs/8f1443d44e57fec96f72fb2412e01d2818767ef2.histidx
  $TESTTMP/hgcache/master/packs/8f1443d44e57fec96f72fb2412e01d2818767ef2.histpack
  $TESTTMP/hgcache/master/packs/f4d50848e0b465e9bfd2875f213044c06cfd7407.dataidx
  $TESTTMP/hgcache/master/packs/f4d50848e0b465e9bfd2875f213044c06cfd7407.datapack
  $TESTTMP/hgcache/repos

# Ensure that file 'w' was prefetched - it was not part of the update operation and therefore
# could only be downloaded by the background prefetch

  $ hg debugdatapack `ls -ct $TESTTMP/hgcache/master/packs/*.datapack | head -n 1`
  $TESTTMP/hgcache/master/packs/f4d50848e0b465e9bfd2875f213044c06cfd7407:
  w:
  Node          Delta Base    Delta Length  Blob Size
  bb6ccd5dceaa  000000000000  2             2
  
  Total:                      2             2         (0.0% bigger)
  x:
  Node          Delta Base    Delta Length  Blob Size
  ef95c5376f34  000000000000  3             3
  1406e7411862  ef95c5376f34  14            2
  
  Total:                      17            5         (240.0% bigger)
  y:
  Node          Delta Base    Delta Length  Blob Size
  076f5e2225b3  000000000000  2             2
  
  Total:                      2             2         (0.0% bigger)
  z:
  Node          Delta Base    Delta Length  Blob Size
  69a1b6752270  000000000000  2             2
  
  Total:                      2             2         (0.0% bigger)

# background prefetch with repack on commit when wcprevset configured

  $ cat >> .hg/hgrc <<EOF
  > [remotefilelog]
  > bgprefetchrevs=0::
  > EOF

  $ clearcache
  $ find $CACHEDIR -type f | sort
  $ echo b > b
.. The following output line about files fetches is globed because it is
.. flaky, the core the test is checked when checking the cache dir, so
.. hopefully this flakyness is not hiding any actual bug.
  $ hg commit -qAm b
  * files fetched over 1 fetches - (* misses, 0.00% hit ratio) over *s (glob) (?)
  $ hg bookmark temporary
  $ find $CACHEDIR -type f | sort
  $TESTTMP/hgcache/master/packs/8f1443d44e57fec96f72fb2412e01d2818767ef2.histidx
  $TESTTMP/hgcache/master/packs/8f1443d44e57fec96f72fb2412e01d2818767ef2.histpack
  $TESTTMP/hgcache/master/packs/f4d50848e0b465e9bfd2875f213044c06cfd7407.dataidx
  $TESTTMP/hgcache/master/packs/f4d50848e0b465e9bfd2875f213044c06cfd7407.datapack
  $TESTTMP/hgcache/repos

# Ensure that file 'w' was prefetched - it was not part of the commit operation and therefore
# could only be downloaded by the background prefetch

  $ hg debugdatapack `ls -ct $TESTTMP/hgcache/master/packs/*.datapack | head -n 1`
  $TESTTMP/hgcache/master/packs/f4d50848e0b465e9bfd2875f213044c06cfd7407:
  w:
  Node          Delta Base    Delta Length  Blob Size
  bb6ccd5dceaa  000000000000  2             2
  
  Total:                      2             2         (0.0% bigger)
  x:
  Node          Delta Base    Delta Length  Blob Size
  ef95c5376f34  000000000000  3             3
  1406e7411862  ef95c5376f34  14            2
  
  Total:                      17            5         (240.0% bigger)
  y:
  Node          Delta Base    Delta Length  Blob Size
  076f5e2225b3  000000000000  2             2
  
  Total:                      2             2         (0.0% bigger)
  z:
  Node          Delta Base    Delta Length  Blob Size
  69a1b6752270  000000000000  2             2
  
  Total:                      2             2         (0.0% bigger)

# background prefetch with repack on rebase when wcprevset configured

  $ hg up -r 2
  3 files updated, 0 files merged, 2 files removed, 0 files unresolved
  (leaving bookmark temporary)
  $ clearcache
  $ find $CACHEDIR -type f | sort
.. The following output line about files fetches is globed because it is
.. flaky, the core the test is checked when checking the cache dir, so
.. hopefully this flakyness is not hiding any actual bug.
  $ hg rebase -s temporary -d foo
  rebasing 3:d9cf06e3b5b6 temporary tip "b"
  saved backup bundle to $TESTTMP/shallow/.hg/strip-backup/d9cf06e3b5b6-e5c3dc63-rebase.hg
  ? files fetched over ? fetches - (? misses, 0.00% hit ratio) over *s (glob)
  $ find $CACHEDIR -type f | sort
  $TESTTMP/hgcache/master/packs/8f1443d44e57fec96f72fb2412e01d2818767ef2.histidx
  $TESTTMP/hgcache/master/packs/8f1443d44e57fec96f72fb2412e01d2818767ef2.histpack
  $TESTTMP/hgcache/master/packs/f4d50848e0b465e9bfd2875f213044c06cfd7407.dataidx
  $TESTTMP/hgcache/master/packs/f4d50848e0b465e9bfd2875f213044c06cfd7407.datapack
  $TESTTMP/hgcache/repos

# Ensure that file 'y' was prefetched - it was not part of the rebase operation and therefore
# could only be downloaded by the background prefetch

  $ hg debugdatapack `ls -ct $TESTTMP/hgcache/master/packs/*.datapack | head -n 1`
  $TESTTMP/hgcache/master/packs/f4d50848e0b465e9bfd2875f213044c06cfd7407:
  w:
  Node          Delta Base    Delta Length  Blob Size
  bb6ccd5dceaa  000000000000  2             2
  
  Total:                      2             2         (0.0% bigger)
  x:
  Node          Delta Base    Delta Length  Blob Size
  ef95c5376f34  000000000000  3             3
  1406e7411862  ef95c5376f34  14            2
  
  Total:                      17            5         (240.0% bigger)
  y:
  Node          Delta Base    Delta Length  Blob Size
  076f5e2225b3  000000000000  2             2
  
  Total:                      2             2         (0.0% bigger)
  z:
  Node          Delta Base    Delta Length  Blob Size
  69a1b6752270  000000000000  2             2
  
  Total:                      2             2         (0.0% bigger)

# Check that foregound prefetch with no arguments blocks until background prefetches finish

  $ hg up -r 3
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ clearcache
  $ hg prefetch --repack --config ui.timeout.warn=-1
  (running background incremental repack)
  * files fetched over 1 fetches - (* misses, 0.00% hit ratio) over *s (glob) (?)

  $ find $CACHEDIR -type f | sort
  $TESTTMP/hgcache/master/packs/8f1443d44e57fec96f72fb2412e01d2818767ef2.histidx
  $TESTTMP/hgcache/master/packs/8f1443d44e57fec96f72fb2412e01d2818767ef2.histpack
  $TESTTMP/hgcache/master/packs/f4d50848e0b465e9bfd2875f213044c06cfd7407.dataidx
  $TESTTMP/hgcache/master/packs/f4d50848e0b465e9bfd2875f213044c06cfd7407.datapack
  $TESTTMP/hgcache/repos

# Ensure that files were prefetched
  $ hg debugdatapack `ls -ct $TESTTMP/hgcache/master/packs/*.datapack | head -n 1`
  $TESTTMP/hgcache/master/packs/f4d50848e0b465e9bfd2875f213044c06cfd7407:
  w:
  Node          Delta Base    Delta Length  Blob Size
  bb6ccd5dceaa  000000000000  2             2
  
  Total:                      2             2         (0.0% bigger)
  x:
  Node          Delta Base    Delta Length  Blob Size
  ef95c5376f34  000000000000  3             3
  1406e7411862  ef95c5376f34  14            2
  
  Total:                      17            5         (240.0% bigger)
  y:
  Node          Delta Base    Delta Length  Blob Size
  076f5e2225b3  000000000000  2             2
  
  Total:                      2             2         (0.0% bigger)
  z:
  Node          Delta Base    Delta Length  Blob Size
  69a1b6752270  000000000000  2             2
  
  Total:                      2             2         (0.0% bigger)

# Check that foreground prefetch fetches revs specified by '. + draft() + bgprefetchrevs + pullprefetch'

  $ clearcache
  $ hg prefetch --repack --config ui.timeout.warn=-1
  (running background incremental repack)
  * files fetched over 1 fetches - (* misses, 0.00% hit ratio) over *s (glob) (?)

  $ find $CACHEDIR -type f | sort
  $TESTTMP/hgcache/master/packs/8f1443d44e57fec96f72fb2412e01d2818767ef2.histidx
  $TESTTMP/hgcache/master/packs/8f1443d44e57fec96f72fb2412e01d2818767ef2.histpack
  $TESTTMP/hgcache/master/packs/f4d50848e0b465e9bfd2875f213044c06cfd7407.dataidx
  $TESTTMP/hgcache/master/packs/f4d50848e0b465e9bfd2875f213044c06cfd7407.datapack
  $TESTTMP/hgcache/repos

# Ensure that files were prefetched
  $ hg debugdatapack `ls -ct $TESTTMP/hgcache/master/packs/*.datapack | head -n 1`
  $TESTTMP/hgcache/master/packs/f4d50848e0b465e9bfd2875f213044c06cfd7407:
  w:
  Node          Delta Base    Delta Length  Blob Size
  bb6ccd5dceaa  000000000000  2             2
  
  Total:                      2             2         (0.0% bigger)
  x:
  Node          Delta Base    Delta Length  Blob Size
  ef95c5376f34  000000000000  3             3
  1406e7411862  ef95c5376f34  14            2
  
  Total:                      17            5         (240.0% bigger)
  y:
  Node          Delta Base    Delta Length  Blob Size
  076f5e2225b3  000000000000  2             2
  
  Total:                      2             2         (0.0% bigger)
  z:
  Node          Delta Base    Delta Length  Blob Size
  69a1b6752270  000000000000  2             2
  
  Total:                      2             2         (0.0% bigger)

# Test that if data was prefetched and repacked we dont need to prefetch it again
# It ensures that Mercurial looks not only in loose files but in packs as well

  $ hg prefetch --repack
  (running background incremental repack)