view tests/test-share.t @ 40326:fed697fa1734

sqlitestore: file storage backend using SQLite

This commit provides an extension which uses SQLite to store file
data (as opposed to revlogs).

As the inline documentation describes, there are still several
aspects to the extension that are incomplete. But it's a start.
The extension does support basic clone, checkout, and commit
workflows, which makes it suitable for simple use cases.

One notable missing feature is support for "bundlerepos." This is
probably responsible for the most test failures when the extension
is activated as part of the test suite.

All revision data is stored in SQLite. Data is stored as zstd
compressed chunks (default if zstd is available), zlib compressed
chunks (default if zstd is not available), or raw chunks (if
configured or if a compressed delta is not smaller than the raw
delta). This makes things very similar to revlogs.

Unlike revlogs, the extension doesn't yet enforce a limit on delta
chain length. This is an obvious limitation and should be addressed.
This is somewhat mitigated by the use of zstd, which is much faster
than zlib to decompress.

There is a dedicated table for storing deltas. Deltas are stored
by the SHA-1 hash of their uncompressed content. The "fileindex" table
has columns that reference the delta for each revision and the base
delta that delta should be applied against. A recursive SQL query
is used to resolve the delta chain along with the delta data.

By storing deltas by hash, we are able to de-duplicate delta storage!
With revlogs, the same deltas in different revlogs would result in
duplicate storage of that delta. In this scheme, inserting the
duplicate delta is a no-op and delta chains simply reference the
existing delta.

When initially implementing this extension, I did not have
content-indexed deltas and deltas could be duplicated across files
(just like revlogs). When I implemented content-indexed deltas, the
size of the SQLite database for a full clone of mozilla-unified
dropped:

before: 2,554,261,504 bytes
after:  2,488,754,176 bytes

Surprisingly, this is still larger than the bytes size of revlog
files:

revlog files: 2,104,861,230 bytes
du -b:        2,254,381,614

I would have expected storage to be smaller since we're not limiting
delta chain length and since we're using zstd instead of zlib. I
suspect the SQLite indexes and per-column overhead account for the
bulk of the differences. (Keep in mind that revlog uses a 64-byte
packed struct for revision index data and deltas are stored without
padding. Aside from the 12 unused bytes in the 32 byte node field,
revlogs are pretty efficient.) Another source of overhead is file
name storage. With revlogs, file names are stored in the filesystem.
But with SQLite, we need to store file names in the database. This is
roughly equivalent to the size of the fncache file, which for the
mozilla-unified repository is ~34MB.

Since the SQLite database isn't append-only and since delta chains
can reference any delta, this opens some interesting possibilities.
For example, we could store deltas in reverse, such that fulltexts
are stored for newer revisions and deltas are applied to reconstruct
older revisions. This is likely a more optimal storage strategy for
version control, as new data tends to be more frequently accessed
than old data. We would obviously need wire protocol support for
transferring revision data from newest to oldest. And we would
probably need some kind of mechanism for "re-encoding" stores. But
it should be doable.

This extension is very much experimental quality. There are a handful
of features that don't work. It probably isn't suitable for day-to-day
use. But it could be used in limited cases (e.g. read-only checkouts
like in CI). And it is also a good proving ground for alternate
storage backends. As we continue to define interfaces for all things
storage, it will be useful to have a viable alternate storage backend
to see how things shake out in practice.

test-storage.py passes on Python 2 and introduces no new test failures on
Python 3. Having the storage-level unit tests has proved to be insanely
useful when developing this extension. Those tests caught numerous bugs
during development and I'm convinced this style of testing is the way
forward for ensuring alternate storage backends work as intended. Of
course, test coverage isn't close to what it needs to be. But it is
a start. And what coverage we have gives me confidence that basic store
functionality is implemented properly.

Differential Revision: https://phab.mercurial-scm.org/D4928

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

prepare repo1

  $ hg init repo1
  $ cd repo1
  $ echo a > a
  $ hg commit -A -m'init'
  adding a

share it

  $ cd ..
  $ hg share repo1 repo2
  updating working directory
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

share shouldn't have a store dir

  $ cd repo2
  $ test -d .hg/store
  [1]

share shouldn't have a cache dir, original repo should

  $ hg branches
  default                        0:d3873e73d99e
  $ hg tags
  tip                                0:d3873e73d99e
  $ test -d .hg/cache
  [1]
  $ ls -1 ../repo1/.hg/cache
  branch2-served
  manifestfulltextcache (reporevlogstore !)
  rbc-names-v1
  rbc-revs-v1
  tags2-visible

Some sed versions appends newline, some don't, and some just fails

  $ cat .hg/sharedpath; echo
  $TESTTMP/repo1/.hg

trailing newline on .hg/sharedpath is ok
  $ hg tip -q
  0:d3873e73d99e
  $ echo '' >> .hg/sharedpath
  $ cat .hg/sharedpath
  $TESTTMP/repo1/.hg
  $ hg tip -q
  0:d3873e73d99e

commit in shared clone

  $ echo a >> a
  $ hg commit -m'change in shared clone'

check original

  $ cd ../repo1
  $ hg log
  changeset:   1:8af4dc49db9e
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     change in shared clone
  
  changeset:   0:d3873e73d99e
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     init
  
  $ hg update
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cat a             # should be two lines of "a"
  a
  a

commit in original

  $ echo b > b
  $ hg commit -A -m'another file'
  adding b

check in shared clone

  $ cd ../repo2
  $ hg log
  changeset:   2:c2e0ac586386
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     another file
  
  changeset:   1:8af4dc49db9e
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     change in shared clone
  
  changeset:   0:d3873e73d99e
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     init
  
  $ hg update
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cat b             # should exist with one "b"
  b

hg serve shared clone

  $ hg serve -n test -p $HGPORT -d --pid-file=hg.pid
  $ cat hg.pid >> $DAEMON_PIDS
  $ get-with-headers.py localhost:$HGPORT 'raw-file/'
  200 Script output follows
  
  
  -rw-r--r-- 4 a
  -rw-r--r-- 2 b
  
  

test unshare command

  $ hg unshare
  $ test -d .hg/store
  $ test -f .hg/sharedpath
  [1]
  $ grep shared .hg/requires
  [1]
  $ hg unshare
  abort: this is not a shared repo
  [255]

check that a change does not propagate

  $ echo b >> b
  $ hg commit -m'change in unshared'
  $ cd ../repo1
  $ hg id -r tip
  c2e0ac586386 tip

  $ cd ..


test sharing bookmarks

  $ hg share -B repo1 repo3
  updating working directory
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd repo1
  $ hg bookmark bm1
  $ hg bookmarks
   * bm1                       2:c2e0ac586386
  $ cd ../repo2
  $ hg book bm2
  $ hg bookmarks
   * bm2                       3:0e6e70d1d5f1
  $ cd ../repo3
  $ hg bookmarks
     bm1                       2:c2e0ac586386
  $ hg book bm3
  $ hg bookmarks
     bm1                       2:c2e0ac586386
   * bm3                       2:c2e0ac586386
  $ cd ../repo1
  $ hg bookmarks
   * bm1                       2:c2e0ac586386
     bm3                       2:c2e0ac586386

check whether HG_PENDING makes pending changes only in relatd
repositories visible to an external hook.

In "hg share" case, another transaction can't run in other
repositories sharing same source repository, because starting
transaction requires locking store of source repository.

Therefore, this test scenario ignores checking visibility of
.hg/bookmakrs.pending in repo2, which shares repo1 without bookmarks.

  $ cat > $TESTTMP/checkbookmarks.sh <<EOF
  > echo "@repo1"
  > hg -R "$TESTTMP/repo1" bookmarks
  > echo "@repo2"
  > hg -R "$TESTTMP/repo2" bookmarks
  > echo "@repo3"
  > hg -R "$TESTTMP/repo3" bookmarks
  > exit 1 # to avoid adding new bookmark for subsequent tests
  > EOF

  $ cd ../repo1
  $ hg --config hooks.pretxnclose="sh $TESTTMP/checkbookmarks.sh" -q book bmX
  @repo1
     bm1                       2:c2e0ac586386
     bm3                       2:c2e0ac586386
   * bmX                       2:c2e0ac586386
  @repo2
   * bm2                       3:0e6e70d1d5f1
  @repo3
     bm1                       2:c2e0ac586386
   * bm3                       2:c2e0ac586386
     bmX                       2:c2e0ac586386
  transaction abort!
  rollback completed
  abort: pretxnclose hook exited with status 1
  [255]
  $ hg book bm1

FYI, in contrast to above test, bmX is invisible in repo1 (= shared
src), because (1) HG_PENDING refers only repo3 and (2)
"bookmarks.pending" is written only into repo3.

  $ cd ../repo3
  $ hg --config hooks.pretxnclose="sh $TESTTMP/checkbookmarks.sh" -q book bmX
  @repo1
   * bm1                       2:c2e0ac586386
     bm3                       2:c2e0ac586386
  @repo2
   * bm2                       3:0e6e70d1d5f1
  @repo3
     bm1                       2:c2e0ac586386
     bm3                       2:c2e0ac586386
   * bmX                       2:c2e0ac586386
  transaction abort!
  rollback completed
  abort: pretxnclose hook exited with status 1
  [255]
  $ hg book bm3

  $ cd ../repo1

test that commits work

  $ echo 'shared bookmarks' > a
  $ hg commit -m 'testing shared bookmarks'
  $ hg bookmarks
   * bm1                       3:b87954705719
     bm3                       2:c2e0ac586386
  $ cd ../repo3
  $ hg bookmarks
     bm1                       3:b87954705719
   * bm3                       2:c2e0ac586386
  $ echo 'more shared bookmarks' > a
  $ hg commit -m 'testing shared bookmarks'
  created new head
  $ hg bookmarks
     bm1                       3:b87954705719
   * bm3                       4:62f4ded848e4
  $ cd ../repo1
  $ hg bookmarks
   * bm1                       3:b87954705719
     bm3                       4:62f4ded848e4
  $ cd ..

non largefiles repos won't enable largefiles

  $ hg share --config extensions.largefiles= repo3 sharedrepo
  The fsmonitor extension is incompatible with the largefiles extension and has been disabled. (fsmonitor !)
  The fsmonitor extension is incompatible with the largefiles extension and has been disabled. (fsmonitor !)
  updating working directory
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ [ -f sharedrepo/.hg/hgrc ]
  [1]

test pushing bookmarks works

  $ hg clone repo3 repo4
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd repo4
  $ hg boo bm4
  $ echo foo > b
  $ hg commit -m 'foo in b'
  $ hg boo
     bm1                       3:b87954705719
     bm3                       4:62f4ded848e4
   * bm4                       5:92793bfc8cad
  $ hg push -B bm4
  pushing to $TESTTMP/repo3
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  exporting bookmark bm4
  $ cd ../repo1
  $ hg bookmarks
   * bm1                       3:b87954705719
     bm3                       4:62f4ded848e4
     bm4                       5:92793bfc8cad
  $ cd ../repo3
  $ hg bookmarks
     bm1                       3:b87954705719
   * bm3                       4:62f4ded848e4
     bm4                       5:92793bfc8cad
  $ cd ..

test behavior when sharing a shared repo

  $ hg share -B repo3 missingdir/repo5
  updating working directory
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd missingdir/repo5
  $ hg book
     bm1                       3:b87954705719
     bm3                       4:62f4ded848e4
     bm4                       5:92793bfc8cad
  $ cd ../..

test what happens when an active bookmark is deleted

  $ cd repo1
  $ hg boo -d bm3
  $ hg boo
   * bm1                       3:b87954705719
     bm4                       5:92793bfc8cad
  $ cd ../repo3
  $ hg boo
     bm1                       3:b87954705719
     bm4                       5:92793bfc8cad
  $ cd ..

verify that bookmarks are not written on failed transaction

  $ cat > failpullbookmarks.py << EOF
  > """A small extension that makes bookmark pulls fail, for testing"""
  > from __future__ import absolute_import
  > from mercurial import (
  >   error,
  >   exchange,
  >   extensions,
  > )
  > def _pullbookmarks(orig, pullop):
  >     orig(pullop)
  >     raise error.HookAbort('forced failure by extension')
  > def extsetup(ui):
  >     extensions.wrapfunction(exchange, '_pullbookmarks', _pullbookmarks)
  > EOF
  $ cd repo4
  $ hg boo
     bm1                       3:b87954705719
     bm3                       4:62f4ded848e4
   * bm4                       5:92793bfc8cad
  $ cd ../repo3
  $ hg boo
     bm1                       3:b87954705719
     bm4                       5:92793bfc8cad
  $ hg --config "extensions.failpullbookmarks=$TESTTMP/failpullbookmarks.py" pull $TESTTMP/repo4
  pulling from $TESTTMP/repo4
  searching for changes
  no changes found
  adding remote bookmark bm3
  abort: forced failure by extension
  [255]
  $ hg boo
     bm1                       3:b87954705719
     bm4                       5:92793bfc8cad
  $ hg pull $TESTTMP/repo4
  pulling from $TESTTMP/repo4
  searching for changes
  no changes found
  adding remote bookmark bm3
  1 local changesets published
  $ hg boo
     bm1                       3:b87954705719
   * bm3                       4:62f4ded848e4
     bm4                       5:92793bfc8cad
  $ cd ..

verify bookmark behavior after unshare

  $ cd repo3
  $ hg unshare
  $ hg boo
     bm1                       3:b87954705719
   * bm3                       4:62f4ded848e4
     bm4                       5:92793bfc8cad
  $ hg boo -d bm4
  $ hg boo bm5
  $ hg boo
     bm1                       3:b87954705719
     bm3                       4:62f4ded848e4
   * bm5                       4:62f4ded848e4
  $ cd ../repo1
  $ hg boo
   * bm1                       3:b87954705719
     bm3                       4:62f4ded848e4
     bm4                       5:92793bfc8cad
  $ cd ..

test shared clones using relative paths work

  $ mkdir thisdir
  $ hg init thisdir/orig
  $ hg share -U thisdir/orig thisdir/abs
  $ hg share -U --relative thisdir/abs thisdir/rel
  $ cat thisdir/rel/.hg/sharedpath
  ../../orig/.hg (no-eol)
  $ grep shared thisdir/*/.hg/requires
  thisdir/abs/.hg/requires:shared
  thisdir/rel/.hg/requires:relshared
  thisdir/rel/.hg/requires:shared

test that relative shared paths aren't relative to $PWD

  $ cd thisdir
  $ hg -R rel root
  $TESTTMP/thisdir/rel
  $ cd ..

now test that relative paths really are relative, survive across
renames and changes of PWD

  $ hg -R thisdir/abs root
  $TESTTMP/thisdir/abs
  $ hg -R thisdir/rel root
  $TESTTMP/thisdir/rel
  $ mv thisdir thatdir
  $ hg -R thatdir/abs root
  abort: .hg/sharedpath points to nonexistent directory $TESTTMP/thisdir/orig/.hg!
  [255]
  $ hg -R thatdir/rel root
  $TESTTMP/thatdir/rel

test unshare relshared repo

  $ cd thatdir/rel
  $ hg unshare
  $ test -d .hg/store
  $ test -f .hg/sharedpath
  [1]
  $ grep shared .hg/requires
  [1]
  $ hg unshare
  abort: this is not a shared repo
  [255]
  $ cd ../..

  $ rm -r thatdir

Demonstrate buggy behavior around requirements validation
See comment in localrepo.py:makelocalrepository() for more.

  $ hg init sharenewrequires
  $ hg share sharenewrequires shareoldrequires
  updating working directory
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ cat >> sharenewrequires/.hg/requires << EOF
  > missing-requirement
  > EOF

We cannot open the repo with the unknown requirement

  $ hg -R sharenewrequires status
  abort: repository requires features unknown to this Mercurial: missing-requirement!
  (see https://mercurial-scm.org/wiki/MissingRequirement for more information)
  [255]

BUG: we don't get the same error when opening the shared repo pointing to it

  $ hg -R shareoldrequires status

Explicitly kill daemons to let the test exit on Windows

  $ killdaemons.py