view mercurial/repair.py @ 32697:19b9fc40cc51

revlog: skeleton support for version 2 revlogs

There are a number of improvements we want to make to revlogs
that will require a new version - version 2. It is unclear what the
full set of improvements will be or when we'll be done with them.
What I do know is that the process will likely take longer than a
single release, will require input from various stakeholders to
evaluate changes, and will have many contentious debates and
bikeshedding.

It is unrealistic to develop revlog version 2 up front: there
are just too many uncertainties that we won't know until things
are implemented and experiments are run. Some changes will also
be invasive and prone to bit rot, so sitting on dozens of patches
is not practical.

This commit introduces skeleton support for version 2 revlogs in
a way that is flexible and not bound by backwards compatibility
concerns.

An experimental repo requirement for denoting revlog v2 has been
added. The requirement string has a sub-version component to it.
This will allow us to declare multiple requirements in the course
of developing revlog v2. Whenever we change the in-development
revlog v2 format, we can tweak the string, creating a new
requirement and locking out old clients. This will allow us to
make as many backwards incompatible changes and experiments to
revlog v2 as we want. In other words, we can land code and make
meaningful progress towards revlog v2 while still maintaining
extreme format flexibility up until the point we freeze the
format and remove the experimental labels.

To enable the new repo requirement, you must supply an experimental
and undocumented config option. But not just any boolean flag
will do: you need to explicitly use a value that no sane person
should ever type. This is an additional guard against enabling
revlog v2 on an installation it shouldn't be enabled on. The
specific scenario I'm trying to prevent is say a user with a
4.4 client with a frozen format enabling the option but then
downgrading to 4.3 and accidentally creating repos with an
outdated and unsupported repo format. Requiring a "challenge"
string should prevent this.

Because the format is not yet finalized and I don't want to take
any chances, revlog v2's version is currently 0xDEAD. I figure
squatting on a value we're likely never to use as an actual revlog
version to mean "internal testing only" is acceptable. And
"dead" is easily recognized as something meaningful.

There is a bunch of cleanup that is needed before work on revlog
v2 begins in earnest. I plan on doing that work once this patch
is accepted and we're comfortable with the idea of starting down
this path.

# repair.py - functions for repository repair for mercurial
#
# Copyright 2005, 2006 Chris Mason <[e-mail]>
# Copyright 2007 Matt Mackall
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

from __future__ import absolute_import

import errno
import hashlib

from .i18n import _
from .node import short
from . import (
    bundle2,
    changegroup,
    discovery,
    error,
    exchange,
    obsolete,
    util,
)

def _bundle(repo, bases, heads, node, suffix, compress=True, obsolescence=True):
    """create a bundle with the specified revisions as a backup"""

    backupdir = "strip-backup"
    vfs = repo.vfs
    if not vfs.isdir(backupdir):
        vfs.mkdir(backupdir)

    # Include a hash of all the nodes in the filename for uniqueness
    allcommits = repo.set('%ln::%ln', bases, heads)
    allhashes = sorted(c.hex() for c in allcommits)
    totalhash = hashlib.sha1(''.join(allhashes)).hexdigest()
    name = "%s/%s-%s-%s.hg" % (backupdir, short(node), totalhash[:8], suffix)

    cgversion = changegroup.safeversion(repo)
    comp = None
    if cgversion != '01':
        bundletype = "HG20"
        if compress:
            comp = 'BZ'
    elif compress:
        bundletype = "HG10BZ"
    else:
        bundletype = "HG10UN"

    outgoing = discovery.outgoing(repo, missingroots=bases, missingheads=heads)
    contentopts = {'cg.version': cgversion, 'obsolescence': obsolescence}
    return bundle2.writenewbundle(repo.ui, repo, 'strip', name, bundletype,
                                  outgoing, contentopts, vfs, compression=comp)

def _collectfiles(repo, striprev):
    """find out the filelogs affected by the strip"""
    files = set()

    for x in xrange(striprev, len(repo)):
        files.update(repo[x].files())

    return sorted(files)

def _collectbrokencsets(repo, files, striprev):
    """return the changesets which will be broken by the truncation"""
    s = set()
    def collectone(revlog):
        _, brokenset = revlog.getstrippoint(striprev)
        s.update([revlog.linkrev(r) for r in brokenset])

    collectone(repo.manifestlog._revlog)
    for fname in files:
        collectone(repo.file(fname))

    return s

def strip(ui, repo, nodelist, backup=True, topic='backup'):
    # This function operates within a transaction of its own, but does
    # not take any lock on the repo.
    # Simple way to maintain backwards compatibility for this
    # argument.
    if backup in ['none', 'strip']:
        backup = False

    repo = repo.unfiltered()
    repo.destroying()

    cl = repo.changelog
    # TODO handle undo of merge sets
    if isinstance(nodelist, str):
        nodelist = [nodelist]
    striplist = [cl.rev(node) for node in nodelist]
    striprev = min(striplist)

    files = _collectfiles(repo, striprev)
    saverevs = _collectbrokencsets(repo, files, striprev)

    # Some revisions with rev > striprev may not be descendants of striprev.
    # We have to find these revisions and put them in a bundle, so that
    # we can restore them after the truncations.
    # To create the bundle we use repo.changegroupsubset which requires
    # the list of heads and bases of the set of interesting revisions.
    # (head = revision in the set that has no descendant in the set;
    #  base = revision in the set that has no ancestor in the set)
    tostrip = set(striplist)
    saveheads = set(saverevs)
    for r in cl.revs(start=striprev + 1):
        if any(p in tostrip for p in cl.parentrevs(r)):
            tostrip.add(r)

        if r not in tostrip:
            saverevs.add(r)
            saveheads.difference_update(cl.parentrevs(r))
            saveheads.add(r)
    saveheads = [cl.node(r) for r in saveheads]

    # compute base nodes
    if saverevs:
        descendants = set(cl.descendants(saverevs))
        saverevs.difference_update(descendants)
    savebases = [cl.node(r) for r in saverevs]
    stripbases = [cl.node(r) for r in tostrip]

    stripobsidx = obsmarkers = ()
    if repo.ui.configbool('devel', 'strip-obsmarkers', True):
        obsmarkers = obsolete.exclusivemarkers(repo, stripbases)
    if obsmarkers:
        stripobsidx = [i for i, m in enumerate(repo.obsstore)
                       if m in obsmarkers]

    # For a set s, max(parents(s) - s) is the same as max(heads(::s - s)), but
    # is much faster
    newbmtarget = repo.revs('max(parents(%ld) - (%ld))', tostrip, tostrip)
    if newbmtarget:
        newbmtarget = repo[newbmtarget.first()].node()
    else:
        newbmtarget = '.'

    bm = repo._bookmarks
    updatebm = []
    for m in bm:
        rev = repo[bm[m]].rev()
        if rev in tostrip:
            updatebm.append(m)

    # create a changegroup for all the branches we need to keep
    backupfile = None
    vfs = repo.vfs
    node = nodelist[-1]
    if backup:
        backupfile = _bundle(repo, stripbases, cl.heads(), node, topic)
        repo.ui.status(_("saved backup bundle to %s\n") %
                       vfs.join(backupfile))
        repo.ui.log("backupbundle", "saved backup bundle to %s\n",
                    vfs.join(backupfile))
    tmpbundlefile = None
    if saveheads:
        # do not compress temporary bundle if we remove it from disk later
        #
        # We do not include obsolescence, it might re-introduce prune markers
        # we are trying to strip.  This is harmless since the stripped markers
        # are already backed up and we did not touched the markers for the
        # saved changesets.
        tmpbundlefile = _bundle(repo, savebases, saveheads, node, 'temp',
                                compress=False, obsolescence=False)

    mfst = repo.manifestlog._revlog

    curtr = repo.currenttransaction()
    if curtr is not None:
        del curtr  # avoid carrying reference to transaction for nothing
        raise error.ProgrammingError('cannot strip from inside a transaction')

    try:
        with repo.transaction("strip") as tr:
            offset = len(tr.entries)

            tr.startgroup()
            cl.strip(striprev, tr)
            mfst.strip(striprev, tr)
            striptrees(repo, tr, striprev, files)

            for fn in files:
                repo.file(fn).strip(striprev, tr)
            tr.endgroup()

            for i in xrange(offset, len(tr.entries)):
                file, troffset, ignore = tr.entries[i]
                with repo.svfs(file, 'a', checkambig=True) as fp:
                    fp.truncate(troffset)
                if troffset == 0:
                    repo.store.markremoved(file)

            deleteobsmarkers(repo.obsstore, stripobsidx)
            del repo.obsstore

        if tmpbundlefile:
            ui.note(_("adding branch\n"))
            f = vfs.open(tmpbundlefile, "rb")
            gen = exchange.readbundle(ui, f, tmpbundlefile, vfs)
            if not repo.ui.verbose:
                # silence internal shuffling chatter
                repo.ui.pushbuffer()
            if isinstance(gen, bundle2.unbundle20):
                with repo.transaction('strip') as tr:
                    tr.hookargs = {'source': 'strip',
                                   'url': 'bundle:' + vfs.join(tmpbundlefile)}
                    bundle2.applybundle(repo, gen, tr, source='strip',
                                        url='bundle:' + vfs.join(tmpbundlefile))
            else:
                gen.apply(repo, 'strip', 'bundle:' + vfs.join(tmpbundlefile),
                          True)
            if not repo.ui.verbose:
                repo.ui.popbuffer()
            f.close()
        repo._phasecache.invalidate()

        for m in updatebm:
            bm[m] = repo[newbmtarget].node()

        with repo.lock():
            with repo.transaction('repair') as tr:
                bm.recordchange(tr)

        # remove undo files
        for undovfs, undofile in repo.undofiles():
            try:
                undovfs.unlink(undofile)
            except OSError as e:
                if e.errno != errno.ENOENT:
                    ui.warn(_('error removing %s: %s\n') %
                            (undovfs.join(undofile), str(e)))

    except: # re-raises
        if backupfile:
            ui.warn(_("strip failed, backup bundle stored in '%s'\n")
                    % vfs.join(backupfile))
        if tmpbundlefile:
            ui.warn(_("strip failed, unrecovered changes stored in '%s'\n")
                    % vfs.join(tmpbundlefile))
            ui.warn(_("(fix the problem, then recover the changesets with "
                      "\"hg unbundle '%s'\")\n") % vfs.join(tmpbundlefile))
        raise
    else:
        if tmpbundlefile:
            # Remove temporary bundle only if there were no exceptions
            vfs.unlink(tmpbundlefile)

    repo.destroyed()
    # return the backup file path (or None if 'backup' was False) so
    # extensions can use it
    return backupfile

def striptrees(repo, tr, striprev, files):
    if 'treemanifest' in repo.requirements: # safe but unnecessary
                                            # otherwise
        for unencoded, encoded, size in repo.store.datafiles():
            if (unencoded.startswith('meta/') and
                unencoded.endswith('00manifest.i')):
                dir = unencoded[5:-12]
                repo.manifestlog._revlog.dirlog(dir).strip(striprev, tr)

def rebuildfncache(ui, repo):
    """Rebuilds the fncache file from repo history.

    Missing entries will be added. Extra entries will be removed.
    """
    repo = repo.unfiltered()

    if 'fncache' not in repo.requirements:
        ui.warn(_('(not rebuilding fncache because repository does not '
                  'support fncache)\n'))
        return

    with repo.lock():
        fnc = repo.store.fncache
        # Trigger load of fncache.
        if 'irrelevant' in fnc:
            pass

        oldentries = set(fnc.entries)
        newentries = set()
        seenfiles = set()

        repolen = len(repo)
        for rev in repo:
            ui.progress(_('rebuilding'), rev, total=repolen,
                        unit=_('changesets'))

            ctx = repo[rev]
            for f in ctx.files():
                # This is to minimize I/O.
                if f in seenfiles:
                    continue
                seenfiles.add(f)

                i = 'data/%s.i' % f
                d = 'data/%s.d' % f

                if repo.store._exists(i):
                    newentries.add(i)
                if repo.store._exists(d):
                    newentries.add(d)

        ui.progress(_('rebuilding'), None)

        if 'treemanifest' in repo.requirements: # safe but unnecessary otherwise
            for dir in util.dirs(seenfiles):
                i = 'meta/%s/00manifest.i' % dir
                d = 'meta/%s/00manifest.d' % dir

                if repo.store._exists(i):
                    newentries.add(i)
                if repo.store._exists(d):
                    newentries.add(d)

        addcount = len(newentries - oldentries)
        removecount = len(oldentries - newentries)
        for p in sorted(oldentries - newentries):
            ui.write(_('removing %s\n') % p)
        for p in sorted(newentries - oldentries):
            ui.write(_('adding %s\n') % p)

        if addcount or removecount:
            ui.write(_('%d items added, %d removed from fncache\n') %
                     (addcount, removecount))
            fnc.entries = newentries
            fnc._dirty = True

            with repo.transaction('fncache') as tr:
                fnc.write(tr)
        else:
            ui.write(_('fncache already up to date\n'))

def stripbmrevset(repo, mark):
    """
    The revset to strip when strip is called with -B mark

    Needs to live here so extensions can use it and wrap it even when strip is
    not enabled or not present on a box.
    """
    return repo.revs("ancestors(bookmark(%s)) - "
                     "ancestors(head() and not bookmark(%s)) - "
                     "ancestors(bookmark() and not bookmark(%s))",
                     mark, mark, mark)

def deleteobsmarkers(obsstore, indices):
    """Delete some obsmarkers from obsstore and return how many were deleted

    'indices' is a list of ints which are the indices
    of the markers to be deleted.

    Every invocation of this function completely rewrites the obsstore file,
    skipping the markers we want to be removed. The new temporary file is
    created, remaining markers are written there and on .close() this file
    gets atomically renamed to obsstore, thus guaranteeing consistency."""
    if not indices:
        # we don't want to rewrite the obsstore with the same content
        return

    left = []
    current = obsstore._all
    n = 0
    for i, m in enumerate(current):
        if i in indices:
            n += 1
            continue
        left.append(m)

    newobsstorefile = obsstore.svfs('obsstore', 'w', atomictemp=True)
    for bytes in obsolete.encodemarkers(left, True, obsstore._version):
        newobsstorefile.write(bytes)
    newobsstorefile.close()
    return n