view contrib/synthrepo.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outdated and unsupported repo format.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.

# synthrepo.py - repo synthesis
#
# Copyright 2012 Facebook
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

'''synthesize structurally interesting change history

This extension is useful for creating a repository with properties
that are statistically similar to an existing repository. During
analysis, a simple probability table is constructed from the history
of an existing repository.  During synthesis, these properties are
reconstructed.

Properties that are analyzed and synthesized include the following:

- Lines added or removed when an existing file is modified
- Number and sizes of files added
- Number of files removed
- Line lengths
- Topological distance to parent changeset(s)
- Probability of a commit being a merge
- Probability of a newly added file being added to a new directory
- Interarrival time, and time zone, of commits
- Number of files in each directory

A few obvious properties that are not currently handled realistically:

- Merges are treated as regular commits with two parents, which is not
  realistic
- Modifications are not treated as operations on hunks of lines, but
  as insertions and deletions of randomly chosen single lines
- Committer ID (always random)
- Executability of files
- Symlinks and binary files are ignored
'''

from __future__ import absolute_import
import bisect
import collections
import itertools
import json
import os
import random
import sys
import time

from mercurial.i18n import _
from mercurial.node import (
    nullid,
    nullrev,
    short,
)
from mercurial import (
    context,
    error,
    hg,
    patch,
    registrar,
    scmutil,
    util,
)

# Note for extension authors: ONLY specify testedwith = 'ships-with-hg-core' for
# extensions which SHIP WITH MERCURIAL. Non-mainline extensions should
# be specifying the version(s) of Mercurial they are tested with, or
# leave the attribute unspecified.
testedwith = 'ships-with-hg-core'

cmdtable = {}
command = registrar.command(cmdtable)

newfile = {'new fi', 'rename', 'copy f', 'copy t'}

def zerodict():
    return collections.defaultdict(lambda: 0)

def roundto(x, k):
    if x > k * 2:
        return int(round(x / float(k)) * k)
    return int(round(x))

def parsegitdiff(lines):
    filename, mar, lineadd, lineremove = None, None, zerodict(), 0
    binary = False
    for line in lines:
        start = line[:6]
        if start == 'diff -':
            if filename:
                yield filename, mar, lineadd, lineremove, binary
            mar, lineadd, lineremove, binary = 'm', zerodict(), 0, False
            filename = patch.gitre.match(line).group(1)
        elif start in newfile:
            mar = 'a'
        elif start == 'GIT bi':
            binary = True
        elif start == 'delete':
            mar = 'r'
        elif start:
            s = start[0]
            if s == '-' and not line.startswith('--- '):
                lineremove += 1
            elif s == '+' and not line.startswith('+++ '):
                lineadd[roundto(len(line) - 1, 5)] += 1
    if filename:
        yield filename, mar, lineadd, lineremove, binary

@command('analyze',
         [('o', 'output', '', _('write output to given file'), _('FILE')),
          ('r', 'rev', [], _('analyze specified revisions'), _('REV'))],
         _('hg analyze'), optionalrepo=True)
def analyze(ui, repo, *revs, **opts):
    '''create a simple model of a repository to use for later synthesis

    This command examines every changeset in the given range (or all
    of history if none are specified) and creates a simple statistical
    model of the history of the repository. It also measures the directory
    structure of the repository as checked out.

    The model is written out to a JSON file, and can be used by
    :hg:`synthesize` to create or augment a repository with synthetic
    commits that have a structure that is statistically similar to the
    analyzed repository.
    '''
    root = repo.root
    if not root.endswith(os.path.sep):
        root += os.path.sep

    revs = list(revs)
    revs.extend(opts['rev'])
    if not revs:
        revs = [':']

    output = opts['output']
    if not output:
        output = os.path.basename(root) + '.json'

    if output == '-':
        fp = sys.stdout
    else:
        fp = open(output, 'w')

    # Always obtain file counts of each directory in the given root directory.
    def onerror(e):
        ui.warn(_('error walking directory structure: %s\n') % e)

    dirs = {}
    rootprefixlen = len(root)
    for dirpath, dirnames, filenames in os.walk(root, onerror=onerror):
        dirpathfromroot = dirpath[rootprefixlen:]
        dirs[dirpathfromroot] = len(filenames)
        if '.hg' in dirnames:
            dirnames.remove('.hg')

    lineschanged = zerodict()
    children = zerodict()
    p1distance = zerodict()
    p2distance = zerodict()
    linesinfilesadded = zerodict()
    fileschanged = zerodict()
    filesadded = zerodict()
    filesremoved = zerodict()
    linelengths = zerodict()
    interarrival = zerodict()
    parents = zerodict()
    dirsadded = zerodict()
    tzoffset = zerodict()

    # If a mercurial repo is available, also model the commit history.
    if repo:
        revs = scmutil.revrange(repo, revs)
        revs.sort()

        progress = ui.progress
        _analyzing = _('analyzing')
        _changesets = _('changesets')
        _total = len(revs)

        for i, rev in enumerate(revs):
            progress(_analyzing, i, unit=_changesets, total=_total)
            ctx = repo[rev]
            pl = ctx.parents()
            pctx = pl[0]
            prev = pctx.rev()
            children[prev] += 1
            p1distance[rev - prev] += 1
            parents[len(pl)] += 1
            tzoffset[ctx.date()[1]] += 1
            if len(pl) > 1:
                p2distance[rev - pl[1].rev()] += 1
            if prev == rev - 1:
                lastctx = pctx
            else:
                lastctx = repo[rev - 1]
            if lastctx.rev() != nullrev:
                timedelta = ctx.date()[0] - lastctx.date()[0]
                interarrival[roundto(timedelta, 300)] += 1
            diff = sum((d.splitlines() for d in ctx.diff(pctx, git=True)), [])
            fileadds, diradds, fileremoves, filechanges = 0, 0, 0, 0
            for filename, mar, lineadd, lineremove, isbin in parsegitdiff(diff):
                if isbin:
                    continue
                added = sum(lineadd.itervalues(), 0)
                if mar == 'm':
                    if added and lineremove:
                        lineschanged[roundto(added, 5),
                                     roundto(lineremove, 5)] += 1
                        filechanges += 1
                elif mar == 'a':
                    fileadds += 1
                    if '/' in filename:
                        filedir = filename.rsplit('/', 1)[0]
                        if filedir not in pctx.dirs():
                            diradds += 1
                    linesinfilesadded[roundto(added, 5)] += 1
                elif mar == 'r':
                    fileremoves += 1
                for length, count in lineadd.iteritems():
                    linelengths[length] += count
            fileschanged[filechanges] += 1
            filesadded[fileadds] += 1
            dirsadded[diradds] += 1
            filesremoved[fileremoves] += 1

    invchildren = zerodict()

    for rev, count in children.iteritems():
        invchildren[count] += 1

    if output != '-':
        ui.status(_('writing output to %s\n') % output)

    def pronk(d):
        return sorted(d.iteritems(), key=lambda x: x[1], reverse=True)

    json.dump({'revs': len(revs),
               'initdirs': pronk(dirs),
               'lineschanged': pronk(lineschanged),
               'children': pronk(invchildren),
               'fileschanged': pronk(fileschanged),
               'filesadded': pronk(filesadded),
               'linesinfilesadded': pronk(linesinfilesadded),
               'dirsadded': pronk(dirsadded),
               'filesremoved': pronk(filesremoved),
               'linelengths': pronk(linelengths),
               'parents': pronk(parents),
               'p1distance': pronk(p1distance),
               'p2distance': pronk(p2distance),
               'interarrival': pronk(interarrival),
               'tzoffset': pronk(tzoffset),
               },
              fp)
    fp.close()

@command('synthesize',
         [('c', 'count', 0, _('create given number of commits'), _('COUNT')),
          ('', 'dict', '', _('path to a dictionary of words'), _('FILE')),
          ('', 'initfiles', 0, _('initial file count to create'), _('COUNT'))],
         _('hg synthesize [OPTION].. DESCFILE'))
def synthesize(ui, repo, descpath, **opts):
    '''synthesize commits based on a model of an existing repository

    The model must have been generated by :hg:`analyze`. Commits will
    be generated randomly according to the probabilities described in
    the model. If --initfiles is set, the repository will be seeded with
    the given number files following the modeled repository's directory
    structure.

    When synthesizing new content, commit descriptions, and user
    names, words will be chosen randomly from a dictionary that is
    presumed to contain one word per line. Use --dict to specify the
    path to an alternate dictionary to use.
    '''
    try:
        fp = hg.openpath(ui, descpath)
    except Exception as err:
        raise error.Abort('%s: %s' % (descpath, err[0].strerror))
    desc = json.load(fp)
    fp.close()

    def cdf(l):
        if not l:
            return [], []
        vals, probs = zip(*sorted(l, key=lambda x: x[1], reverse=True))
        t = float(sum(probs, 0))
        s, cdfs = 0, []
        for v in probs:
            s += v
            cdfs.append(s / t)
        return vals, cdfs

    lineschanged = cdf(desc['lineschanged'])
    fileschanged = cdf(desc['fileschanged'])
    filesadded = cdf(desc['filesadded'])
    dirsadded = cdf(desc['dirsadded'])
    filesremoved = cdf(desc['filesremoved'])
    linelengths = cdf(desc['linelengths'])
    parents = cdf(desc['parents'])
    p1distance = cdf(desc['p1distance'])
    p2distance = cdf(desc['p2distance'])
    interarrival = cdf(desc['interarrival'])
    linesinfilesadded = cdf(desc['linesinfilesadded'])
    tzoffset = cdf(desc['tzoffset'])

    dictfile = opts.get('dict') or '/usr/share/dict/words'
    try:
        fp = open(dictfile, 'rU')
    except IOError as err:
        raise error.Abort('%s: %s' % (dictfile, err.strerror))
    words = fp.read().splitlines()
    fp.close()

    initdirs = {}
    if desc['initdirs']:
        for k, v in desc['initdirs']:
            initdirs[k.encode('utf-8').replace('.hg', '_hg')] = v
        initdirs = renamedirs(initdirs, words)
    initdirscdf = cdf(initdirs)

    def pick(cdf):
        return cdf[0][bisect.bisect_left(cdf[1], random.random())]

    def pickpath():
        return os.path.join(pick(initdirscdf), random.choice(words))

    def makeline(minimum=0):
        total = max(minimum, pick(linelengths))
        c, l = 0, []
        while c < total:
            w = random.choice(words)
            c += len(w) + 1
            l.append(w)
        return ' '.join(l)

    wlock = repo.wlock()
    lock = repo.lock()

    nevertouch = {'.hgsub', '.hgignore', '.hgtags'}

    progress = ui.progress
    _synthesizing = _('synthesizing')
    _files = _('initial files')
    _changesets = _('changesets')

    # Synthesize a single initial revision adding files to the repo according
    # to the modeled directory structure.
    initcount = int(opts['initfiles'])
    if initcount and initdirs:
        pctx = repo[None].parents()[0]
        dirs = set(pctx.dirs())
        files = {}

        def validpath(path):
            # Don't pick filenames which are already directory names.
            if path in dirs:
                return False
            # Don't pick directories which were used as file names.
            while path:
                if path in files:
                    return False
                path = os.path.dirname(path)
            return True

        for i in xrange(0, initcount):
            ui.progress(_synthesizing, i, unit=_files, total=initcount)

            path = pickpath()
            while not validpath(path):
                path = pickpath()
            data = '%s contents\n' % path
            files[path] = context.memfilectx(repo, path, data)
            dir = os.path.dirname(path)
            while dir and dir not in dirs:
                dirs.add(dir)
                dir = os.path.dirname(dir)

        def filectxfn(repo, memctx, path):
            return files[path]

        ui.progress(_synthesizing, None)
        message = 'synthesized wide repo with %d files' % (len(files),)
        mc = context.memctx(repo, [pctx.node(), nullid], message,
                            files.iterkeys(), filectxfn, ui.username(),
                            '%d %d' % util.makedate())
        initnode = mc.commit()
        if ui.debugflag:
            hexfn = hex
        else:
            hexfn = short
        ui.status(_('added commit %s with %d files\n')
                  % (hexfn(initnode), len(files)))

    # Synthesize incremental revisions to the repository, adding repo depth.
    count = int(opts['count'])
    heads = set(map(repo.changelog.rev, repo.heads()))
    for i in xrange(count):
        progress(_synthesizing, i, unit=_changesets, total=count)

        node = repo.changelog.node
        revs = len(repo)

        def pickhead(heads, distance):
            if heads:
                lheads = sorted(heads)
                rev = revs - min(pick(distance), revs)
                if rev < lheads[-1]:
                    rev = lheads[bisect.bisect_left(lheads, rev)]
                else:
                    rev = lheads[-1]
                return rev, node(rev)
            return nullrev, nullid

        r1 = revs - min(pick(p1distance), revs)
        p1 = node(r1)

        # the number of heads will grow without bound if we use a pure
        # model, so artificially constrain their proliferation
        toomanyheads = len(heads) > random.randint(1, 20)
        if p2distance[0] and (pick(parents) == 2 or toomanyheads):
            r2, p2 = pickhead(heads.difference([r1]), p2distance)
        else:
            r2, p2 = nullrev, nullid

        pl = [p1, p2]
        pctx = repo[r1]
        mf = pctx.manifest()
        mfk = mf.keys()
        changes = {}
        if mfk:
            for __ in xrange(pick(fileschanged)):
                for __ in xrange(10):
                    fctx = pctx.filectx(random.choice(mfk))
                    path = fctx.path()
                    if not (path in nevertouch or fctx.isbinary() or
                            'l' in fctx.flags()):
                        break
                lines = fctx.data().splitlines()
                add, remove = pick(lineschanged)
                for __ in xrange(remove):
                    if not lines:
                        break
                    del lines[random.randrange(0, len(lines))]
                for __ in xrange(add):
                    lines.insert(random.randint(0, len(lines)), makeline())
                path = fctx.path()
                changes[path] = context.memfilectx(repo, path,
                                                   '\n'.join(lines) + '\n')
            for __ in xrange(pick(filesremoved)):
                path = random.choice(mfk)
                for __ in xrange(10):
                    path = random.choice(mfk)
                    if path not in changes:
                        changes[path] = None
                        break
        if filesadded:
            dirs = list(pctx.dirs())
            dirs.insert(0, '')
        for __ in xrange(pick(filesadded)):
            pathstr = ''
            while pathstr in dirs:
                path = [random.choice(dirs)]
                if pick(dirsadded):
                    path.append(random.choice(words))
                path.append(random.choice(words))
                pathstr = '/'.join(filter(None, path))
            data = '\n'.join(makeline()
                             for __ in xrange(pick(linesinfilesadded))) + '\n'
            changes[pathstr] = context.memfilectx(repo, pathstr, data)
        def filectxfn(repo, memctx, path):
            return changes[path]
        if not changes:
            continue
        if revs:
            date = repo['tip'].date()[0] + pick(interarrival)
        else:
            date = time.time() - (86400 * count)
        # dates in mercurial must be positive, fit in 32-bit signed integers.
        date = min(0x7fffffff, max(0, date))
        user = random.choice(words) + '@' + random.choice(words)
        mc = context.memctx(repo, pl, makeline(minimum=2),
                            sorted(changes.iterkeys()),
                            filectxfn, user, '%d %d' % (date, pick(tzoffset)))
        newnode = mc.commit()
        heads.add(repo.changelog.rev(newnode))
        heads.discard(r1)
        heads.discard(r2)

    lock.release()
    wlock.release()

def renamedirs(dirs, words):
    '''Randomly rename the directory names in the per-dir file count dict.'''
    wordgen = itertools.cycle(words)
    replacements = {'': ''}
    def rename(dirpath):
        '''Recursively rename the directory and all path prefixes.

        The mapping from path to renamed path is stored for all path prefixes
        as in dynamic programming, ensuring linear runtime and consistent
        renaming regardless of iteration order through the model.
        '''
        if dirpath in replacements:
            return replacements[dirpath]
        head, _ = os.path.split(dirpath)
        if head:
            head = rename(head)
        else:
            head = ''
        renamed = os.path.join(head, next(wordgen))
        replacements[dirpath] = renamed
        return renamed
    result = []
    for dirpath, count in dirs.iteritems():
        result.append([rename(dirpath.lstrip(os.sep)), count])
    return result