annotate hgext/inotify/server.py @ 9115:b55d44719b47

inotify: server: new data structure to keep track of changes.

== Rationale for the new structure ==

Current structure was a dictionary tree. One directory was tracked
as a dictionary:
 - keys: file/subdir name
 - values:
    - for a file, the status (a/r/m/...)
    - for a subdir, the directory representing the subdir

It allowed efficient lookups, no matter of the type of the terminal leaf:
    for part in path.split('/'): tree = tree[part]

However, there is no way to represent a directory and a file with the same name
because keys are conflicting in the dictionary. Concrete example:

Initial state:

root dir
 |- foo (file)
 |- bar (file)

# data state is: {'foo': 'n', 'bar': 'n'}

Remove foo:

root dir
 |- bar (file)

# Data becomes {'foo': 'r'} until next commit.

Add foo, as a directory, and foo/barbar file:

root dir
 |- bar (file)
 |-> foo (dir)
  |- barbar (file)

# New state should be represented as:
  {'foo': {'barbar': 'a'}, 'bar': 'n'}
  however, the key "foo" is already used and represents the old file.

The dirstate:
 D foo
 A foo/barbar
cannot be represented, hence the need for a new structure.

== The new structure ==

'directory' class. Represents one directory level.
* Notable attributes:
  Two dictionaries:
   - 'files' Maps filename -> status for the current dir.
   - 'dirs' Maps subdir's name -> directory object representing the subdir
* methods
  - walk(), formerly server.walk
  - lookup(), old server.lookup
  - dir(), old server.dir

This new class allows embedding all the tree walks/lookups in its own class,
instead of having everything mixed together in server.

Incidently, since files and directories are not stored in the same
dictionaries, we are solving the previous key conflict problem.

The small drawback is that lookup operation is a bit more complex:
for a path a/b/c/d/e we have to check twice the leaf, if e is a directory or a
file.

# server.py - inotify status server
#
# Copyright 2006, 2007, 2008 Bryan O'Sullivan <[e-mail]>
# Copyright 2007, 2008 Brendan Cully <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2, incorporated herein by reference.

from mercurial.i18n import _
from mercurial import osutil, util
import common
import errno, os, select, socket, stat, struct, sys, tempfile, time

try:
    import linux as inotify
    from linux import watcher
except ImportError:
    raise

class AlreadyStartedException(Exception): pass

def join(a, b):
    if a:
        if a[-1] == '/':
            return a + b
        return a + '/' + b
    return b

def split(path):
    c = path.rfind('/')
    if c == -1:
        return '', path
    return path[:c], path[c+1:]

walk_ignored_errors = (errno.ENOENT, errno.ENAMETOOLONG)

def walkrepodirs(repo):
    '''Iterate over all subdirectories of this repo.
    Exclude the .hg directory, any nested repos, and ignored dirs.'''
    rootslash = repo.root + os.sep

    def walkit(dirname, top):
        fullpath = rootslash + dirname
        try:
            for name, kind in osutil.listdir(fullpath):
                if kind == stat.S_IFDIR:
                    if name == '.hg':
                        if not top:
                            return
                    else:
                        d = join(dirname, name)
                        if repo.dirstate._ignore(d):
                            continue
                        for subdir in walkit(d, False):
                            yield subdir
        except OSError, err:
            if err.errno not in walk_ignored_errors:
                raise
        yield fullpath

    return walkit('', True)

def walk(repo, root):
    '''Like os.walk, but only yields regular files.'''

    # This function is critical to performance during startup.

    rootslash = repo.root + os.sep

    def walkit(root, reporoot):
        files, dirs = [], []

        try:
            fullpath = rootslash + root
            for name, kind in osutil.listdir(fullpath):
                if kind == stat.S_IFDIR:
                    if name == '.hg':
                        if not reporoot:
                            return
                    else:
                        dirs.append(name)
                        path = join(root, name)
                        if repo.dirstate._ignore(path):
                            continue
                        for result in walkit(path, False):
                            yield result
                elif kind in (stat.S_IFREG, stat.S_IFLNK):
                    files.append(name)
            yield fullpath, dirs, files

        except OSError, err:
            if err.errno not in walk_ignored_errors:
                raise

    return walkit(root, root == '')

def _explain_watch_limit(ui, repo):
    path = '/proc/sys/fs/inotify/max_user_watches'
    try:
        limit = int(file(path).read())
    except IOError, err:
        if err.errno != errno.ENOENT:
            raise
        raise util.Abort(_('this system does not seem to '
                           'support inotify'))
    ui.warn(_('*** the current per-user limit on the number '
              'of inotify watches is %s\n') % limit)
    ui.warn(_('*** this limit is too low to watch every '
              'directory in this repository\n'))
    ui.warn(_('*** counting directories: '))
    ndirs = len(list(walkrepodirs(repo)))
    ui.warn(_('found %d\n') % ndirs)
    newlimit = min(limit, 1024)
    while newlimit < ((limit + ndirs) * 1.1):
        newlimit *= 2
    ui.warn(_('*** to raise the limit from %d to %d (run as root):\n') %
            (limit, newlimit))
    ui.warn(_('***  echo %d > %s\n') % (newlimit, path))
    raise util.Abort(_('cannot watch %s until inotify watch limit is raised')
                     % repo.root)

class pollable(object):
    """
    Interface to support polling.
    The file descriptor returned by fileno() is registered to a polling
    object.
    Usage:
        Every tick, check if an event has happened since the last tick:
        * If yes, call handle_events
        * If no, call handle_timeout
    """
    poll_events = select.POLLIN
    instances = {}
    poll = select.poll()

    def fileno(self):
        raise NotImplementedError

    def handle_events(self, events):
        raise NotImplementedError

    def handle_timeout(self):
        raise NotImplementedError

    def shutdown(self):
        raise NotImplementedError

    def register(self, timeout):
        fd = self.fileno()

        pollable.poll.register(fd, pollable.poll_events)
        pollable.instances[fd] = self

        self.registered = True
        self.timeout = timeout

    def unregister(self):
        pollable.poll.unregister(self)
        self.registered = False

    @classmethod
    def run(cls):
        while True:
            timeout = None
            timeobj = None
            for obj in cls.instances.itervalues():
                if obj.timeout is not None and (timeout is None or obj.timeout < timeout):
                    timeout, timeobj = obj.timeout, obj
            try:
                events = cls.poll.poll(timeout)
            except select.error, err:
                if err[0] == errno.EINTR:
                    continue
                raise
            if events:
                by_fd = {}
                for fd, event in events:
                    by_fd.setdefault(fd, []).append(event)

                for fd, events in by_fd.iteritems():
                    cls.instances[fd].handle_pollevents(events)

            elif timeobj:
                timeobj.handle_timeout()

def eventaction(code):
    """
    Decorator to help handle events in repowatcher
    """
    def decorator(f):
        def wrapper(self, wpath):
            if code == 'm' and wpath in self.lastevent and \
                self.lastevent[wpath] in 'cm':
                return
            self.lastevent[wpath] = code
            self.timeout = 250

            f(self, wpath)

        wrapper.func_name = f.func_name
        return wrapper
    return decorator

class directory(object):
    """
    Representing a directory

    * path is the relative path from repo root to this directory
    * files is a dict listing the files in this directory
        - keys are file names
        - values are file status
    * dirs is a dict listing the subdirectories
        - key are subdirectories names
        - values are directory objects
    """
    def __init__(self, relpath=''):
        self.path = relpath
        self.files = {}
        self.dirs = {}

    def dir(self, relpath):
        """
        Returns the directory contained at the relative path relpath.
        Creates the intermediate directories if necessary.
        """
        if not relpath:
            return self
        l = relpath.split('/')
        ret = self
        while l:
            next = l.pop(0)
            try:
                ret = ret.dirs[next]
            except KeyError:
                d = directory(join(ret.path, next))
                ret.dirs[next] = d
                ret = d
        return ret

    def walk(self, states):
        """
        yield (filename, status) pairs for items in the trees
        that have status in states.
        filenames are relative to the repo root
        """
        for file, st in self.files.iteritems():
            if st in states:
                yield join(self.path, file), st
        for dir in self.dirs.itervalues():
            for e in dir.walk(states):
                yield e

    def lookup(self, states, path):
        """
        yield root-relative filenames that match path, and whose
        status are in states:
        * if path is a file, yield path
        * if path is a directory, yield directory files
        * if path is not tracked, yield nothing
        """
        if path[-1] == '/':
            path = path[:-1]

        paths = path.split('/')

        # we need to check separately for last node
        last = paths.pop()

        tree = self
        try:
            for dir in paths:
                tree = tree.dirs[dir]
        except KeyError:
            # path is not tracked
            return

        try:
            # if path is a directory, walk it
            for file, st in tree.dirs[last].walk(states):
                yield file
        except KeyError:
            try:
                if tree.files[last] in states:
                    # path is a file
                    yield path
            except KeyError:
                # path is not tracked
                pass

class repowatcher(pollable):
    """
    Watches inotify events
    """
    statuskeys = 'almr!?'
    mask = (
        inotify.IN_ATTRIB |
        inotify.IN_CREATE |
        inotify.IN_DELETE |
        inotify.IN_DELETE_SELF |
        inotify.IN_MODIFY |
        inotify.IN_MOVED_FROM |
        inotify.IN_MOVED_TO |
        inotify.IN_MOVE_SELF |
        inotify.IN_ONLYDIR |
        inotify.IN_UNMOUNT |
        0)

    def __init__(self, ui, repo):
        self.ui = ui
        self.repo = repo
        self.wprefix = self.repo.wjoin('')
        try:
            self.watcher = watcher.watcher()
        except OSError, err:
            raise util.Abort(_('inotify service not available: %s') %
                             err.strerror)
        self.threshold = watcher.threshold(self.watcher)
        self.fileno = self.watcher.fileno

        self.tree = directory()
        self.statcache = {}
        self.statustrees = dict([(s, directory()) for s in self.statuskeys])

        self.last_event = None

        self.lastevent = {}

        self.register(timeout=None)

        self.ds_info = self.dirstate_info()
        self.handle_timeout()
        self.scan()

    def event_time(self):
        last = self.last_event
        now = time.time()
        self.last_event = now

        if last is None:
            return 'start'
        delta = now - last
        if delta < 5:
            return '+%.3f' % delta
        if delta < 50:
            return '+%.2f' % delta
        return '+%.1f' % delta

    def dirstate_info(self):
        try:
            st = os.lstat(self.repo.join('dirstate'))
            return st.st_mtime, st.st_ino
        except OSError, err:
            if err.errno != errno.ENOENT:
                raise
            return 0, 0

    def add_watch(self, path, mask):
        if not path:
            return
        if self.watcher.path(path) is None:
            if self.ui.debugflag:
                self.ui.note(_('watching %r\n') % path[len(self.wprefix):])
            try:
                self.watcher.add(path, mask)
            except OSError, err:
                if err.errno in (errno.ENOENT, errno.ENOTDIR):
                    return
                if err.errno != errno.ENOSPC:
                    raise
                _explain_watch_limit(self.ui, self.repo)

    def setup(self):
        self.ui.note(_('watching directories under %r\n') % self.repo.root)
        self.add_watch(self.repo.path, inotify.IN_DELETE)
        self.check_dirstate()

    def filestatus(self, fn, st):
        try:
            type_, mode, size, time = self.repo.dirstate._map[fn][:4]
        except KeyError:
            type_ = '?'
        if type_ == 'n':
            st_mode, st_size, st_mtime = st
            if size == -1:
                return 'l'
            if size and (size != st_size or (mode ^ st_mode) & 0100):
                return 'm'
            if time != int(st_mtime):
                return 'l'
            return 'n'
        if type_ == '?' and self.repo.dirstate._ignore(fn):
            return 'i'
        return type_

    def updatefile(self, wfn, osstat):
        '''
        update the file entry of an existing file.

        osstat: (mode, size, time) tuple, as returned by os.lstat(wfn)
        '''

        self._updatestatus(wfn, self.filestatus(wfn, osstat))

    def deletefile(self, wfn, oldstatus):
        '''
        update the entry of a file which has been deleted.

        oldstatus: char in statuskeys, status of the file before deletion
        '''
        if oldstatus == 'r':
            newstatus = 'r'
        elif oldstatus in 'almn':
            newstatus = '!'
        else:
            newstatus = None

        self.statcache.pop(wfn, None)
        self._updatestatus(wfn, newstatus)

    def _updatestatus(self, wfn, newstatus):
        '''
        Update the stored status of a file.

        newstatus: - char in (statuskeys + 'ni'), new status to apply.
                   - or None, to stop tracking wfn
        '''
        root, fn = split(wfn)
        d = self.tree.dir(root)

        oldstatus = d.files.get(fn)
        # oldstatus can be either:
        # - None : fn is new
        # - a char in statuskeys: fn is a (tracked) file

        if self.ui.debugflag and oldstatus != newstatus:
            self.ui.note(_('status: %r %s -> %s\n') %
                             (wfn, oldstatus, newstatus))

        if oldstatus and oldstatus in self.statuskeys \
            and oldstatus != newstatus:
            del self.statustrees[oldstatus].dir(root).files[fn]
        if newstatus and newstatus != 'i':
            d.files[fn] = newstatus
            if newstatus in self.statuskeys:
                dd = self.statustrees[newstatus].dir(root)
                if oldstatus != newstatus or fn not in dd.files:
                    dd.files[fn] = newstatus
        else:
            d.files.pop(fn, None)


    def check_deleted(self, key):
        # Files that had been deleted but were present in the dirstate
        # may have vanished from the dirstate; we must clean them up.
        nuke = []
        for wfn, ignore in self.statustrees[key].walk(key):
            if wfn not in self.repo.dirstate:
                nuke.append(wfn)
        for wfn in nuke:
            root, fn = split(wfn)
            del self.statustrees[key].dir(root).files[fn]
            del self.tree.dir(root).files[fn]

    def scan(self, topdir=''):
        ds = self.repo.dirstate._map.copy()
        self.add_watch(join(self.repo.root, topdir), self.mask)
        for root, dirs, files in walk(self.repo, topdir):
            for d in dirs:
                self.add_watch(join(root, d), self.mask)
            wroot = root[len(self.wprefix):]
            for fn in files:
                wfn = join(wroot, fn)
                self.updatefile(wfn, self.getstat(wfn))
                ds.pop(wfn, None)
        wtopdir = topdir
        if wtopdir and wtopdir[-1] != '/':
            wtopdir += '/'
        for wfn, state in ds.iteritems():
            if not wfn.startswith(wtopdir):
                continue
            try:
                st = self.stat(wfn)
            except OSError:
                status = state[0]
                self.deletefile(wfn, status)
            else:
                self.updatefile(wfn, st)
        self.check_deleted('!')
        self.check_deleted('r')

    def check_dirstate(self):
        ds_info = self.dirstate_info()
        if ds_info == self.ds_info:
            return
        self.ds_info = ds_info
        if not self.ui.debugflag:
            self.last_event = None
        self.ui.note(_('%s dirstate reload\n') % self.event_time())
        self.repo.dirstate.invalidate()
        self.handle_timeout()
        self.scan()
        self.ui.note(_('%s end dirstate reload\n') % self.event_time())

    def update_hgignore(self):
        # An update of the ignore file can potentially change the
        # states of all unknown and ignored files.

        # XXX If the user has other ignore files outside the repo, or
        # changes their list of ignore files at run time, we'll
        # potentially never see changes to them.  We could get the
        # client to report to us what ignore data they're using.
        # But it's easier to do nothing than to open that can of
        # worms.

        if '_ignore' in self.repo.dirstate.__dict__:
            delattr(self.repo.dirstate, '_ignore')
            self.ui.note(_('rescanning due to .hgignore change\n'))
            self.handle_timeout()
            self.scan()

    def getstat(self, wpath):
        try:
            return self.statcache[wpath]
        except KeyError:
            try:
                return self.stat(wpath)
            except OSError, err:
                if err.errno != errno.ENOENT:
                    raise

    def stat(self, wpath):
        try:
            st = os.lstat(join(self.wprefix, wpath))
            ret = st.st_mode, st.st_size, st.st_mtime
            self.statcache[wpath] = ret
            return ret
        except OSError:
            self.statcache.pop(wpath, None)
            raise

    @eventaction('c')
    def created(self, wpath):
        if wpath == '.hgignore':
            self.update_hgignore()
        try:
            st = self.stat(wpath)
            if stat.S_ISREG(st[0]):
                self.updatefile(wpath, st)
        except OSError:
            pass

    @eventaction('m')
    def modified(self, wpath):
        if wpath == '.hgignore':
            self.update_hgignore()
        try:
            st = self.stat(wpath)
            if stat.S_ISREG(st[0]):
                if self.repo.dirstate[wpath] in 'lmn':
                    self.updatefile(wpath, st)
        except OSError:
            pass

    @eventaction('d')
    def deleted(self, wpath):
        if wpath == '.hgignore':
            self.update_hgignore()
        elif wpath.startswith('.hg/'):
            if wpath == '.hg/wlock':
                self.check_dirstate()
            return

        self.deletefile(wpath, self.repo.dirstate[wpath])

    def process_create(self, wpath, evt):
        if self.ui.debugflag:
            self.ui.note(_('%s event: created %s\n') %
                         (self.event_time(), wpath))

        if evt.mask & inotify.IN_ISDIR:
            self.scan(wpath)
        else:
            self.created(wpath)

    def process_delete(self, wpath, evt):
        if self.ui.debugflag:
            self.ui.note(_('%s event: deleted %s\n') %
                         (self.event_time(), wpath))

        if evt.mask & inotify.IN_ISDIR:
            tree = self.tree.dir(wpath)
            todelete = [wfn for wfn, ignore in tree.walk('?')]
            for fn in todelete:
                self.deletefile(fn, '?')
            self.scan(wpath)
        else:
            self.deleted(wpath)

    def process_modify(self, wpath, evt):
        if self.ui.debugflag:
            self.ui.note(_('%s event: modified %s\n') %
                         (self.event_time(), wpath))

        if not (evt.mask & inotify.IN_ISDIR):
            self.modified(wpath)

    def process_unmount(self, evt):
        self.ui.warn(_('filesystem containing %s was unmounted\n') %
                     evt.fullpath)
        sys.exit(0)

    def handle_pollevents(self, events):
        if self.ui.debugflag:
            self.ui.note(_('%s readable: %d bytes\n') %
                         (self.event_time(), self.threshold.readable()))
        if not self.threshold():
            if self.registered:
                if self.ui.debugflag:
                    self.ui.note(_('%s below threshold - unhooking\n') %
                                 (self.event_time()))
                self.unregister()
                self.timeout = 250
        else:
            self.read_events()

    def read_events(self, bufsize=None):
        events = self.watcher.read(bufsize)
        if self.ui.debugflag:
            self.ui.note(_('%s reading %d events\n') %
                         (self.event_time(), len(events)))
        for evt in events:
            assert evt.fullpath.startswith(self.wprefix)
            wpath = evt.fullpath[len(self.wprefix):]

            if evt.mask & inotify.IN_UNMOUNT:
                self.process_unmount(wpath, evt)
            elif evt.mask & (inotify.IN_MODIFY | inotify.IN_ATTRIB):
                self.process_modify(wpath, evt)
            elif evt.mask & (inotify.IN_DELETE | inotify.IN_DELETE_SELF |
                             inotify.IN_MOVED_FROM):
                self.process_delete(wpath, evt)
            elif evt.mask & (inotify.IN_CREATE | inotify.IN_MOVED_TO):
                self.process_create(wpath, evt)

        self.lastevent.clear()

    def handle_timeout(self):
        if not self.registered:
            if self.ui.debugflag:
                self.ui.note(_('%s hooking back up with %d bytes readable\n') %
                             (self.event_time(), self.threshold.readable()))
            self.read_events(0)
            self.register(timeout=None)

        self.timeout = None

    def shutdown(self):
        self.watcher.close()

    def debug(self):
        """
        Returns a sorted list of relatives paths currently watched,
        for debugging purposes.
        """
        return sorted(tuple[0][len(self.wprefix):] for tuple in self.watcher)

class server(pollable):
    """
    Listens for client queries on unix socket inotify.sock
    """
    def __init__(self, ui, repo, repowatcher, timeout):
        self.ui = ui
        self.repo = repo
        self.repowatcher = repowatcher
        self.sock = socket.socket(socket.AF_UNIX)
        self.sockpath = self.repo.join('inotify.sock')
        self.realsockpath = None
        try:
            self.sock.bind(self.sockpath)
        except socket.error, err:
            if err[0] == errno.EADDRINUSE:
                raise AlreadyStartedException(_('could not start server: %s')
                                              % err[1])
            if err[0] == "AF_UNIX path too long":
                tempdir = tempfile.mkdtemp(prefix="hg-inotify-")
                self.realsockpath = os.path.join(tempdir, "inotify.sock")
                try:
                    self.sock.bind(self.realsockpath)
                    os.symlink(self.realsockpath, self.sockpath)
                except (OSError, socket.error), inst:
                    try:
                        os.unlink(self.realsockpath)
                    except:
                        pass
                    os.rmdir(tempdir)
                    if inst.errno == errno.EEXIST:
                        raise AlreadyStartedException(_('could not start server: %s')
                                                      % inst.strerror)
                    raise
            else:
                raise
        self.sock.listen(5)
        self.fileno = self.sock.fileno
        self.register(timeout=timeout)

    def handle_timeout(self):
        pass

    def answer_stat_query(self, cs):
        names = cs.read().split('\0')

        states = names.pop()

        self.ui.note(_('answering query for %r\n') % states)

        if self.repowatcher.timeout:
            # We got a query while a rescan is pending.  Make sure we
            # rescan before responding, or we could give back a wrong
            # answer.
            self.repowatcher.handle_timeout()

        if not names:
            def genresult(states, tree):
                for fn, state in tree.walk(states):
                    yield fn
        else:
            def genresult(states, tree):
                for fn in names:
                    for f in tree.lookup(states, fn):
                        yield f

        return ['\0'.join(r) for r in [
            genresult('l', self.repowatcher.statustrees['l']),
            genresult('m', self.repowatcher.statustrees['m']),
            genresult('a', self.repowatcher.statustrees['a']),
            genresult('r', self.repowatcher.statustrees['r']),
            genresult('!', self.repowatcher.statustrees['!']),
            '?' in states
                and genresult('?', self.repowatcher.statustrees['?'])
                or [],
            [],
            'c' in states and genresult('n', self.repowatcher.tree) or [],
            ]]

    def answer_dbug_query(self):
        return ['\0'.join(self.repowatcher.debug())]

    def handle_pollevents(self, events):
        for e in events:
            self.handle_pollevent()

    def handle_pollevent(self):
        sock, addr = self.sock.accept()

        cs = common.recvcs(sock)
        version = ord(cs.read(1))

        if version != common.version:
            self.ui.warn(_('received query from incompatible client '
                           'version %d\n') % version)
            try:
                # try to send back our version to the client
                # this way, the client too is informed of the mismatch
                sock.sendall(chr(common.version))
            except:
                pass
            return

        type = cs.read(4)

        if type == 'STAT':
            results = self.answer_stat_query(cs)
        elif type == 'DBUG':
            results = self.answer_dbug_query()
        else:
            self.ui.warn(_('unrecognized query type: %s\n') % type)
            return

        try:
            try:
                v = chr(common.version)

                sock.sendall(v + type + struct.pack(common.resphdrfmts[type],
                                            *map(len, results)))
                sock.sendall(''.join(results))
            finally:
                sock.shutdown(socket.SHUT_WR)
        except socket.error, err:
            if err[0] != errno.EPIPE:
                raise

    def shutdown(self):
        self.sock.close()
        try:
            os.unlink(self.sockpath)
            if self.realsockpath:
                os.unlink(self.realsockpath)
                os.rmdir(os.path.dirname(self.realsockpath))
        except OSError, err:
            if err.errno != errno.ENOENT:
                raise

class master(object):
    def __init__(self, ui, repo, timeout=None):
        self.ui = ui
        self.repo = repo
        self.repowatcher = repowatcher(ui, repo)
        self.server = server(ui, repo, self.repowatcher, timeout)

    def shutdown(self):
        for obj in pollable.instances.itervalues():
            obj.shutdown()

    def run(self):
        self.repowatcher.setup()
        self.ui.note(_('finished setup\n'))
        if os.getenv('TIME_STARTUP'):
            sys.exit(0)
        pollable.run()

def start(ui, repo):
    def closefds(ignore):
        # (from python bug #1177468)
        # close all inherited file descriptors
        # Python 2.4.1 and later use /dev/urandom to seed the random module's RNG
        # a file descriptor is kept internally as os._urandomfd (created on demand
        # the first time os.urandom() is called), and should not be closed
        try:
            os.urandom(4)
            urandom_fd = getattr(os, '_urandomfd', None)
        except AttributeError:
            urandom_fd = None
        ignore.append(urandom_fd)
        for fd in range(3, 256):
            if fd in ignore:
                continue
            try:
                os.close(fd)
            except OSError:
                pass

    m = master(ui, repo)
    sys.stdout.flush()
    sys.stderr.flush()

    pid = os.fork()
    if pid:
        return pid

    closefds(pollable.instances.keys())
    os.setsid()

    fd = os.open('/dev/null', os.O_RDONLY)
    os.dup2(fd, 0)
    if fd > 0:
        os.close(fd)

    fd = os.open(ui.config('inotify', 'log', '/dev/null'),
                 os.O_RDWR | os.O_CREAT | os.O_TRUNC)
    os.dup2(fd, 1)
    os.dup2(fd, 2)
    if fd > 2:
        os.close(fd)

    try:
        m.run()
    finally:
        m.shutdown()
        os._exit(0)