hgext/chgserver.py

fsmonitor: hook up state-enter, state-leave signals

Keeping the codebase in sync with upstream:

Watchman 4.4 introduced an advanced settling feature that allows publishing
tools to notify subscribing tools of the boundaries for important filesystem
operations.

https://facebook.github.io/watchman/docs/cmd/subscribe.html#advanced-settling
has more information about how this feature works.

This diff connects a signal that we're calling `hg.update` to the mercurial
update function so that mercurial can indirectly notify tools (such as IDEs or
build machinery) when it is changing the working copy.  This will allow those
tools to pause their normal actions as the files are changing and defer them
until the end of the operation.

In addition to sending the enter/leave signals for the state, we are able to
publish useful metadata along the same channel.  In this case we are passing
the following pieces of information:

1. destination revision hash
2. An estimate of the distance between the current state and the target state
3. A success indicator.
4. Whether it is a partial update

The distance is estimate may be useful to tools that wish to change their
strategy after the update has complete.  For example, a large update may be
efficient to deal with by walking some internal state in the subscriber rather
than feeding every individual file notification through its normal (small)
delta mechanism.

We estimate the distance by comparing the repository revision number.  In some
cases we cannot come up with a number so we report 0.  This is ok; we're
offering this for informational purposes only and don't guarantee its accuracy.

The success indicator is only really meaningful when we generate the
state-leave notification; it indicates the overall success of the update.

# chgserver.py - command server extension for cHg
#
# Copyright 2011 Yuya Nishihara <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

"""command server extension for cHg (EXPERIMENTAL)

'S' channel (read/write)
    propagate ui.system() request to client

'attachio' command
    attach client's stdio passed by sendmsg()

'chdir' command
    change current directory

'getpager' command
    checks if pager is enabled and which pager should be executed

'setenv' command
    replace os.environ completely

'setumask' command
    set umask

'validate' command
    reload the config and check if the server is up to date

'SIGHUP' signal
    reload configuration files

Config
------

::

  [chgserver]
  idletimeout = 3600 # seconds, after which an idle server will exit
  skiphash = False   # whether to skip config or env change checks
"""

from __future__ import absolute_import

import SocketServer
import errno
import inspect
import os
import re
import signal
import struct
import sys
import threading
import time
import traceback

from mercurial.i18n import _

from mercurial import (
    cmdutil,
    commands,
    commandserver,
    dispatch,
    error,
    extensions,
    osutil,
    util,
)

# Note for extension authors: ONLY specify testedwith = 'internal' 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 = 'internal'

_log = commandserver.log

def _hashlist(items):
    """return sha1 hexdigest for a list"""
    return util.sha1(str(items)).hexdigest()

# sensitive config sections affecting confighash
_configsections = ['extensions']

# sensitive environment variables affecting confighash
_envre = re.compile(r'''\A(?:
                    CHGHG
                    |HG.*
                    |LANG(?:UAGE)?
                    |LC_.*
                    |LD_.*
                    |PATH
                    |PYTHON.*
                    |TERM(?:INFO)?
                    |TZ
                    )\Z''', re.X)

def _confighash(ui):
    """return a quick hash for detecting config/env changes

    confighash is the hash of sensitive config items and environment variables.

    for chgserver, it is designed that once confighash changes, the server is
    not qualified to serve its client and should redirect the client to a new
    server. different from mtimehash, confighash change will not mark the
    server outdated and exit since the user can have different configs at the
    same time.
    """
    sectionitems = []
    for section in _configsections:
        sectionitems.append(ui.configitems(section))
    sectionhash = _hashlist(sectionitems)
    envitems = [(k, v) for k, v in os.environ.iteritems() if _envre.match(k)]
    envhash = _hashlist(sorted(envitems))
    return sectionhash[:6] + envhash[:6]

def _getmtimepaths(ui):
    """get a list of paths that should be checked to detect change

    The list will include:
    - extensions (will not cover all files for complex extensions)
    - mercurial/__version__.py
    - python binary
    """
    modules = [m for n, m in extensions.extensions(ui)]
    try:
        from mercurial import __version__
        modules.append(__version__)
    except ImportError:
        pass
    files = [sys.executable]
    for m in modules:
        try:
            files.append(inspect.getabsfile(m))
        except TypeError:
            pass
    return sorted(set(files))

def _mtimehash(paths):
    """return a quick hash for detecting file changes

    mtimehash calls stat on given paths and calculate a hash based on size and
    mtime of each file. mtimehash does not read file content because reading is
    expensive. therefore it's not 100% reliable for detecting content changes.
    it's possible to return different hashes for same file contents.
    it's also possible to return a same hash for different file contents for
    some carefully crafted situation.

    for chgserver, it is designed that once mtimehash changes, the server is
    considered outdated immediately and should no longer provide service.
    """
    def trystat(path):
        try:
            st = os.stat(path)
            return (st.st_mtime, st.st_size)
        except OSError:
            # could be ENOENT, EPERM etc. not fatal in any case
            pass
    return _hashlist(map(trystat, paths))[:12]

class hashstate(object):
    """a structure storing confighash, mtimehash, paths used for mtimehash"""
    def __init__(self, confighash, mtimehash, mtimepaths):
        self.confighash = confighash
        self.mtimehash = mtimehash
        self.mtimepaths = mtimepaths

    @staticmethod
    def fromui(ui, mtimepaths=None):
        if mtimepaths is None:
            mtimepaths = _getmtimepaths(ui)
        confighash = _confighash(ui)
        mtimehash = _mtimehash(mtimepaths)
        _log('confighash = %s mtimehash = %s\n' % (confighash, mtimehash))
        return hashstate(confighash, mtimehash, mtimepaths)

# copied from hgext/pager.py:uisetup()
def _setuppagercmd(ui, options, cmd):
    if not ui.formatted():
        return

    p = ui.config("pager", "pager", os.environ.get("PAGER"))
    usepager = False
    always = util.parsebool(options['pager'])
    auto = options['pager'] == 'auto'

    if not p:
        pass
    elif always:
        usepager = True
    elif not auto:
        usepager = False
    else:
        attended = ['annotate', 'cat', 'diff', 'export', 'glog', 'log', 'qdiff']
        attend = ui.configlist('pager', 'attend', attended)
        ignore = ui.configlist('pager', 'ignore')
        cmds, _ = cmdutil.findcmd(cmd, commands.table)

        for cmd in cmds:
            var = 'attend-%s' % cmd
            if ui.config('pager', var):
                usepager = ui.configbool('pager', var)
                break
            if (cmd in attend or
                (cmd not in ignore and not attend)):
                usepager = True
                break

    if usepager:
        ui.setconfig('ui', 'formatted', ui.formatted(), 'pager')
        ui.setconfig('ui', 'interactive', False, 'pager')
        return p

_envvarre = re.compile(r'\$[a-zA-Z_]+')

def _clearenvaliases(cmdtable):
    """Remove stale command aliases referencing env vars; variable expansion
    is done at dispatch.addaliases()"""
    for name, tab in cmdtable.items():
        cmddef = tab[0]
        if (isinstance(cmddef, dispatch.cmdalias) and
            not cmddef.definition.startswith('!') and  # shell alias
            _envvarre.search(cmddef.definition)):
            del cmdtable[name]

def _newchgui(srcui, csystem):
    class chgui(srcui.__class__):
        def __init__(self, src=None):
            super(chgui, self).__init__(src)
            if src:
                self._csystem = getattr(src, '_csystem', csystem)
            else:
                self._csystem = csystem

        def system(self, cmd, environ=None, cwd=None, onerr=None,
                   errprefix=None):
            # copied from mercurial/util.py:system()
            self.flush()
            def py2shell(val):
                if val is None or val is False:
                    return '0'
                if val is True:
                    return '1'
                return str(val)
            env = os.environ.copy()
            if environ:
                env.update((k, py2shell(v)) for k, v in environ.iteritems())
            env['HG'] = util.hgexecutable()
            rc = self._csystem(cmd, env, cwd)
            if rc and onerr:
                errmsg = '%s %s' % (os.path.basename(cmd.split(None, 1)[0]),
                                    util.explainexit(rc)[0])
                if errprefix:
                    errmsg = '%s: %s' % (errprefix, errmsg)
                raise onerr(errmsg)
            return rc

    return chgui(srcui)

def _renewui(srcui, args=None):
    if not args:
        args = []

    newui = srcui.__class__()
    for a in ['fin', 'fout', 'ferr', 'environ']:
        setattr(newui, a, getattr(srcui, a))
    if util.safehasattr(srcui, '_csystem'):
        newui._csystem = srcui._csystem

    # load wd and repo config, copied from dispatch.py
    cwds = dispatch._earlygetopt(['--cwd'], args)
    cwd = cwds and os.path.realpath(cwds[-1]) or None
    rpath = dispatch._earlygetopt(["-R", "--repository", "--repo"], args)
    path, newui = dispatch._getlocal(newui, rpath, wd=cwd)

    # internal config: extensions.chgserver
    # copy it. it can only be overrided from command line.
    newui.setconfig('extensions', 'chgserver',
                    srcui.config('extensions', 'chgserver'), '--config')

    # command line args
    dispatch._parseconfig(newui, dispatch._earlygetopt(['--config'], args))

    # stolen from tortoisehg.util.copydynamicconfig()
    for section, name, value in srcui.walkconfig():
        source = srcui.configsource(section, name)
        if ':' in source or source == '--config':
            # path:line or command line
            continue
        if source == 'none':
            # ui.configsource returns 'none' by default
            source = ''
        newui.setconfig(section, name, value, source)
    return newui

class channeledsystem(object):
    """Propagate ui.system() request in the following format:

    payload length (unsigned int),
    cmd, '\0',
    cwd, '\0',
    envkey, '=', val, '\0',
    ...
    envkey, '=', val

    and waits:

    exitcode length (unsigned int),
    exitcode (int)
    """
    def __init__(self, in_, out, channel):
        self.in_ = in_
        self.out = out
        self.channel = channel

    def __call__(self, cmd, environ, cwd):
        args = [util.quotecommand(cmd), cwd or '.']
        args.extend('%s=%s' % (k, v) for k, v in environ.iteritems())
        data = '\0'.join(args)
        self.out.write(struct.pack('>cI', self.channel, len(data)))
        self.out.write(data)
        self.out.flush()

        length = self.in_.read(4)
        length, = struct.unpack('>I', length)
        if length != 4:
            raise error.Abort(_('invalid response'))
        rc, = struct.unpack('>i', self.in_.read(4))
        return rc

_iochannels = [
    # server.ch, ui.fp, mode
    ('cin', 'fin', 'rb'),
    ('cout', 'fout', 'wb'),
    ('cerr', 'ferr', 'wb'),
]

class chgcmdserver(commandserver.server):
    def __init__(self, ui, repo, fin, fout, sock, hashstate, baseaddress):
        super(chgcmdserver, self).__init__(
            _newchgui(ui, channeledsystem(fin, fout, 'S')), repo, fin, fout)
        self.clientsock = sock
        self._oldios = []  # original (self.ch, ui.fp, fd) before "attachio"
        self.hashstate = hashstate
        self.baseaddress = baseaddress
        if hashstate is not None:
            self.capabilities = self.capabilities.copy()
            self.capabilities['validate'] = chgcmdserver.validate

    def cleanup(self):
        # dispatch._runcatch() does not flush outputs if exception is not
        # handled by dispatch._dispatch()
        self.ui.flush()
        self._restoreio()

    def attachio(self):
        """Attach to client's stdio passed via unix domain socket; all
        channels except cresult will no longer be used
        """
        # tell client to sendmsg() with 1-byte payload, which makes it
        # distinctive from "attachio\n" command consumed by client.read()
        self.clientsock.sendall(struct.pack('>cI', 'I', 1))
        clientfds = osutil.recvfds(self.clientsock.fileno())
        _log('received fds: %r\n' % clientfds)

        ui = self.ui
        ui.flush()
        first = self._saveio()
        for fd, (cn, fn, mode) in zip(clientfds, _iochannels):
            assert fd > 0
            fp = getattr(ui, fn)
            os.dup2(fd, fp.fileno())
            os.close(fd)
            if not first:
                continue
            # reset buffering mode when client is first attached. as we want
            # to see output immediately on pager, the mode stays unchanged
            # when client re-attached. ferr is unchanged because it should
            # be unbuffered no matter if it is a tty or not.
            if fn == 'ferr':
                newfp = fp
            else:
                # make it line buffered explicitly because the default is
                # decided on first write(), where fout could be a pager.
                if fp.isatty():
                    bufsize = 1  # line buffered
                else:
                    bufsize = -1  # system default
                newfp = os.fdopen(fp.fileno(), mode, bufsize)
                setattr(ui, fn, newfp)
            setattr(self, cn, newfp)

        self.cresult.write(struct.pack('>i', len(clientfds)))

    def _saveio(self):
        if self._oldios:
            return False
        ui = self.ui
        for cn, fn, _mode in _iochannels:
            ch = getattr(self, cn)
            fp = getattr(ui, fn)
            fd = os.dup(fp.fileno())
            self._oldios.append((ch, fp, fd))
        return True

    def _restoreio(self):
        ui = self.ui
        for (ch, fp, fd), (cn, fn, _mode) in zip(self._oldios, _iochannels):
            newfp = getattr(ui, fn)
            # close newfp while it's associated with client; otherwise it
            # would be closed when newfp is deleted
            if newfp is not fp:
                newfp.close()
            # restore original fd: fp is open again
            os.dup2(fd, fp.fileno())
            os.close(fd)
            setattr(self, cn, ch)
            setattr(ui, fn, fp)
        del self._oldios[:]

    def validate(self):
        """Reload the config and check if the server is up to date

        Read a list of '\0' separated arguments.
        Write a non-empty list of '\0' separated instruction strings or '\0'
        if the list is empty.
        An instruction string could be either:
            - "unlink $path", the client should unlink the path to stop the
              outdated server.
            - "redirect $path", the client should try to connect to another
              server instead.
        """
        args = self._readlist()
        self.ui = _renewui(self.ui, args)
        newhash = hashstate.fromui(self.ui, self.hashstate.mtimepaths)
        insts = []
        if newhash.mtimehash != self.hashstate.mtimehash:
            addr = _hashaddress(self.baseaddress, self.hashstate.confighash)
            insts.append('unlink %s' % addr)
        if newhash.confighash != self.hashstate.confighash:
            addr = _hashaddress(self.baseaddress, newhash.confighash)
            insts.append('redirect %s' % addr)
        _log('validate: %s\n' % insts)
        self.cresult.write('\0'.join(insts) or '\0')

    def chdir(self):
        """Change current directory

        Note that the behavior of --cwd option is bit different from this.
        It does not affect --config parameter.
        """
        path = self._readstr()
        if not path:
            return
        _log('chdir to %r\n' % path)
        os.chdir(path)

    def setumask(self):
        """Change umask"""
        mask = struct.unpack('>I', self._read(4))[0]
        _log('setumask %r\n' % mask)
        os.umask(mask)

    def getpager(self):
        """Read cmdargs and write pager command to r-channel if enabled

        If pager isn't enabled, this writes '\0' because channeledoutput
        does not allow to write empty data.
        """
        args = self._readlist()
        try:
            cmd, _func, args, options, _cmdoptions = dispatch._parse(self.ui,
                                                                     args)
        except (error.Abort, error.AmbiguousCommand, error.CommandError,
                error.UnknownCommand):
            cmd = None
            options = {}
        if not cmd or 'pager' not in options:
            self.cresult.write('\0')
            return

        pagercmd = _setuppagercmd(self.ui, options, cmd)
        if pagercmd:
            self.cresult.write(pagercmd)
        else:
            self.cresult.write('\0')

    def setenv(self):
        """Clear and update os.environ

        Note that not all variables can make an effect on the running process.
        """
        l = self._readlist()
        try:
            newenv = dict(s.split('=', 1) for s in l)
        except ValueError:
            raise ValueError('unexpected value in setenv request')

        diffkeys = set(k for k in set(os.environ.keys() + newenv.keys())
                       if os.environ.get(k) != newenv.get(k))
        _log('change env: %r\n' % sorted(diffkeys))

        os.environ.clear()
        os.environ.update(newenv)

        if set(['HGPLAIN', 'HGPLAINEXCEPT']) & diffkeys:
            # reload config so that ui.plain() takes effect
            self.ui = _renewui(self.ui)

        _clearenvaliases(commands.table)

    capabilities = commandserver.server.capabilities.copy()
    capabilities.update({'attachio': attachio,
                         'chdir': chdir,
                         'getpager': getpager,
                         'setenv': setenv,
                         'setumask': setumask})

# copied from mercurial/commandserver.py
class _requesthandler(SocketServer.StreamRequestHandler):
    def handle(self):
        # use a different process group from the master process, making this
        # process pass kernel "is_current_pgrp_orphaned" check so signals like
        # SIGTSTP, SIGTTIN, SIGTTOU are not ignored.
        os.setpgid(0, 0)
        ui = self.server.ui
        repo = self.server.repo
        sv = chgcmdserver(ui, repo, self.rfile, self.wfile, self.connection,
                          self.server.hashstate, self.server.baseaddress)
        try:
            try:
                sv.serve()
            # handle exceptions that may be raised by command server. most of
            # known exceptions are caught by dispatch.
            except error.Abort as inst:
                ui.warn(_('abort: %s\n') % inst)
            except IOError as inst:
                if inst.errno != errno.EPIPE:
                    raise
            except KeyboardInterrupt:
                pass
            finally:
                sv.cleanup()
        except: # re-raises
            # also write traceback to error channel. otherwise client cannot
            # see it because it is written to server's stderr by default.
            traceback.print_exc(file=sv.cerr)
            raise

def _tempaddress(address):
    return '%s.%d.tmp' % (address, os.getpid())

def _hashaddress(address, hashstr):
    return '%s-%s' % (address, hashstr)

class AutoExitMixIn:  # use old-style to comply with SocketServer design
    lastactive = time.time()
    idletimeout = 3600  # default 1 hour

    def startautoexitthread(self):
        # note: the auto-exit check here is cheap enough to not use a thread,
        # be done in serve_forever. however SocketServer is hook-unfriendly,
        # you simply cannot hook serve_forever without copying a lot of code.
        # besides, serve_forever's docstring suggests using thread.
        thread = threading.Thread(target=self._autoexitloop)
        thread.daemon = True
        thread.start()

    def _autoexitloop(self, interval=1):
        while True:
            time.sleep(interval)
            if not self.issocketowner():
                _log('%s is not owned, exiting.\n' % self.server_address)
                break
            if time.time() - self.lastactive > self.idletimeout:
                _log('being idle too long. exiting.\n')
                break
        self.shutdown()

    def process_request(self, request, address):
        self.lastactive = time.time()
        return SocketServer.ForkingMixIn.process_request(
            self, request, address)

    def server_bind(self):
        # use a unique temp address so we can stat the file and do ownership
        # check later
        tempaddress = _tempaddress(self.server_address)
        self.socket.bind(tempaddress)
        self._socketstat = os.stat(tempaddress)
        # rename will replace the old socket file if exists atomically. the
        # old server will detect ownership change and exit.
        util.rename(tempaddress, self.server_address)

    def issocketowner(self):
        try:
            stat = os.stat(self.server_address)
            return (stat.st_ino == self._socketstat.st_ino and
                    stat.st_mtime == self._socketstat.st_mtime)
        except OSError:
            return False

    def unlinksocketfile(self):
        if not self.issocketowner():
            return
        # it is possible to have a race condition here that we may
        # remove another server's socket file. but that's okay
        # since that server will detect and exit automatically and
        # the client will start a new server on demand.
        try:
            os.unlink(self.server_address)
        except OSError as exc:
            if exc.errno != errno.ENOENT:
                raise

class chgunixservice(commandserver.unixservice):
    def init(self):
        signal.signal(signal.SIGHUP, self._reloadconfig)
        self._inithashstate()
        class cls(AutoExitMixIn, SocketServer.ForkingMixIn,
                  SocketServer.UnixStreamServer):
            ui = self.ui
            repo = self.repo
            hashstate = self.hashstate
            baseaddress = self.baseaddress
        self.server = cls(self.address, _requesthandler)
        self.server.idletimeout = self.ui.configint(
            'chgserver', 'idletimeout', self.server.idletimeout)
        self.server.startautoexitthread()
        self._createsymlink()
        # avoid writing "listening at" message to stdout before attachio
        # request, which calls setvbuf()

    def _inithashstate(self):
        self.baseaddress = self.address
        if self.ui.configbool('chgserver', 'skiphash', False):
            self.hashstate = None
            return
        self.hashstate = hashstate.fromui(self.ui)
        self.address = _hashaddress(self.address, self.hashstate.confighash)

    def _createsymlink(self):
        if self.baseaddress == self.address:
            return
        tempaddress = _tempaddress(self.baseaddress)
        os.symlink(os.path.basename(self.address), tempaddress)
        util.rename(tempaddress, self.baseaddress)

    def _reloadconfig(self, signum, frame):
        self.ui = self.server.ui = _renewui(self.ui)

    def run(self):
        try:
            self.server.serve_forever()
        finally:
            self.server.unlinksocketfile()

def uisetup(ui):
    commandserver._servicemap['chgunix'] = chgunixservice

    # CHGINTERNALMARK is temporarily set by chg client to detect if chg will
    # start another chg. drop it to avoid possible side effects.
    if 'CHGINTERNALMARK' in os.environ:
        del os.environ['CHGINTERNALMARK']