annotate mercurial/sshpeer.py @ 35460:8652ab4046e4

osutil: add a function to unblock signals

Signals could be blocked by something like:

  #include <unistd.h>
  #include <signal.h>
  int main(int argc, char * const argv[]) {
    sigset_t set;
    sigfillset(&set);
    sigprocmask(SIG_BLOCK, &set, NULL);
    execv("/bin/hg", argv);
    return 0;
  }

One of the problems is if SIGCHLD is blocked, chgserver would not reap
zombie workers since it depends on SIGCHLD handler entirely.

While it's the parent process to blame but it seems a good idea to just
unblock the signal from hg. FWIW git does that for SIGPIPE already [1].

Unfortunately Python 2 does not reset or provide APIs to change signal
masks. Therefore let's add one in osutil. Note: Python 3.3 introduced
`signal.pthread_sigmask` which solves the problem.

`sigprocmask` is part of POSIX [2] so there is no feature testing in
`setup.py`.

[1]: https://github.com/git/git/commit/7559a1be8a0afb10df41d25e4cf4c5285a5faef1
[2]: http://pubs.opengroup.org/onlinepubs/7908799/xsh/sigprocmask.html

Differential Revision: https://phab.mercurial-scm.org/D1736

# sshpeer.py - ssh repository proxy class for mercurial
#
# Copyright 2005, 2006 Matt Mackall <[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.

from __future__ import absolute_import

import re

from .i18n import _
from . import (
    error,
    pycompat,
    util,
    wireproto,
)

def _serverquote(s):
    """quote a string for the remote shell ... which we assume is sh"""
    if not s:
        return s
    if re.match('[a-zA-Z0-9@%_+=:,./-]*$', s):
        return s
    return "'%s'" % s.replace("'", "'\\''")

def _forwardoutput(ui, pipe):
    """display all data currently available on pipe as remote output.

    This is non blocking."""
    s = util.readpipe(pipe)
    if s:
        for l in s.splitlines():
            ui.status(_("remote: "), l, '\n')

class doublepipe(object):
    """Operate a side-channel pipe in addition of a main one

    The side-channel pipe contains server output to be forwarded to the user
    input. The double pipe will behave as the "main" pipe, but will ensure the
    content of the "side" pipe is properly processed while we wait for blocking
    call on the "main" pipe.

    If large amounts of data are read from "main", the forward will cease after
    the first bytes start to appear. This simplifies the implementation
    without affecting actual output of sshpeer too much as we rarely issue
    large read for data not yet emitted by the server.

    The main pipe is expected to be a 'bufferedinputpipe' from the util module
    that handle all the os specific bits. This class lives in this module
    because it focus on behavior specific to the ssh protocol."""

    def __init__(self, ui, main, side):
        self._ui = ui
        self._main = main
        self._side = side

    def _wait(self):
        """wait until some data are available on main or side

        return a pair of boolean (ismainready, issideready)

        (This will only wait for data if the setup is supported by `util.poll`)
        """
        if getattr(self._main, 'hasbuffer', False): # getattr for classic pipe
            return (True, True) # main has data, assume side is worth poking at.
        fds = [self._main.fileno(), self._side.fileno()]
        try:
            act = util.poll(fds)
        except NotImplementedError:
            # non supported yet case, assume all have data.
            act = fds
        return (self._main.fileno() in act, self._side.fileno() in act)

    def write(self, data):
        return self._call('write', data)

    def read(self, size):
        r = self._call('read', size)
        if size != 0 and not r:
            # We've observed a condition that indicates the
            # stdout closed unexpectedly. Check stderr one
            # more time and snag anything that's there before
            # letting anyone know the main part of the pipe
            # closed prematurely.
            _forwardoutput(self._ui, self._side)
        return r

    def readline(self):
        return self._call('readline')

    def _call(self, methname, data=None):
        """call <methname> on "main", forward output of "side" while blocking
        """
        # data can be '' or 0
        if (data is not None and not data) or self._main.closed:
            _forwardoutput(self._ui, self._side)
            return ''
        while True:
            mainready, sideready = self._wait()
            if sideready:
                _forwardoutput(self._ui, self._side)
            if mainready:
                meth = getattr(self._main, methname)
                if data is None:
                    return meth()
                else:
                    return meth(data)

    def close(self):
        return self._main.close()

    def flush(self):
        return self._main.flush()

class sshpeer(wireproto.wirepeer):
    def __init__(self, ui, path, create=False):
        self._url = path
        self._ui = ui
        self._pipeo = self._pipei = self._pipee = None

        u = util.url(path, parsequery=False, parsefragment=False)
        if u.scheme != 'ssh' or not u.host or u.path is None:
            self._abort(error.RepoError(_("couldn't parse location %s") % path))

        util.checksafessh(path)

        if u.passwd is not None:
            self._abort(error.RepoError(_("password in URL not supported")))

        self._user = u.user
        self._host = u.host
        self._port = u.port
        self._path = u.path or '.'

        sshcmd = self.ui.config("ui", "ssh")
        remotecmd = self.ui.config("ui", "remotecmd")
        sshaddenv = dict(self.ui.configitems("sshenv"))
        sshenv = util.shellenviron(sshaddenv)

        args = util.sshargs(sshcmd, self._host, self._user, self._port)

        if create:
            cmd = '%s %s %s' % (sshcmd, args,
                util.shellquote("%s init %s" %
                    (_serverquote(remotecmd), _serverquote(self._path))))
            ui.debug('running %s\n' % cmd)
            res = ui.system(cmd, blockedtag='sshpeer', environ=sshenv)
            if res != 0:
                self._abort(error.RepoError(_("could not create remote repo")))

        self._validaterepo(sshcmd, args, remotecmd, sshenv)

    # Begin of _basepeer interface.

    @util.propertycache
    def ui(self):
        return self._ui

    def url(self):
        return self._url

    def local(self):
        return None

    def peer(self):
        return self

    def canpush(self):
        return True

    def close(self):
        pass

    # End of _basepeer interface.

    # Begin of _basewirecommands interface.

    def capabilities(self):
        return self._caps

    # End of _basewirecommands interface.

    def _validaterepo(self, sshcmd, args, remotecmd, sshenv=None):
        # cleanup up previous run
        self._cleanup()

        cmd = '%s %s %s' % (sshcmd, args,
            util.shellquote("%s -R %s serve --stdio" %
                (_serverquote(remotecmd), _serverquote(self._path))))
        self.ui.debug('running %s\n' % cmd)
        cmd = util.quotecommand(cmd)

        # while self._subprocess isn't used, having it allows the subprocess to
        # to clean up correctly later
        #
        # no buffer allow the use of 'select'
        # feel free to remove buffering and select usage when we ultimately
        # move to threading.
        sub = util.popen4(cmd, bufsize=0, env=sshenv)
        self._pipeo, self._pipei, self._pipee, self._subprocess = sub

        self._pipei = util.bufferedinputpipe(self._pipei)
        self._pipei = doublepipe(self.ui, self._pipei, self._pipee)
        self._pipeo = doublepipe(self.ui, self._pipeo, self._pipee)

        def badresponse():
            msg = _("no suitable response from remote hg")
            hint = self.ui.config("ui", "ssherrorhint")
            self._abort(error.RepoError(msg, hint=hint))

        try:
            # skip any noise generated by remote shell
            self._callstream("hello")
            r = self._callstream("between", pairs=("%s-%s" % ("0"*40, "0"*40)))
        except IOError:
            badresponse()

        lines = ["", "dummy"]
        max_noise = 500
        while lines[-1] and max_noise:
            try:
                l = r.readline()
                self._readerr()
                if lines[-1] == "1\n" and l == "\n":
                    break
                if l:
                    self.ui.debug("remote: ", l)
                lines.append(l)
                max_noise -= 1
            except IOError:
                badresponse()
        else:
            badresponse()

        self._caps = set()
        for l in reversed(lines):
            if l.startswith("capabilities:"):
                self._caps.update(l[:-1].split(":")[1].split())
                break

    def _readerr(self):
        _forwardoutput(self.ui, self._pipee)

    def _abort(self, exception):
        self._cleanup()
        raise exception

    def _cleanup(self):
        if self._pipeo is None:
            return
        self._pipeo.close()
        self._pipei.close()
        try:
            # read the error descriptor until EOF
            for l in self._pipee:
                self.ui.status(_("remote: "), l)
        except (IOError, ValueError):
            pass
        self._pipee.close()

    __del__ = _cleanup

    def _submitbatch(self, req):
        rsp = self._callstream("batch", cmds=wireproto.encodebatchcmds(req))
        available = self._getamount()
        # TODO this response parsing is probably suboptimal for large
        # batches with large responses.
        toread = min(available, 1024)
        work = rsp.read(toread)
        available -= toread
        chunk = work
        while chunk:
            while ';' in work:
                one, work = work.split(';', 1)
                yield wireproto.unescapearg(one)
            toread = min(available, 1024)
            chunk = rsp.read(toread)
            available -= toread
            work += chunk
        yield wireproto.unescapearg(work)

    def _callstream(self, cmd, **args):
        args = pycompat.byteskwargs(args)
        self.ui.debug("sending %s command\n" % cmd)
        self._pipeo.write("%s\n" % cmd)
        _func, names = wireproto.commands[cmd]
        keys = names.split()
        wireargs = {}
        for k in keys:
            if k == '*':
                wireargs['*'] = args
                break
            else:
                wireargs[k] = args[k]
                del args[k]
        for k, v in sorted(wireargs.iteritems()):
            self._pipeo.write("%s %d\n" % (k, len(v)))
            if isinstance(v, dict):
                for dk, dv in v.iteritems():
                    self._pipeo.write("%s %d\n" % (dk, len(dv)))
                    self._pipeo.write(dv)
            else:
                self._pipeo.write(v)
        self._pipeo.flush()

        return self._pipei

    def _callcompressable(self, cmd, **args):
        return self._callstream(cmd, **args)

    def _call(self, cmd, **args):
        self._callstream(cmd, **args)
        return self._recv()

    def _callpush(self, cmd, fp, **args):
        r = self._call(cmd, **args)
        if r:
            return '', r
        for d in iter(lambda: fp.read(4096), ''):
            self._send(d)
        self._send("", flush=True)
        r = self._recv()
        if r:
            return '', r
        return self._recv(), ''

    def _calltwowaystream(self, cmd, fp, **args):
        r = self._call(cmd, **args)
        if r:
            # XXX needs to be made better
            raise error.Abort(_('unexpected remote reply: %s') % r)
        for d in iter(lambda: fp.read(4096), ''):
            self._send(d)
        self._send("", flush=True)
        return self._pipei

    def _getamount(self):
        l = self._pipei.readline()
        if l == '\n':
            self._readerr()
            msg = _('check previous remote output')
            self._abort(error.OutOfBandError(hint=msg))
        self._readerr()
        try:
            return int(l)
        except ValueError:
            self._abort(error.ResponseError(_("unexpected response:"), l))

    def _recv(self):
        return self._pipei.read(self._getamount())

    def _send(self, data, flush=False):
        self._pipeo.write("%d\n" % len(data))
        if data:
            self._pipeo.write(data)
        if flush:
            self._pipeo.flush()
        self._readerr()

instance = sshpeer