mercurial/server.py

manifest: add some documentation to _lazymanifest python code

It was not particularly easy figuring out the design of this class and keeping
track of how the pieces work.  So might as well write some of it down for the
next person.

# server.py - utility and factory of server
#
# Copyright 2005-2007 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 os

from .i18n import _

from . import (
    chgserver,
    cmdutil,
    commandserver,
    error,
    hgweb,
    pycompat,
    util,
)

from .utils import (
    procutil,
)

def runservice(opts, parentfn=None, initfn=None, runfn=None, logfile=None,
               runargs=None, appendpid=False):
    '''Run a command as a service.'''

    postexecargs = {}

    if opts['daemon_postexec']:
        for inst in opts['daemon_postexec']:
            if inst.startswith('unlink:'):
                postexecargs['unlink'] = inst[7:]
            elif inst.startswith('chdir:'):
                postexecargs['chdir'] = inst[6:]
            elif inst != 'none':
                raise error.Abort(_('invalid value for --daemon-postexec: %s')
                                  % inst)

    # When daemonized on Windows, redirect stdout/stderr to the lockfile (which
    # gets cleaned up after the child is up and running), so that the parent can
    # read and print the error if this child dies early.  See 594dd384803c.  On
    # other platforms, the child can write to the parent's stdio directly, until
    # it is redirected prior to runfn().
    if pycompat.iswindows and opts['daemon_postexec']:
        if 'unlink' in postexecargs and os.path.exists(postexecargs['unlink']):
            procutil.stdout.flush()
            procutil.stderr.flush()

            fd = os.open(postexecargs['unlink'],
                         os.O_WRONLY | os.O_APPEND | os.O_BINARY)
            try:
                os.dup2(fd, procutil.stdout.fileno())
                os.dup2(fd, procutil.stderr.fileno())
            finally:
                os.close(fd)

    def writepid(pid):
        if opts['pid_file']:
            if appendpid:
                mode = 'ab'
            else:
                mode = 'wb'
            fp = open(opts['pid_file'], mode)
            fp.write('%d\n' % pid)
            fp.close()

    if opts['daemon'] and not opts['daemon_postexec']:
        # Signal child process startup with file removal
        lockfd, lockpath = pycompat.mkstemp(prefix='hg-service-')
        os.close(lockfd)
        try:
            if not runargs:
                runargs = procutil.hgcmd() + pycompat.sysargv[1:]
            runargs.append('--daemon-postexec=unlink:%s' % lockpath)
            # Don't pass --cwd to the child process, because we've already
            # changed directory.
            for i in pycompat.xrange(1, len(runargs)):
                if runargs[i].startswith('--cwd='):
                    del runargs[i]
                    break
                elif runargs[i].startswith('--cwd'):
                    del runargs[i:i + 2]
                    break
            def condfn():
                return not os.path.exists(lockpath)
            pid = procutil.rundetached(runargs, condfn)
            if pid < 0:
                # If the daemonized process managed to write out an error msg,
                # report it.
                if pycompat.iswindows and os.path.exists(lockpath):
                    with open(lockpath, 'rb') as log:
                        for line in log:
                            procutil.stderr.write(line)
                raise error.Abort(_('child process failed to start'))
            writepid(pid)
        finally:
            util.tryunlink(lockpath)
        if parentfn:
            return parentfn(pid)
        else:
            return

    if initfn:
        initfn()

    if not opts['daemon']:
        writepid(procutil.getpid())

    if opts['daemon_postexec']:
        try:
            os.setsid()
        except AttributeError:
            pass

        if 'chdir' in postexecargs:
            os.chdir(postexecargs['chdir'])
        procutil.hidewindow()
        procutil.stdout.flush()
        procutil.stderr.flush()

        nullfd = os.open(os.devnull, os.O_RDWR)
        logfilefd = nullfd
        if logfile:
            logfilefd = os.open(logfile, os.O_RDWR | os.O_CREAT | os.O_APPEND,
                                0o666)
        os.dup2(nullfd, procutil.stdin.fileno())
        os.dup2(logfilefd, procutil.stdout.fileno())
        os.dup2(logfilefd, procutil.stderr.fileno())
        stdio = (procutil.stdin.fileno(), procutil.stdout.fileno(),
                 procutil.stderr.fileno())
        if nullfd not in stdio:
            os.close(nullfd)
        if logfile and logfilefd not in stdio:
            os.close(logfilefd)

        # Only unlink after redirecting stdout/stderr, so Windows doesn't
        # complain about a sharing violation.
        if 'unlink' in postexecargs:
            os.unlink(postexecargs['unlink'])

    if runfn:
        return runfn()

_cmdservicemap = {
    'chgunix': chgserver.chgunixservice,
    'pipe': commandserver.pipeservice,
    'unix': commandserver.unixforkingservice,
}

def _createcmdservice(ui, repo, opts):
    mode = opts['cmdserver']
    try:
        servicefn = _cmdservicemap[mode]
    except KeyError:
        raise error.Abort(_('unknown mode %s') % mode)
    commandserver.setuplogging(ui, repo)
    return servicefn(ui, repo, opts)

def _createhgwebservice(ui, repo, opts):
    # this way we can check if something was given in the command-line
    if opts.get('port'):
        opts['port'] = util.getport(opts.get('port'))

    alluis = {ui}
    if repo:
        baseui = repo.baseui
        alluis.update([repo.baseui, repo.ui])
    else:
        baseui = ui
    webconf = opts.get('web_conf') or opts.get('webdir_conf')
    if webconf:
        if opts.get('subrepos'):
            raise error.Abort(_('--web-conf cannot be used with --subrepos'))

        # load server settings (e.g. web.port) to "copied" ui, which allows
        # hgwebdir to reload webconf cleanly
        servui = ui.copy()
        servui.readconfig(webconf, sections=['web'])
        alluis.add(servui)
    elif opts.get('subrepos'):
        servui = ui

        # If repo is None, hgweb.createapp() already raises a proper abort
        # message as long as webconf is None.
        if repo:
            webconf = dict()
            cmdutil.addwebdirpath(repo, "", webconf)
    else:
        servui = ui

    optlist = ("name templates style address port prefix ipv6"
               " accesslog errorlog certificate encoding")
    for o in optlist.split():
        val = opts.get(o, '')
        if val in (None, ''): # should check against default options instead
            continue
        for u in alluis:
            u.setconfig("web", o, val, 'serve')

    app = hgweb.createapp(baseui, repo, webconf)
    return hgweb.httpservice(servui, app, opts)

def createservice(ui, repo, opts):
    if opts["cmdserver"]:
        return _createcmdservice(ui, repo, opts)
    else:
        return _createhgwebservice(ui, repo, opts)