view mercurial/server.py @ 36855:2cdf47e14c30

hgweb: refactor the request draining code

The previous code for draining was only invoked in a few places in
the wire protocol. Behavior wasn't consist. Furthermore, it was
difficult to reason about.

With us converting the input stream to a capped reader, it is now
safe to always drain the input stream when its size is known because
we can never overrun the input and read into the next HTTP request.
The only question is "should we?"

This commit changes the draining code so every request is examined.
Draining now kicks in for a few requests where it wouldn't before.
But I think the code is sufficiently restricted so the behavior is
safe. Possibly the most dangerous part of this code is the issuing
of Connection: close for POST and PUT requests that don't have a
Content-Length. I don't think there are any such uses in our WSGI
application, so this should be safe.

In the near future, I plan to significantly refactor the WSGI
response handling. I anticipate this code evolving a bit. So any
minor regressions around draining or connection closing behavior
might be fixed as a result of that work.

All tests pass with this change. That scares me a bit because it
means we are lacking low-level tests for the HTTP protocol.

Differential Revision: https://phab.mercurial-scm.org/D2769

# 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
import tempfile

from .i18n import _

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

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

    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 = tempfile.mkstemp(prefix='hg-service-')
        os.close(lockfd)
        try:
            if not runargs:
                runargs = util.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 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 = util.rundetached(runargs, condfn)
            if pid < 0:
                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(util.getpid())

    if opts['daemon_postexec']:
        try:
            os.setsid()
        except AttributeError:
            pass
        for inst in opts['daemon_postexec']:
            if inst.startswith('unlink:'):
                lockpath = inst[7:]
                os.unlink(lockpath)
            elif inst.startswith('chdir:'):
                os.chdir(inst[6:])
            elif inst != 'none':
                raise error.Abort(_('invalid value for --daemon-postexec: %s')
                                  % inst)
        util.hidewindow()
        util.stdout.flush()
        util.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, 0)
        os.dup2(logfilefd, 1)
        os.dup2(logfilefd, 2)
        if nullfd not in (0, 1, 2):
            os.close(nullfd)
        if logfile and logfilefd not in (0, 1, 2):
            os.close(logfilefd)

    if runfn:
        return runfn()

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

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

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)