comparison mercurial/server.py @ 37212:f09a2eab11cf

server: add an error feedback mechanism for when the daemon fails to launch

There's a recurring problem on Windows where `hg serve -d` will randomly fail to
spawn a detached process.  The reason for the failure is completely hidden, and
it takes hours to get a single failure on my laptop.  All this does is redirect
stdout/stderr of the child to a file until the lock file is freed, and then the
parent dumps it out if it fails to spawn.

I chose to put the output into the lock file because that is always cleaned up.
There's no way to report errors after that anyway.  On Windows, killdaemons.py
is roughly `kill -9`, so this ensures that junk won't pile up.

This may end up being a case of EADDRINUSE.  At least that's what I saw spit out
a few times (among other odd errors and missing output on Windows).  But I also
managed to get the same thing on Fedora 26 by running test-hgwebdir.t with
--loop -j10 for several hours.  Running `netstat` immediately after killing that
run printed a wall of sockets in the TIME_WAIT state, which were gone a couple
seconds later.  I couldn't match up ports that failed, because --loop doesn't
print out the message about the port that was used.  So maybe the fix is to
rotate the use of HGPORT[12] in the tests.  But, let's collect some more data
first.

37211:77f9e95fe3c4

)

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'

                    break
            def condfn():
                return not os.path.exists(lockpath)
            pid = procutil.rundetached(runargs, condfn)
            if pid < 0:
                raise error.Abort(_('child process failed to start'))
            writepid(pid)
        finally:
            util.tryunlink(lockpath)
        if parentfn:

    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)

        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,

37212:f09a2eab11cf

)

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

    # 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']:
        for inst in opts['daemon_postexec']:
            if inst.startswith('unlink:'):
                lockpath = inst[7:]
                if os.path.exists(lockpath):
                    procutil.stdout.flush()
                    procutil.stderr.flush()

                    fd = os.open(lockpath,
                                 os.O_WRONLY | os.O_APPEND | os.O_BINARY)
                    try:
                        os.dup2(fd, 1)
                        os.dup2(fd, 2)
                    finally:
                        os.close(fd)

    def writepid(pid):
        if opts['pid_file']:
            if appendpid:
                mode = 'ab'

                    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) 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:

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

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

        if nullfd not in (0, 1, 2):
            os.close(nullfd)
        if logfile and logfilefd not in (0, 1, 2):
            os.close(logfilefd)

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

    if runfn:
        return runfn()

_cmdservicemap = {
    'chgunix': chgserver.chgunixservice,