serve.py

# Most of this code is:

# (c) 2005 Ian Bicking and contributors; written for Paste (http://pythonpaste.org)
# Licensed under the MIT license: http://www.opensource.org/licenses/mit-license.php

# The server command includes the additional header:

# For discussion of daemonizing:
#   http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/278731
# Code taken also from QP:
#   http://www.mems-exchange.org/software/qp/
#   From lib/site.py

# Galaxy originally used PasteScript and PasteDeploy for application
# loading, to maintain compatibility we've internalized some of that
# code here, stripping out uneeded functionality.

# All top level imports from each package moved here and organized
import ConfigParser
import atexit
import errno
import getpass
import logging
import optparse
import os
import re
import subprocess
import sys
import textwrap
import threading
import time
from logging.config import fileConfig

from loadwsgi import loadapp, loadserver


difflib = None

# ---- from paste.script.bool_optparse --------------------------------

"""
A subclass of ``optparse.OptionParser`` that allows boolean long
options (like ``--verbose``) to also take arguments (like
``--verbose=true``).  Arguments *must* use ``=``.
"""

try:
    _ = optparse._
except AttributeError:
    from gettext import gettext as _

class BoolOptionParser(optparse.OptionParser):

    def _process_long_opt(self, rargs, values):
        arg = rargs.pop(0)

        # Value explicitly attached to arg?  Pretend it's the next
        # argument.
        if "=" in arg:
            (opt, next_arg) = arg.split("=", 1)
            rargs.insert(0, next_arg)
            had_explicit_value = True
        else:
            opt = arg
            had_explicit_value = False

        opt = self._match_long_opt(opt)
        option = self._long_opt[opt]
        if option.takes_value():
            nargs = option.nargs
            if len(rargs) < nargs:
                if nargs == 1:
                    self.error(_("%s option requires an argument") % opt)
                else:
                    self.error(_("%s option requires %d arguments")
                               % (opt, nargs))
            elif nargs == 1:
                value = rargs.pop(0)
            else:
                value = tuple(rargs[0:nargs])
                del rargs[0:nargs]

        elif had_explicit_value:
            value = rargs[0].lower().strip()
            del rargs[0:1]
            if value in ('true', 'yes', 'on', '1', 'y', 't'):
                value = None
            elif value in ('false', 'no', 'off', '0', 'n', 'f'):
                # Don't process
                return
            else:
                self.error(_('%s option takes a boolean value only (true/false)') % opt)

        else:
            value = None

        option.process(opt, value, values, self)

# ---- from paste.script.command --------------------------------------

# (c) 2005 Ian Bicking and contributors; written for Paste (http://pythonpaste.org)
# Licensed under the MIT license: http://www.opensource.org/licenses/mit-license.php

class BadCommand(Exception):

    def __init__(self, message, exit_code=2):
        self.message = message
        self.exit_code = exit_code
        Exception.__init__(self, message)

    def _get_message(self):
        """Getter for 'message'; needed only to override deprecation
        in BaseException."""
        return self.__message

    def _set_message(self, value):
        """Setter for 'message'; needed only to override deprecation
        in BaseException."""
        self.__message = value

    # BaseException.message has been deprecated since Python 2.6.
    # To prevent DeprecationWarning from popping up over this
    # pre-existing attribute, use a new property that takes lookup
    # precedence.
    message = property(_get_message, _set_message)

class NoDefault(object):
    pass

# run and invoke methods moved below ServeCommand

class Command(object):

    def __init__(self, name):
        self.command_name = name

    max_args = None
    max_args_error = 'You must provide no more than %(max_args)s arguments'
    min_args = None
    min_args_error = 'You must provide at least %(min_args)s arguments'
    required_args = None
    # If this command takes a configuration file, set this to 1 or -1
    # Then if invoked through #! the config file will be put into the positional
    # arguments -- at the beginning with 1, at the end with -1
    takes_config_file = None

    # Grouped in help messages by this:
    group_name = ''

    required_args = ()
    description = None
    usage = ''
    hidden = False
    # This is the default verbosity level; --quiet subtracts,
    # --verbose adds:
    default_verbosity = 0
    # This is the default interactive state:
    default_interactive = 0
    return_code = 0

    BadCommand = BadCommand

    # Must define:
    #   parser
    #   summary
    #   command()

    def run(self, args):
        self.parse_args(args)

        # Setup defaults:
        for name, default in [('verbose', 0),
                              ('quiet', 0),
                              ('interactive', False),
                              ('overwrite', False)]:
            if not hasattr(self.options, name):
                setattr(self.options, name, default)
        if getattr(self.options, 'simulate', False):
            self.options.verbose = max(self.options.verbose, 1)
        self.interactive = self.default_interactive
        if getattr(self.options, 'interactive', False):
            self.interactive += self.options.interactive
        if getattr(self.options, 'no_interactive', False):
            self.interactive = False
        self.verbose = self.default_verbosity
        self.verbose += self.options.verbose
        self.verbose -= self.options.quiet
        self.simulate = getattr(self.options, 'simulate', False)

        # For #! situations:
        if (os.environ.get('PASTE_CONFIG_FILE')
            and self.takes_config_file is not None):
            take = self.takes_config_file
            filename = os.environ.get('PASTE_CONFIG_FILE')
            if take == 1:
                self.args.insert(0, filename)
            elif take == -1:
                self.args.append(filename)
            else:
                assert 0, (
                    "Value takes_config_file must be None, 1, or -1 (not %r)"
                    % take)

        if (os.environ.get('PASTE_DEFAULT_QUIET')):
            self.verbose = 0

        # Validate:
        if self.min_args is not None and len(self.args) < self.min_args:
            raise BadCommand(
                self.min_args_error % {'min_args': self.min_args,
                                       'actual_args': len(self.args)})
        if self.max_args is not None and len(self.args) > self.max_args:
            raise BadCommand(
                self.max_args_error % {'max_args': self.max_args,
                                       'actual_args': len(self.args)})
        for var_name, option_name in self.required_args:
            if not getattr(self.options, var_name, None):
                raise BadCommand(
                    'You must provide the option %s' % option_name)
        result = self.command()
        if result is None:
            return self.return_code
        else:
            return result

    def parse_args(self, args):
        if self.usage:
            usage = ' '+self.usage
        else:
            usage = ''
        self.parser.usage = "%%prog [options]%s\n%s" % (
            usage, self.summary)
        self.parser.prog = self._prog_name()
        if self.description:
            desc = self.description
            desc = textwrap.dedent(desc)
            self.parser.description = desc
        self.options, self.args = self.parser.parse_args(args)

    def _prog_name(self):
        return '%s %s' % (os.path.basename(sys.argv[0]), self.command_name)

    ########################################
    ## Utility methods
    ########################################

    def pad(self, s, length, dir='left'):
        if len(s) >= length:
            return s
        if dir == 'left':
            return s + ' '*(length-len(s))
        else:
            return ' '*(length-len(s)) + s

    def standard_parser(cls, verbose=True,
                        interactive=False,
                        no_interactive=False,
                        simulate=False,
                        quiet=False,
                        overwrite=False):
        """
        Create a standard ``OptionParser`` instance.

        Typically used like::

            class MyCommand(Command):
                parser = Command.standard_parser()

        Subclasses may redefine ``standard_parser``, so use the
        nearest superclass's class method.
        """
        parser = BoolOptionParser()
        if verbose:
            parser.add_option('-v', '--verbose',
                              action='count',
                              dest='verbose',
                              default=0)
        if quiet:
            parser.add_option('-q', '--quiet',
                              action='count',
                              dest='quiet',
                              default=0)
        if no_interactive:
            parser.add_option('--no-interactive',
                              action="count",
                              dest="no_interactive",
                              default=0)
        if interactive:
            parser.add_option('-i', '--interactive',
                              action='count',
                              dest='interactive',
                              default=0)
        if simulate:
            parser.add_option('-n', '--simulate',
                              action='store_true',
                              dest='simulate',
                              default=False)
        if overwrite:
            parser.add_option('-f', '--overwrite',
                              dest="overwrite",
                              action="store_true",
                              help="Overwrite files (warnings will be emitted for non-matching files otherwise)")
        return parser

    standard_parser = classmethod(standard_parser)

    def quote_first_command_arg(self, arg):
        """
        There's a bug in Windows when running an executable that's
        located inside a path with a space in it.  This method handles
        that case, or on non-Windows systems or an executable with no
        spaces, it just leaves well enough alone.
        """
        if (sys.platform != 'win32'
            or ' ' not in arg):
            # Problem does not apply:
            return arg
        try:
            import win32api
        except ImportError:
            raise ValueError(
                "The executable %r contains a space, and in order to "
                "handle this issue you must have the win32api module "
                "installed" % arg)
        arg = win32api.GetShortPathName(arg)
        return arg

    def parse_vars(self, args):
        """
        Given variables like ``['a=b', 'c=d']`` turns it into ``{'a':
        'b', 'c': 'd'}``
        """
        result = {}
        for arg in args:
            if '=' not in arg:
                raise BadCommand(
                    'Variable assignment %r invalid (no "=")'
                    % arg)
            name, value = arg.split('=', 1)
            result[name] = value
        return result


    def logging_file_config(self, config_file):
        """
        Setup logging via the logging module's fileConfig function with the
        specified ``config_file``, if applicable.

        ConfigParser defaults are specified for the special ``__file__``
        and ``here`` variables, similar to PasteDeploy config loading.
        """
        parser = ConfigParser.ConfigParser()
        parser.read([config_file])
        if parser.has_section('loggers'):
            config_file = os.path.abspath(config_file)
            fileConfig(config_file, dict(__file__=config_file,
                                         here=os.path.dirname(config_file)))

class NotFoundCommand(Command):

    def run(self, args):
        #for name, value in os.environ.items():
        #    print '%s: %s' % (name, value)
        #print sys.argv
        print ('Command %r not known (you may need to run setup.py egg_info)'
               % self.command_name)
        commands = get_commands().items()
        commands.sort()
        if not commands:
            print 'No commands registered.'
            print 'Have you installed Paste Script?'
            print '(try running python setup.py develop)'
            return 2
        print 'Known commands:'
        longest = max([len(n) for n, c in commands])
        for name, command in commands:
            print '  %s  %s' % (self.pad(name, length=longest),
                                command.load().summary)
        return 2


# ---- From paste.script.serve ----------------------------------------

MAXFD = 1024

jython = sys.platform.startswith('java')

class DaemonizeException(Exception):
    pass


class ServeCommand(Command):

    min_args = 0
    usage = 'CONFIG_FILE [start|stop|restart|status] [var=value]'
    takes_config_file = 1
    summary = "Serve the described application"
    description = """\
    This command serves a web application that uses a paste.deploy
    configuration file for the server and application.

    If start/stop/restart is given, then --daemon is implied, and it will
    start (normal operation), stop (--stop-daemon), or do both.

    You can also include variable assignments like 'http_port=8080'
    and then use %(http_port)s in your config files.
    """

    # used by subclasses that configure apps and servers differently
    requires_config_file = True

    parser = Command.standard_parser(quiet=True)
    parser.add_option('-n', '--app-name',
                      dest='app_name',
                      metavar='NAME',
                      help="Load the named application (default main)")
    parser.add_option('-s', '--server',
                      dest='server',
                      metavar='SERVER_TYPE',
                      help="Use the named server.")
    parser.add_option('--server-name',
                      dest='server_name',
                      metavar='SECTION_NAME',
                      help="Use the named server as defined in the configuration file (default: main)")
    if hasattr(os, 'fork'):
        parser.add_option('--daemon',
                          dest="daemon",
                          action="store_true",
                          help="Run in daemon (background) mode")
    parser.add_option('--pid-file',
                      dest='pid_file',
                      metavar='FILENAME',
                      help="Save PID to file (default to paster.pid if running in daemon mode)")
    parser.add_option('--log-file',
                      dest='log_file',
                      metavar='LOG_FILE',
                      help="Save output to the given log file (redirects stdout)")
    parser.add_option('--reload',
                      dest='reload',
                      action='store_true',
                      help="Use auto-restart file monitor")
    parser.add_option('--reload-interval',
                      dest='reload_interval',
                      default=1,
                      help="Seconds between checking files (low number can cause significant CPU usage)")
    parser.add_option('--monitor-restart',
                      dest='monitor_restart',
                      action='store_true',
                      help="Auto-restart server if it dies")
    parser.add_option('--status',
                      action='store_true',
                      dest='show_status',
                      help="Show the status of the (presumably daemonized) server")


    if hasattr(os, 'setuid'):
        # I don't think these are available on Windows
        parser.add_option('--user',
                          dest='set_user',
                          metavar="USERNAME",
                          help="Set the user (usually only possible when run as root)")
        parser.add_option('--group',
                          dest='set_group',
                          metavar="GROUP",
                          help="Set the group (usually only possible when run as root)")

    parser.add_option('--stop-daemon',
                      dest='stop_daemon',
                      action='store_true',
                      help='Stop a daemonized server (given a PID file, or default paster.pid file)')

    if jython:
        parser.add_option('--disable-jython-reloader',
                          action='store_true',
                          dest='disable_jython_reloader',
                          help="Disable the Jython reloader")


    _scheme_re = re.compile(r'^[a-z][a-z]+:', re.I)

    default_verbosity = 1

    _reloader_environ_key = 'PYTHON_RELOADER_SHOULD_RUN'
    _monitor_environ_key = 'PASTE_MONITOR_SHOULD_RUN'

    possible_subcommands = ('start', 'stop', 'restart', 'status')

    def command(self):
        if self.options.stop_daemon:
            return self.stop_daemon()

        if not hasattr(self.options, 'set_user'):
            # Windows case:
            self.options.set_user = self.options.set_group = None
        # @@: Is this the right stage to set the user at?
        self.change_user_group(
            self.options.set_user, self.options.set_group)

        if self.requires_config_file:
            if not self.args:
                raise BadCommand('You must give a config file')
            app_spec = self.args[0]
            if (len(self.args) > 1
                and self.args[1] in self.possible_subcommands):
                cmd = self.args[1]
                restvars = self.args[2:]
            else:
                cmd = None
                restvars = self.args[1:]
        else:
            app_spec = ""
            if (self.args
                and self.args[0] in self.possible_subcommands):
                cmd = self.args[0]
                restvars = self.args[1:]
            else:
                cmd = None
                restvars = self.args[:]

        if (getattr(self.options, 'daemon', False)
            and getattr(self.options, 'reload', False)):
            raise BadCommand('The --daemon and --reload options may not be used together')

        jython_monitor = False
        if self.options.reload:
            if jython and not self.options.disable_jython_reloader:
                # JythonMonitor raises the special SystemRestart
                # exception that'll cause the Jython interpreter to
                # reload in the existing Java process (avoiding
                # subprocess startup time)
                try:
                    from paste.reloader import JythonMonitor
                except ImportError:
                    pass
                else:
                    jython_monitor = JythonMonitor(poll_interval=int(
                            self.options.reload_interval))
                    if self.requires_config_file:
                        jython_monitor.watch_file(self.args[0])

            if not jython_monitor:
                if os.environ.get(self._reloader_environ_key):
                    from paste import reloader
                    if self.verbose > 1:
                        print 'Running reloading file monitor'
                    reloader.install(int(self.options.reload_interval))
                    if self.requires_config_file:
                        reloader.watch_file(self.args[0])
                else:
                    return self.restart_with_reloader()

        if cmd not in (None, 'start', 'stop', 'restart', 'status'):
            raise BadCommand(
                'Error: must give start|stop|restart (not %s)' % cmd)

        if cmd == 'status' or self.options.show_status:
            return self.show_status()

        if cmd == 'restart' or cmd == 'stop':
            result = self.stop_daemon()
            if result:
                print "Could not stop daemon"
                # It's ok to continue trying to restart if stop_daemon returns
                # a 1, otherwise shortcut and return.
                if cmd == 'restart' and result != 1:
                    return result
            if cmd == 'stop':
                return result
            self.options.daemon = True

        if cmd == 'start':
            self.options.daemon = True

        app_name = self.options.app_name
        vars = self.parse_vars(restvars)
        if not self._scheme_re.search(app_spec):
            app_spec = 'config:' + app_spec
        server_name = self.options.server_name
        if self.options.server:
            server_spec = 'egg:PasteScript'
            assert server_name is None
            server_name = self.options.server
        else:
            server_spec = app_spec
        base = os.getcwd()

        if getattr(self.options, 'daemon', False):
            if not self.options.pid_file:
                self.options.pid_file = 'paster.pid'
            if not self.options.log_file:
                self.options.log_file = 'paster.log'

        # Ensure the log file is writeable
        if self.options.log_file:
            try:
                writeable_log_file = open(self.options.log_file, 'a')
            except IOError, ioe:
                msg = 'Error: Unable to write to log file: %s' % ioe
                raise BadCommand(msg)
            writeable_log_file.close()

        # Ensure the pid file is writeable
        if self.options.pid_file:
            try:
                writeable_pid_file = open(self.options.pid_file, 'a')
            except IOError, ioe:
                msg = 'Error: Unable to write to pid file: %s' % ioe
                raise BadCommand(msg)
            writeable_pid_file.close()

        if getattr(self.options, 'daemon', False):
            try:
                self.daemonize()
            except DaemonizeException, ex:
                if self.verbose > 0:
                    print str(ex)
                return

        if (self.options.monitor_restart
            and not os.environ.get(self._monitor_environ_key)):
            return self.restart_with_monitor()

        if self.options.pid_file:
            self.record_pid(self.options.pid_file)

        if self.options.log_file:
            stdout_log = LazyWriter(self.options.log_file, 'a')
            sys.stdout = stdout_log
            sys.stderr = stdout_log
            logging.basicConfig(stream=stdout_log)

        log_fn = app_spec
        if log_fn.startswith('config:'):
            log_fn = app_spec[len('config:'):]
        elif log_fn.startswith('egg:'):
            log_fn = None
        if log_fn:
            log_fn = os.path.join(base, log_fn)
            self.logging_file_config(log_fn)

        server = loadserver(server_spec, name=server_name, relative_to=base, global_conf=vars)

        app = loadapp( app_spec, name=app_name, relative_to=base, global_conf=vars)

        if self.verbose > 0:
            if hasattr(os, 'getpid'):
                msg = 'Starting server in PID %i.' % os.getpid()
            else:
                msg = 'Starting server.'
            print msg

        def serve():
            try:
                server(app)
            except (SystemExit, KeyboardInterrupt), e:
                if self.verbose > 1:
                    raise
                if str(e):
                    msg = ' '+str(e)
                else:
                    msg = ''
                print 'Exiting%s (-v to see traceback)' % msg

        if jython_monitor:
            # JythonMonitor has to be ran from the main thread
            threading.Thread(target=serve).start()
            print 'Starting Jython file monitor'
            jython_monitor.periodic_reload()
        else:
            serve()

    def daemonize(self):
        pid = live_pidfile(self.options.pid_file)
        if pid:
            raise DaemonizeException(
                "Daemon is already running (PID: %s from PID file %s)"
                % (pid, self.options.pid_file))

        if self.verbose > 0:
            print 'Entering daemon mode'
        pid = os.fork()
        if pid:
            # The forked process also has a handle on resources, so we
            # *don't* want proper termination of the process, we just
            # want to exit quick (which os._exit() does)
            os._exit(0)
        # Make this the session leader
        os.setsid()
        # Fork again for good measure!
        pid = os.fork()
        if pid:
            os._exit(0)

        # @@: Should we set the umask and cwd now?

        import resource  # Resource usage information.
        maxfd = resource.getrlimit(resource.RLIMIT_NOFILE)[1]
        if (maxfd == resource.RLIM_INFINITY):
            maxfd = MAXFD
        # Iterate through and close all file descriptors.
        for fd in range(0, maxfd):
            try:
                os.close(fd)
            except OSError:  # ERROR, fd wasn't open to begin with (ignored)
                pass

        if (hasattr(os, "devnull")):
            REDIRECT_TO = os.devnull
        else:
            REDIRECT_TO = "/dev/null"
        os.open(REDIRECT_TO, os.O_RDWR)  # standard input (0)
        # Duplicate standard input to standard output and standard error.
        os.dup2(0, 1)  # standard output (1)
        os.dup2(0, 2)  # standard error (2)

    def record_pid(self, pid_file):
        pid = os.getpid()
        if self.verbose > 1:
            print 'Writing PID %s to %s' % (pid, pid_file)
        f = open(pid_file, 'w')
        f.write(str(pid))
        f.close()
        atexit.register(_remove_pid_file, pid, pid_file, self.verbose)

    def stop_daemon(self):
        pid_file = self.options.pid_file or 'paster.pid'
        if not os.path.exists(pid_file):
            print 'No PID file exists in %s' % pid_file
            return 1
        pid = read_pidfile(pid_file)
        if not pid:
            print "Not a valid PID file in %s" % pid_file
            return 1
        pid = live_pidfile(pid_file)
        if not pid:
            print "PID in %s is not valid (deleting)" % pid_file
            try:
                os.unlink(pid_file)
            except (OSError, IOError), e:
                print "Could not delete: %s" % e
                return 2
            return 1
        for j in range(10):
            if not live_pidfile(pid_file):
                break
            import signal
            os.kill(pid, signal.SIGTERM)
            time.sleep(1)
        else:
            print "failed to kill web process %s" % pid
            return 3
        if os.path.exists(pid_file):
            os.unlink(pid_file)
        return 0

    def show_status(self):
        pid_file = self.options.pid_file or 'paster.pid'
        if not os.path.exists(pid_file):
            print 'No PID file %s' % pid_file
            return 1
        pid = read_pidfile(pid_file)
        if not pid:
            print 'No PID in file %s' % pid_file
            return 1
        pid = live_pidfile(pid_file)
        if not pid:
            print 'PID %s in %s is not running' % (pid, pid_file)
            return 1
        print 'Server running in PID %s' % pid
        return 0

    def restart_with_reloader(self):
        self.restart_with_monitor(reloader=True)

    def restart_with_monitor(self, reloader=False):
        if self.verbose > 0:
            if reloader:
                print 'Starting subprocess with file monitor'
            else:
                print 'Starting subprocess with monitor parent'
        while 1:
            args = [self.quote_first_command_arg(sys.executable)] + sys.argv
            new_environ = os.environ.copy()
            if reloader:
                new_environ[self._reloader_environ_key] = 'true'
            else:
                new_environ[self._monitor_environ_key] = 'true'
            proc = None
            try:
                try:
                    _turn_sigterm_into_systemexit()
                    proc = subprocess.Popen(args, env=new_environ)
                    exit_code = proc.wait()
                    proc = None
                except KeyboardInterrupt:
                    print '^C caught in monitor process'
                    if self.verbose > 1:
                        raise
                    return 1
            finally:
                if (proc is not None
                    and hasattr(os, 'kill')):
                    import signal
                    try:
                        os.kill(proc.pid, signal.SIGTERM)
                    except (OSError, IOError):
                        pass

            if reloader:
                # Reloader always exits with code 3; but if we are
                # a monitor, any exit code will restart
                if exit_code != 3:
                    return exit_code
            if self.verbose > 0:
                print '-'*20, 'Restarting', '-'*20

    def change_user_group(self, user, group):
        if not user and not group:
            return
        import pwd, grp
        uid = gid = None
        if group:
            try:
                gid = int(group)
                group = grp.getgrgid(gid).gr_name
            except ValueError:
                import grp
                try:
                    entry = grp.getgrnam(group)
                except KeyError:
                    raise BadCommand(
                        "Bad group: %r; no such group exists" % group)
                gid = entry.gr_gid
        try:
            uid = int(user)
            user = pwd.getpwuid(uid).pw_name
        except ValueError:
            try:
                entry = pwd.getpwnam(user)
            except KeyError:
                raise BadCommand(
                    "Bad username: %r; no such user exists" % user)
            if not gid:
                gid = entry.pw_gid
            uid = entry.pw_uid
        if self.verbose > 0:
            print 'Changing user to %s:%s (%s:%s)' % (
                user, group or '(unknown)', uid, gid)
        if hasattr(os, 'initgroups'):
            os.initgroups(user, gid)
        else:
            os.setgroups([e.gr_gid for e in grp.getgrall()
                          if user in e.gr_mem] + [gid])
        if gid:
            os.setgid(gid)
        if uid:
            os.setuid(uid)

class LazyWriter(object):

    """
    File-like object that opens a file lazily when it is first written
    to.
    """

    def __init__(self, filename, mode='w'):
        self.filename = filename
        self.fileobj = None
        self.lock = threading.Lock()
        self.mode = mode

    def open(self):
        if self.fileobj is None:
            self.lock.acquire()
            try:
                if self.fileobj is None:
                    self.fileobj = open(self.filename, self.mode)
            finally:
                self.lock.release()
        return self.fileobj

    def write(self, text):
        fileobj = self.open()
        fileobj.write(text)
        fileobj.flush()

    def writelines(self, text):
        fileobj = self.open()
        fileobj.writelines(text)
        fileobj.flush()

    def flush(self):
        self.open().flush()

def live_pidfile(pidfile):
    """(pidfile:str) -> int | None
    Returns an int found in the named file, if there is one,
    and if there is a running process with that process id.
    Return None if no such process exists.
    """
    pid = read_pidfile(pidfile)
    if pid:
        try:
            os.kill(int(pid), 0)
            return pid
        except OSError, e:
            if e.errno == errno.EPERM:
                return pid
    return None

def read_pidfile(filename):
    if os.path.exists(filename):
        try:
            f = open(filename)
            content = f.read()
            f.close()
            return int(content.strip())
        except (ValueError, IOError):
            return None
    else:
        return None

def _remove_pid_file(written_pid, filename, verbosity):
    current_pid = os.getpid()
    if written_pid != current_pid:
        # A forked process must be exiting, not the process that
        # wrote the PID file
        return
    if not os.path.exists(filename):
        return
    f = open(filename)
    content = f.read().strip()
    f.close()
    try:
        pid_in_file = int(content)
    except ValueError:
        pass
    else:
        if pid_in_file != current_pid:
            print "PID file %s contains %s, not expected PID %s" % (
                filename, pid_in_file, current_pid)
            return
    if verbosity > 0:
        print "Removing PID file %s" % filename
    try:
        os.unlink(filename)
        return
    except OSError, e:
        # Record, but don't give traceback
        print "Cannot remove PID file: %s" % e
    # well, at least lets not leave the invalid PID around...
    try:
        f = open(filename, 'w')
        f.write('')
        f.close()
    except OSError, e:
        print 'Stale PID left in file: %s (%e)' % (filename, e)
    else:
        print 'Stale PID removed'


def ensure_port_cleanup(bound_addresses, maxtries=30, sleeptime=2):
    """
    This makes sure any open ports are closed.

    Does this by connecting to them until they give connection
    refused.  Servers should call like::

        import paste.script
        ensure_port_cleanup([80, 443])
    """
    atexit.register(_cleanup_ports, bound_addresses, maxtries=maxtries,
                    sleeptime=sleeptime)

def _cleanup_ports(bound_addresses, maxtries=30, sleeptime=2):
    # Wait for the server to bind to the port.
    import socket
    import errno
    for bound_address in bound_addresses:
        for attempt in range(maxtries):
            sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
            try:
                sock.connect(bound_address)
            except socket.error, e:
                if e.args[0] != errno.ECONNREFUSED:
                    raise
                break
            else:
                time.sleep(sleeptime)
        else:
            raise SystemExit('Timeout waiting for port.')
        sock.close()

def _turn_sigterm_into_systemexit():
    """
    Attempts to turn a SIGTERM exception into a SystemExit exception.
    """
    try:
        import signal
    except ImportError: