"""Site services for use with a Web Site Process Bus."""
import os
import re
try:
set
except NameError:
from sets import Set
import signal as _signal
import sys
import time
import threading
class SimplePlugin(object):
"""Plugin base class which auto-subscribes methods for known channels."""
def __init__(self, bus):
self.bus = bus
def subscribe(self):
"""Register this object as a (multi-channel) listener on the bus."""
for channel in self.bus.listeners:
# Subscribe self.start, self.exit, etc. if present.
method = getattr(self, channel, None)
if method is not None:
self.bus.subscribe(channel, method)
def unsubscribe(self):
"""Unregister this object as a listener on the bus."""
for channel in self.bus.listeners:
# Unsubscribe self.start, self.exit, etc. if present.
method = getattr(self, channel, None)
if method is not None:
self.bus.unsubscribe(channel, method)
class SignalHandler(object):
"""Register bus channels (and listeners) for system signals.
By default, instantiating this object subscribes the following signals
and listeners:
TERM: bus.exit
HUP : bus.restart
USR1: bus.graceful
"""
# Map from signal numbers to names
signals = {}
for k, v in vars(_signal).items():
if k.startswith('SIG') and not k.startswith('SIG_'):
signals[v] = k
del k, v
def __init__(self, bus):
self.bus = bus
# Set default handlers
self.handlers = {'SIGTERM': self.bus.exit,
'SIGHUP': self.handle_SIGHUP,
'SIGUSR1': self.bus.graceful,
}
self._previous_handlers = {}
def subscribe(self):
for sig, func in self.handlers.iteritems():
try:
self.set_handler(sig, func)
except ValueError:
pass
def unsubscribe(self):
for signum, handler in self._previous_handlers.iteritems():
signame = self.signals[signum]
if handler is None:
self.bus.log("Restoring %s handler to SIG_DFL." % signame)
handler = _signal.SIG_DFL
else:
self.bus.log("Restoring %s handler %r." % (signame, handler))
try:
our_handler = _signal.signal(signum, handler)
if our_handler is None:
self.bus.log("Restored old %s handler %r, but our "
"handler was not registered." %
(signame, handler), level=30)
except ValueError:
self.bus.log("Unable to restore %s handler %r." %
(signame, handler), level=40, traceback=True)
def set_handler(self, signal, listener=None):
"""Subscribe a handler for the given signal (number or name).
If the optional 'listener' argument is provided, it will be
subscribed as a listener for the given signal's channel.
If the given signal name or number is not available on the current
platform, ValueError is raised.
"""
if isinstance(signal, basestring):
signum = getattr(_signal, signal, None)
if signum is None:
raise ValueError("No such signal: %r" % signal)
signame = signal
else:
try:
signame = self.signals[signal]
except KeyError:
raise ValueError("No such signal: %r" % signal)
signum = signal
prev = _signal.signal(signum, self._handle_signal)
self._previous_handlers[signum] = prev
if listener is not None:
self.bus.log("Listening for %s." % signame)
self.bus.subscribe(signame, listener)
def _handle_signal(self, signum=None, frame=None):
"""Python signal handler (self.set_handler subscribes it for you)."""
signame = self.signals[signum]
self.bus.log("Caught signal %s." % signame)
self.bus.publish(signame)
def handle_SIGHUP(self):
if os.isatty(sys.stdin.fileno()):
# not daemonized (may be foreground or background)
self.bus.log("SIGHUP caught but not daemonized. Exiting.")
self.bus.exit()
else:
self.bus.log("SIGHUP caught while daemonized. Restarting.")
self.bus.restart()
try:
import pwd, grp
except ImportError:
pwd, grp = None, None
class DropPrivileges(SimplePlugin):
"""Drop privileges. uid/gid arguments not available on Windows.
Special thanks to Gavin Baker: http://antonym.org/node/100.
"""
def __init__(self, bus, umask=None, uid=None, gid=None):
SimplePlugin.__init__(self, bus)
self.finalized = False
self.uid = uid
self.gid = gid
self.umask = umask
def _get_uid(self):
return self._uid
def _set_uid(self, val):
if val is not None:
if pwd is None:
self.bus.log("pwd module not available; ignoring uid.",
level=30)
val = None
elif isinstance(val, basestring):
val = pwd.getpwnam(val)[2]
self._uid = val
uid = property(_get_uid, _set_uid, doc="The uid under which to run.")
def _get_gid(self):
return self._gid
def _set_gid(self, val):
if val is not None:
if grp is None:
self.bus.log("grp module not available; ignoring gid.",
level=30)
val = None
elif isinstance(val, basestring):
val = grp.getgrnam(val)[2]
self._gid = val
gid = property(_get_gid, _set_gid, doc="The gid under which to run.")
def _get_umask(self):
return self._umask
def _set_umask(self, val):
if val is not None:
try:
os.umask
except AttributeError:
self.bus.log("umask function not available; ignoring umask.",
level=30)
val = None
self._umask = val
umask = property(_get_umask, _set_umask, doc="The umask under which to run.")
def start(self):
# uid/gid
def current_ids():
"""Return the current (uid, gid) if available."""
name, group = None, None
if pwd:
name = pwd.getpwuid(os.getuid())[0]
if grp:
group = grp.getgrgid(os.getgid())[0]
return name, group
if self.finalized:
if not (self.uid is None and self.gid is None):
self.bus.log('Already running as uid: %r gid: %r' %
current_ids())
else:
if self.uid is None and self.gid is None:
if pwd or grp:
self.bus.log('uid/gid not set', level=30)
else:
self.bus.log('Started as uid: %r gid: %r' % current_ids())
if self.gid is not None:
os.setgid(self.gid)
if self.uid is not None:
os.setuid(self.uid)
self.bus.log('Running as uid: %r gid: %r' % current_ids())
# umask
if self.finalized:
if self.umask is not None:
self.bus.log('umask already set to: %03o' % self.umask)
else:
if self.umask is None:
self.bus.log('umask not set', level=30)
else:
old_umask = os.umask(self.umask)
self.bus.log('umask old: %03o, new: %03o' %
(old_umask, self.umask))
self.finalized = True
# This is slightly higher than the priority for server.start
# in order to facilitate the most common use: starting on a low
# port (which requires root) and then dropping to another user.
start.priority = 77
class Daemonizer(SimplePlugin):
"""Daemonize the running script.
Use this with a Web Site Process Bus via:
Daemonizer(bus).subscribe()
When this component finishes, the process is completely decoupled from
the parent environment. Please note that when this component is used,
the return code from the parent process will still be 0 if a startup
error occurs in the forked children. Errors in the initial daemonizing
process still return proper exit codes. Therefore, if you use this
plugin to daemonize, don't use the return code as an accurate indicator
of whether the process fully started. In fact, that return code only
indicates if the process succesfully finished the first fork.
"""
def __init__(self, bus, stdin='/dev/null', stdout='/dev/null',
stderr='/dev/null'):
SimplePlugin.__init__(self, bus)
self.stdin = stdin
self.stdout = stdout
self.stderr = stderr
self.finalized = False
def start(self):
if self.finalized:
self.bus.log('Already deamonized.')
# forking has issues with threads:
# http://www.opengroup.org/onlinepubs/000095399/functions/fork.html
# "The general problem with making fork() work in a multi-threaded
# world is what to do with all of the threads..."
# So we check for active threads:
if threading.activeCount() != 1:
self.bus.log('There are %r active threads. '
'Daemonizing now may cause strange failures.' %
threading.enumerate(), level=30)
# See http://www.erlenstar.demon.co.uk/unix/faq_2.html#SEC16
# (or http://www.faqs.org/faqs/unix-faq/programmer/faq/ section 1.7)
# and http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/66012
# Finish up with the current stdout/stderr
sys.stdout.flush()
sys.stderr.flush()
# Do first fork.
try:
pid = os.fork()
if pid == 0:
# This is the child process. Continue.
pass
else:
# This is the first parent. Exit, now that we've forked.
self.bus.log('Forking once.')
os._exit(0)
except OSError, exc:
# Python raises OSError rather than returning negative numbers.
sys.exit("%s: fork #1 failed: (%d) %s\n"
% (sys.argv[0], exc.errno, exc.strerror))
os.setsid()
# Do second fork
try:
pid = os.fork()
if pid > 0:
self.bus.log('Forking twice.')
os._exit(0) # Exit second parent
except OSError, exc:
sys.exit("%s: fork #2 failed: (%d) %s\n"
% (sys.argv[0], exc.errno, exc.strerror))
os.chdir("/")
os.umask(0)
si = open(self.stdin, "r")
so = open(self.stdout, "a+")
se = open(self.stderr, "a+", 0)
# os.dup2(fd, fd2) will close fd2 if necessary,
# so we don't explicitly close stdin/out/err.
# See http://docs.python.org/lib/os-fd-ops.html
os.dup2(si.fileno(), sys.stdin.fileno())
os.dup2(so.fileno(), sys.stdout.fileno())
os.dup2(se.fileno(), sys.stderr.fileno())
self.bus.log('Daemonized to PID: %s' % os.getpid())
self.finalized = True
start.priority = 65
class PIDFile(SimplePlugin):
"""Maintain a PID file via a WSPBus."""
def __init__(self, bus, pidfile):
SimplePlugin.__init__(self, bus)
self.pidfile = pidfile
self.finalized = False
def start(self):
pid = os.getpid()
if self.finalized:
self.bus.log('PID %r already written to %r.' % (pid, self.pidfile))
else:
open(self.pidfile, "wb").write(str(pid))
self.bus.log('PID %r written to %r.' % (pid, self.pidfile))
self.finalized = True
start.priority = 70
def exit(self):
try:
os.remove(self.pidfile)
self.bus.log('PID file removed: %r.' % self.pidfile)
except (KeyboardInterrupt, SystemExit):
raise
except:
pass
class PerpetualTimer(threading._Timer):
"""A subclass of threading._Timer whose run() method repeats."""
def run(self):
while True:
self.finished.wait(self.interval)
if self.finished.isSet():
return
self.function(*self.args, **self.kwargs)
class Monitor(SimplePlugin):
"""WSPBus listener to periodically run a callback in its own thread.
bus: a Web Site Process Bus object.
callback: the function to call at intervals.
frequency: the time in seconds between callback runs.
"""
frequency = 60
def __init__(self, bus, callback, frequency=60):
SimplePlugin.__init__(self, bus)
self.callback = callback
self.frequency = frequency
self.thread = None
def start(self):
"""Start our callback in its own perpetual timer thread."""
if self.frequency > 0:
threadname = self.__class__.__name__
if self.thread is None:
self.thread = PerpetualTimer(self.frequency, self.callback)
self.thread.setName(threadname)
self.thread.start()
self.bus.log("Started monitor thread %r." % threadname)
else:
self.bus.log("Monitor thread %r already started." % threadname)
start.priority = 70
def stop(self):
"""Stop our callback's perpetual timer thread."""
if self.thread is None:
self.bus.log("No thread running for %s." % self.__class__.__name__)
else:
if self.thread is not threading.currentThread():
name = self.thread.getName()
self.thread.cancel()
self.thread.join()
self.bus.log("Stopped thread %r." % name)
self.thread = None
def graceful(self):
"""Stop the callback's perpetual timer thread and restart it."""
self.stop()
self.start()
class Autoreloader(Monitor):
"""Monitor which re-executes the process when files change."""
frequency = 1
match = '.*'
def __init__(self, bus, frequency=1, match='.*'):
self.mtimes = {}
self.files = set()
self.match = match
Monitor.__init__(self, bus, self.run, frequency)
def start(self):
"""Start our own perpetual timer thread for self.run."""
if self.thread is None:
self.mtimes = {}
Monitor.start(self)
start.priority = 70
def run(self):
"""Reload the process if registered files have been modified."""
sysfiles = set()
for k, m in sys.modules.items():
if re.match(self.match, k):
if hasattr(m, '__loader__'):
if hasattr(m.__loader__, 'archive'):
k = m.__loader__.archive
k = getattr(m, '__file__', None)
sysfiles.add(k)
for filename in sysfiles | self.files:
if filename:
if filename.endswith('.pyc'):
filename = filename[:-1]
oldtime = self.mtimes.get(filename, 0)
if oldtime is None:
# Module with no .py file. Skip it.
continue
try:
mtime = os.stat(filename).st_mtime
except OSError:
# Either a module with no .py file, or it's been deleted.
mtime = None
if filename not in self.mtimes:
# If a module has no .py file, this will be None.
self.mtimes[filename] = mtime
else:
if mtime is None or mtime > oldtime:
# The file has been deleted or modified.
self.bus.log("Restarting because %s changed." % filename)
self.thread.cancel()
self.bus.log("Stopped thread %r." % self.thread.getName())
self.bus.restart()
return
class ThreadManager(SimplePlugin):
"""Manager for HTTP request threads.
If you have control over thread creation and destruction, publish to
the 'acquire_thread' and 'release_thread' channels (for each thread).
This will register/unregister the current thread and publish to
'start_thread' and 'stop_thread' listeners in the bus as needed.
If threads are created and destroyed by code you do not control
(e.g., Apache), then, at the beginning of every HTTP request,
publish to 'acquire_thread' only. You should not publish to
'release_thread' in this case, since you do not know whether
the thread will be re-used or not. The bus will call
'stop_thread' listeners for you when it stops.
"""
def __init__(self, bus):
self.threads = {}
SimplePlugin.__init__(self, bus)
self.bus.listeners.setdefault('acquire_thread', set())
self.bus.listeners.setdefault('release_thread', set())
def acquire_thread(self):
"""Run 'start_thread' listeners for the current thread.
If the current thread has already been seen, any 'start_thread'
listeners will not be run again.
"""
thread_ident = threading._get_ident()
if thread_ident not in self.threads:
# We can't just use _get_ident as the thread ID
# because some platforms reuse thread ID's.
i = len(self.threads) + 1
self.threads[thread_ident] = i
self.bus.publish('start_thread', i)
def release_thread(self):
"""Release the current thread and run 'stop_thread' listeners."""
thread_ident = threading._get_ident()
i = self.threads.pop(thread_ident, None)
if i is not None:
self.bus.publish('stop_thread', i)
def stop(self):
"""Release all threads and run all 'stop_thread' listeners."""
for thread_ident, i in self.threads.iteritems():
self.bus.publish('stop_thread', i)
self.threads.clear()
graceful = stop
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