Source code for cherrypy.process.plugins

"""Site services for use with a Web Site Process Bus."""

import os
import re
import signal as _signal
import sys
import time
import threading

from six.moves import _thread

from cherrypy._cpcompat import text_or_bytes
from cherrypy._cpcompat import ntob, Timer

# _module__file__base is used by Autoreload to make
# absolute any filenames retrieved from sys.modules which are not
# already absolute paths.  This is to work around Python's quirk
# of importing the startup script and using a relative filename
# for it in sys.modules.
# Autoreload examines sys.modules afresh every time it runs. If an application
# changes the current directory by executing os.chdir(), then the next time
# Autoreload runs, it will not be able to find any filenames which are
# not absolute paths, because the current directory is not the same as when the
# module was first imported.  Autoreload will then wrongly conclude the file
# has "changed", and initiate the shutdown/re-exec sequence.
# See ticket #917.
# For this workaround to have a decent probability of success, this module
# needs to be imported as early as possible, before the app has much chance
# to change the working directory.
_module__file__base = os.getcwd()

[docs]class SimplePlugin(object): """Plugin base class which auto-subscribes methods for known channels.""" bus = None """A :class:`Bus <cherrypy.process.wspbus.Bus>`, usually cherrypy.engine. """ def __init__(self, bus): self.bus = bus
[docs] 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)
[docs] 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)
[docs]class SignalHandler(object): """Register bus channels (and listeners) for system signals. You can modify what signals your application listens for, and what it does when it receives signals, by modifying :attr:`SignalHandler.handlers`, a dict of {signal name: callback} pairs. The default set is:: handlers = {'SIGTERM': self.bus.exit, 'SIGHUP': self.handle_SIGHUP, 'SIGUSR1': self.bus.graceful, } The :func:`SignalHandler.handle_SIGHUP`` method calls :func:`bus.restart()<cherrypy.process.wspbus.Bus.restart>` if the process is daemonized, but :func:`bus.exit()<cherrypy.process.wspbus.Bus.exit>` if the process is attached to a TTY. This is because Unix window managers tend to send SIGHUP to terminal windows when the user closes them. Feel free to add signals which are not available on every platform. The :class:`SignalHandler` will ignore errors raised from attempting to register handlers for unknown signals. """ handlers = {} """A map from signal names (e.g. 'SIGTERM') to handlers (e.g. bus.exit).""" signals = {} """A map from signal numbers to names.""" 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, } if sys.platform[:4] == 'java': del self.handlers['SIGUSR1'] self.handlers['SIGUSR2'] = self.bus.graceful self.bus.log('SIGUSR1 cannot be set on the JVM platform. ' 'Using SIGUSR2 instead.') self.handlers['SIGINT'] = self._jython_SIGINT_handler self._previous_handlers = {} # used to determine is the process is a daemon in `self._is_daemonized` self._original_pid = os.getpid() def _jython_SIGINT_handler(self, signum=None, frame=None): # See self.bus.log('Keyboard Interrupt: shutting down bus') self.bus.exit() def _is_daemonized(self): """Return boolean indicating if the current process is running as a daemon. The criteria to determine the `daemon` condition is to verify if the current pid is not the same as the one that got used on the initial construction of the plugin *and* the stdin is not connected to a terminal. The sole validation of the tty is not enough when the plugin is executing inside other process like in a CI tool (Buildbot, Jenkins). """ return ( self._original_pid != os.getpid() and not os.isatty(sys.stdin.fileno()) )
[docs] def subscribe(self): """Subscribe self.handlers to signals.""" for sig, func in self.handlers.items(): try: self.set_handler(sig, func) except ValueError: pass
[docs] def unsubscribe(self): """Unsubscribe self.handlers from signals.""" for signum, handler in self._previous_handlers.items(): 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)
[docs] 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, text_or_bytes): 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)
[docs] def handle_SIGHUP(self): """Restart if daemonized, else exit.""" if self._is_daemonized(): self.bus.log('SIGHUP caught while daemonized. Restarting.') self.bus.restart() else: # not daemonized (may be foreground or background) self.bus.log('SIGHUP caught but not daemonized. Exiting.') self.bus.exit()
try: import pwd import grp except ImportError: pwd, grp = None, None
[docs]class DropPrivileges(SimplePlugin): """Drop privileges. uid/gid arguments not available on Windows. Special thanks to `Gavin Baker <>`_ """ 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, text_or_bytes): val = pwd.getpwnam(val)[2] self._uid = val uid = property(_get_uid, _set_uid, doc='The uid under which to run. Availability: Unix.') 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, text_or_bytes): val = grp.getgrnam(val)[2] self._gid = val gid = property(_get_gid, _set_gid, doc='The gid under which to run. Availability: Unix.') 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 default permission mode for newly created files and directories. Usually expressed in octal format, for example, ``0644``. Availability: Unix, Windows. """)
[docs] 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) os.setgroups([]) 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
[docs]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 successfully 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
[docs] def start(self): if self.finalized: self.bus.log('Already deamonized.') # forking has issues with threads: # # "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 # (or section 1.7) # and # 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: # Python raises OSError rather than returning negative numbers. exc = sys.exc_info()[1] 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.exc_info()[1] sys.exit('%s: fork #2 failed: (%d) %s\n' % (sys.argv[0], exc.errno, exc.strerror)) os.umask(0) si = open(self.stdin, 'r') so = open(self.stdout, 'a+') se = open(self.stderr, 'a+') # os.dup2(fd, fd2) will close fd2 if necessary, # so we don't explicitly close stdin/out/err. # See 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
[docs]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
[docs] 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(ntob('%s\n' % pid, 'utf8')) self.bus.log('PID %r written to %r.' % (pid, self.pidfile)) self.finalized = True
start.priority = 70
[docs] def exit(self): try: os.remove(self.pidfile) self.bus.log('PID file removed: %r.' % self.pidfile) except (KeyboardInterrupt, SystemExit): raise except: pass
[docs]class PerpetualTimer(Timer): """A responsive subclass of threading.Timer whose run() method repeats. Use this timer only when you really need a very interruptible timer; this checks its 'finished' condition up to 20 times a second, which can results in pretty high CPU usage """ def __init__(self, *args, **kwargs): "Override parent constructor to allow 'bus' to be provided." self.bus = kwargs.pop('bus', None) super(PerpetualTimer, self).__init__(*args, **kwargs)
[docs] def run(self): while True: self.finished.wait(self.interval) if self.finished.isSet(): return try: self.function(*self.args, **self.kwargs) except Exception: if self.bus: self.bus.log( 'Error in perpetual timer thread function %r.' % self.function, level=40, traceback=True) # Quit on first error to avoid massive logs. raise
[docs]class BackgroundTask(threading.Thread): """A subclass of threading.Thread whose run() method repeats. Use this class for most repeating tasks. It uses time.sleep() to wait for each interval, which isn't very responsive; that is, even if you call self.cancel(), you'll have to wait until the sleep() call finishes before the thread stops. To compensate, it defaults to being daemonic, which means it won't delay stopping the whole process. """ def __init__(self, interval, function, args=[], kwargs={}, bus=None): super(BackgroundTask, self).__init__() self.interval = interval self.function = function self.args = args self.kwargs = kwargs self.running = False self.bus = bus # default to daemonic self.daemon = True
[docs] def cancel(self): self.running = False
[docs] def run(self): self.running = True while self.running: time.sleep(self.interval) if not self.running: return try: self.function(*self.args, **self.kwargs) except Exception: if self.bus: self.bus.log('Error in background task thread function %r.' % self.function, level=40, traceback=True) # Quit on first error to avoid massive logs. raise
[docs]class Monitor(SimplePlugin): """WSPBus listener to periodically run a callback in its own thread.""" callback = None """The function to call at intervals.""" frequency = 60 """The time in seconds between callback runs.""" thread = None """A :class:`BackgroundTask<cherrypy.process.plugins.BackgroundTask>` thread. """ def __init__(self, bus, callback, frequency=60, name=None): SimplePlugin.__init__(self, bus) self.callback = callback self.frequency = frequency self.thread = None = name
[docs] def start(self): """Start our callback in its own background thread.""" if self.frequency > 0: threadname = or self.__class__.__name__ if self.thread is None: self.thread = BackgroundTask(self.frequency, self.callback, bus=self.bus) 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
[docs] def stop(self): """Stop our callback's background task thread.""" if self.thread is None: self.bus.log('No thread running for %s.' % or self.__class__.__name__) else: if self.thread is not threading.currentThread(): name = self.thread.getName() self.thread.cancel() if not self.thread.daemon: self.bus.log('Joining %r' % name) self.thread.join() self.bus.log('Stopped thread %r.' % name) self.thread = None
[docs] def graceful(self): """Stop the callback's background task thread and restart it.""" self.stop() self.start()
[docs]class Autoreloader(Monitor): """Monitor which re-executes the process when files change. This :ref:`plugin<plugins>` restarts the process (via :func:`os.execv`) if any of the files it monitors change (or is deleted). By default, the autoreloader monitors all imported modules; you can add to the set by adding to ``autoreload.files``:: cherrypy.engine.autoreload.files.add(myFile) If there are imported files you do *not* wish to monitor, you can adjust the ``match`` attribute, a regular expression. For example, to stop monitoring cherrypy itself:: cherrypy.engine.autoreload.match = r'^(?!cherrypy).+' Like all :class:`Monitor<cherrypy.process.plugins.Monitor>` plugins, the autoreload plugin takes a ``frequency`` argument. The default is 1 second; that is, the autoreloader will examine files once each second. """ files = None """The set of files to poll for modifications.""" frequency = 1 """The interval in seconds at which to poll for modified files.""" match = '.*' """A regular expression by which to match filenames.""" def __init__(self, bus, frequency=1, match='.*'): self.mtimes = {} self.files = set() self.match = match Monitor.__init__(self, bus,, frequency)
[docs] def start(self): """Start our own background task thread for""" if self.thread is None: self.mtimes = {} Monitor.start(self)
start.priority = 70
[docs] def sysfiles(self): """Return a Set of sys.modules filenames to monitor.""" files = set() for k, m in list(sys.modules.items()): if re.match(self.match, k): if ( hasattr(m, '__loader__') and hasattr(m.__loader__, 'archive') ): f = m.__loader__.archive else: f = getattr(m, '__file__', None) if f is not None and not os.path.isabs(f): # ensure absolute paths so a os.chdir() in the app # doesn't break me f = os.path.normpath( os.path.join(_module__file__base, f)) files.add(f) return files
[docs] def run(self): """Reload the process if registered files have been modified.""" for filename in self.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
[docs]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. """ threads = None """A map of {thread ident: index number} pairs.""" def __init__(self, bus): self.threads = {} SimplePlugin.__init__(self, bus) self.bus.listeners.setdefault('acquire_thread', set()) self.bus.listeners.setdefault('start_thread', set()) self.bus.listeners.setdefault('release_thread', set()) self.bus.listeners.setdefault('stop_thread', set())
[docs] 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 = _thread.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)
[docs] def release_thread(self): """Release the current thread and run 'stop_thread' listeners.""" thread_ident = _thread.get_ident() i = self.threads.pop(thread_ident, None) if i is not None: self.bus.publish('stop_thread', i)
[docs] def stop(self): """Release all threads and run all 'stop_thread' listeners.""" for thread_ident, i in self.threads.items(): self.bus.publish('stop_thread', i) self.threads.clear()
graceful = stop