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Diffstat (limited to 'pkg/osx/daemon/runner.py')
| -rw-r--r-- | pkg/osx/daemon/runner.py | 324 |
1 files changed, 324 insertions, 0 deletions
diff --git a/pkg/osx/daemon/runner.py b/pkg/osx/daemon/runner.py new file mode 100644 index 00000000..de9025d3 --- /dev/null +++ b/pkg/osx/daemon/runner.py @@ -0,0 +1,324 @@ +# -*- coding: utf-8 -*- + +# daemon/runner.py +# Part of ‘python-daemon’, an implementation of PEP 3143. +# +# Copyright © 2009–2015 Ben Finney <ben+python@benfinney.id.au> +# Copyright © 2007–2008 Robert Niederreiter, Jens Klein +# Copyright © 2003 Clark Evans +# Copyright © 2002 Noah Spurrier +# Copyright © 2001 Jürgen Hermann +# +# This is free software: you may copy, modify, and/or distribute this work +# under the terms of the Apache License, version 2.0 as published by the +# Apache Software Foundation. +# No warranty expressed or implied. See the file ‘LICENSE.ASF-2’ for details. + +""" Daemon runner library. + """ + +from __future__ import (absolute_import, unicode_literals) + +import sys +import os +import signal +import errno +try: + # Python 3 standard library. + ProcessLookupError +except NameError: + # No such class in Python 2. + ProcessLookupError = NotImplemented + +import lockfile + +from . import pidfile +from .daemon import (basestring, unicode) +from .daemon import DaemonContext +from .daemon import _chain_exception_from_existing_exception_context + + +class DaemonRunnerError(Exception): + """ Abstract base class for errors from DaemonRunner. """ + + def __init__(self, *args, **kwargs): + self._chain_from_context() + + super(DaemonRunnerError, self).__init__(*args, **kwargs) + + def _chain_from_context(self): + _chain_exception_from_existing_exception_context(self, as_cause=True) + + +class DaemonRunnerInvalidActionError(DaemonRunnerError, ValueError): + """ Raised when specified action for DaemonRunner is invalid. """ + + def _chain_from_context(self): + # This exception is normally not caused by another. + _chain_exception_from_existing_exception_context(self, as_cause=False) + + +class DaemonRunnerStartFailureError(DaemonRunnerError, RuntimeError): + """ Raised when failure starting DaemonRunner. """ + + +class DaemonRunnerStopFailureError(DaemonRunnerError, RuntimeError): + """ Raised when failure stopping DaemonRunner. """ + + +class DaemonRunner: + """ Controller for a callable running in a separate background process. + + The first command-line argument is the action to take: + + * 'start': Become a daemon and call `app.run()`. + * 'stop': Exit the daemon process specified in the PID file. + * 'restart': Stop, then start. + + """ + + __metaclass__ = type + + start_message = "started with pid {pid:d}" + + def __init__(self, app): + """ Set up the parameters of a new runner. + + :param app: The application instance; see below. + :return: ``None``. + + The `app` argument must have the following attributes: + + * `stdin_path`, `stdout_path`, `stderr_path`: Filesystem paths + to open and replace the existing `sys.stdin`, `sys.stdout`, + `sys.stderr`. + + * `pidfile_path`: Absolute filesystem path to a file that will + be used as the PID file for the daemon. If ``None``, no PID + file will be used. + + * `pidfile_timeout`: Used as the default acquisition timeout + value supplied to the runner's PID lock file. + + * `run`: Callable that will be invoked when the daemon is + started. + + """ + self.parse_args() + self.app = app + self.daemon_context = DaemonContext() + self.daemon_context.stdin = open(app.stdin_path, 'rt') + self.daemon_context.stdout = open(app.stdout_path, 'w+t') + self.daemon_context.stderr = open( + app.stderr_path, 'w+t', buffering=0) + + self.pidfile = None + if app.pidfile_path is not None: + self.pidfile = make_pidlockfile( + app.pidfile_path, app.pidfile_timeout) + self.daemon_context.pidfile = self.pidfile + + def _usage_exit(self, argv): + """ Emit a usage message, then exit. + + :param argv: The command-line arguments used to invoke the + program, as a sequence of strings. + :return: ``None``. + + """ + progname = os.path.basename(argv[0]) + usage_exit_code = 2 + action_usage = "|".join(self.action_funcs.keys()) + message = "usage: {progname} {usage}".format( + progname=progname, usage=action_usage) + emit_message(message) + sys.exit(usage_exit_code) + + def parse_args(self, argv=None): + """ Parse command-line arguments. + + :param argv: The command-line arguments used to invoke the + program, as a sequence of strings. + + :return: ``None``. + + The parser expects the first argument as the program name, the + second argument as the action to perform. + + If the parser fails to parse the arguments, emit a usage + message and exit the program. + + """ + if argv is None: + argv = sys.argv + + min_args = 2 + if len(argv) < min_args: + self._usage_exit(argv) + + self.action = unicode(argv[1]) + if self.action not in self.action_funcs: + self._usage_exit(argv) + + def _start(self): + """ Open the daemon context and run the application. + + :return: ``None``. + :raises DaemonRunnerStartFailureError: If the PID file cannot + be locked by this process. + + """ + if is_pidfile_stale(self.pidfile): + self.pidfile.break_lock() + + try: + self.daemon_context.open() + except lockfile.AlreadyLocked: + error = DaemonRunnerStartFailureError( + "PID file {pidfile.path!r} already locked".format( + pidfile=self.pidfile)) + raise error + + pid = os.getpid() + message = self.start_message.format(pid=pid) + emit_message(message) + + self.app.run() + + def _terminate_daemon_process(self): + """ Terminate the daemon process specified in the current PID file. + + :return: ``None``. + :raises DaemonRunnerStopFailureError: If terminating the daemon + fails with an OS error. + + """ + pid = self.pidfile.read_pid() + try: + os.kill(pid, signal.SIGTERM) + except OSError as exc: + error = DaemonRunnerStopFailureError( + "Failed to terminate {pid:d}: {exc}".format( + pid=pid, exc=exc)) + raise error + + def _stop(self): + """ Exit the daemon process specified in the current PID file. + + :return: ``None``. + :raises DaemonRunnerStopFailureError: If the PID file is not + already locked. + + """ + if not self.pidfile.is_locked(): + error = DaemonRunnerStopFailureError( + "PID file {pidfile.path!r} not locked".format( + pidfile=self.pidfile)) + raise error + + if is_pidfile_stale(self.pidfile): + self.pidfile.break_lock() + else: + self._terminate_daemon_process() + + def _restart(self): + """ Stop, then start. + """ + self._stop() + self._start() + + action_funcs = { + 'start': _start, + 'stop': _stop, + 'restart': _restart, + } + + def _get_action_func(self): + """ Get the function for the specified action. + + :return: The function object corresponding to the specified + action. + :raises DaemonRunnerInvalidActionError: if the action is + unknown. + + The action is specified by the `action` attribute, which is set + during `parse_args`. + + """ + try: + func = self.action_funcs[self.action] + except KeyError: + error = DaemonRunnerInvalidActionError( + "Unknown action: {action!r}".format( + action=self.action)) + raise error + return func + + def do_action(self): + """ Perform the requested action. + + :return: ``None``. + + The action is specified by the `action` attribute, which is set + during `parse_args`. + + """ + func = self._get_action_func() + func(self) + + +def emit_message(message, stream=None): + """ Emit a message to the specified stream (default `sys.stderr`). """ + if stream is None: + stream = sys.stderr + stream.write("{message}\n".format(message=message)) + stream.flush() + + +def make_pidlockfile(path, acquire_timeout): + """ Make a PIDLockFile instance with the given filesystem path. """ + if not isinstance(path, basestring): + error = ValueError("Not a filesystem path: {path!r}".format( + path=path)) + raise error + if not os.path.isabs(path): + error = ValueError("Not an absolute path: {path!r}".format( + path=path)) + raise error + lockfile = pidfile.TimeoutPIDLockFile(path, acquire_timeout) + + return lockfile + + +def is_pidfile_stale(pidfile): + """ Determine whether a PID file is stale. + + :return: ``True`` iff the PID file is stale; otherwise ``False``. + + The PID file is “stale” if its contents are valid but do not + match the PID of a currently-running process. + + """ + result = False + + pidfile_pid = pidfile.read_pid() + if pidfile_pid is not None: + try: + os.kill(pidfile_pid, signal.SIG_DFL) + except ProcessLookupError: + # The specified PID does not exist. + result = True + except OSError as exc: + if exc.errno == errno.ESRCH: + # Under Python 2, process lookup error is an OSError. + # The specified PID does not exist. + result = True + + return result + + +# Local variables: +# coding: utf-8 +# mode: python +# End: +# vim: fileencoding=utf-8 filetype=python : |