| # Copyright (c) 2013 The Chromium OS Authors. All rights reserved. |
| # Use of this source code is governed by a BSD-style license that can be |
| # found in the LICENSE file. |
| |
| import contextlib |
| import dbus |
| import errno |
| import functools |
| import logging |
| import select |
| import signal |
| import threading |
| import SimpleXMLRPCServer |
| |
| |
| class XmlRpcServer(threading.Thread): |
| """Simple XMLRPC server implementation. |
| |
| In theory, Python should provide a sane XMLRPC server implementation as |
| part of its standard library. In practice the provided implementation |
| doesn't handle signals, not even EINTR. As a result, we have this class. |
| |
| Usage: |
| |
| server = XmlRpcServer(('localhost', 43212)) |
| server.register_delegate(my_delegate_instance) |
| server.run() |
| |
| """ |
| |
| def __init__(self, host, port): |
| """Construct an XmlRpcServer. |
| |
| @param host string hostname to bind to. |
| @param port int port number to bind to. |
| |
| """ |
| super(XmlRpcServer, self).__init__() |
| logging.info('Binding server to %s:%d', host, port) |
| self._server = SimpleXMLRPCServer.SimpleXMLRPCServer((host, port), |
| allow_none=True) |
| self._server.register_introspection_functions() |
| # After python 2.7.10, BaseServer.handle_request automatically retries |
| # on EINTR, so handle_request will be blocked at select.select forever |
| # if timeout is None. Set a timeout so server can be shut down |
| # gracefully. Check issue crbug.com/571737 and |
| # https://bugs.python.org/issue7978 for the explanation. |
| self._server.timeout = 0.5 |
| self._keep_running = True |
| self._delegates = [] |
| # Gracefully shut down on signals. This is how we expect to be shut |
| # down by autotest. |
| signal.signal(signal.SIGTERM, self._handle_signal) |
| signal.signal(signal.SIGINT, self._handle_signal) |
| |
| |
| def register_delegate(self, delegate): |
| """Register delegate objects with the server. |
| |
| The server will automagically look up all methods not prefixed with an |
| underscore and treat them as potential RPC calls. These methods may |
| only take basic Python objects as parameters, as noted by the |
| SimpleXMLRPCServer documentation. The state of the delegate is |
| persisted across calls. |
| |
| @param delegate object Python object to be exposed via RPC. |
| |
| """ |
| self._server.register_instance(delegate) |
| self._delegates.append(delegate) |
| |
| |
| def run(self): |
| """Block and handle many XmlRpc requests.""" |
| logging.info('XmlRpcServer starting...') |
| # TODO(wiley) nested is deprecated, but we can't use the replacement |
| # until we move to Python 3.0. |
| with contextlib.nested(*self._delegates): |
| while self._keep_running: |
| try: |
| self._server.handle_request() |
| except select.error as v: |
| # In a cruel twist of fate, the python library doesn't |
| # handle this kind of error. |
| if v[0] != errno.EINTR: |
| raise |
| logging.info('XmlRpcServer exited.') |
| |
| |
| def _handle_signal(self, _signum, _frame): |
| """Handle a process signal by gracefully quitting. |
| |
| SimpleXMLRPCServer helpfully exposes a method called shutdown() which |
| clears a flag similar to _keep_running, and then blocks until it sees |
| the server shut down. Unfortunately, if you call that function from |
| a signal handler, the server will just hang, since the process is |
| paused for the signal, causing a deadlock. Thus we are reinventing the |
| wheel with our own event loop. |
| |
| """ |
| self._keep_running = False |
| |
| |
| def dbus_safe(default_return_value): |
| """Catch all DBus exceptions and return a default value instead. |
| |
| Wrap a function with a try block that catches DBus exceptions and |
| returns default values instead. This is convenient for simple error |
| handling since XMLRPC doesn't understand DBus exceptions. |
| |
| @param wrapped_function function to wrap. |
| @param default_return_value value to return on exception (usually False). |
| |
| """ |
| def decorator(wrapped_function): |
| """Call a function and catch DBus errors. |
| |
| @param wrapped_function function to call in dbus safe context. |
| @return function return value or default_return_value on failure. |
| |
| """ |
| @functools.wraps(wrapped_function) |
| def wrapper(*args, **kwargs): |
| """Pass args and kwargs to a dbus safe function. |
| |
| @param args formal python arguments. |
| @param kwargs keyword python arguments. |
| @return function return value or default_return_value on failure. |
| |
| """ |
| logging.debug('%s()', wrapped_function.__name__) |
| try: |
| return wrapped_function(*args, **kwargs) |
| |
| except dbus.exceptions.DBusException as e: |
| logging.error('Exception while performing operation %s: %s: %s', |
| wrapped_function.__name__, |
| e.get_dbus_name(), |
| e.get_dbus_message()) |
| return default_return_value |
| |
| return wrapper |
| |
| return decorator |
| |
| |
| class XmlRpcDelegate(object): |
| """A super class for XmlRPC delegates used with XmlRpcServer. |
| |
| This doesn't add much helpful functionality except to implement the trivial |
| status check method expected by autotest's host.xmlrpc_connect() method. |
| Subclass this class to add more functionality. |
| |
| """ |
| |
| |
| def __enter__(self): |
| logging.debug('Bringing up XmlRpcDelegate: %r.', self) |
| pass |
| |
| |
| def __exit__(self, exception, value, traceback): |
| logging.debug('Tearing down XmlRpcDelegate: %r.', self) |
| pass |
| |
| |
| def ready(self): |
| """Confirm that the XMLRPC server is up and ready to serve. |
| |
| @return True (always). |
| |
| """ |
| logging.debug('ready()') |
| return True |