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383 lines
12 KiB
Python
383 lines
12 KiB
Python
# Copyright 2017, David Wilson
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#
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# Redistribution and use in source and binary forms, with or without
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# modification, are permitted provided that the following conditions are met:
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#
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# 1. Redistributions of source code must retain the above copyright notice,
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# this list of conditions and the following disclaimer.
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#
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# 2. Redistributions in binary form must reproduce the above copyright notice,
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# this list of conditions and the following disclaimer in the documentation
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# and/or other materials provided with the distribution.
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#
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# 3. Neither the name of the copyright holder nor the names of its contributors
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# may be used to endorse or promote products derived from this software without
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# specific prior written permission.
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#
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# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
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# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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# POSSIBILITY OF SUCH DAMAGE.
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import pprint
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import sys
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import threading
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import mitogen.core
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import mitogen.master
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from mitogen.core import LOG
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class Policy(object):
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"""
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Base security policy.
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"""
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def is_authorized(self, service, msg):
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raise NotImplementedError()
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class AllowAny(Policy):
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def is_authorized(self, service, msg):
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return True
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class AllowParents(Policy):
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def is_authorized(self, service, msg):
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return (msg.auth_id in mitogen.parent_ids or
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msg.auth_id == mitogen.context_id)
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def validate_arg_spec(spec, args):
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for name in spec:
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try:
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obj = args[name]
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except KeyError:
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raise mitogen.core.CallError(
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'Required argument %r missing.' % (name,)
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)
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if not isinstance(obj, spec[name]):
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raise mitogen.core.CallError(
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'Argument %r type incorrect, got %r, expected %r' % (
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name,
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type(obj),
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spec[name]
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)
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)
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def arg_spec(spec):
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"""
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Annotate a method as requiring arguments with a specific type. This only
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validates required arguments. For optional arguments, write a manual check
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within the function.
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::
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@mitogen.service.arg_spec({
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'path': str
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})
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def fetch_path(self, path, optional=None):
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...
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:param dict spec:
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Mapping from argument name to expected type.
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"""
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def wrapper(func):
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func.mitogen_service__arg_spec = spec
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return func
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return wrapper
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def expose(policy):
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"""
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Annotate a method to permit access to contexts matching an authorization
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policy. The annotation may be specified multiple times. Methods lacking any
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authorization policy are not accessible.
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::
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@mitogen.service.expose(policy=mitogen.service.AllowParents())
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def unsafe_operation(self):
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...
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:param mitogen.service.Policy policy:
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The policy to require.
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"""
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def wrapper(func):
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func.mitogen_service__policies = (
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[policy] +
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getattr(func, 'mitogen_service__policies', [])
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)
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return func
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return wrapper
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def no_reply():
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"""
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Annotate a method as one that does not generate a response. Messages sent
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by the method are done so explicitly. This can be used for fire-and-forget
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endpoints where the requestee never receives a reply.
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"""
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def wrapper(func):
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func.mitogen_service__no_reply = True
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return func
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return wrapper
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class Service(object):
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#: Sentinel object to suppress reply generation, since returning ``None``
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#: will trigger a response message containing the pickled ``None``.
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NO_REPLY = object()
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#: If ``None``, a handle is dynamically allocated, otherwise the fixed
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#: integer handle to use.
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handle = None
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max_message_size = 0
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def __init__(self, router):
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self.router = router
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self.recv = mitogen.core.Receiver(router, self.handle)
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self.recv.service = self
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self.handle = self.recv.handle
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self.running = True
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def __repr__(self):
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return '%s()' % (self.__class__.__name__,)
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def on_shutdown(self):
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"""
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Called by Pool.shutdown() once the last worker thread has exitted.
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"""
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def dispatch(self, args, msg):
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raise NotImplementedError()
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def _validate_message(self, msg):
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if len(msg.data) > self.max_message_size:
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raise mitogen.core.CallError('Message size exceeded.')
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pair = msg.unpickle(throw=False)
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if not (isinstance(pair, tuple) and
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len(pair) == 2 and
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isinstance(pair[0], basestring)):
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raise mitogen.core.CallError('Invalid message format.')
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method_name, kwargs = pair
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method = getattr(self, method_name, None)
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if method is None:
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raise mitogen.core.CallError('No such method exists.')
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policies = getattr(method, 'mitogen_service__policies', None)
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if not policies:
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raise mitogen.core.CallError('Method has no policies set.')
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if not all(p.is_authorized(self, msg) for p in policies):
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raise mitogen.core.CallError('Unauthorized')
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required = getattr(method, 'mitogen_service__arg_spec', {})
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validate_arg_spec(required, kwargs)
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return method_name, kwargs
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def _on_receive_message(self, msg):
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method_name, kwargs = self._validate_message(msg)
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method = getattr(self, method_name)
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if 'msg' in method.func_code.co_varnames:
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kwargs['msg'] = msg # TODO: hack
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no_reply = getattr(method, 'mitogen_service__no_reply', False)
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ret = None
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try:
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ret = method(**kwargs)
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if no_reply:
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return self.NO_REPLY
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return ret
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except Exception:
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if no_reply:
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LOG.exception('While calling no-reply method %s.%s',
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type(self).__name__, method.func_name)
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else:
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raise
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def on_receive_message(self, msg):
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try:
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response = self._on_receive_message(msg)
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if response is not self.NO_REPLY:
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msg.reply(response)
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except mitogen.core.CallError:
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e = sys.exc_info()[1]
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LOG.warning('%r: call error: %s: %s', self, msg, e)
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msg.reply(e)
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except Exception:
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LOG.exception('While invoking %r.dispatch()', self)
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e = sys.exc_info()[1]
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msg.reply(mitogen.core.CallError(e))
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class DeduplicatingService(Service):
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"""
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A service that deduplicates and caches expensive responses. Requests are
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deduplicated according to a customizable key, and the single expensive
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response is broadcast to all requestors.
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A side effect of this class is that processing of the single response is
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always serialized according to the result of :py:meth:`key_from_request`.
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Only one pool thread is blocked during generation of the response,
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regardless of the number of requestors.
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"""
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def __init__(self, router):
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super(DeduplicatingService, self).__init__(router)
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self._responses = {}
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self._waiters = {}
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self._lock = threading.Lock()
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def key_from_request(self, method_name, kwargs):
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"""
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Generate a deduplication key from the request. The default
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implementation returns a string based on a stable representation of the
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input dictionary generated by :py:func:`pprint.pformat`.
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"""
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return pprint.pformat((method_name, kwargs))
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def get_response(self, args):
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raise NotImplementedError()
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def _produce_response(self, key, response):
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self._lock.acquire()
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try:
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assert key not in self._responses
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assert key in self._waiters
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self._responses[key] = response
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for msg in self._waiters.pop(key):
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msg.reply(response)
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finally:
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self._lock.release()
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def _on_receive_message(self, msg):
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method_name, kwargs = self._validate_message(msg)
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key = self.key_from_request(method_name, kwargs)
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self._lock.acquire()
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try:
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if key in self._responses:
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return self._responses[key]
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if key in self._waiters:
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self._waiters[key].append(msg)
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return self.NO_REPLY
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self._waiters[key] = [msg]
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finally:
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self._lock.release()
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# I'm the unlucky thread that must generate the response.
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try:
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response = getattr(self, method_name)(**kwargs)
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self._produce_response(key, response)
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except mitogen.core.CallError:
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e = sys.exc_info()[1]
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self._produce_response(key, e)
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except Exception:
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e = sys.exc_info()[1]
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self._produce_response(key, mitogen.core.CallError(e))
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return self.NO_REPLY
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class Pool(object):
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"""
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Manage a pool of at least one thread that will be used to process messages
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for a collection of services.
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Internally this is implemented by subscribing every :py:class:`Service`'s
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:py:class:`mitogen.core.Receiver` using a single
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:py:class:`mitogen.master.Select`, then arranging for every thread to
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consume messages delivered to that select.
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In this way the threads are fairly shared by all available services, and no
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resources are dedicated to a single idle service.
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There is no penalty for exposing large numbers of services; the list of
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exposed services could even be generated dynamically in response to your
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program's configuration or its input data.
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"""
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def __init__(self, router, services, size=1):
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assert size > 0
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self.router = router
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self.services = list(services)
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self.size = size
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self._select = mitogen.master.Select(
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receivers=[
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service.recv
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for service in self.services
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],
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oneshot=False,
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)
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self._threads = []
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for x in xrange(size):
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thread = threading.Thread(
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name='mitogen.service.Pool.%x.worker-%d' % (id(self), x,),
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target=self._worker_main,
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)
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thread.start()
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self._threads.append(thread)
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def stop(self):
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self._select.close()
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for th in self._threads:
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th.join()
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for service in self.services:
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service.on_shutdown()
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def _worker_run(self):
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while True:
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try:
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msg = self._select.get()
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except (mitogen.core.ChannelError, mitogen.core.LatchError):
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e = sys.exc_info()[1]
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LOG.info('%r: channel or latch closed, exitting: %s', self, e)
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return
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service = msg.receiver.service
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try:
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service.on_receive_message(msg)
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except Exception:
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LOG.exception('While handling %r using %r', msg, service)
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def _worker_main(self):
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try:
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self._worker_run()
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except Exception:
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th = threading.currentThread()
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LOG.exception('%r: worker %r crashed', self, th.name)
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raise
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def __repr__(self):
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th = threading.currentThread()
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return 'mitogen.service.Pool(%#x, size=%d, th=%r)' % (
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id(self),
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self.size,
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th.name,
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)
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def call_async(context, handle, method, kwargs=None):
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LOG.debug('service.call_async(%r, %r, %r, %r)',
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context, handle, method, kwargs)
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pair = (method, kwargs or {})
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msg = mitogen.core.Message.pickled(pair, handle=handle)
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return context.send_async(msg)
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def call(context, handle, method, kwargs):
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recv = call_async(context, handle, method, kwargs)
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return recv.get().unpickle()
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