1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
|
# Copyright 2014-2016 OpenMarket Ltd
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import logging
from typing import Any, Callable, Dict, List
from twisted.internet import defer
from synapse.logging.context import make_deferred_yieldable, run_in_background
from synapse.metrics.background_process_metrics import run_as_background_process
from synapse.util.async_helpers import maybe_awaitable
logger = logging.getLogger(__name__)
def user_left_room(distributor, user, room_id):
distributor.fire("user_left_room", user=user, room_id=room_id)
class Distributor:
"""A central dispatch point for loosely-connected pieces of code to
register, observe, and fire signals.
Signals are named simply by strings.
TODO(paul): It would be nice to give signals stronger object identities,
so we can attach metadata, docstrings, detect typos, etc... But this
model will do for today.
"""
def __init__(self) -> None:
self.signals: Dict[str, Signal] = {}
self.pre_registration: Dict[str, List[Callable]] = {}
def declare(self, name: str) -> None:
if name in self.signals:
raise KeyError("%r already has a signal named %s" % (self, name))
self.signals[name] = Signal(name)
if name in self.pre_registration:
signal = self.signals[name]
for observer in self.pre_registration[name]:
signal.observe(observer)
def observe(self, name: str, observer: Callable) -> None:
if name in self.signals:
self.signals[name].observe(observer)
else:
# TODO: Avoid strong ordering dependency by allowing people to
# pre-register observations on signals that don't exist yet.
if name not in self.pre_registration:
self.pre_registration[name] = []
self.pre_registration[name].append(observer)
def fire(self, name: str, *args, **kwargs) -> None:
"""Dispatches the given signal to the registered observers.
Runs the observers as a background process. Does not return a deferred.
"""
if name not in self.signals:
raise KeyError("%r does not have a signal named %s" % (self, name))
run_as_background_process(name, self.signals[name].fire, *args, **kwargs)
class Signal:
"""A Signal is a dispatch point that stores a list of callables as
observers of it.
Signals can be "fired", meaning that every callable observing it is
invoked. Firing a signal does not change its state; it can be fired again
at any later point. Firing a signal passes any arguments from the fire
method into all of the observers.
"""
def __init__(self, name: str):
self.name: str = name
self.observers: List[Callable] = []
def observe(self, observer: Callable) -> None:
"""Adds a new callable to the observer list which will be invoked by
the 'fire' method.
Each observer callable may return a Deferred."""
self.observers.append(observer)
def fire(self, *args, **kwargs) -> "defer.Deferred[List[Any]]":
"""Invokes every callable in the observer list, passing in the args and
kwargs. Exceptions thrown by observers are logged but ignored. It is
not an error to fire a signal with no observers.
Returns a Deferred that will complete when all the observers have
completed."""
async def do(observer):
try:
return await maybe_awaitable(observer(*args, **kwargs))
except Exception as e:
logger.warning(
"%s signal observer %s failed: %r",
self.name,
observer,
e,
)
deferreds = [run_in_background(do, o) for o in self.observers]
return make_deferred_yieldable(
defer.gatherResults(deferreds, consumeErrors=True)
)
def __repr__(self):
return "<Signal name=%r>" % (self.name,)
|
