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
|
import asyncio
import inspect
import json
from typing import Callable, Union
import aioredis
class RedisMessageRelay:
"""A class for relaying messages across services using redis lists and pubsub."""
def __init__(
self,
name: str,
redis_channel: Union[aioredis.Channel, str],
redis_list: str,
redis_pool: aioredis.Redis,
) -> None:
self.name = name
self.channel = redis_channel
self.redis_list = redis_list
self.redis = redis_pool
def __repr__(self) -> str:
return f"<{self.__class__.__name__} name={self.name} channel={self.channel} list={self.redis_list}>"
class RedisMessageProducer(RedisMessageRelay):
def __init__(
self,
name: str,
redis_channel: Union[aioredis.Channel, str],
redis_list: str,
redis_pool: aioredis.Redis,
) -> None:
super().__init__(name, redis_channel, redis_list, redis_pool)
async def relay(self, data: dict) -> int:
"""
Push message and notify consumer.
returns:
- Number of subscribers the notification was delivered to.
"""
serialised = json.dumps(data)
await self.redis.rpush(self.redis_list, serialised)
# Notify consumer about new message.
subs: int = await self.redis.publish_json(
self.channel,
{"pushed": True}
)
return subs
class RedisMessageConsumer(RedisMessageRelay):
def __init__(
self,
name: str,
redis_channel: Union[aioredis.Channel, str],
redis_list: str,
redis_pool: aioredis.Redis,
callback: Callable,
loop: asyncio.AbstractEventLoop
) -> None:
super().__init__(name, redis_channel, redis_list, redis_pool)
self.callback = callback
self.loop = loop
async def listen(self) -> None:
res = await self.redis.subscribe(self.channel)
self.channel = res[0]
await self.wait_until_message()
async def pre_callback(self, data: dict):
if inspect.iscoroutinefunction(self.callback):
await self.callback(data)
return
self.callback(data)
async def read_redis_list(self) -> None:
serialised = await self.redis.lpop(self.redis_list)
try:
data = json.loads(serialised)
except (json.JSONDecodeError, TypeError):
pass
else:
await self.pre_callback(data)
async def wait_until_message(self) -> None:
"""Receive message from a channel."""
# Empty queue before receiving messages.
queue: list = await self.redis.lrange(self.redis_list, 0, -1)
await self.redis.delete(self.redis_list)
for item in queue:
await self.pre_callback(item)
while await self.channel.wait_message():
data = await self.channel.get_json()
if data["pushed"]:
await self.read_redis_list()
|
