Consumers

因为建立Channels最底层的解释接口是ASGI，被用来连接复杂应用的操作接口

当然你也可以忽略consumers而使用其他Channels部分，像routing，session等等

基础布局

consumers 的子类有

channels.consumer.AsyncConsumer
channels.consumer.SyncConsumer

SyncConsumer的一个基础例子

from channels.consumer import SyncConsumerclass EchoConsumer(SyncConsumer):def websocket_connect(self, event):self.send({"type": "websocket.accept",})def websocket_receive(self, event):self.send({"type": "websocket.send","text": event["text"],})

通过在ASGI设置，我们可以获取到信息。

self.send(event)可以将事件发送到客户端或是服务器

与AsyncConsumer相似，其他的处理方法也要有self.send

from channels.consumer import AsyncConsumerclass EchoConsumer(AsyncConsumer):async def websocket_connect(self, event):await self.send({"type": "websocket.accept",})async def websocket_receive(self, event):await self.send({"type": "websocket.send","text": event["text"],})

什么时候使用AsyncConsumer或SyncConsumer？

当你使用慢同步函数循环整个事件时使用AsymcConsumer，如果你到用Django的ORM模型就应该使用SyncConsumer。一般使用SyncConsumer为默认值。

Closing Consumers关闭用户

当已连接的consumer要关闭时，需要使用http.disconnect或websocket.disconnect

当结束时会触发channels.exceptions.StopConsumer

Channel Layers

Consumer通过使用Channel Layers来相互发送消息或广播消息

Scope领域、范围

Consumuer能够接收连接所在的范围的消息

scope["path"], the path on the request. (HTTP and WebSocket)
scope["headers"], raw name/value header pairs from the request (HTTP and WebSocket)
scope["method"], the method name used for the request. (HTTP)

WebSocketConsumer

这个包channels.generic.websocket.WebsocketConsumer是处理发送和接收消息。

from channels.generic.websocket import WebsocketConsumerclass MyConsumer(WebsocketConsumer):groups = ["broadcast"]def connect(self):# Called on connection.# To accept the connection call:self.accept()# Or accept the connection and specify a chosen subprotocol.# A list of subprotocols specified by the connecting client# will be available in self.scope['subprotocols']self.accept("subprotocol")# To reject the connection, call:self.close()def receive(self, text_data=None, bytes_data=None):# Called with either text_data or bytes_data for each frame# You can call:self.send(text_data="Hello world!")# Or, to send a binary frame:self.send(bytes_data="Hello world!")# Want to force-close the connection? Call:self.close()# Or add a custom WebSocket error code!self.close(code=4123)def disconnect(self, close_code):# Called when the socket closes

AsyncWebsocketConsumer

from channels.generic.websocket import AsyncWebsocketConsumerclass MyConsumer(AsyncWebsocketConsumer):groups = ["broadcast"]async def connect(self):# Called on connection.# To accept the connection call:await self.accept()# Or accept the connection and specify a chosen subprotocol.# A list of subprotocols specified by the connecting client# will be available in self.scope['subprotocols']await self.accept("subprotocol")# To reject the connection, call:await self.close()async def receive(self, text_data=None, bytes_data=None):# Called with either text_data or bytes_data for each frame# You can call:await self.send(text_data="Hello world!")# Or, to send a binary frame:await self.send(bytes_data="Hello world!")# Want to force-close the connection? Call:await self.close()# Or add a custom WebSocket error code!await self.close(code=4123)async def disconnect(self, close_code):# Called when the socket closes

AsyncHttpConsumer

from channels.generic.http import AsyncHttpConsumerclass BasicHttpConsumer(AsyncHttpConsumer):async def handle(self, body):await asyncio.sleep(10)await self.send_response(200, b"Your response bytes", headers=[(b"Content-Type", b"text/plain"),])

import json
from channels.generic.http import AsyncHttpConsumerclass LongPollConsumer(AsyncHttpConsumer):async def handle(self, body):await self.send_headers(headers=[(b"Content-Type", b"application/json"),])# Headers are only sent after the first body event.# Set "more_body" to tell the interface server to not# finish the response yet:await self.send_body(b"", more_body=True)async def chat_message(self, event):# Send JSON and finish the response:await self.send_body(json.dumps(event).encode("utf-8"))

from datetime import datetime
from channels.generic.http import AsyncHttpConsumerclass ServerSentEventsConsumer(AsyncHttpConsumer):async def handle(self, body):await self.send_headers(headers=[(b"Cache-Control", b"no-cache"),(b"Content-Type", b"text/event-stream"),(b"Transfer-Encoding", b"chunked"),])while True:payload = "data: %s\n\n" % datetime.now().isoformat()await self.send_body(payload.encode("utf-8"), more_body=True)await asyncio.sleep(1)

参考资料https://channels.readthedocs.io/en/stable/topics/consumers.html

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