Python+Django+Channels之Consumers（用户）

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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 SyncConsumer
class 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"],
    })</code></pre> 

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 AsyncConsumer
class 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"],
    })</code></pre> 

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 WebsocketConsumer
class 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</code></pre> 

AsyncWebsocketConsumer
 
from channels.generic.websocket import AsyncWebsocketConsumer
class 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</code></pre> 

AsyncHttpConsumer
 
from channels.generic.http import AsyncHttpConsumer
class 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 AsyncHttpConsumer
class 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"))</code></pre> 

 
 
from datetime import datetime
from channels.generic.http import AsyncHttpConsumer
class 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