mirror of https://github.com/tiangolo/fastapi.git
Export WebSocketDisconnect and add example handling disconnections to docs (#1822)
Co-authored-by: Sebastián Ramírez <tiangolo@gmail.com>
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Rupsi Kaushik
GitHub
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@ -137,6 +137,33 @@ With that you can connect the WebSocket and then send and receive messages:
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<img src="/img/tutorial/websockets/image05.png">
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## Handling disconnections and multiple clients
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When a WebSocket connection is closed, the `await websocket.receive_text()` will raise a `WebSocketDisconnect` exception, which you can then catch and handle like in this example.
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```Python hl_lines="81-83"
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{!../../../docs_src/websockets/tutorial003.py!}
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```
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To try it out:
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* Open the app with several browser tabs.
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* Write messages from them.
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* Then close one of the tabs.
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That will raise the `WebSocketDisconnect` exception, and all the other clients will receive a message like:
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```
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Client #1596980209979 left the chat
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```
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!!! tip
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The app above is a minimal and simple example to demonstrate how to handle and broadcast messages to several WebSocket connections.
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But have in mind that, as everything is handled in memory, in a single list, it will only work while the process is running, and will only work with a single process.
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If you need something easy to integrate with FastAPI but that is more robust, supported by Redis, PostgreSQL or others, check <a href="https://github.com/encode/broadcaster" class="external-link" target="_blank">encode/broadcaster</a>.
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## More info
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To learn more about the options, check Starlette's documentation for:
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@ -0,0 +1,83 @@
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from typing import List
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from fastapi import FastAPI, WebSocket, WebSocketDisconnect
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from fastapi.responses import HTMLResponse
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app = FastAPI()
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html = """
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<!DOCTYPE html>
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<html>
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<head>
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<title>Chat</title>
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</head>
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<body>
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<h1>WebSocket Chat</h1>
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<h2>Your ID: <span id="ws-id"></span></h2>
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<form action="" onsubmit="sendMessage(event)">
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<input type="text" id="messageText" autocomplete="off"/>
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<button>Send</button>
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</form>
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<ul id='messages'>
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</ul>
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<script>
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var client_id = Date.now()
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document.querySelector("#ws-id").textContent = client_id;
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var ws = new WebSocket(`ws://localhost:8000/ws/${client_id}`);
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ws.onmessage = function(event) {
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var messages = document.getElementById('messages')
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var message = document.createElement('li')
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var content = document.createTextNode(event.data)
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message.appendChild(content)
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messages.appendChild(message)
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};
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function sendMessage(event) {
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var input = document.getElementById("messageText")
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ws.send(input.value)
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input.value = ''
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event.preventDefault()
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}
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</script>
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</body>
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</html>
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"""
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class ConnectionManager:
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def __init__(self):
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self.active_connections: List[WebSocket] = []
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async def connect(self, websocket: WebSocket):
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await websocket.accept()
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self.active_connections.append(websocket)
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def disconnect(self, websocket: WebSocket):
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self.active_connections.remove(websocket)
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async def send_personal_message(self, message: str, websocket: WebSocket):
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await websocket.send_text(message)
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async def broadcast(self, message: str):
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for connection in self.active_connections:
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await connection.send_text(message)
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manager = ConnectionManager()
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@app.get("/")
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async def get():
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return HTMLResponse(html)
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@app.websocket("/ws/{client_id}")
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async def websocket_endpoint(websocket: WebSocket, client_id: int):
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await manager.connect(websocket)
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try:
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while True:
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data = await websocket.receive_text()
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await manager.send_personal_message(f"You wrote: {data}", websocket)
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await manager.broadcast(f"Client #{client_id} says: {data}")
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except WebSocketDisconnect:
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manager.disconnect(websocket)
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await manager.broadcast(f"Client #{client_id} left the chat")
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@ -22,4 +22,4 @@ from .param_functions import (
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from .requests import Request
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from .responses import Response
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from .routing import APIRouter
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from .websockets import WebSocket
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from .websockets import WebSocket, WebSocketDisconnect
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@ -0,0 +1,22 @@
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from fastapi.testclient import TestClient
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from docs_src.websockets.tutorial003 import app
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client = TestClient(app)
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def test_websocket_handle_disconnection():
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with client.websocket_connect("/ws/1234") as connection, client.websocket_connect(
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"/ws/5678"
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) as connection_two:
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connection.send_text("Hello from 1234")
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data1 = connection.receive_text()
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assert data1 == "You wrote: Hello from 1234"
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data2 = connection_two.receive_text()
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client1_says = "Client #1234 says: Hello from 1234"
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assert data2 == client1_says
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data1 = connection.receive_text()
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assert data1 == client1_says
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connection_two.close()
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data1 = connection.receive_text()
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assert data1 == "Client #5678 left the chat"
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