Export WebSocketDisconnect and add example handling disconnections to docs (#1822

)

Co-authored-by: Sebastián Ramírez <tiangolo@gmail.com>
5 years ago · 5ed48ccdc8
4 changed files with 133 additions and 1 deletions
--- a/docs/en/docs/advanced/websockets.md
+++ b/docs/en/docs/advanced/websockets.md
@ -137,6 +137,33 @@ With that you can connect the WebSocket and then send and receive messages:
 <img src="/img/tutorial/websockets/image05.png">
 ## Handling disconnections and multiple clients
 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.
 ```Python hl_lines="81-83"
 {!../../../docs_src/websockets/tutorial003.py!}
 ```
 To try it out:
 * Open the app with several browser tabs.
 * Write messages from them.
 * Then close one of the tabs.
 That will raise the `WebSocketDisconnect` exception, and all the other clients will receive a message like:
 ```
 Client #1596980209979 left the chat
 ```
 !!! tip
    The app above is a minimal and simple example to demonstrate how to handle and broadcast messages to several WebSocket connections.
    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.
    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>.
 ## More info
 To learn more about the options, check Starlette's documentation for:
--- a/docs_src/websockets/tutorial003.py
+++ b/docs_src/websockets/tutorial003.py
@ -0,0 +1,83 @@
 from typing import List
 from fastapi import FastAPI, WebSocket, WebSocketDisconnect
 from fastapi.responses import HTMLResponse
 app = FastAPI()
 html = """
 <!DOCTYPE html>
 <html>
    <head>
        <title>Chat</title>
    </head>
    <body>
        <h1>WebSocket Chat</h1>
        <h2>Your ID: <span id="ws-id"></span></h2>
        <form action="" onsubmit="sendMessage(event)">
            <input type="text" id="messageText" autocomplete="off"/>
            <button>Send</button>
        </form>
        <ul id='messages'>
        </ul>
        <script>
            var client_id = Date.now()
            document.querySelector("#ws-id").textContent = client_id;
            var ws = new WebSocket(`ws://localhost:8000/ws/${client_id}`);
            ws.onmessage = function(event) {
                var messages = document.getElementById('messages')
                var message = document.createElement('li')
                var content = document.createTextNode(event.data)
                message.appendChild(content)
                messages.appendChild(message)
            };
            function sendMessage(event) {
                var input = document.getElementById("messageText")
                ws.send(input.value)
                input.value = ''
                event.preventDefault()
            }
        </script>
    </body>
 </html>
 """
 class ConnectionManager:
    def __init__(self):
        self.active_connections: List[WebSocket] = []
    async def connect(self, websocket: WebSocket):
        await websocket.accept()
        self.active_connections.append(websocket)
    def disconnect(self, websocket: WebSocket):
        self.active_connections.remove(websocket)
    async def send_personal_message(self, message: str, websocket: WebSocket):
        await websocket.send_text(message)
    async def broadcast(self, message: str):
        for connection in self.active_connections:
            await connection.send_text(message)
 manager = ConnectionManager()
@app.get("/")
 async def get():
    return HTMLResponse(html)
@app.websocket("/ws/{client_id}")
 async def websocket_endpoint(websocket: WebSocket, client_id: int):
    await manager.connect(websocket)
    try:
        while True:
            data = await websocket.receive_text()
            await manager.send_personal_message(f"You wrote: {data}", websocket)
            await manager.broadcast(f"Client #{client_id} says: {data}")
    except WebSocketDisconnect:
        manager.disconnect(websocket)
        await manager.broadcast(f"Client #{client_id} left the chat")
--- a/fastapi/init.py
+++ b/fastapi/init.py
@ -22,4 +22,4 @@ from .param_functions import (
 from .requests import Request
 from .responses import Response
 from .routing import APIRouter
-from .websockets import WebSocket
+from .websockets import WebSocket, WebSocketDisconnect
--- a/tests/test_tutorial/test_websockets/test_tutorial003.py
+++ b/tests/test_tutorial/test_websockets/test_tutorial003.py
@ -0,0 +1,22 @@
 from fastapi.testclient import TestClient
 from docs_src.websockets.tutorial003 import app
 client = TestClient(app)
 def test_websocket_handle_disconnection():
    with client.websocket_connect("/ws/1234") as connection, client.websocket_connect(
        "/ws/5678"
    ) as connection_two:
        connection.send_text("Hello from 1234")
        data1 = connection.receive_text()
        assert data1 == "You wrote: Hello from 1234"
        data2 = connection_two.receive_text()
        client1_says = "Client #1234 says: Hello from 1234"
        assert data2 == client1_says
        data1 = connection.receive_text()
        assert data1 == client1_says
        connection_two.close()
        data1 = connection.receive_text()
        assert data1 == "Client #5678 left the chat"