Web API: 2. WebSocket Chat#
This tutorial shows how to create a Web chat on FastAPI using websockets.
You can see the result at http://127.0.0.1:8000/.
This tutorial is a modified version of the FastAPI tutorial on WebSockets: https://fastapi.tiangolo.com/advanced/websockets/.
As mentioned in that tutorial,
… for this example, we’ll use a very simple HTML document with some JavaScript, all inside a long string. This, of course, is not optimal and you wouldn’t use it for production.
Here, CallbackMessengerInterface is used to process requests.
Message is used to represent text messages.
[1]:
# installing dependencies
%pip install -q chatsky uvicorn fastapi
Note: you may need to restart the kernel to use updated packages.
[2]:
from chatsky.messengers.common.interface import CallbackMessengerInterface
from chatsky import Message, Pipeline
from chatsky.utils.testing import TOY_SCRIPT_KWARGS, is_interactive_mode
import uvicorn
from fastapi import FastAPI, WebSocket, WebSocketDisconnect
from fastapi.responses import HTMLResponse
[3]:
messenger_interface = CallbackMessengerInterface()
pipeline = Pipeline(
**TOY_SCRIPT_KWARGS, messenger_interface=messenger_interface
)
[4]:
app = FastAPI()
PORT = 8000
html = f"""
<!DOCTYPE html>
<html>
<head>
<title>Chat</title>
</head>
<body>
<h1>WebSocket Chat</h1>
<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();
var ws = new WebSocket(`ws://localhost:{PORT}/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>
"""
@app.get("/")
async def get():
return HTMLResponse(html)
@app.websocket("/ws/{client_id}")
async def websocket_endpoint(websocket: WebSocket, client_id: int):
await websocket.accept()
try:
while True:
data = await websocket.receive_text()
await websocket.send_text(f"User: {data}")
request = Message(data)
context = await messenger_interface.on_request_async(
request, client_id
)
response = context.last_response.text
if response is not None:
await websocket.send_text(f"Bot: {response}")
else:
await websocket.send_text("Bot did not return text.")
except WebSocketDisconnect: # ignore disconnections
pass
[5]:
if __name__ == "__main__":
if is_interactive_mode(): # do not run this during doc building
pipeline.run()
uvicorn.run(
app,
host="127.0.0.1",
port=PORT,
)