Rhubarb is a library that simplifies realtime streaming for a number of backends into a single API
Project description
Rhubarb
Rhubarb is a library that simplifies realtime streaming of events for a number of backends in to a single API. Currently supports Postgres, kafka, RabbitMQ, redis as well as an internal memory backend useful for testing.
Installation
There are a number of backends that can be used with Rhubarb:
| Kafka | Postgres | Redis | RabbitMQ |
|---|---|---|---|
pip install rhubarb-py[kafka] |
pip install rhubarb-py[postgres] |
pip install rhubarb-py[redis] |
pip install rhubarb-py[rabbitmq] |
Backends
Rhubarb("redis://localhost:6379/0")Rhubarb("kafka://localhost:9092")Rhubarb("postgres://postgres:postgres@localhost:5432/rhubarb")Rhubarb("amqp://guest:guest@localhost/")Rhubarb("memory://")
Quick start
Simple event consumer
async with Rhubarb("redis://localhost:6379/0") as events:
async with events.subscribe(channel="CHATROOM") as subscriber:
async for event in subscriber:
await websocket.send_text(event.message)
Simple event producer
async with Rhubarb("redis://localhost:6379/0") as events:
await events.publish("test message")
History retrieval
async with Rhubarb("redis://localhost:6379/0") as events:
async with events.subscribe(channel="CHATROOM", history=10) as subscriber: # read the last 10 events published to the channel
async for event in subscriber:
await websocket.send_text(event.message)
Custom serializer & deserializer
async with Rhubarb("redis://localhost:6379/0", serializer=json.dumps, deserializer=json.loads) as events:
async with events.subscribe(channel="CHATROOM", history=10) as subscriber: # read the last 10 events published to the channel
async for event in subscriber:
await websocket.send_text(event.message)
Group subscribing (at-most-once processing)
async with Rhubarb("redis://localhost:6379/0", serializer=json.dumps, deserializer=json.loads) as events:
async with events.subscribe(
"TEST-GROUP-CHANNEL", group_name="TEST_GROUP", consumer_name="sub_1"
) as subscriber_1:
async for event in subscriber:
await process_job(event)
Example
A minimal working example can be found in example directory.
import os
from starlette.applications import Starlette
from starlette.concurrency import run_until_first_complete
from starlette.responses import HTMLResponse
from starlette.routing import Route, WebSocketRoute
from rhubarb import Rhubarb
URL = os.environ.get("URL", "redis://localhost:6379/0")
events = Rhubarb(URL)
html = """
<!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 ws = new WebSocket("ws://localhost:8000/ws");
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>
"""
async def homepage(_):
return HTMLResponse(html)
async def room_consumer(websocket):
async for message in websocket.iter_text():
await events.publish(channel="chatroom", message=message)
async def room_producer(websocket):
async with events.subscribe(channel="chatroom") as subscriber:
async for event in subscriber:
await websocket.send_text(event.message)
async def ws(websocket):
await websocket.accept()
await run_until_first_complete(
(room_consumer, {"websocket": websocket}),
(room_producer, {"websocket": websocket}),
)
routes = [
Route("/", homepage),
WebSocketRoute("/ws", ws, name="chatroom_ws"),
]
app = Starlette(
routes=routes,
on_startup=[events.connect],
on_shutdown=[events.disconnect],
)
🛡 License
This project is licensed under the terms of the MIT license. See LICENSE for more details.
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