Flask-like “global” request context in Sanic (asyncio)

Hi there! Ani here. I am a Polyglot Software Engineer hacking away from the sunny shores of Singapore 🇸🇬.

Whatever you read here, are my opinions in my personal capacity.

aiotask-context

This nifty Python module can maintain a distinct context against each asyncio Task. Which means, each request can have an associated context we can use to store and pass around passive details.

$ pip install aiotask-context

from sanic import Sanic from sanic.response import json # import aiotask-context import aiotask_context as context app = Sanic() # hook aiotask-context @app.listener('after_server_start') async def hook_context(app, loop): loop.set_task_factory(context.task_factory) @app.route("/") async def test(request): return json({"hello": "world"}) if __name__ == "__main__": app.run(host="0.0.0.0", port=8000)

Now we have a simple Sanic app with the context hooked up.

Implementing Correlation ID Generation and Passing

Now, let’s grab the correlation ID if it comes with the request, or generate our own otherwise. Afterwards, we need to save that value to the context for future use in other parts of the code (i.e. logging, requests to other microservices and so on).

from uuid import uuid4 import aiotask_context as context @app.middleware('request') async def handle_correlation_id(request): cid = request.headers.get('X-Correlation-ID') or str(uuid4()) context.set('cid', cid)

And throughout the code, if you need the cid or any context value you have set, simply use context.get(key).

And the last step is definitely all about responding with the Correlation ID. We’ll be sticking to the middleware for this too. We just need to update the response object from the context.

@app.middleware('response') async def insert_correlation_id(request, response): response.headers["X-Correlation-ID"] = context.get('cid')

Great! Now we don’t have to write spaghetti code and get lost in passing CIDs from functions to functions. Cheers!

Flask-like “global” request context in Sanic (asyncio)

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More from this blog

aiotask-context

Implementing Correlation ID Generation and Passing