How to use an aiohttp ClientSession with Sanic?

Question

I am trying to understand what is the right way to use aiohttp with Sanic.

From aiohttp documentation, I find the following:

Don’t cr

Answer 1

In order to use a single aiohttp.ClientSession we need to instantiate the session only once and use that specific instance in the rest of the application.

To achieve this we can use a before_server_start listener which will allow us to create the instance before the app serves the first byte.

from sanic import Sanic 
from sanic.response import json

import aiohttp

app = Sanic(__name__)

@app.listener('before_server_start')
def init(app, loop):
    app.aiohttp_session = aiohttp.ClientSession(loop=loop)

@app.listener('after_server_stop')
def finish(app, loop):
    loop.run_until_complete(app.aiohttp_session.close())
    loop.close()

@app.route("/")
async def test(request):
    """
    Download and serve example JSON
    """
    url = "https://api.github.com/repos/channelcat/sanic"

    async with app.aiohttp_session.get(url) as response:
        return await response.json()


app.run(host="0.0.0.0", port=8000, workers=2)

Breakdown of the code:

• We are creating an aiohttp.ClientSession, passing as argument the loop that Sanic apps create at the start, avoiding this pitfall in the process.
• We store that session in the Sanic app.
• Finally, we are using this session to make our requests.