Custom extensions

It is possible to create your own custom extensions.

Version 22.9 added the Extend.register method. This makes it extremely easy to add custom expensions to an application.

Anatomy of an extension

All extensions must subclass Extension.

Required

name: By convention, the name is an all-lowercase string
startup: A method that runs when the extension is added

Optional

label: A method that returns additional information about the extension in the MOTD
included: A method that returns a boolean whether the extension should be enabled or not (could be used for example to check config state)

Example

from sanic import Request, Sanic, json
from sanic_ext import Extend, Extension

app = Sanic(__name__)
app.config.MONITOR = True

class AutoMonitor(Extension):
    name = "automonitor"

    def startup(self, bootstrap) -> None:
        if self.included():
            self.app.before_server_start(self.ensure_monitor_set)
            self.app.on_request(self.monitor)

    @staticmethod
    async def monitor(request: Request):
        if request.route and request.route.ctx.monitor:
            print("....")

    @staticmethod
    async def ensure_monitor_set(app: Sanic):
        for route in app.router.routes:
            if not hasattr(route.ctx, "monitor"):
                route.ctx.monitor = False

    def label(self):
        has_monitor = [
            route
            for route in self.app.router.routes
            if getattr(route.ctx, "monitor", None)
        ]
        return f"{len(has_monitor)} endpoint(s)"

    def included(self):
        return self.app.config.MONITOR

Extend.register(AutoMonitor)

@app.get("/", ctx_monitor=True)
async def handler(request: Request):
    return json({"foo": "bar"})

Extension preregistration

.. column::

`Extend.register` simplifies the addition of custom extensions.