Writing an Azure Function that serves all traffic to a subdomain

Azure Functions default to serving traffic from a path like /api/FunctionName - for example https://your-subdomain.azurewebsites.net/api/MyFunction.

If you want to serve an entire website through a single function (e.g. using Datasette) you need that function to we called for any traffic to that subdomain.

Here's how to do that - to capture all traffic to any path under https://your-subdomain.azurewebsites.net/.

First add the following section to your host.json file:

    "extensions": {
        "http": {
            "routePrefix": ""

Then add "route": "{*route}" to the function.json file for the function that you would like to serve all traffic. Mine ended up looking like this:

    "scriptFile": "__init__.py",
    "bindings": [
            "authLevel": "Anonymous",
            "type": "httpTrigger",
            "direction": "in",
            "name": "req",
            "route": "{*route}",
            "methods": [
            "type": "http",
            "direction": "out",
            "name": "$return"

See https://github.com/simonw/azure-functions-datasette for an example that uses this pattern.

Created 2021-03-27T20:49:56-07:00 · Edit