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:

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

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:

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

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