verify-loader-azure-functions.md

Verify Azure Functions host in Loader.io

Loader.io is a nice simple Cloud-based load-testing service. I use it often for load-testing APIs. Before you load test a host you must verify it; you can upload a static file or create a DNS entry. Hosting static files in Azure Functions is tricky and changing the DNS for a Function (without a custom domain) is impossible. But there is a feature called Azure Functions Proxies that can help out.

📖 https://docs.microsoft.com/en-us/azure/azure-functions/functions-proxies

Azure Functions proxies are pretty handy - you can rewrite request URLs and even rewrite requests and responses. One way to do this is create a proxies.json file and upload it with your Functions App code. Example:

{
    "$schema": "http://json.schemastore.org/proxies",
    "proxies": {
        "loader": {
            "matchCondition": {
                "methods": [ "GET" ],
                "route": "/loaderio-f13b281951404283979f7a0050f04c00"
            },
            "responseOverrides": {
                "response.body": "loaderio-f13b281951404283979f7a0050f04c00",
                "response.headers.Content-Type": "text/plain"
            }
        }
    }
}

This proxy, named loader, is configured for any GET request to /loaderio-f13b281951404283979f7a0050f04c00. A response override is configured to respond with a plain-text response of "loaderio-f13b281951404283979f7a0050f04c00". In this scenario I don't even need to back it with a Function. This is all Loader.io needs to verify the Functions host.

I guess I could also host other small static assets like favico in this manner. Pretty sweet!

Read about Azure Function Proxies, response overrides and more here: https://docs.microsoft.com/en-us/azure/azure-functions/functions-proxies#responseOverrides