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Function App

General notes

App hosting options:

• Consumption (serverless)
• Functions Premium (event based scaling isolation - for workloads running continuously; mitigates cold start)
• App service plan (fully isolated + dedicated for workloads that need large SKUs or need to co-locate WebApps and Functions)

Cold start

• Microsoft Blog
  • Stages:
    • azure allocates unspecializesd server
    • worker becomes specialized (files mounted, app settings applied)
    • function runtime resets (function read, extensions loaded)
    • function lodaded into memory
    • FINALLY: Code runs
• To avoid cold start:
  • consider using Premium tier (prefered option)
  • consider dedicated (App Service Plan) - if really needed
• To mitgate issues:
  • Write in C#, F#, Javascript
  • Write shorter code
  • Use less dependencies

Additionally - if used as part of AppScope - may need to set “Always On” How do I decrease the response time for the first request after idle time?

Installation

As per: https://learn.microsoft.com/en-us/azure/azure-functions/functions-run-local?tabs=v4%2Clinux%2Ccsharp%2Cportal%2Cbash#v2

You need this package for Azure Function for Java…

curl https://packages.microsoft.com/keys/microsoft.asc | gpg --dearmor > microsoft.gpg && \
    sudo sh -c 'echo "deb [arch=amd64] https://packages.microsoft.com/repos/microsoft-ubuntu-$(lsb_release -cs)-prod $(lsb_release -cs) main" > /etc/apt/sources.list.d/dotnetdev.list' && \
    sudo mv microsoft.gpg /etc/apt/trusted.gpg.d/microsoft.gpg && \
    sudo apt-get update && \
    sudo apt-get install azure-functions-core-tools-4

Check all stuff:

func --version
az --version

Login:

az login

Serverless architecture.

https://azure.microsoft.com/en-us/solutions/serverless

Creating a function

In .NET functions:

Thje #r "Newtonsoft.json is an external file/dependency:

#r "Newtonsoft.Json"  

using System.Net;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Primitives;
using Newtonsoft.Json;

public static async Task<IActionResult> Run(HttpRequest req, ILogger log) {


    log.LogInformation("C# HTTP Tritgger function processed a request");
    // ...

    // req.Query["name"] -> query valuye
    // req.Body -> body

    string responseMessage = string.IsNullOrEmpty(name) ? "
    Something" : "Something  else";
    return new OkObjectResult(rewsponseMessage);
}

Publishing C# from VisualStudio:

“Your app is currently in read only mode because you are running from a package file. To make any changes update the content in your zip file and WEBSITE_RUN_FROM_PACKAGE app setting”

• simply: https://stackoverflow.com/questions/70046081/azure-function-app-showing-message-your-app-is-currently-in-read-only-mode-becau change setting in description or publish again.