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Running Azure Functions in IIS

Have you ever wanted to run Azure Functions in IIS? No? "Why would you want to run serverless functions in IIS," you ask.

I won't try to answer why, but I can tell you how. I recently needed to do this and found a void where info should be, so this post is to fill that void.

In Azure, functions are hosted in IIS. (Weird right? Like, I assumed it was something sophisticated and new, not just some duct tapey IIS plugin thing.) I want to find out how much of a function app we can get functioning on-prem with IIS. Yeah, we could just run azure function core tools, but what would we learn from following that well-documented process?

πŸŽͺ Basic IIS setup

Let's add a plain, empty site, and bind it to a really good domain.
Plain empty site in IIS

Since we used a really good domain, we'll need to update our hosts file.
Hosts file entry for no good reason

Here's quick test to prove that IIS is set up OK.
Sweet new web page

Cool so we have a site set up in IIS, and we can deploy a function app to it. Next we'll make a function app, give it a bunch of trigger types, just to see which triggers work in this janky setup.

πŸ§ͺ A Guinea Pig Function App

Here's a link to the source code.

Pretty basic, there's are 4 triggers, and each one just logs. There's a timer, HTTP, queue, and blob trigger. It's logging to a file, so that when it's silently running in IIS, I can see the function app is doing stuff.

public IActionResult TestHttp(
    [HttpTrigger(AuthorizationLevel.Anonymous, "get", "post", Route = null)] HttpRequest req)
    logger.LogInformation("HttpTrigger ran");
    return new OkObjectResult("Perfect! πŸ™ƒ");

public void TestQueue([QueueTrigger("iis-q-test")]string item)
    => logger.LogInformation($"QueueTrigger ran value: {item}");

public void TestStorage([BlobTrigger("iis-blob-test/{name}")]Stream blob, string name)
    => logger.LogInformation($"BlobTrigger ran file name: {name}, size: {blob.Length}");

public void TestTimer([TimerTrigger("*/20 * * * * *")]TimerInfo timer)
    => logger.LogInformation($"TimerTrigger ran"); 

I have confirmed that, running from Visual Studio, the function app works as expected. All triggers work and log as configured.

Next from Visual Studio, I'll publish locally to the web site folder. πŸ’₯

func app site looking broke

Yeah, of course that doesn't work. I haven't configured IIS to know what to do with a function app.

🀫 Azure Function IIS Secret Sauce

Check out this cool github page. Azure Functions Host has releases like this one, 3.0.BLAH which we can download and use with IIS.

Download and unzip the somewhere. Next make a web.config file where your function app is published. In the web.config, configure IIS to run aspNetCore module for all paths and verbs, and set the processPath for aspNetCore to the path of Function Host's Microsoft.Azure.WebJobs.Script.WebHost.exe file.

Like this:

<?xml version="1.0" encoding="utf-8"?>
      <remove name="aspNetCore" />
      <add name="aspNetCore" path="*" verb="*" modules="AspNetCoreModuleV2" resourceType="Unspecified" />
    <aspNetCore processPath="C:\hosting\Functions.3.0.14191\3.0.14191\64bit\Microsoft.Azure.WebJobs.Script.WebHost.exe" hostingModel="InProcess">
        <environmentVariable name="AzureWebJobsStorage" value="UseDevelopmentStorage=true" />

Now what do we get?
For real tho?

Weird, right? It's that default page that you get in azure. What about when we hit the HttpTrigger route?

So HTTP works of course. What about the other triggers? The log says

2020-07-19 21:28:00.0158|INFO|IIS.FuncTest.Tests|TimerTrigger ran
2020-07-19 21:28:20.0162|INFO|IIS.FuncTest.Tests|TimerTrigger ran
2020-07-19 21:28:36.0969|INFO|IIS.FuncTest.Tests|QueueTrigger ran value: adsf
2020-07-19 21:28:40.0181|INFO|IIS.FuncTest.Tests|TimerTrigger ran
2020-07-19 21:28:43.7516|INFO|IIS.FuncTest.Tests|HttpTrigger ran
2020-07-19 21:28:44.1831|INFO|IIS.FuncTest.Tests|BlobTrigger ran file name: 2019_TaxReturn.pdf, size: 637435
2020-07-19 21:29:00.0530|INFO|IIS.FuncTest.Tests|TimerTrigger ran
2020-07-19 21:29:20.0069|INFO|IIS.FuncTest.Tests|TimerTrigger ran

🌻 Summary

Yeah, you can run azure functions in IIS and the vanilla triggers work just fine, and there's really just 2 steps to get it working.

  1. Download the functions runtime
  2. Point to it from your web.config

I'd love to see someone get durable functions working.

Top comments (19)

icyfire0573 profile image

Building on your article, I went through this myself and ran into a bunch of issues. I tried to put it all together in this github GIST. Talks about what to install and common trooubleshooting issues

jakenuts_6 profile image
jakenuts ✊🏽🌎❀️πŸ”₯

I’m pretty sure 90% of Azure is IIS awkwardly canvassed by disgruntled SharePoint devs.

So, after a long & costly β€œmove it all to app services” experiment, I’m going back to my VM and unadulterated IIS - but what to do with the darn functions was an open question, thanks for the info!

hariss profile image

Whenever I publish azure function its not generating IIS.deps.json config file for me. Correct me if I'm wrong, I believe my function app is not running due to missing of that config file. If I miss any configuration please guide me.

ductranit profile image

Thanks for your great article.
I tried your setup and get the web.config error "The requested page cannot be accessed because the related configuration data for the page is invalid"
I pointed to correct path to Microsoft.Azure.WebJobs.Script.WebHost.exe
Do you have any idea for it?

gjcampbell profile image

Yes! You might need to install ASP.NET Core Runtime Hosting Bundle

hosting bundle

jakenuts_6 profile image
jakenuts ✊🏽🌎❀️πŸ”₯

As I pull back from expensive & slow app service plans to a VM this is a godsend. Have my functions running in IIS without a hitch. I tried making them scheduled tasks at first (mostly timer based) but this is 100% easier especially in deployment. Deploying a local service or scheduled task required lots of extra work, but Devops IIS WebApp deployment is a treat.

psaillesh profile image
Saillesh pawar

This is amazing, never ever thought of running an Azure function in IIS.

abdmabdullah profile image

Great article. I used this tutorial to set up Azure functions on IIS.

However, now I'm unable to use them with my Blazor application, because CORS apparently isn't working. Did you encounter something like this or do you have any idea how to handle this in IIS?

ankitjain0906 profile image

What if a function app has Authorizationlevel set as Function. The call from postman will fail. Anyway to handle this.
Sorry if this question is weird, I am comparatively new to function app. I know that there needs to be a key to call function apps with Auth level other than Anonymous but don't know where to get and set that key to be able to work with IIS

pavanpillay profile image

Did you get any ways to handle this one with AuthorizationLevel.Function ?

pavanpillay profile image


I followed the same steps and i am able to run the function app but when i create new function and run, i am not getting the results.

Image description

When i try to run the same from visual studio, i get the response. any idea if i am missing anything here ?

psaillesh profile image
Saillesh pawar

I just tried running my timer trigger azure function and followed the steps mentioned above. but I am getting Function host is not running.
Any idea about this error and root cause.

manjerekarrao profile image

the azure function is running as expected locally. however, i'm not able to see those logs

manjerekarrao profile image

i tried adding a ServiceBusTrigger and deployed it locally.

But i see that the function is not running.

erro - Function host is not running.

thescifibrarian profile image
Danielle Mayabb

I'm having the same issue. My function will run locally, but the function host won't run on IIS. I've tried downloading different versions of it, as well as various versions of the .NET hosting bundle (3.1, 5, 6). No luck. Did you ever solve?

themajix profile image
Majid Shams • Edited

Nice article, thank you. You can find a web.config file having almost the same contents in Azure, inside this folder: "D:\Program Files (x86)\SiteExtensions\Functions\3.0.14251\64bit":

sagar_narkar_80189b74f96c profile image
Sagar Narkar

I just tried running my timer trigger azure function and followed the steps mentioned above. But Timer trigger not getting executed in IIS. Please Help

andreabnm13 profile image
Andrea • Edited

I followed the article, but something doesn't work for me. I can browse to the landing page, but the endpoint are unreachable. What can I check out?

andreabnm13 profile image

SOLVED: i didn't realized you don't have to deploy all the AzureFunction folder but only the content of the bin folder on the root of the site