Azure Function learning

I’m playing around with an Azure Function that I’m going to eventually call from an Azure Automation runbook (post to come in the near future).

During this process, I learned some pretty key things as I was testing and going along. I’m a little embarrassed to post them publicly, but eventually a non-coder like myself somewhere is going to be trying the same thing and maybe this will help.

Function error-ing out during testing

In my function, I used a ForEach loop to add a string to a List<string> for each instances of a collection. My function would compile just fine but would always error out on this one line, with a really generic error. I only knew it was erroring out on this line because I placed a log output on the next line and it would never reach it.

[Error] Executed 'Functions.HttpTriggerCSharp2'

This was my poor coding skills, not beginning the list properly. I was starting it like this:

List<string> collectedIP = null;
But it really needed to be this to initialize it properly:
List<string> collectedIP = new List<string>();
Without this, adding to the collection isn’t possible. I’m sure that anyone who actually knows C# is shaking their head reading this, but I guess that’s what you get when you learn organically without real training.

Building the query string

I want to pass in a parameter to my function, using the query string. At the same time, I also want to use a function key so that this can’t be run anonymously.

Originally, I was trying this, with the ampersand delineating the second query parameter (after the function key):

Invoke-WebRequest https://appname.azurewebsites.net/api/functionName?code=functionKey&amp;name=www.microsoft.com

In PowerShell, this returned the error:

The ampersand (&amp;) character is not allowed. The &amp; operator is reserved for future use; wrap an ampersand in double quotation marks ("&amp;") to pass it as part of a string.

So I tried this string:

Invoke-WebRequest 'https://appname.azurewebsites.net/api/functionName?code=functionKey"&amp;"name=www.microsoft.com'

But then I received the error:

Invoke-WebRequest : The remote server returned an error: (401) Unauthorized.

Well, I knew it wasn’t unauthorized because it ran properly in the browser. The actual fix was stupidly easy, I hadn’t put any quotes around the whole string – either single or double quotes was fine:

Invoke-WebRequest "https://appname.azurewebsites.net/api/functionName?code=functionKey&amp;name=www.microsoft.com"

TLS Support in PowerShell

When I got to actually testing my function, I tried to call it from PowerShell in this format:

Invoke-WebRequest 'https://appname.azurewebsites.net/api/functionName?code=functionKey'

However, upon doing so I received this error:

iwr : The underlying connection was closed: An unexpected error occurred on a send.

A google search led me to discover that PowerShell by default will attempt to use TLS 1.0 for Invoke-WebRequest, unless you’re using PowerShell Core 6.

My Azure Function uses TLS 1.2 by default and as a minimum. This can be found on the “Platform Settings” page of the Function, under “SSL”:

The solution (at least as a workaround) is to force that session to use TLS 1.2 like this:

[System.Net.ServicePointManager]::SecurityProtocol = [System.Net.SecurityProtocolType]::Tls12

Primary source for this information was here.

 

 

 

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