Monthly Archives: April 2022

Introduction to Azure Chaos Studio

Some time ago, I investigated the concept of chaos engineering. The principle behind Chaos Engineering is a very simply one: since your software is likely to encounter hostile conditions in the wild, why not introduce those conditions while (and when) you can control them, and then deal with the fallout then, instead of at 3am on a Sunday.

At the time, I was trying to deal with an on-site issue where the connection seemed to be randomly dropping. In the end, I solved this by writing something similar to Polly – albeit a much simpler version.

Microsoft have recently released a preview of something called Chaos Studio. It’s very much in its infancy now, but what is there looks very interesting.

The product is essentially divided into two sections: targets and experiments. Targets represent the thing that you intend to wrought chaos upon, and experiments are how that chaos will be wrought.


For this test, I’m going to use a VM. That’s mainly because what you can do with this product is currently limited to VMs, AKS, and Redis.

Create a VM and Check Availability

The first step is to create a VM. To be honest, it doesn’t matter what the VM is, because all we’ll be doing is switching it off. Start by checking the availability – you should be able to do that in Logs – and you should notice 100% availability, unless something has gone catastrophically wrong with your deployment.


The next step is to configure our target. In chaos studio, select Targets and pick the new VM:

Not that you’ve enabled the targets, you’ll need to grant permission to the chaos studio for the VMs. Inside the VM blade, select Access Control:

If you don’t grant this access, you’ll get a permissions error when you run the experiment. The next step is to create the experiment. In Chaos Studio, select Experiments and then Create:

This will bring up a screen similar to the following:

Let’s discuss a little the concepts here: we have step, branch, and fault. A step is a sequential action that you will execute, whilst a branch is a parallel action; that is, actions in different branches can happen at the same time. A fault is what you actually do – so the fault is the chaos! Let’s add a fault:

This asks me two things, what do I want the fault to happen on (you can only select targets that have previously been created) and what do I want the fault to be. In my case, I’ve created a two step process that turns the machine off, waits a minute, then turns it off again:

Now that the experiment is created, you can start it. You get a warning at this point that basically says “it’s your foot, and you’re currently pointing a high powered rifle at it!”:

If you now run this, and it’s worth bearing in mind that there’s no simulation here – if you do this on production infrastructure it will shut it down for you, then you’ll see the update of it running:

You can drill down into the details to see exactly what it’s doing, what stage, etc.:

The experiment kills the machine for 1 minute, then waits for a minute, then kills it again. If you have a look at the availability graph, you should be able to see that:


So far, I’m pretty impressed with this tool. When they’ve finished (and by that, I mean, they’ve given the ability to create your own chaos, and have expanded the targets to cover the entire Azure ecosystem), it’s going to be a really interesting testing tool.


Azure Friday Introduction to Chaos Studio

Azure Monitor – Failures and Triggering an Alert from Application Insights

Azure Application Monitoring allows for a lot more functionality than just Application Insights. In this post, I’m going to walk through setting up and triggering an an alert.

Before we trigger an alert, we need to have something to trigger an alert for. If you’re reading this, you may already have an app service deployed into Azure, but for testing purposes, I’ve created a fresh MVC template, and added the following code:

This will cause an error when the privacy menu option is pressed, around 1 in 3 times (ctrl-f5 can give you several).


If you have Application Insights set-up for the app service, you can select the Failures blade:

Looking at this image, there’s three points of particular interest. First, I’ve selected the Exceptions tab – this lets me see only the requests and any exceptions that resulted. As you can see, there was a spike where I’ve highlighted. Finally, on the right-hand side of the screen, the exceptions are broken down by type; in this case, I only have one. I can drill into this by selecting the count, or by selecting Samples at the bottom.

The next step is to set up an alert when I get a given number of exceptions.

Creating an Alert

To set up a new alert, select Alerts under Monitoring:

As you can see, it tells us that we have no alerts. In fact, there’s a distinction to be drawn here; what this means is that no alerts have actually been activated. To create a new Alert Rule select Create -> Alert rule:

In creating a new alert, there’s three main things to consider: scope, condition, and action.


The scope of the alert is what it can monitor: that is, what do you want to be alerted about. In our case, that’s the app service:


The next section is condition. There are many options here, but the one that we’re interested for this is Exceptions:

After selecting this, you’ll be asked about the Signal Logic – that is, what is it about the exceptions that you wish to cause an alert. In our case, we want an alert where the number (count) of exceptions exceeds 3 in a 5 minute period:

Once you select this, it’ll give you an idea of what this might cost. In my tests so far, this has been around $1 – 2 / year or so.


The next section is Actions: once the alert fires, what do you want it to do? This brings into play Action Groups. Here, we’ll create a new Action Group

You can tell it here to e-mail, send an SMS, etc.:

It is not obvious (at least to me) from the screen above, but on the right-hand side, you need to select OK before it will let you continue.

We’re going to skip the other tabs in the Action Group and jump to Review + create, then select Create. This will bring you back to the Actions tab, and select that as the default action. You’ll also get a notification that you’re in that action group:

Finally, in Details you can name the alert, and give it a severity; for example:

Once you create this, you’ll be taken back to the Alerts tab – which will still, and confusingly, be empty. You can see your new Alert in the Alert rules section:

Triggering the Alert

To trigger the alert, I’m now going to force my site to crash (as described earlier) – remember that the condition is greater than 3. Once I get four exceptions, I wait for the alert to trigger. At this point, I should get an e-mail, telling me that the alert is triggered:

Finally, we can see that this triggered in the Alerts section. If you drill into this, it will helpfully tell you why it has triggered:

Once the period has passed, and the exceptions have dropped below 4, you’ll get another mail informing you that the danger has passed.


We’ve just scratched the surface of Azure Alerts here, but even this gives us a taste for how useful these things are. In future posts, I’m going to drill into this a bit further.

Azure Automation Run Books – Setup

I’ve recently been investigating Azure Automation RunBooks. Essentially, this gives you a way to execute some code (currently Powershell or Python) to perform some basic tasks against your infrastructure.

For this post, we’ll focus on setting up a (default) runbook, and just making it run. Let’s start by creating an automation account:

From here, you can create your automation account:

Once this creates, it gives you a couple of example run-books:

If we have a look at the tutorial with identity, it gives us the following Powershell Script:

        An example runbook which gets all the ARM resources using the Managed Identity
        AUTHOR: Azure Automation Team
        LASTEDIT: Oct 26, 2021
"Please enable appropriate RBAC permissions to the system identity of this automation account. Otherwise, the runbook may fail..."
    "Logging in to Azure..."
    Connect-AzAccount -Identity
catch {
    Write-Error -Message $_.Exception
    throw $_.Exception
#Get all ARM resources from all resource groups
$ResourceGroups = Get-AzResourceGroup
foreach ($ResourceGroup in $ResourceGroups)
    Write-Output ("Showing resources in resource group " + $ResourceGroup.ResourceGroupName)
    $Resources = Get-AzResource -ResourceGroupName $ResourceGroup.ResourceGroupName
    foreach ($Resource in $Resources)
        Write-Output ($Resource.Name + " of type " +  $Resource.ResourceType)
    Write-Output ("")

Looking at this script, it only really does two things: connects to Azure using managed identity, and then runs through all the resource groups in the subscription and prints them out.

If you run this:

Then you’ll see the following warning in the output (basically saying that you should set-up the permissions, or things won’t work):

If you now switch to Errors, you’ll see a confusing error (caused by the fact that we haven’t set-up the permissions, and so things don’t work):

In order to correct this, you need to give the run-book appropriate permissions. Head over to the automation account resource, and select Identity:

Select Add role assignments.

Because this script is listing the resources in the subscription, you’ll need to be generous with the permissions:

If you run that now, it should display all the resource groups fine:

Composable Delegates

I’ve been playing around with delegates recently, and came across something that was new to me. Whilst I was familiar with the concept of assigning a delegate; for example:

delegate void delegate1();

private static void UseDelegate()
    delegate1 mydelegate;
    mydelegate = func1;


static void func1() =>

I hadn’t realised that it was possible to create a composed delegate, that is, you can simply do the following:

delegate void myDelegate();

private static void ComposableDelegate()
    myDelegate del1 = M1;
    myDelegate del2 = M2;
    myDelegate composedDel = del1 + del2;

private static void M1() => Console.WriteLine("M1");
private static void M2() => Console.WriteLine("M2");

You can do the exact same thing with Action or Func delegates; for example:

Action action = () => Console.WriteLine("M1");
Action action2 = () => Console.WriteLine("M2");
Action composedDel = action + action2;



Combining Delegates