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All of my children are big fans of Minecraft, and recently my son asked me to help him set up a Minecraft server so he could play online with his friends. Obviously, one option would have been to create a Virtual Machine and install the Minecraft server on that. However, that's quite an expensive option - at about £30 a month for a virtual machine that would sit idle for most of the time.

Now of course in Azure a VM can be put into a "stopped deallocated" state, during which you are not charged for compute. But when you restart the VM, you have a bit of a wait for boot-up, and it will have a different IP address, which my son would then need to communicate to all his friends.

And this is actually a great use case for Azure Container Instances. We can simply ask Azure to spin up a container running the Minecraft server (using a Minecraft server image from Docker Hub), use it, and stop it when we've finished. ACI containers start and stop quickly, and we can assign them a friendly domain name that will remain the same when we start up again. And so long as we map the data folder to an Azure Storage File Share, all the state stored on the server will be persisted while our container is not running. This keeps our costs to a minimum.

In this post, I'll show you how we can automate the creation of all the infrastructure we need with the Azure Az PowerShell module. Normally my preference would be to do this with the Azure CLI, but I'm opting to do this all with the PowerShell module, for reasons I'll explain in a bit.

Get started with Az PowerShell

First, if like me you're fairly new to the Az PowerShell module, here's the basic commands you'll need to get logged in, select your subscription, and explore your resource groups:

# login to Azure PowerShell
Connect-AzAccount

# see what subscriptions are available
Get-AzContext -ListAvailable

# to see the current subscription name
$azContext = Get-AzContext
$azContext.Subscription.Name

# select the subscription we want to use
Set-AzContext -SubscriptionName "My Azure Subscription"

# see what resource groups we have
Get-AzResourceGroup | select ResourceGroupName

Now, let's create a Resource Group to hold the resources we'll create in this demo with New-AzResourceGroup:

# create a resource group
$resourceGroupName = "MinecraftTest"
$location = "westeurope"
New-AzResourceGroup -Name $resourceGroupName -Location $location

Creating a Storage Account and File Share

To ensure that we can persist the state of the server, we need to create Storage Account and a file share within that Storage Account. I've created a PowerShell function called SetupStorage which uses New-AzStorageAccount to create a Storage Account and New-AzStorageShare to create a file share. I wanted this function to be idempotent and not fail if the Storage Account and share already existed, and the way I did that was to use the Get- methods first, with the -ErrorAction SilentlyContinue flag set.

Once we've ensured that the Storage Account and the file share are present, we need to get hold of the Storage Account key with Get-AzStorageAccountKey and turn that into a PSCredential object which we'll need to mount the share as a volume on our container.

function SetupStorage {
    param( [string]$StorageResourceGroupName, 
           [string]$StorageAccountName, 
           [string]$ShareName,
           [string]$Location)

    # check if storage account exists
    $storageAccount = Get-AzStorageAccount `
        -ResourceGroupName $StorageResourceGroupName `
        -Name $StorageAccountName `
        -ErrorAction SilentlyContinue

    if ($storageAccount -eq $null) {
        # create the storage account
        $storageAccount = New-AzStorageAccount `
            -ResourceGroupName $StorageResourceGroupName `
            -Name $StorageAccountName `
            -SkuName Standard_LRS `
            -Location $Location
    }

    # check if the file share already exists
    $share = Get-AzStorageShare `
        -Name $ShareName -Context $storageAccount.Context `
        -ErrorAction SilentlyContinue

    if ($share -eq $null) {
        # create the share
        $share = New-AzStorageShare `
            -Name $ShareName `
            -Context $storageAccount.Context
    }

    # get the credentials
    $storageAccountKeys = Get-AzStorageAccountKey `
        -ResourceGroupName $StorageResourceGroupName `
        -Name $StorageAccountName

    $storageAccountKey = $storageAccountKeys[0].Value
    $storageAccountKeySecureString = ConvertTo-SecureString $storageAccountKey -AsPlainText -Force
    $storageAccountCredentials = New-Object System.Management.Automation.PSCredential ($storageAccountName, $storageAccountKeySecureString)
    
    return $storageAccountCredentials
}

Now we have the SetupStorage function, let's pick a name for the Storage Account and file share and get hold of the credentials.

$storageAccountName = "minecraft20190514" # must be unique across azure
$shareName = "minecraft"
$storageAccountCredentials = SetupStorage `
    -StorageResourceGroupName $resourceGroupName `
    -StorageAccountName $storageAccountName `
    -ShareName $shareName `
    -Location $location

Creating an ACI Container Group

Now we're ready to create the container group that will run the Minecraft server. First we need to pick a name for the container group and a unique DNS name prefix to give our Minecraft server a friendly DNS name. We also need to set up some environment variables - one to accept the EULA, and one to set a particular Minecraft user as the admin for this server (this will get written into the ops.json file in the file share the first time this container starts up).

We can create the container group with New-AzContainerGroup and the DOcker image we're using is itzg/minecraft-server from Docker Hub which is a well maintained Minecraft server image with options to configure Bukkit and Spigot (not claiming to know what they are, but my kids tell me they're good!). I need to ensure the container group has a public IP address, and mounts the file share to the /data path. We also need to open the default Minecraft server port of 25565.

$containerGroupName = "minecraft20190514"
$dnsNameLabel = "minecrafttest"
$environmentVariables = @{ EULA = "TRUE"; OPS = "YourMinecraftUserName";
}

New-AzContainerGroup -ResourceGroupName $resourceGroupName `
    -Name $containerGroupName `
    -Image "itzg/minecraft-server" `
    -AzureFileVolumeAccountCredential $storageAccountCredentials `
    -AzureFileVolumeShareName $shareName `
    -AzureFileVolumeMountPath "/data" `
    -IpAddressType Public `
    -OsType Linux `
    -DnsNameLabel $dnsNameLabel `
    -Port 25565 `
    -EnvironmentVariable $environmentVariables

And with that one command, our Minecraft server will be up and running. It will start up very quickly, and we can check up on its status with Get-AzContainerGroup which will tell us the fully qualified domain name of the server.

# check up on the status
$containerGroup = Get-AzContainerGroup -ResourceGroupName $resourceGroupName -Name $containerGroupName

# view the domain name (e.g. minecrafttest.westeurope.azurecontainer.io)
$containerGroup.Fqdn

Starting and stopping the container group

I was hoping that the PowerShell Az module would have a nice and simple command to start and stop container groups like you can with the Azure CLI's az container stop and az container start commands. Unfortunately equivalent commands haven't been created for the Azure Az PowerShell module yet (please vote for my feature request here).

How can we start and stop the container without built-in commands? Well, we can call the Azure REST API's directly, such as this API to stop a container group. However, we need to provide a bearer token, and this turned out to be a challenge to get hold of. After a bit of experimenting, I found that the following code could get me a valid bearer token I could use to call the Azure REST API.

function Get-AccessToken($tenantId) {
    $azureRmProfile = [Microsoft.Azure.Commands.Common.Authentication.Abstractions.AzureRmProfileProvider]::Instance.Profile;
    $profileClient = New-Object Microsoft.Azure.Commands.ResourceManager.Common.RMProfileClient($azureRmProfile);
    $profileClient.AcquireAccessToken($tenantId).AccessToken;
}

With that in place, we can define a Send-ContainerGroupCommand function that can call any of the start, stop, and restart endpoints for container groups:

function Send-ContainerGroupCommand($resourceGroupName, $containerGroupName, $command) {
    $azContext = Get-AzContext
    $subscriptionId = $azContext.Subscription.Id
    $commandUri = "https://management.azure.com/subscriptions/$subscriptionId/resourceGroups/$resourceGroupName/providers/Microsoft.ContainerInstance/containerGroups/$containerGroupName/$command" + "?api-version=2018-10-01"
    $accessToken = Get-AccessToken $azContext.Tenant.TenantId
    $response = Invoke-RestMethod -Method Post -Uri $commandUri -Headers @{ Authorization="Bearer $accessToken" }
    $response
}

And then creating our own helper functions to stop and start container groups becomes easy:

function Stop-ContainerGroup($resourceGroupName, $containerGroupName) {
    Send-ContainerGroupCommand $resourceGroupName $containerGroupName  "stop"
}

function Start-ContainerGroup($resourceGroupName, $containerGroupName) {
    Send-ContainerGroupCommand $resourceGroupName $containerGroupName "start"
}

function Restart-ContainerGroup($resourceGroupName, $containerGroupName) {
    Send-ContainerGroupCommand $resourceGroupName $containerGroupName "restart"
}

So now I can stop the Minecraft server we just created with this command:

Stop-ContainerGroup $resourceGroupName $containerGroupName

The great thing about this is that we are no longer paying anything for our container group - they are free while in the stopped state. The only cost is associated with what's in the file share. And when we restart the container group, it will come back up with the same domain name. This is great to allow my children to share the address of the server with their friends, which can remain constant. In fact, I was able to map a custom domain with a DNS CNAME record to the container group's domain name to make the server address even easier to share.

Summary and what's next?

In this post we saw how to fully automate the creation of a Minecraft server running in Azure Container Instances, along with a file share that can persist the server data. But obviously whenever my children want to start the server, they need me to connect to Azure PowerShell and run the start command. And I also need to remember to stop the server at the end of the gaming session or I'll end up with an unexpectedly high bill.

So what would be great next is to automate the process, so I can give my children a way to start the server themselves, that doesn't require them to have access to my Azure subscription, and also a way to automatically shut it down after a certain elapsed duration.

Now that Azure Functions v2 supports PowerShell functions, and integrates directly with the Az Module, it's an obvious choice for the automation. So I'm hoping to follow on with another post soon showing how we can create a PowerShell Azure Functions App to automate the starting and stopping of the Minecraft container.

Want to learn more about how easy it is to get up and running with Azure Container Instances? Be sure to check out my Pluralsight course Azure Container Instances: Getting Started.

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I've finally got round to releasing NAudio 1.9.0. The big news is that this version targets .NET Standard 2.0, opening the door to NAudio being used on a wider variety of platforms.

Of course, it's important to point out that a large part of NAudio consists of wrappers for various Windows APIs, giving you access to audio input and output devices, as well as taking advantage of audio codecs from ACM or Media Foundation. None of that functionality will work cross-platform, as it's relying on underlying Windows components to do its work.

But there is still a lot of NAudio that is portable to other platforms, so hopefully this will prove useful to people. In addition to targeting .NET Standard 2.0, NAudio still supports .NET 3.5 and also UAP 10.0.240, thanks to the very helpful MSBuild.Sdk.Extras tools from Oren Novotny.

There are a few minor bugfixes included in the latest release. Probably the most notable is that AsioOut no longer auto-stops when it reaches the end of playback. That caused serious problems with many ASIO drivers, so it's disabled by default, although you can restore the original behaviour if you want.

Future of NAudio

I should probably say a few words about the future of NAudio. Although I continue to reply to the many questions asked on GitHub and Stack Overflow every day, you've probably noticed that development hasn't proceeded very rapidly in recent years. That's due to the fact that I simply no longer have the time I used to for maintaining an open source project. My day job is very focused on Azure now, and for the last four years I haven't needed to use NAudio as part of my daily work.

What this means is that NAudio 1.9.0 is not likely to pick up major new features. I'll probably still fix a few bugs from time to time, and when there are pull requests that I am able to easily verify don't break existing functionality (which is not always possible unfortunately), I will also endeavour to accept them into the project as well.

If there were ever to be a version 2 of NAudio, then it would make sense to rethink a number of the core design decisions, in particular to incorporate new language innovations like Span<T> and compiler intrinsics which could bring major performance improvements. I have done a fair bit of experimentation with this (you can see some of my efforts here), and maybe in the future I'll find time to do some more work on that. But unless I find myself actively using NAudio for commercial development again, which doesn't seem likely in the near future, progress is likely to be slow.

So I guess the summary is that although NAudio isn't "dead", it is currently in "maintenance mode". It's a project that means a lot to me - I started it back in 2002 as my first ever open source application, and I'm very glad that it's been of use to so many people over the years. But my focus currently is much more in the Azure space.

If there is anyone out there interested in becoming a maintainer of NAudio, I would be glad to have a conversation with you. And to all those who are still waiting for replies to your questions and requests for help, please accept my apologies - the volume is now too great for me to respond to everything.

I know that several long-running open-source projects with lone maintainers are facing similar issues. Geoff Huntley hosted a fascinating discussion about this problem at the Microsoft MVP Summit earlier this year. And one of my programming heroes, Alexandre Mutel, recently took the decision to retire SharpDX. Maybe there will come a time where I need to do the same, but I'm not completely stepping away just yet.

Want to get up to speed with the the fundamentals principles of digital audio and how to got about writing audio applications with NAudio? Be sure to check out my Pluralsight courses, Digital Audio Fundamentals, and Audio Programming with NAudio.

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Back in January 2017 I released my Azure Functions Fundamentals Pluralsight Course. But of course a lot has happened in the world of Azure Functions in the last two years, and so I'm pleased to announce that I have just released a completely updated version of my course that covers Azure Functions v2.

It is a complete re-record of the entire course, and is now just over three and a half hours long. Some of the new things that I've been able to include this time round are:

I've also put the demo code from the course up on GitHub, allowing me to keep it updated to reflect the latest changes to Azure Functions.

Azure Functions remains one my favourite Azure services. It's great to see just how far it's come in the past two years, and the amazing team behind Azure Functions is continuing to improve it with all kinds of new capabilities, so I'm sure that it won't be too long before another round of updates to my course are required.

Anyway I hope you enjoy the updated course!