Today I'm going to go through how you can setup automatic deployments when using a combination of Azure App Service (e.g. a Web App), deployment slots on the App Service and GitHub Actions. This is a setup to achieve zero downtime.

What are GitHub Actions?

GitHub Actions are the continuous integration and continuous delivery (CI/CD) platform from GitHub. If you're working with the Microsoft tech stack you may have used tools such as Team City or Azure Dev Opps in the past and this is just GitHubs version. Like the newer Azure Devops pipelines GitHub Actions define the pipeline in yaml files and while they are not the same they are very similar.

What are App Service Deployment Slots?

Deployment slots solve two issues; Firstly they allow zero downtime deployments by deploying the application to a separate instance to production, warming up that instance and then swapping it. Secondly, they can also be used as separate environments to preview changes without affecting the production code.

One thing to note is that although they are separate from the production code, they do share the same resources. So if your change has a processor-hungry bug, then that will have an affect your live environment. For this reason its also best to not leave them running all the time.

Configure App Service Deployment Slows

As a pre-requisite you need an App Service configured in Azure. Once you have this head to the Deployment slots section in the left nav.

Click the Add Slot button, and create a slot named staging.

Auto Swap Slots

At this point you could setup a deployment pipeline that deploys to the staging slot and then performs a slot swap, to change which one is in production. However Azure has a nifty setting that will do this all for you.

Click into the Deployment slot you just created and then go to Configuration, in the left-hand nav.

Switch to the General settings tab.

Scroll down to a section called Deployment Slot, and turn on auto swap. Within the drop-down select production.

Now when a deployment is made to the staging slot it will warm up and then automatically swap with the production slot.

Configure GitHub Action

To configure the GitHub Action first make sure you are still in the staging deployment slot and select Deployment Center in the left nav.

From the source drop-down select GitHub.

Next select the Organization, Repository and branch to deploy for. This will give you the option to add a workflow. You may need to edit this file to get the build to work as needed but, this will provide the basics for building a .NET application and configuring the publish profile to get it into Azure.

Normally when I work with SQL Azure I handle DB schema changes with Entity Framework migrations. However if you using Azure Functions rather than Web Jobs it seems there's a number of issues with this and I could not find a decent guide which resulted in a working solution.

Migrations isn't the only way to release a DB change though. SQL Server Database projects have existed for a long time and are a perfectly good way of automating a DB change. My preference to use EF Migrations really comes from a place of not wanting to have an EF model and a separate table scheme when they're essentially a duplicate of each other.

Trying to find out how to deploy this through Azure Devops Pipelines however was far harder than I expected (my expectation was about 5 mins). A lot of guides weren't very good and virtually all of them start with Click new pipeline, then select Use the classic editor. WAIT Classic Editor on an article written 3 months ago!?!?! Excuse me while I search for a solution slightly more up to date.

Creating a dacpac file

High level the solution solution is to have a SQL Server Database project, use an Azure Pipeline to compile that to a dacpac file. Then use a release pipeline to deploy that to the SQL Azure DB.

I'm not going to go into any details about how you create a SQL Server Database project, its relatively straightforward, but the one thing to be aware of is the project needs to have a target platform of Microsoft Azure SQL Database otherwise you'll get a compatibility error when you try to deploy.

Building a SQL Server Database project in Azure Devops

To build a dacpac file create a new pipeline in Azure Devops (the yaml kind), select your repo and get yourself a blank configuration file. Also at this point make sure your code is actually in the repo!

The configuration I used looks like this; I've included notes in the code to explain what's going on.

Releasing to SQL Azure

Once the pipeline has run you should have an artifact coming out of it that contains the dacpac file.

To deploy the dacpac to SQL Azure you need to create a release pipeline. You can do this within the build pipeline, but personally I think builds and releases are different things and should therefore be kept separate. Particularly as releases should be promoted through environments.

Go to the releases section in Azure Devops and click New and then New release pipeline.

There is no template for this kind of release, so choose Empty job on the next screen that appears.

On the left you will be able to select the artifact getting built from your pipeline.

Then from the Tasks drop down select Stage 1. Stages can represent the different environments your build will be deployed to, so you may want to rename this something like Dev or Production.

On Agent Job click the plus button to add a task to the agent job. Search for dacpac and click the Add button on Azure SQL Database deployment.

Complete the fields to configure which DB it will be deployed to (as shown in the picture but with your details).

And that's it. You can now run the pipelines and your SQL Project will be deployed to SQL Azure.

Some other tips

On the Azure SQL Database deployment task there is a property called Additional SqlPackage.exe Arguments this can be used to specify things like should loss of data be allows. You can find the list of these at this url https://docs.microsoft.com/en-us/sql/tools/sqlpackage/sqlpackage?view=sql-server-ver15#properties

If you are deploying to multiple environments you will want to use variables for the server details rather than having them on the actual task. This will make it easier to clone the stages and have all connections details configured in one place.

One of the cache’s that Sitecore has is the Media Cache. Whenever you use an image from Sitecore’s media library, Sitecore will retrieve the image from the database, scale it to the size you requested and then store it to disk in the media cache folder. On any subsequent request the image will now be retrieved from the media cache rather than the database.

By default each content management and content delivery server will locate the media cache in /App_Data/MediaCache

This is a relatively logical place to store a cache for images that wont cause you many issues. However, if you have automated deployments setup then you are likely wiping the whole of your website folder each time you do a deploy to ensure that your deploy remains the same on all environments. As the App_Data folder is in the website, your Media Cache will be deleted too.

Depending on your site then deleting the media cache potentially isn’t much of an issue. After all it’s a cache so all that will happen is the images will get cached the next time they are requested. But depending how many images get retrieved at the same time this could slow down performance, particularly if your content editors decided to put every image they ever uploaded into the same folder. Opening the that folder in the admin will create a nice amount of load on your server, particularly if you also have some extra image optimization logic installed.

Like most things in Sitecore though, you can change the location through a config setting.

In Sitecore.config you will find a property called Media.CacheFolder. Change this to somewhere outside of your website folder and Sitecore will now start storing the Media Cache in this location and it will be safe your all your deploys.