Back when we all used Azure Cloud Services for running websites and backend worker tasks, we had the fabulous concept of deployment slots. Since January 2014, this concept was also introduced in the offering than called Azure Websites. Now, in Azure App Services Web Apps, the concept is still alive.

• For every web app, Azure provides four non-production deployment slots on which we can deploy the website. Every deployment slot provides a different URL to access the web app for the verification of the application. What is the usage of Deployment Slots? Deployment slots provide the option to deploy websites in other environments rather than.
• Change deployment slots for a web app. Az webapp deployment source: Manage web app deployment via source control. Az webapp deployment source config: Manage deployment from git or Mercurial repositories. Az webapp deployment source config-local-git: Get a URL for a git repository endpoint to clone and push to for web app deployment.

What is a deployment slot?

Web Apps for Containers allows you to use Linux-based containers to deploy your application into an Azure App Services Web App. This way, you can make sure that the environment that you use locally, is exactly the same as the one in the cloud. Limitations at this tier includes support for only a single SSL certificate per Plan. If you can leverage SNI then you can run multiple web apps on SSL. If not, it’s one app per Plan then! If you need to connect to a private Azure network or use Deployment Slots then this tier is also not suitable for you. Azure: Pricing of deployment slots for an Azure App Service. Using an S1 App Service Plan, my web site has up to 5 slots for web app staging. How are those slots charged? Are they billed only if used? Included in the S1 fee? Or something else.

Basically, a deployment slot is another Web App that runs next to your original one. This means that you could create a deployment slot for your production environment and call that the pre-production slot, or staging slot, as in the illustration below:

At the time of this writing, you can create up to:

Azure Web App Deployment Slots Pricing List

• 4 slots for Web Apps in the standard tier in addition to production
• 19 slots in the premium tier in addition to production

Note that a deployment slot is a fully fledged Web App, hosted in the same pricing tier as the Web App it is spawned from. Therefore it will incur costs.

Benefits

Azure Web App Deployment Slots Pricing Guide

Using a deployment slot can provide the following benefits:

• Test it in pre-production - you can deploy a pre-production version of your site and test it before it goes into production. You can do functional and automated testing on this, and also use it to do performance testing, to make sure that everything is alright without testing in production
• Easily deploy - once you are happy that your website in the staging slot works as expected, you can use the swap function (or even use Auto Swap) to get your version seamlessly in production.
  • What happens here, is that the Virtual IP Address of the swap target (in my example the production slot) is re-pointed to the swap source (the staging slot) and vice versa.
  • Also, before the swap happens, the website in the staging slot is pre-warmed to make sure that the website is ready to go when you swap it
  • These mechanisms ensure that there is no downtime when you swap and makes for a great deployment mechanism
• Revert deployment - If for whatever reason, you’re not happy with the result of website now in production, you can easily revert back to the situation that was working before by swapping back to the staging slot

Limitations

• You cannot use linked resource management in a non-production slot
• You cannot scale out a non-production slot (meaning that you cannot scale the number of instances)

Traffic Routing

Azure Web App Deployment Slots Pricing Chart

Traffic Routing (previously called testing in production), can help you with doing A/B testing (actual testing in production).

Azure Web App Deployment Slots Pricing Strategy

You can set it up to route a percentage of all traffic to one or more deployment slots, as in the illustration below. By doing this, users are redirected to your deployment slot and they are testing in “production”.

Take advantage of deployment slots. It’s a simple enough mechanism to use with huge benefits. Try it out!