App Service plans

An App Service Plan (ASP) is a set of capacities (the instance size and instance count on which the application is hosted) and features. Capacity is directly linked to cost and hence it is similar to choosing a pricing tier. There are different capabilities and limits within ASPs.

There are five pricing tiers, namely Free, Shared, Basic, Standard, and Premium. Each ASP can be used for different purposes and they are different in providing features too. SLAs for Basic, Standard, and Premium are 99.95 percent. Autoscale, geo-distributed deployment, VPN hybrid connectivity, deployment slots, and automated backups are available only in the Standard and Premium tiers. In the Standard tier, five deployment slots are available, while in the Premium tier, 20 slots are available. Another major difference is the maximum instances, as they are directly associated with scaling. Hence, it is important to pick the proper tier or ASP to gain the desired performance. The Basic, Standard, and Premium tiers allow up to 3, 10, and 50 instances respectively.

The App Service or Azure Web Apps is a main or Production slot. In Standard and Premium tiers, we can create other deployment slots other than the main slot where we deploy an application. We can use deployment slots for different environments before deploying an application into the Production slot. Slots are not different from a live web app. They have their own set of content, configurations, and hostnames. We can swap slots to roll back failures too.

The following are some important points regarding ASPs:

• ASPs can be shared by multiple applications
• Deployment slots are usually deployed on the same ASP
• Azure Web Apps configured with an ASP are changed and these changes affect all applications hosted on the ASP
• By default, an ASP comes with a single instance. If we increase the instance count, then applications hosted on a single instance will be hosted on other instances too
• The number of instances in an ASP is directly associated with the price of the Azure Web Apps

Let's consider the Azure calculator and understand how the pricing works. Go to https://azure.microsoft.com/en-in/pricing/calculator/. Click on +Add items and click on App Service in the Featured category:

Select REGION, TIER, INSTANCE SIZE; by default, the instance size is 1 and the hours are 744. Verify the cost estimate:

Now change the instance count and verify the cost:

As the instance count directly affects pricing, let's see from where we can change the instance size as we need to be careful while doing it.

Let's create an ASP and verify the instance count. Go to the left-hand side menu bar, find App Service plans, and click on +Add.

Select the eTutorialsWorld resource group we created; select Operating System, Location, and Pricing tier. Click on Create:

Once the ASP is created, verify its Overview section. Verify the Apps / Slots count. It is 0 / 0 as no app or the slot is using the ASP:

Go to the Scale out (App Service plan) section in APP SERVICE PLAN, and verify the default number of instances. As we kept the Basic pricing tier, it allows us to scale up to three instances only:

If we want to cancel the changes, click on Discard.

This pricing and features information is latest on the day this chapter was written. For the latest information visit https://azure.microsoft.com/en-in/pricing/details/app-service/plans/.