An App Service plan (ASP) is a combination of capacities (instance size and instance count on which the application is hosted) and features. Capacity is directly related to cost and hence it is similar to choosing a pricing tier. There are different capabilities and limits available in pricing plans.
Each ASP can be used for different purposes and they provide different features too. There are five pricing tiers as follows:
- Free: no scaling
- Shared: no scaling
- Basic: SLA - 99.95%; maximum instances for scaling - 3
- Standard: SLA - 99.95%; autoscale, 5 deployment slots; Geo-distributed deployment, VPN hybrid connectivity, deployment slots, and automated backups; maximum instances for scaling - 10
- Premium: SLA - 99.95%; 20 deployment slots; autoscale, geo-distributed deployment, VPN hybrid connectivity, deployment slots, and automated backups; maximum instances for scaling - 50
App Service or Azure Web App is the main production slot. In the standard and premium tiers, we can create other deployment slots other than the main slot in which we deploy the application. We can use deployment slots for different environments before deploying applications into the main slot. Slots are not different from a live web app. They have their own set of content and configurations and hostnames. We can swap slots to roll back failures too.
The following are some important points regarding an App Service plan:
- An App Service plan can be shared by multiple applications.
- Deployment slots are usually deployed on the same App Service plan.
- Azure Web Apps configured with an App Service plan are changed, and then these changes affect all the applications hosted on the App Service plan.
- By default, ASP comes with a single instance. If we increase the instance count, then the applications hosted on a single instance will be hosted on other instances too.
- The number of instances in ASP is directly associated with the price of Azure Web Apps.
Let's create an App Service plan in Microsoft Azure Portal:
- Click on More services in the left sidebar and find App Service plans.
- Click on + Add.
- Provide the App Service plan name, Subscription, Resource Group, Operating System, Location and Pricing tier, and then click on Create:
- Click on Notifications to get the progress details of the App Service plan deployment:
- Once App Service plan is created successfully, click on the Overview section to get details about it in the Azure Portal:
We can deploy Azure App Services or Azure Functions on App Service plan.