Azure Functions
Overview
Azure Functions is built on the WebJobs SDK.
- triggers - way to start execution of the logic.
- bindings - way to simplify coding for input and output data.
Azure Functions and Logic Apps
Both are serveless. Can mix and match.
| Azure Functions | Logic Apps | |
|---|---|---|
| Development | Code-first (imperative ) | Designer-first (declarative) |
| Monitoring | Azure Application Insights | Azure portal, Azure Monitor logs |
App Service WebJobs
Enables to run a program or script in the same instance as a web app (using App Service plan). WebJobs is not yet supported for App Service on Linux.
WebJobs and WebJobs SDK work best together but WebJob can run any program.
Hosting Options
Any plan requires Azure Storage account to manage triggers and logging functions execution.
Main hosting plans:
- Consumption plan: Default hosting plan. Scales automatically. Uses cold start.
- Functions Premium plan: Scales automatically. Uses pre-warmed workers. Runs on more powerful instances, and connects to virtual networks.
- App Service plan: Runs at regular App Service plan rates. Best for long-running scenarios where Durable Functions can't be used. Allows manual scaling. Auto-scaling is slower then elastic scale of the Premium plan.
Isolated hosting plans:
- App Service Environment (ASE): App Service feature that provides a fully iselated and dedicated environment for securely running App Service apps at high scale.
- Kubernetes: isolated and dedicated environment running on top of the Kubernetes platform.
App Service Always On
Always on should be enabled for the App Service plans. Otherwise finctions runtime goes idle after few minutes of inactivity, so only HTTP triggers will "wake up" functions.
Scaling
Azure Functions uses a component called the scale controller. It uses heuristics for each trigger type. The unit of scale is the Function App.
Maximum scale:
- in Consumption plan is 200 instances,
- in Premium plan is 100 instances.
Maximum scale speed:
- for HTTP triggers is once per seconds,
- for non-HTTP triggers is once per 30 seconds.
Scaling is faster in a Premium plan.