Up:: Microsoft Azure Developer Associate AZ-204 2023

Azure Functions

Azure Functions is a FaaS (Function as a Service)

• A function App
  • A Function
    • Trigger (Only one)
    • Input Bindings (Parameters)
    • Output Bindings (Return Data)
• Requires Storage account to operate
  • Blob Storage
  • Azure Files
  • Queue Storage
  • Table Storage
• Anatomy
  • function.json
    • Configurations
  • index.js
    • Code
  • host.json
    • Global app configurations
  • .funcignore
    • Files to ignore
• Authorization Levels
  • anonynmous - No API key
  • function - function level key
  • admin - master (app) key
  • Change authorization on selecting trigger
• Debugging
  • Streaming Logs
    • Near real time
      • Built-in log stream
      • Live Metrics Stream
• Key Concepts
  • Lightweight and can be serverless
  • Easier to write and deploy
  • fast to execute because there is no large application
    • cold starts should be taken into account
  • triggered when an event is fired
  • no need for infrastructure and have zero maintenance
  • built, tested and deployed using Azure Portal on a browser
  • easy to upgrade (subjected to code)
  • industry standard to communicate with APIs, databases and services
  • pay while function is running
  • Scales to meet demand
  • Can scale to Zero Cost
  • Built in monitoring with Azure Monitor
  • Built in CI/CD via Azure DevOps
  • Event-driven will be triggered based on event data and will emit event data
• Use Cases
  • Business Use Cases
  • Technical Use Cases
  • Best suited for smaller apps that have events that can work independantly of othe websites
• VSCode Extension
  • Install via Extensions
  • Can manage all function stuff via extension
• Runtimes
  • Application runtime is a compute environment configured to run application code
    • .Net
    • Java
    • Node.js
    • Powershell Core
    • Python
    • Custom Handler for code which does not have the runtime available
  • Just Docker Containers
    • View on Docker Hub
• Hosting
  • Windows vs Linux
    • Differences
      • performance
      • functionality
      • features
• Templates
  • For Common Scenarios
    • Http Trigger
    • Timer
    • Blob Storage
    • Cosmos DB
    • Queue Storage
    • Event Grid
      • Many Azure Services can be triggered via event grid
      • Event Grid is serverless event bus integrated with Azure Services
    • Event Hub
    • Service Bus Queue
    • Service Bus Topics - Pub/Sub
    • SendGrid
• Function Configuration
  • function.json
    • type
    • direction
    • name
• Hosts Configuration
  • hosts.json
    • global configuration
    • LOT of configuration options
• Plan Services
  • 3 available plans
    • Consumption Plan (Serverless) - Cold Starts
    • Premium Plan (Functions Premium) - Pre-Warmed
    • App Service Plan - VM Sharing
• Triggers and Bindings
  • Trigger - Specific type of event which causes the function to run
    • defines how function is invoked, can have only one
  • Supported Bindings
    • Blob Storage
    • Cosmo DB
    • Azure SQL
    • Dapr
    • Event Grid
    • Event Hub
    • Http and WebHooks
    • …
• Binding Direction
  • Trigger direction is always In
  • Input and Output binding use In and/or Out
  • special bindings Inout
• Binding Expressions
  • curly braces container/{queueTrigger}
    • Lots of types
• Local Settings File
  • local.settings.json
    • Local Configurations for local development
    • do not put in remote repository
• Core Tools
  • Azure Function Core Tools - func
  • func init - new project
  • func logs - logs of running functions
  • func start
  • …
• Custom Handlers
  • lightweight webserver to receive events
  • used to support languages not supported by Azure
  • Application Structure
    • host.json
    • local.settings.json
    • function.json
    • command, script or executable to run the web server
    • Could not get it up and running, really difficult.
• Unreachable
  • Error - Runtime Unreachable
    • Storage account deleted
      • settings were deleted
      • credentials are invalid
• Durable Functions
  • Create statuful functions
  • two types
    • Orchestrator function - define stateful workflows
    • Entity Function
  • Currently supported by:
    • C#
    • Javascript
    • Python
    • F#
    • Powershell
  • Need to install library to support language in use. ie npm install durable-functions
• Patterns of Durable Functions
  • Function Chaining
  • Fan-out/Fan-in
    • Fanning out
    • Fanning in
  • Async HTTP Api
  • Monitor
    • polling till conditions are met
  • Human Interaction
  • Aggregator (Stateful entities)
• Azure function on Kubernetes
  • KEDA Kubernetes Event driven Autoscaling

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