.Net: Azure Functions

Azure Functions can be hosted as

Consumption plan (serverless - auto scale, has time limit of 5 minutes for each method invocation, pay per use)
Azure app service (no time limit, monthly plan service)
Premium plan (faster performance, reserved instances, enhanced security)
Docker container (on premises or any cloud provider)

Azure Function types

HTTP Function Triggers (web hooks, use for APIs invocation)
Timer Trigger (scheduled tasks, CRON expression)
Blob Storage Trigger (data operation, run when a new file is uploaded to Blob storage)
Queue Trigger (run in response to a message on a queue)
Cosmos DB Trigger (run when a document is created or updated)
Event Trigger
Graph Trigger
SendGrid Trigger (3rd party - send email)
Twilio Trigger (3rd party - send text)

Every Azure function has exactly one trigger

HTTP Request Trigger

Security considerations:

Anonymous (no key required)

Security key per function

Admin: key per function app

Input and Output Bindings

Example for Input Bindings:

Blob storage binding - read all contents of a file in Blob storage

Cosmos DB binding - look up a document in a cosmos DB database

Queue storage binding - read a message from queue

Microsoft Graph binding - access OneDrive

To develop locally,

Azure Functions VS Code extension

we can use Azure storage emulator, Azure Cosmos DB Emulator

Command to run the function: func start

Call the endpoint using postman or powershell command "Invoke-WebRequest <endpoint>"

When a message is posted to a queue, we can use a free tool "Azure storage explorer" to view the queue and actual message

Azure Durable Functions (for workflows)

Create stateful, serverless workflows / orchestration

Orchestration Patters:

Function Chaining

Fan-out Fan-in

Asynchronous HTTP APIs

Monitor pattern (Poll and sleep)

Human Interaction (Process approval / escalate)

Install Microsoft.Azure.WebJobs.Extensions.DurableTask nuget package

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