Azure Functions Overview

Posted Aug 27, 2024

By Jarrod Lilkendey

5 min read

You will need to be familiar with Azure Functions if you are taking the AZ-204 Azure Developer Associate certification exam.

This is some of the exam preparation notes I have taken for Azure Functions.

You can check out my other exam prepation notes for other Azure services covered on the AZ-204 exam here.

Explain functional differences between Azure Functions, Azure Logic Apps, and WebJobs

Azure Functions

Serverless solution
No need to maintain servers
Functions can be triggered based on events that happen against your Azure resources
Triggers and bindings
Consumption billing
Can be orchestrated to invoke other Azure Functions
Can be long running with Durable Functions

Azure Logic Apps

Serverless solution
Serverless workflow integration toool
Can be orchestrated to invoke other actions
Configured in a GUI
Out of the box library of actions you can reuse

WebJobs

Azure Functions is built on the WebJobs SDK
Both are code first solutions
Some of the same triggers in Azure Functions are available in WebJobs
WebJobs doesn’t support serverless app model with automatic scaling
WebJobs doesn’t support pay-per-use pricing
WebJobs doesn’t support integration with Logic Apps
In most scenarios, Azure Functions is the preferred option

Describe Azure Functions hosting plan options

Consumption plan

Default function timeout of 5 minutes, maximum function timeout of 10 minutes
Pay as you go
Automatic scaling
Function host instances are dynamically added and removed based on the number incoming events

Flexible Consumption plan

Default function timeout of 30 minutes, unlimited maximum function timeout (guaranteed for up to 60 mins)
Pay as you go
Virtual networking supported
Function host instances are dynamically added and removed based on the configured per instance concurrency and the number incoming events
Pre-provisioned always ready instances can be added to reduce cold starts
Scales automatically based on demand

Premium plan

Default function timeout of 30 minutes, unlimited maximum function timeout (guaranteed for up to 60 mins)
Consider if:
- Your function apps run continuously, or nearly continuously.
- You want more control of your instances and want to deploy multiple function apps on the same plan with event-driven scaling.
- You have a high number of small executions and a high execution bill, but low GB seconds in the Consumption plan.
- You need more CPU or memory options than are provided by consumption plans.
- Your code needs to run longer than the maximum execution time allowed on the Consumption plan.
- You require virtual network connectivity.
- You want to provide a custom Linux image in which to run your functions.

Dedicated plan

Default function timeout of 30 minutes, unlimited maximum function timeout (guaranteed for up to 60 mins)
Consider if:
- You must have fully predictable billing, or you need to manually scale instances.
- You want to run multiple web apps and function apps on the same plan
- You need access to larger compute size choices.
- Full compute isolation and secure network access provided by an App Service Environment (ASE).
- High memory usage and high scale (ASE).

Container Apps

Default function timeout of 30 minutes, unlimited maximum function timeout (guaranteed for up to 60 mins)
Consider if:
- You want to package custom libraries with your function code to support line-of-business apps.
- You need to migration code execution from on-premises or legacy apps to cloud native microservices running in containers.
- You want to avoid the overhead and complexity of managing Kubernetes clusters and dedicated compute.
- You need the high-end processing power provided by dedicated CPU compute resources for your functions.

Describe how Azure Functions scale to meet business needs

Consumption plan slace out

Event driven
Scales out automatically, even during periods of high load
Functions infrastructure scales CPU and memory resources by adding more instances based on the number of incoming trigger events
Max # instances per Function App:
- Windows: 200
- Linux: 100

Flexible Consumption plan scale out

Per-function scaling
Event-driven scaling decisions are calculated on a per-function basis, which provides a more deterministic way of scaling the functions in your app
Max # instances per Function App:
- Limited only by total memory usage of all instances across a given region

Premium plan scale out

Event driven
Scale out automatically based on the number of events that its functions are triggered
Max # instances per Plan:
- Windows: 100
- Linux: 20-100

Dedicated plan scale out

Manual/autoscale
Max # instances per Plan:
- 10-30
- 100 (ASE)

Container Apps scale out

Event driven
Scale out automatically by adding more instances of the Functions host, based on the number of events that its functions are triggered on
Max # instances
- 10-300

Explain the key components of a function and how they are structured

Triggers (required)
Bindings (optional)
- Data from bindings is provided to the function as parameters
- Input Bindings
- Output Bindings
- host.json
- local.settings.json
- functions.json can be used to define bindings
  - dataType
    - binary
    - stream
    - string
  - binding direction
    - For triggers, the direction is always in
    - Input and output bindings use in and out
    - Some bindings support a special direction inout
  - type
    - queueTrigger
    - blob
    - table

        
      
{
  "disabled": false,
  "bindings": [
    {
      "type": "queueTrigger",
      "direction": "in",
      "name": "myQueueItem",
      "queueName": "myqueue-items",
      "connection": "MyStorageConnectionAppSetting"
    },
    {
      "tableName": "Person",
      "connection": "MyStorageConnectionAppSetting",
      "name": "tableBinding",
      "type": "table",
      "direction": "out"
    }
  ]
}

Create triggers and bindings to control when a function runs and where the output is directed

Azure Function Storage Queue Trigger Node.js Tutorial

Connect a function to services in Azure

Azure Function Storage Queue Trigger Node.js Tutorial

Create a function by using Azure Functions Core Tools

How to Create Azure Functions with Azure Function Core Tools and the Azure CLI