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Introduction to Triggers

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Overview
DifficultyIntermediate
Duration46m
Students694
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Description

This course is an introduction to Azure Functions. It explains how Azure Functions are little bits of your application logic that live in the cloud. The course includes how to activate—or what we call trigger—your Azure Functions, how to pass data to and from them, and also how to tie different Azure Functions together using an extension of Azure Functions called Durable Functions. 

This course provides hands-on demonstrations of how to create different kinds of Azure Functions, how to create bindings to other Azure Services from those functions, and how to create a Durable Function to manage state from one Azure Function to the next.

If you have any feedback related to this course, please contact us at support@cloudacademy.com.

Learning Objectives

  • Create Azure Functions with different types of Triggers
  • Implement input and output bindings to different types of data resources
  • Create Durable Functions to orchestrate related Azure Functions
  • Log the results with Dependency Injection

Intended Audience

Software developers who want to learn how to implement Azure Functions as a part of their cloud software design.

Prerequisites

To get the most out of this course, you should have some experience will the following:

  • Event-driven programming
  • Servers and APIs
  • Coding with C# and JSON
  • Project creation in Visual Studio

Resources

The GitHub repository for this course can be found here.

Transcript

Triggers are how your Azure Function starts, so it seems the best place for us to start as well. A trigger defines how your function is invoked. There are several kinds of triggers you can employ to run your function when desired. In general, they have three primary types, including HTTP/Webhooks, timers, and data operations.

So for HTTP trigger, your Azure Function fires whenever an HTTP request hits that endpoint.

For a generic webhook trigger, your function fires when a webhook HTTP request, hits that endpoint from any service that supports webhooks, such as Stripe or Twilio.

A GitHub webhook trigger in specific means that your function fires when an event occurs in your GitHub repository, such as create, delete, download, fork, push, pull requests, commit comment or any of the other several dozen GitHub events.

For a timer trigger your function is called at intervals, we'll actually be creating a timer trigger in our exercise.

A queue trigger means your function fires when a new message comes into your Azure queue storage. The message contents are then passed on as input to the function. We will also be doing a queue trigger in our exercise.

For a service bus trigger, your function fires when a new message arrives from a service bus queue or topic. The message contents are then passed in as input to your function.

A BLOB trigger means that your function fires when a new or updated BLOB is detected, and then the BLOB contents are passed to your function as input or an event hub trigger your function fires when any events are delivered to an Azure Event Hub.

To define those triggers and other bindings for your Azure Function, you create a function.json file that creates the configuration metadata for the function itself. Here you can see an example of a function.json file.

You can see within it that a function can only have a single trigger binding. As we'll discuss later, it can have multiple input slash output bindings. All bindings and triggers will have a direction property and note that for triggers, the direction is always in.

Here you can see examples of several common types of trigger bindings used for implementation of those that we just listed. This code would all be found in your function.json file, typically auto generated by Visual Studio, but you do have direct access to edit it when you desire.

So you can see httpTrigger with an authorization level, a timerTrigger with a schedule, a blobTrigger with the file path to the blob, a queueTrigger with the name of the queue, and so on all of the details necessary for your binding to enable itself to be properly connected to whichever resource you are binding to.

The easiest way to create an Azure Function, and to see all of this is using Visual Studio. You just write your functions, starting with the templates provided, and then publish in the usual way to your Azure Cloud. Note that because any Azure Function can have exactly only one trigger as specified, the trigger type you intend to use is what differentiates your Azure Functions when you create them in Visual Studio, so let's take a look at that.

About the Author

David Gaynes is a software and cloud architect for .NET, NodeJS, Azure and AWS. He has been developing .NET and Cloud software for more than 20 years, with some of that time spent at Microsoft, and has authored both technical and non-technical teaching materials as books and in other formats. He enjoys physics, meditation, and experiencing the natural wonders of Hawaii.