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Introduction

Quickstart guide to the Functions Framework for Dart.

Background

The Functions Framework for Dart is an open source FaaS (Function as a Service) framework that lets you write and deploy lightweight, event-driven functions.

This means that not only do you not need to worry about managing physical infrastructure, you don't even need to worry about writing the HTTP server and request handling logic in your own code.

Instead, you use the framework to declare functions that will be wired up to specific events your app is concerned with; you only write code for what should happen once a function is triggered.

Functions created with this framework:

  • Have a minimum amount of boilerplate, allowing you to focus on the business logic of your functions
  • Support standard HTTP requests and requests triggered by CloudEvents
  • Can be tested on your own machine
  • Are packaged in an industry-standard, portable format (Docker images), which can be deployed to various hosted Cloud environments for running containers

The Google Cloud team defines the specification for Functions Framework conformance (the contract between a framework and your code) for a number of programming languages. You can find more details here.

Hello, World

Here is a simple example of how to write a function that responds to HTTP request events with a "Hello, World!" greeting:

import 'package:functions_framework/functions_framework.dart';
import 'package:shelf/shelf.dart';

@CloudFunction()
Response function(Request request) => Response.ok('Hello, World!');

If you deploy this simple example to Cloud Run, you can easily choose to make access public and test it over the Internet. The following image demonstrates using an auto-generated public assigned by Cloud Run; the function is triggered by an HTTP GET request event simply by accessing the URL with a browser.


img.png

When you are interactively testing your function, you can use tools like curl or postman, which are helpful for making and automating more complex web request tests.

A best practice is to incorporate automated tests as part of your continuous integration (CI) process during development. The example demonstrates the use of Dart tests, which we'll cover as part of this quickstart.

What's next

Using the example presented above, we will walk through a few quickstart scenarios that demonstrate running the function

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