A simple web app written in the Dart programming language that you can use for testing Dart on cloud run. It reads in the env variable TARGET and prints "Hello $TARGET". If TARGET is not specified, it will use "World" as TARGET.

• A working gcloud console

• A dart-sdk installed and configured if you want to run the program locally.

• Courtesy of Google you can click the 'Run on Google Cloud' button above to deploy the application - try it!

While you can clone all of the code from this repository, it is useful to know how to build a hello world Dart server application step-by-step. This application can be created using the following instructions.

1. Create a new directory and write pubspec.yaml as follows:

   name: hello_world_dart
   private: True # let's not accidentally publish this to pub.dartlang.org
   description: >-
     Hello world server example in dart.
   dependencies:
     shelf: ^0.7.3
   environment:
     sdk: ">=2.0.0 <3.0.0"

2. If you want to run locally, install dependencies. If you only want to run in cloud run you can skip this step.

   pub get

3. Create a new file bin/server.dart and write the following code:

   import 'dart:io';
   
   import 'package:shelf/shelf.dart';
   import 'package:shelf/shelf_io.dart';
   
   Future main() async {
     // Find port to listen on from environment variable.
     var port = int.tryParse(Platform.environment['PORT'] ?? '8080');
   
     // Read $TARGET from environment variable.
     var target = Platform.environment['TARGET'] ?? 'World';
   
     Response handler(Request request) => Response.ok('Hello $target');
   
     // Serve handler on given port.
     var server = await serve(
       Pipeline().addMiddleware(logRequests()).addHandler(handler),
       InternetAddress.anyIPv4,
       port,
     );
     print('Serving at http://${server.address.host}:${server.port}');
   }

4. Create a new file named Dockerfile, this file defines instructions for dockerizing your applications, for dart apps this can be done as follows:

   # Use Google's official Dart image.
   # https://hub.docker.com/r/google/dart-runtime/
   FROM google/dart-runtime
   
   # Service must listen to $PORT environment variable.
   # This default value facilitates local development.
   ENV PORT 8080
   
   # The target variable
   ENV TARGET "World + Dog"

Once you have recreated the sample code files (or used the existing files) you're ready to build and deploy the sample app.

1. Build your container image using Cloud Build, by running the following command from the top level directory containing the Dockerfile:

   builds submit --tag gcr.io/[PROJECT-ID]/helloworld

   where [PROJECT-ID] is your GCP project ID. You can get it by running gcloud config get-value project.

   Upon success, you will see a SUCCESS message containing the image name (gcr.io/[PROJECT-ID]/helloworld). The image is stored in Container Registry and can be re-used if desired.

2. Deploy the build above using the following command:

   gcloud beta run deploy --image gcr.io/[PROJECT-ID]/helloworld

   where [PROJECT-ID] is again your GCP project ID. You can get it by running gcloud config get-value project.

   When prompted, select a region (for example us-central1), confirm the service name, and respond 'y' to allow unauthenticated invocations.

   Then wait a few moments until the deployment is complete. On success, the command line displays the service URL. Visit your deployed container by opening the service URL in a web browser.

   Congratulations! You have just deployed a Dart application packaged in a container image to Cloud Run. Cloud Run automatically and horizontally scales your container image to handle the received requests, then scales down when demand decreases. You only pay for the CPU, memory, and networking consumed during request handling. If you change your project you can just re-build and redeploy as you wish.

To remove the built image you can delete the image. You can also delete your GCP project to avoid incurring charges. Deleting your GCP project stops billing for all the resources used within that project.