appengine

Description:

appengine

Dart support for Google AppEngine #
This package provides support for running server applications written in Dart on
Google App Engine using
Custom Runtimes with Flex Environment.
Status: Experimental #
NOTE: This package is currently experimental and published under the
labs.dart.dev pub publisher in order to
solicit feedback.
For packages in the labs.dart.dev publisher we generally plan to either graduate
the package into a supported publisher (dart.dev, tools.dart.dev) after a period
of feedback and iteration, or discontinue the package. These packages have a
much higher expected rate of API and breaking changes.
Your feedback is valuable and will help us evolve this package. For general
feedback, suggestions, and comments, please file an issue in the
bug tracker.
Prerequisites #
Install Dart and Cloud SDKs #
This page assumes the Dart SDK (see
dart.dev/get-dart) as well as the Google
Cloud SDK (see cloud.google.com/sdk) were
installed and their bin folders have been added to PATH.
Setup gcloud #
To ensure gcloud was authorized to access the cloud project and we have the
app component installed, we assume the following has been run:
$ gcloud auth login
$ gcloud auth application-default login
$ gcloud config set project <project-name>
$ gcloud components update app
copied to clipboard
Instead of running gcloud auth application-default login it is also possible
to authenticate by making the environment variable
GOOGLE_APPLICATION_CREDENTIALS point to a file containing
exported service account credentials.
Creating a hello world application #
To setup a hello world application we need 4 different things:
An app/pubspec.yaml file describing the Dart package:
name: hello_world
version: 0.1.0
environment:
sdk: '>=2.0.0 <3.0.0'

dependencies:
appengine: ^0.12.0
copied to clipboard
An app/app.yaml file describing the AppEngine app:
runtime: custom
env: flex
service: default
copied to clipboard
An app/Dockerfile describing how to build/bundle the app:
FROM google/dart-runtime

### NOTE: Uncomment the following lines for local testing:
#ADD key.json /project/key.json
#ENV GOOGLE_APPLICATION_CREDENTIALS /project/key.json
#ENV GOOGLE_CLOUD_PROJECT dartlang-pub
copied to clipboard
This requires exported service account credentials in key.json.
An app/bin/server.dart containing the app code
import 'dart:io';
import 'package:appengine/appengine.dart';

requestHandler(HttpRequest request) {
request.response
..write('Hello, world!')
..close();
}

main() async {
await runAppEngine(requestHandler);
}
copied to clipboard
Running the app locally #
There are two ways to run the application locally - with or without docker.
Running without Docker #
The simplest way to run the application is on the command line like this:
$ gcloud auth application-default login
$ export GOOGLE_CLOUD_PROJECT=<project-name>
$ dart bin/server.dart
copied to clipboard
This will serve the application at localhost:8080!
Running with Docker #
To be closer to the production environment one can run the application inside a
docker container. In order to do so, docker needs to be installed first (see the
official instructions.
In order to run the application locally we uncomment the 3 lines in the
Dockerfile and place the service account key in key.json:
ADD key.json /project/key.json
ENV GOOGLE_APPLICATION_CREDENTIALS /project/key.json
ENV GOOGLE_CLOUD_PROJECT dartlang-pub
copied to clipboard
We can then run the application via:
$ docker build .
...
Sucessfully built <docker-imgage-hash>
$ docker run -it <docker-imgage-hash>
...
copied to clipboard
In order to find out at which IP the Docker container is available we inspect
the running container via:
$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
<container-id> ...
app % docker inspect --format '{{ .NetworkSettings.IPAddress }}' <container-id>
172.17.0.2
copied to clipboard
Then the application will be available at 172.17.0.2:8080.
Deployment #
Before deploying the app, be sure to remove the environment variables in the
Dockerfile which we used for local testing!
To deploy the application to the cloud we run the following command (optionally
passing the --no-promote flag to avoid replacing the production version)
$ gcloud app deploy --no-promote app.yaml
...
Updating service [default]...done.
Deployed service [default] to [https://<version-id>-dot-<project-id>.appspot.com]
...
copied to clipboard
This will perform a remote docker build in the cloud and deploy a new version.
You can find the URL to the version that got deployed
in the output of gcloud app deploy (as well as via the
Cloud Console under AppEngine > Versions).
Regenerating protobuf #
You need to have protoc in $PATH.
Run the tool/fetch_protos_and_regenerate_dart.sh script. It will fetch the latest protos and compile them for dart using the protoc_plugin in dev_dependencies.