$ curl https://sdk.cloud.google.com | bash
$ exec -l $SHELL
$ gcloud init

This project has one or more associated Git repositories.
Pick Git repository to clone to your local machine:
 \[1\] \[default\]
 \[2\] Do not clone
Please enter your numeric choice:

$ cd ~/Desktop/gaerailssample
$ rails new .

\# /app/controllers/hello\_world\_controller.rb

class HelloWorldController < ApplicationController
  def index
    # Say hello!
    render text: "Hello, world!"
  end
end

root 'hello\_world#index'

`rails s`で動作確認をします。

$ gcloud preview app deploy
WARNING: The \`gcloud preview app\` surface is rapidly improving. Look out for
changing flags and new commands before the transition out of the \`preview\`
component. These changes will be documented in the Cloud SDK release notes
<https://goo.gl/X8apDJ> and via deprecation notices for changing commands.

If you would like to avoid changing behavior, please pin to a fixed version of
the Google Cloud SDK as described under the "Alternative Methods" section of the
Cloud SDK web site: <https://cloud.google.com/sdk/#alternative>.

Deployment to Google App Engine requires an app.yaml file. This
command will run \`gcloud preview app gen-config\` to generate an
app.yaml file for you in the current directory (if the current
directory does not contain an App Engine module, please answer "no").

Do you want to continue (Y/n)?

This looks like a Ruby application.

Proceed to configure deployment for Ruby? (Y/n)?  Y

NOTICE: We will deploy your application using a recent version of the standard "MRI" Ruby runtime by default. If you want to use a specific Ruby runtime, you can create a ".ruby-version" file in this directory. (For best performance, we recommend MRI version 2.3.0.)

Please enter the command to run this Ruby app in production, or leave
blank to accept the default:
\[bundle exec rackup -p 8080 -E deployment config.ru\]

ERROR: (gcloud.preview.app.deploy) Server responded with code \[400\]:
  Bad Request Unexpected HTTP status 400.
  Failed Project Preparation (app\_id='s~gaerailssample'). Out of retries.  Last error: TEMPORARY\_ERROR: Operation does not satisfy the following requirements: billing-enabled {Billing must be enabled for activation of service '' in project 'gaerailssample' to proceed., https://console.developers.google.com/project/gaerailssample/settings}

ERROR: (gcloud.preview.app.deploy) There is a Dockerfile in the current directory, and the runtime field in /Users/moritanaoki/Desktop/gaerailssample/app.yaml is currently set to \[runtime: ruby\]. To use your Dockerfile to build a custom runtime, set the runtime field in /Users/moritanaoki/Desktop/gaerailssample/app.yaml to \[runtime: custom\]. To continue using the \[ruby\] runtime, please omit the Dockerfile from this directory.

runtime: custom
vm: true
entrypoint: bundle exec rackup -p 8080 -E production config.ru
env\_variables:
  SECRET\_KEY\_BASE: "hogehoge"