Google App Engine Integration Tools

This repository contains the "appengine" gem, a collection of libraries and plugins for integrating Ruby apps with Google App Engine. It is not required for deploying a ruby application to Google App Engine, but it provides a number of convenience hooks and tools for integrating into the App Engine environment.

Currently, it includes:

• Automatic Stackdriver instrumentation for Rails apps. This means logs, error reports, and latency traces are reported to the cloud console, and debugger integration is available.
• A client and rake tasks for executing application commands in the App Engine environment against production resources, useful for tasks such as running production database migrations.
• Convenient access to environment information such as project ID and VM properties.

Potential future directions:

• Tools for generating "app.yaml" configuration files for Ruby applications.
• Streamlined implementation of health checks and other lifecycle hooks.

For more information on using Google Cloud Platform to deploy Ruby apps, please visit http://cloud.google.com/ruby

To install, include the "appengine" gem in your Gemfile. e.g.

gem "appengine"

If you are running Ruby On Rails 4.0 or later, this gem will automatically install a Railtie that provides its capabilities. You may need to include the line:

require "appengine"

in your config/application.rb file if you aren't already requiring all bundled gems.

If you are running a different Rack-based web framework, include the following line in your main Ruby file or config.ru:

require "appengine"

Then, to activate Stackdriver instrumentation, add the following middleware:

use Google::Cloud::Logging::Middleware
use Google::Cloud::ErrorReporting::Middleware
use Google::Cloud::Trace::Middleware
use Google::Cloud::Debugger::Middleware

You can add the Rake tasks to your application by adding the following to your Rakefile:

require "appengine/tasks"

This gem is commonly used for its appengine:exec Rake task that provides a way to run production tasks such as database migrations in the cloud. If you are getting started with this feature, you should read the documentation (available on the AppEngine::Exec module) carefully, for important tips. In particular:

• The strategy used by the gem is different depending on whether your app is deployed to the App Engine standard environment or flexible environment. It is important to understand which strategy is in use, because it affects which version of your application code is used to run the task, and various other factors.
• You may need to grant additional permissions to the service account that runs the task. Again, the documentation will describe this in detail.
• If your app is running on the flexible environment and uses a VPC (and connects to your database via a private IP address), then you will need to use a special configuration for the task.

This library automatically installs the "stackdriver" gem, which instruments your application to report logs, unhandled exceptions, and latency traces to your project's Google Cloud Console. For more information on the application monitoring features of Google App Engine, see:

• google-cloud-logging instrumentation
• google-cloud-error_reporting instrumentation
• google-cloud-trace instrumentation
• google-cloud-debugger instrumentation

Rails applications automatically activate this instrumentation when the gem is present. You may opt out of individual services by providing appropriate Rails configuration. See AppEngine::Railtie for more information.

Non-Rails applications must provide initialization code to activate this instrumentation, typically by installing a Rack middleware. You can find the basic code for installing these middlewares in the Rack Quick Start section above. See the individual service documentation links above for more information and configuration options.

This library provides rake tasks for App Engine remote execution, allowing App Engine applications to perform on-demand tasks in the App Engine environment. This may be used for safe running of ops and maintenance tasks, such as database migrations, that access production cloud resources. For example, you could run a production database migration in a Rails app using:

bundle exec rake appengine:exec -- bundle exec rake db:migrate

The migration would be run in containers on Google Cloud infrastructure, which is much easier and safer than running the task on a local workstation and granting that workstation direct access to your production database.

See AppEngine::Exec for more information on App Engine remote execution.

See AppEngine::Tasks for more information on running the Rake tasks. The tasks are available automatically in Rails applications when the gem is present. Non-Rails applications may install the tasks by adding the line require "appengine/tasks" to the Rakefile.

The source code for this gem is available on Github at https://github.com/GoogleCloudPlatform/appengine-ruby

Report bugs on Github issues at https://github.com/GoogleCloudPlatform/appengine-ruby/issues

Contributions are welcome. Please review the CONTRIBUTING.md file.