Tag: TodoApp


Using Amazon RDS with Ruby on Rails and AWS OpsWorks

by Alex Wood | on | in Ruby | | Comments

Earlier in this blog series, we showed you how to deploy a Ruby on Rails application to Amazon Web Services using AWS OpsWorks. In that example, we used an OpsWorks-managed MySQL database run on an Amazon EC2 instance. One common piece of feedback on that post was a desire to see how you can set up your stack with Amazon RDS. Today, we are going to show you how.

Prerequisites

We are going to assume you’re familiar with our earlier post on how to deploy with OpsWorks in general. For this tutorial you can take one of the following approaches:

  • Take your existing stack from following along with that post, delete your database and MySQL layers, then follow this tutorial.
  • Clone your existing stack (in case you don’t want to lose your work), create a new app server instance, delete the new stack’s MySQL layer, then follow along.
  • Start from a brand new stack, and go between both tutorials, replacing the DB steps from the previous tutorial with the DB steps here. If you’re going to go that route, we would recommend reading this tutorial first to understand the differences in approach.

Whichever approach you choose, you can be up and running in just a few minutes!

Create an RDS Instance

AWS OpsWorks will not create Amazon RDS instances on your behalf. You will need to create an instance and link it to OpsWorks.

  1. Open up the RDS console, navigate to Instances, and click Launch DB Instances.
  2. To be able to use our Rails example code unaltered, choose the MySQL engine (you can choose another engine if you like, see the next section for details).
  3. On the next screen, you can choose either Multi-AZ deployments or single-AZ, but if you want to stay within the RDS Free Usage Tier, then you should not choose a multi-AZ deployment.
  4. Make sure that you keep track of your Master Username, Master Password, and the Database Name from the rest of the form.
  5. Within Configure Advanced Settings, make sure you set your VPC Security Groups to include AWS-OpsWorks-DB-Master-Server and AWS-OpsWorks-Rails-App-Server. You can set Publicly Accessible to "No" as well.
  6. Once you’ve completed the forms, click Launch DB Instance. It may take a few minutes for your instance to launch, so now is not a bad time for tea or coffee.

Don’t Want MySQL?

You do not need to use MySQL as your database backend, that is just what we have chosen for this example. Want to use a different database backend? Just do the following:

  1. Replace the mysql2 gem with the adapter gem appropriate to your DB engine selection.
  2. Make sure you also use your adapter selection in your custom deployment JSON, found in your stack settings if you used our exact tutorial steps.
  3. Of course, select that database engine when creating your RDS instance.

Create an RDS Layer

Now that you have an RDS Instance, you need to register it with OpsWorks.

  1. Navigate to the OpsWorks console, to the Layers section.
  2. Click + Layer, and select the RDS tab.
  3. Your RDS instance should be on this screen to select. Select it, then enter your User and Password from the RDS instance creation step.
  4. Click Register with Stack.

This registers your database with OpsWorks, and next you need to connect your app.

Attach Your RDS Instance to Your App

  1. From the Apps section, click on Edit for TodoApp (or whatever app you are developing for).
  2. Under the Data Sources section, select RDS.
  3. It should auto-select your instance; select it if not. Then, fill in your Database name from the RDS instance creation process.
  4. Click Save to save your changes.

Note that this should work for any of the topic branches we’ve made for TodoApp, as your choice of database host is transparent to your app so long as you have the correct database adapter gem in your Gemfile.

Deploy the App

To use your new database, simply run an app deployment, making sure you select the Migrate database option so that Rails can set up your database.

Once that’s done, navigate to your app server host and play around with your app. You’re now running on RDS!

Caching the Rails Asset Pipeline with Amazon CloudFront

by Alex Wood | on | in Ruby | | Comments

Amazon CloudFront is a content delivery web service. It integrates with other Amazon Web Services to give developers and businesses an easy way to distribute content to end users with low latency, high data transfer speeds, and no minimum usage commitments.

Ruby on Rails introduced the asset pipeline in version 3.1. The Rails asset pipeline provides a framework to concatenate and minify or compress JavaScript and CSS assets. It also adds the ability to write these assets in other languages and pre-processors such as CoffeeScript, Sass and ERB.

With CloudFront’s support for custom origin servers, and features of the Rails asset pipeline, building a CDN for your static assets is simple. In this blog post, we will show you how to set this up for your environment.

Do You Have Geographically Diverse Users?

Amazon CloudFront provides 52 (as of when this was written*) edge locations around the world. Your static content can be cached by these edge locations to reduce the latency of your web application. Additionally, this can reduce the load on your app servers, as it limits the number of times your app server needs to serve large static files.

* See the current list of edge locations here.

Prerequisites

You should be able to deploy your Ruby on Rails application to the Internet, and you should know the hostname or IP address for where your application is hosted. If you have followed along with the series and deployed our sample application on AWS OpsWorks, you can complete this tutorial. If not, consider trying out a deployment first.

Creating a CloudFront Distribution

First, we will create a new CloudFront distribution that uses our app as the custom origin. From the Amazon CloudFront console, click Create Distribution. Under "Web", click Get Started.

Within this form, call the Origin ID "Rails App Server", and for the Origin Domain Name, we will point to the URL of our Rails application. Here is how:

  • If you have a domain name (e.g., "www.example.com"), then use that.
  • If not, you should use as stable of a hostname as possible. For example, the hostname of your ELB instance, or at least an Elastic IP. For demonstration purposes, the public host name of your app server instance will also work.

If you’re using something other than a domain name, don’t worry, you can change the origin address later if you need to. All other options can be left at their default values, though you can turn on logging if you want. We aren’t going to talk about using your own domain for the CDN just yet. Once you have your origin options set, click Create Distribution.

Configuring the Ruby on Rails App to Use CloudFront

Using CloudFront as the asset Host for your static assets is truly a one line change.

In config/environments/production.rb:

config.action_controller.asset_host = ENV['CLOUDFRONT_ENDPOINT']

This tells Rails to use your CloudFront endpoint as the hostname for static assets. Your endpoint hostname will be specified in a host environment variable.

To pick up that change if you’re following along at home, go in to the OpsWorks console and edit your app:

  • Under "Application Source", point to the cloudfront branch.
  • Add a new environment variable pair:

    • Key: CLOUDFRONT_ENDPOINT
    • Value: The URL of your CloudFront endpoint, available in the CloudFront console. For e.g., "lettersandnumbers.cloudfront.net"
    • You do not need to "Protect" this value.

Now, deploy your app! You do not need to run a database migration.

How It Works

While we wait for the deployment to complete, how does all of this work?

If you look at the page source of our application before adding the CloudFront CDN, you’ll see lines like this:

<link data-turbolinks-track="true" href="/assets/application-0f3bf7fe135e88baa2cb9deb7a660251.css" media="all" rel="stylesheet" />
<script data-turbolinks-track="true" src="/assets/application-2ab5007aba477451ae5c38028892fd78.js"></script>

Those lines are how the page is including your application.css and application.js files. In app/views/layouts/application.html.erb, they correspond to these lines:

<%= stylesheet_link_tag 'application', media: 'all', 'data-turbolinks-track' => true %>
<%= javascript_include_tag 'application', 'data-turbolinks-track' => true %>

In turn, these include statements source from app/assets/stylesheets/application.css.scss and app/assets/javascripts/application.js. If you run the command rake assets:precompile, these files will be compiled and a fingerprint will be added to the filename. For example, I ran rake assets:precompile and the following files were generated:

  • public/assets/application-f3fd37796ac920546df412f68b0d9820.js
  • public/assets/application-68a6279b040bd09341327b6c951d74bc.css

The fingerprinting is a big part of what makes all of this work so smoothly. Let’s take a look at the page source after our latest deployment:

<link data-turbolinks-track="true" href="http://lettersandnumbers.cloudfront.net/assets/application-bfe54945dee8eb9f51b20d52b93aa177.css" media="all" rel="stylesheet" />
<script data-turbolinks-track="true" src="http://lettersandnumbers.cloudfront.net/assets/application-4984ddfbabfbae63ef17d0c8dca28d6c.js"></script>

You can see that we are now sourcing our static assets from CloudFront, and that nothing broke in the process. You can also see the compiled assets with fingerprints added to the filenames. When we loaded the page, the stylesheet_link_tag and javascript_include_tag used our asset host as the host, adding the expected asset filenames to the end of the hostname. When CloudFront received the request, these assets did not exist in the cache, so it forwarded the request to the Rails server, which served the files to CloudFront, which cached the files and sent them to you, the requestor. Future requests would simply hit the CDN, see the file present, and serve it to you from the fastest edge node.

Because fingerprinting is included out of the box, we do not need to deal with cache invalidations. When the assets change, the fingerprint will change. When that happens, CloudFront will not have the new file, and it will make a request to the origin server to get it. Eventually, the old, unused files will expire. It just works.

Wrap-Up

In this post, we took a Ruby on Rails application and cached its static assets using Amazon CloudFront and the Ruby on Rails asset pipeline. We also discussed the broad strokes of how CloudFront and Rails work together to make this simple to do.

Have any questions, comments, or problems getting your application to cache static content with Amazon CloudFront? Suggestions for topics you would like to see next? Please let us know in the comments!

Deploying Ruby on Rails Applications to AWS OpsWorks

by Alex Wood | on | in Ruby | | Comments

To begin our series on using Ruby on Rails with Amazon Web Services, we are going to start at the beginning: deploying our application. Today, we will be deploying our application to AWS OpsWorks.

Following along with this post, you should be able to deploy our "Todo Sample App" to AWS using OpsWorks, with your application and database running on different machine instances.

Getting Your Application Ready to Deploy

You can deploy the Todo sample application to OpsWorks directly from its public GitHub repo, using the ‘opsworks’ branch. If you explore the repo, you will notice that we’ve made a few design choices:

  • Our secrets file at config/secrets.yml expects the RAILS_SECRET_TOKEN environment variable to be set on our application servers.
  • We have required the mysql2 gem, to interface with a MySQL database.
  • We have required the unicorn gem, and will use unicorn as our app server.

Creating an OpsWorks Stack

Log in to the AWS Console and navigate to the AWS OpsWorks Console. Click Add Stack and fill out the form like so:

Add Stack Screen

Don’t worry about the "Advanced" settings for now – we won’t need them during this part of the tutorial. Once you’ve filled out the form, just press Create Stack and you’re done.

Creating the Rails App Server Layer

After creating a stack, you’ll find yourself at a page prompting you to create a layer, an instance, and an app. To start, click Add a layer.

We are making a few changes to the default options here. They are:

  • Using Ruby version 2.1.
  • Using "nginx and Unicorn" instead of "Apache2 and Passenger".
  • Using RubyGems version 2.2.1.

Once you’re all done, click Add Layer. You’ll be redirected to the "Layers" screen.

Creating the Database Layer

Next, we’re going to create our database layer. On the layers screen, click + Layer.

Add MySQL Layer

Choose "MySQL" from the drop down box, and leave everything else as-is. Of course, if you’re taking your own screenshots, it is best to avoid sharing your passwords of choice as well!

Click Add Layer and you’re done with this step.

MySQL Layer vs. Amazon RDS Layer

When creating your stack, you can choose to use an OpsWorks-managed EC2 instance running MySQL, called a "MySQL" layer, or you can create a layer that points to an existing Amazon RDS instance.

For this example, we are going to use a MySQL layer. You could substitute an RDS layer if you so chose. In future posts, we may explore this option in depth.

Adding Instances

We’ve made layers for our application servers and database, but we do not yet have application servers or a database. We will next create an instance of each.

Create an App Server Instance

From the "Layers" screen, click Add instance in the "Rails App Server" layer.

Add Rails Instance

We’re creating a t2.micro instance to optimize for cost (this is a demo after all). You may also want to create an SSH key and specify it here in order to be able to log in to your host for debugging purposes, but we don’t strictly need it so we are going to skip that for now.

Click Add Instance once you’re done, then start to begin the instance setup process. While that runs, we are going to make our database instance.

One quick aside about using a t2.micro instance: you can only create them in a VPC. We have created a VPC in this example, but if you were creating a stack without a VPC, t2.micro instances will not be available to you. Other instance types will, of course, work for this example.

Create a Database Instance

You’ll note that, if you’re following along with each step, you’re now at the "Instances" page. From either here or the layers page, under "MySQL", click Add an instance.

Add MySQL Instance

As before, we are creating a t2.micro instance. Click Add Instance to create the instance, and start to begin instance setup.

Adding the Application

While our instances are set up, let’s add our application. Click the Apps link on the sidebar, then click Add an app.

Add App

For this example, we’re using the Git repository at https://github.com/awslabs/todo-sample-app.git as our Application Source, and using the opsworks branch to ensure that you’re deploying the same code I was as this post was written. You can name the app whatever you’d like, but the "TodoApp" name will match with fields we will fill out later, so if you do change the name, make sure to use that new name going forward wherever we use "TodoApp".

Add App

To generate a value for the RAILS_SECRET_KEY environment variable, you can use the command rake secret within your copy of the repo. Just remember to set this as a "Protected value", and if you’re taking screenshots of your process, this is a good time to remove the placeholder value you used for the screenshot and to add a new value generated with rake secret.

Click Add App when you are done.

Deploying the Application

It is likely that your instances are done being created and set up by now, but double check that they are both online before continuing to this step. If by chance they are not quite set up, by the time you prepare a cup of tea and come back, they should be ready.

Click the Deployments link on the sidebar, then click the Deploy an App button.

Deploy App

Since we have not done so yet, remember to check "Yes" for the "Migrate database" setting. We will also need this custom JSON to ensure the "mysql2" adapter is used as intended:

{
  "deploy":
  {
    "todoapp":
    {
      "database":
      {
        "adapter": "mysql2"
      }
    }
  }
}

Click Deploy, and grab another cup of tea. You’ve now deployed the Ruby on Rails "Todo" sample app to AWS OpsWorks!

Use Custom JSON for All Deployments

You probably don’t want to be filling in the custom JSON for your adapter choice with every deployment. Fortunately, you can move this custom JSON into your stack settings to have it go with every deployment.

Click the Stack link on the sidebar, open Stack Settings, and click Edit.

Stack Settings

Add the custom JSON you used for your deployment earlier, and click Save.

Try It Out

To view the app in action, click on your app server’s name on the deployment screen to go to the server’s info page. Click the link next to "Public DNS", and you should see the front page of the application:

You can add tasks, mark them complete, and delete them as you like. In short, your application is running and performing database transactions.

Hello TodoApp!

Wrap-Up

In this post, we started with a Ruby on Rails application, and went step-by-step through the process to get it up and running on AWS with OpsWorks. Now, you can follow this same process to get your own Rails application running on AWS.

Now that we can deploy our application, we will begin to explore ways to make our app scale, improve availability, and optimize some common speed bottlenecks.

Have any questions, comments, or problems getting the app up and running? Suggestions for topics you would like to see next? Please reach out to us in the comments!

Blog Series: Ruby on Rails on Amazon Web Services

by Alex Wood | on | in Ruby | | Comments

Welcome to a series on how to integrate Ruby on Rails apps with Amazon Web Services. In this series, we’re going to start from scratch with a simple app, and show you how to make it scalable, highly available, and fault tolerant.

The Sample App

For this blog series, we have built a sample app in Ruby on Rails. You can find it on GitHub as awslabs/todo-sample-app.

The app itself is designed to be simple to follow. It is a very basic todo list, where you can add tasks, mark them complete, or delete them, all on a single page. In this way, we can focus on the code changes needed to integrate the app with Amazon Web Services, without worrying about confusion over what the app itself does.

There’s no hand-waving here: all the code you need to do this is in this repo, and all the setup you need to do in AWS is in the posts.

What the Series Will Cover

We’re going to start by covering how to deploy the TodoApp to the cloud using AWS OpsWorks. Then, we will talk about speeding up your app by caching your static assets with Amazon CloudFront. We will go on to discuss other scaling and performance improvements you can make to solve real-world problems in the cloud.

Have a topic you’d love for us to cover? Let us know in the comments!

Up Next

The first post, showing you how to deploy the Todo Sample App to AWS OpsWorks will be out soon. Stay tuned!