$ sudo yum install -y postgresql postgresql-server postgresql-devel
Ruby on Rails is a popular web framework written in Ruby. This guide covers using Rails 4 on OpenShift Container Platform.
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We strongly advise going through the whole tutorial to have an overview of all the steps necessary to run your application on the OpenShift Container Platform. If you experience a problem try reading through the entire tutorial and then going back to your issue. It can also be useful to review your previous steps to ensure that all the steps were executed correctly. |
For this guide you will need:
Basic Ruby/Rails knowledge
Locally installed version of Ruby 2.0.0+, Rubygems, Bundler
Basic Git knowledge
Running instance of OpenShift Container Platform v3
First make sure that an instance of OpenShift Container Platform is running and is available.
For
more info on how to get OpenShift Container Platform up and running check the
installation methods.
Also make sure that your oc CLI
client is installed and the command is accessible from your command shell, so
you can use it to
log in
using your email address and password.
Rails applications are almost always used with a database. For the local development we chose the PostgreSQL database. To install it type:
$ sudo yum install -y postgresql postgresql-server postgresql-devel
Next you need to initialize the database with:
$ sudo postgresql-setup initdb
This command will create the /var/lib/pgsql/data directory, in which the data will be stored.
Start the database by typing:
$ sudo systemctl start postgresql.service
When the database is running, create your rails user:
$ sudo -u postgres createuser -s rails
Note that the user we created has no password.
If you are starting your Rails application from scratch, you need to install the Rails gem first.
$ gem install rails Successfully installed rails-4.2.0 1 gem installed
After you install the Rails gem create a new application, with PostgreSQL as your database:
$ rails new rails-app --database=postgresql
Then change into your new application directory.
$ cd rails-app
If you already have an application, make sure the pg (postgresql) gem is present in your Gemfile. If not
edit your Gemfile by adding the gem:
gem 'pg'
To generate a new Gemfile.lock with all your dependencies run:
$ bundle install
In addition to using the postgresql database with the pg gem, you’ll also need to ensure the config/database.yml is using the postgresql adapter.
Make sure you updated default section in the config/database.yml file, so it looks like this:
default: &default adapter: postgresql encoding: unicode pool: 5 host: localhost username: rails password:
Create your application’s development and test databases by using this rake command:
$ rake db:create
This will create development and test database in your PostgreSQL server.
Since Rails 4 no longer serves a static public/index.html page in production, we need to create a
new root page.
In order to have a custom welcome page we need to do following steps:
Create a controller with an index action
Create a view page for the welcome controller index action
Create a route that will serve applications root page with the created controller and view
Rails offers a generator that will do all this necessary steps for you.
$ rails generate controller welcome index
All the necessary files have been created, now we just need to edit line 2 in config/routes.rb
file to look like:
root 'welcome#index'
Run the rails server to verify the page is available.
$ rails server
You should see your page by visiting http://localhost:3000 in your browser. If you don’t see the page, check the logs that are output to your server to debug.
In order to have your application communicating with the PostgreSQL database service that will be running in OpenShift Container Platform, you will need to edit the default section in your config/database.yml to use environment variables, which you will define later, upon the database service creation.
The default section in your edited config/database.yml together with pre-defined variables should look like:
<% user = ENV.key?("POSTGRESQL_ADMIN_PASSWORD") ? "root" : ENV["POSTGRESQL_USER"] %>
<% password = ENV.key?("POSTGRESQL_ADMIN_PASSWORD") ? ENV["POSTGRESQL_ADMIN_PASSWORD"] : ENV["POSTGRESQL_PASSWORD"] %>
<% db_service = ENV.fetch("DATABASE_SERVICE_NAME","").upcase %>
default: &default
adapter: postgresql
encoding: unicode
# For details on connection pooling, see rails configuration guide
# http://guides.rubyonrails.org/configuring.html#database-pooling
pool: <%= ENV["POSTGRESQL_MAX_CONNECTIONS"] || 5 %>
username: <%= user %>
password: <%= password %>
host: <%= ENV["#{db_service}_SERVICE_HOST"] %>
port: <%= ENV["#{db_service}_SERVICE_PORT"] %>
database: <%= ENV["POSTGRESQL_DATABASE"] %>
For an example of how the final file should look, see Ruby on Rails example application config/database.yml.
OpenShift Container Platform requires git, if you don’t have it installed you will need to install it.
Building an application in OpenShift Container Platform usually requires that the source code be stored in a git repository, so you will need to install git if you do not already have it.
Make sure you are in your Rails application directory by running the ls -1 command. The output of the command should look like:
$ ls -1 app bin config config.ru db Gemfile Gemfile.lock lib log public Rakefile README.rdoc test tmp vendor
Now run these commands in your Rails app directory to initialize and commit your code to git:
$ git init $ git add . $ git commit -m "initial commit"
Once your application is committed you need to push it to a remote repository. For this you would need a GitHub account, in which you create a new repository.
Set the remote that points to your git repository:
$ git remote add origin git@github.com:<namespace/repository-name>.git
After that, push your application to your remote git repository.
$ git push
To deploy your Ruby on Rails application, create a new Project for the application:
$ oc new-project rails-app --description="My Rails application" --display-name="Rails Application"
After creating the the rails-app project, you will be automatically switched to the new project namespace.
Deploying your application in OpenShift Container Platform involves three steps:
Creating a database service from OpenShift Container Platform’s PostgreSQL image
Creating a frontend service from OpenShift Container Platform’s Ruby 2.0 builder image and your Ruby on Rails source code, which we wire with the database service
Creating a route for your application.
Your Rails application expects a running database service. For this service use PostgeSQL database image.
To create the database service you will use the oc new-app command. To this command you will need to pass some necessary environment variables which will be used inside the database container. These environment variables are required to set the username, password, and name of the database. You can change the values of these environment variables to anything you would like. The variables we are going to be setting are as follows:
POSTGRESQL_DATABASE
POSTGRESQL_USER
POSTGRESQL_PASSWORD
Setting these variables ensures:
A database exists with the specified name
A user exists with the specified name
The user can access the specified database with the specified password
For example:
$ oc new-app postgresql -e POSTGRESQL_DATABASE=db_name -e POSTGRESQL_USER=username -e POSTGRESQL_PASSWORD=password
To also set the password for the database administrator, append to the previous command with:
-e POSTGRESQL_ADMIN_PASSWORD=admin_pw
To watch the progress of this command:
$ oc get pods --watch
To bring your application to OpenShift Container Platform, you need to specify a repository in which your application lives, using once again the oc new-app command, in which you will need to specify database related environment variables we setup in the Creating the Database Service:
$ oc new-app path/to/source/code --name=rails-app -e POSTGRESQL_USER=username -e POSTGRESQL_PASSWORD=password -e POSTGRESQL_DATABASE=db_name -e DATABASE_SERVICE_NAME=postgresql
With this command, OpenShift Container Platform fetches the source code, sets up the builder image, builds your application image, and deploys the newly created image together with the specified environment variables. The application is named rails-app.
You can verify the environment variables have been added by viewing the JSON document of the rails-app DeploymentConfig:
$ oc get dc rails-app -o json
You should see the following section:
env": [
{
"name": "POSTGRESQL_USER",
"value": "username"
},
{
"name": "POSTGRESQL_PASSWORD",
"value": "password"
},
{
"name": "POSTGRESQL_DATABASE",
"value": "db_name"
},
{
"name": "DATABASE_SERVICE_NAME",
"value": "postgresql"
}
],
To check the build process:
$ oc logs -f build rails-app-1
Once the build is complete, you can look at the running pods in OpenShift Container Platform.
$ oc get pods
You should see a line starting with myapp-<number>-<hash>, and that is your
application running in OpenShift Container Platform.
Before your application will be functional, you need to initialize the database by running the database migration script. There are two ways you can do this:
Manually from the running frontend container:
First you need to exec into frontend container with rsh command:
$ oc rsh <FRONTEND_POD_ID>
Run the migration from inside the container:
$ RAILS_ENV=production bundle exec rake db:migrate
If you are running your Rails application in a development or test environment you don’t have to specify the RAILS_ENV environment variable.
By adding pre-deployment lifecycle hooks in your template. For example check the hooks example in our Rails example application.
To expose a service by giving it an externally-reachable hostname like www.example.com use OpenShift Container Platform route. In your case you need to expose the frontend service by typing:
$ oc expose service rails-app --hostname=www.example.com
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It’s the user’s responsibility to ensure the hostname they specify resolves into the IP address of the router. For more information, check the OpenShift Container Platform documentation on: |