Chapter 1. Introduction to OpenShift Online

OpenShift Online by Red Hat is a Platform as a Service (PaaS) that provides developers and IT organizations with an auto-scaling, cloud application platform for deploying new applications on secure, scalable resources with minimal configuration and management overhead. OpenShift Online supports a wide selection of programming languages and frameworks, such as Java, Ruby, and PHP. Integrated developer tools, such as Eclipse integration, JBoss Developer Studio, and Jenkins, support the application life cycle.
Built on Red Hat Enterprise Linux, OpenShift Online provides a secure and scalable multi-tenant operating system for today's enterprise-class applications while providing integrated application runtimes and libraries.

1.1. Basic Architecture

OpenShift Online provides disk space, CPU resources, memory, network connectivity, and an Apache or JBoss server to create, deploy, and manage applications in the cloud. For most types of applications, OpenShift Online creates a file system layout that you can use as a template for building an application. It also generates a limited Domain Name System (DNS) so your application is accessible online.
The following table describes the basic system components of OpenShift Online.

Table 1.1. Basic Components

System Component Description
Gears Resource-constrained containers for application code where cartridges run. Gears determine the amount of RAM and disk space available to a cartridge.
Cartridges Cartridges provide the functionality to run applications. Numerous cartridges are currently available to support languages such as Perl, PHP, and Ruby, as well as many database cartridges, such as PostgreSQL and MySQL.
The following gear sizes are available with OpenShift Online:
  • Small gears provide 512MB of RAM, 100MB of swap space, and 1GB of disk space
  • Small.highcpu gears provide 512MB of RAM, double the CPU performance of Small gears, 100MB of swap space, and 1GB of disk space
  • Medium gears provide 1GB of RAM, 100MB of swap space, and 1GB of disk space
  • Large gears provide 2GB of RAM, 100MB of swap space, and 1GB of disk space
By default, there are three small gears available with a total of 1.5GB of RAM and 3GB of disk space. OpenShift Online can assign these three gears to a single application and its cartridges (Cron, MySQL, etc.), use each gear for a separate application, or use the gears for scaling an application.