Overview of CloudFoundry
CloudFoundry is an opensource Platform as a Service (PaaS) technology originally introduced and commercially supported by Pivotal. The software makes it possible to very easily stage, deploy and scale applications, thanks in part to its adoption of buildpacks which were originally introduced by Heroku.
Some software design principles are required to achieve scale with cloud foundry. The most notable design choice is a complete abstraction of persistence, including filesystem, datastore and even in memory cache. This is because instances of an application are transient and stateless. Since this is generally good design anyway, many applications may find it easy to migrate to CloudFoundry.
CloudFoundry can be viewed from two perspectives: CloudFoundry internals and Application Developers who want to deploy on CloudFoundry. The image directly below is from the CloudFoundry architecture overview.
This shows the internal components that make up CloudFoundry. The router is the internet facing component that matches requests up with application instances. It performs load balancing among instances of an application. Unlike a load balancer, there is no concept of sticky sessions, since application instances are assumed to be stateless.
The DEA is a compute resource (usually a virtual server, but it can be any compute resource, including bare metal). CloudFoundry uses a technology called Warden for containerization. Other distributions use alternative technologies, like docker.
Services, such as database, cache, filesystem, etc. must implement a Service Broker API. Through this API, CloudFoundry is able to discover, provision and facilitate communication of credentials to each instance of an application.
Application Developers interact with CloudFoundry in a few different ways. Two common methods include the command line client and Eclipse plugin. Using these tools, developers may login to a CloudFoundry installation and deploy apps under organizations and spaces. The following diagram illustrates this.
When a developer is ready to deploy, he pushes his app. CloudFoundry then identifies a suitable buildpack and stages the application resulting in a droplet. A droplet is a compressed tar file which contains all the application files and runtime dependencies. After staging, app instances are created and the droplet is extracted on the new instance at which point the application is started. If services are required, these are provisioned when the application is pushed.
There are many contributors to open source CloudFoundry. This has resulted in various distributions of CloudFoundry aside from Pivotal’s commercial offering.
ActiveState distributes CloudFoundry under the brand name Stackato. Some notable differences include the use of docker for instances and a web interface that includes an app store for deploying common applications.
HP Helion Development Platform
Hewlett Packard then offers an enterprise focused distribution of Stackato as HP Helion Development Platform. The enterprise focus includes an emphasis on the ability to use private cloud, public cloud and traditional IT to cost effectively, securely and reliably deploy and scale mission critical applications.
Getting started with CloudFoundry
It’s easy to get started with CloudFoundry. Here are a couple of tutorials that will get you ready to quickly deploy apps.