Cloud control systems tame the ether

3tera, Enomaly, Kaavo, and RightScale take myriad and mixed approaches to managing virtual servers in the sky

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If you want to go it on your own, Kaavo has a self-serve plan that begins with a 30-day free trial. After that, you pay a fixed monthly fee for a fixed number of CPU hours. Exceed the available hours, and you fall into a pay-as-you-go scheme for any additional time. Users who need guidance will want the Enterprise Solution, which provides 24/7 support and training; contact Kaavo for pricing. Currently, Kaavo supports only Amazon's EC2, but expects to add support for other cloud providers in the near future.

RightScale

RightScale takes a non-intuitive approach to preparing and managing cloud-based systems. Rather than preconfigure a machine image, the RightScale methodology is to launch a "bare" image and have that instance configure itself by executing pre-installed scripts. Such scripts are called RightScripts, and they are the essential ingredients of a RightScale-powered cloud system.

A RightScript can be written in any of the well-known scripting languages: shell script, Python, Perl, or Ruby, to name a few. The language is unimportant. What is important is the fact that RightScripts can include parameters, and those parameters can be programmatically filled in by the RightScale system at runtime. RightScripts are therefore reusable, so a RightScript that installs MySQL, for example, can work on any cloud server that needs a MySQL installation.

There are three types of RightScripts, each designed to run at a specific point in a machine image's lifetime. Boot RightScripts execute just after the machine image is booted. Operational RightScripts execute once the image is running. And a decommission RightScript will execute just prior to the image being shut down. RightScripts can be used for just about any operation imaginable, but typically they install, configure, and start applications on the machine image they occupy.

To be accurate, RightScale images aren't completely barren. First, RightScale images include a small piece of software that, at boot time, contacts the RightScale system and basically asks: "I just booted, what am I supposed to do?" The RightScale system then begins feeding the image whatever RightScripts it is configured to use. And, of course, the necessary scripting languages are pre-installed on RightScale images. For example, RightScale pre-installs Ruby; I was told by a RightScale engineer that they use Ruby "extensively." These modifications convert a basic machine image into a "RightImage."

Ultimately, a RightScript will end up as part of a ServerTemplate. A ServerTemplate is a base server image, associated with the RightScripts that configure the server to do its assigned work. For example, an Ubuntu-based MySQL ServerTemplate would consist of an Ubuntu machine image and all the RightScripts needed to install, configure, and launch MySQL. RightScale provides a number of prebuilt, application-specific ServerTemplates. To create your own, you merely clone a copy of the original, add or modify the associated RightScripts, and save the result in your local repository.

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The life-blood of the RightScale system is the RightScript. Here, a shell-script-based RightScript installs MySQL on whatever server image the script is associated with.
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