classes in a script file, so you can create scripts that are not only descriptive, but executable as well. It is this "descriptive executability" that permits IMOD to roll everything it needs to know about a system into a single file.
[ Simple, hosted, database-driven Web apps: See the InfoWorld Test Center review of Caspio Bridge, "A Web-based app builder with a Microsoft twist," and "Application builders in the sky." ]
IMOD's user interface is a three-tabbed control panel. Foremost on the list is the N-Tier tab, where you can view available templates and systems (the latter being the configured and executable form of the former). Select a system, and you can view it either in graphical, "run-time" form, or as a text-only XML file (the system definition file mentioned above). You can also open a tree view of the system, which shows the state of each of its Amazon Machine Images (running/terminated), its instance identifier, firewall rules, and more. Click the "start system button," and the selected system is deployed and launched in accordance with the system definition file.
Kaavo provides a number of prebuilt templates that you can use to jump-start your own applications. These include a variety of JIRA configurations (JIRA is a popular issue-tracking system), a MySQL cluster system, a template for the PHP-based collaborative project management system phpCollab, and more.
Other entries on the control panel include the Profile tab, where you can configure your account. This tab also includes billing and user management. From the Accounting tab, you can review your service usage over a selectable time range.
IMOD's system definition file is a two-edged sword. On the one hand, it keeps everything in one place, and that bookkeeping advantage should not be underrated. Also, if something goes wrong, you pretty much know where to look. On the other hand, it's one more language's syntax you have to learn. Because it depends on Velocity, an understanding of Java is a definite advantage. Nevertheless, Kaavo's documentation is good enough that even new users can find their way around with few bruised noses.
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
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