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Archive for February, 2009

Above the Clouds – This Sounds Familiar…

24 February 2009 Leave a comment

I found a link to Above the Clouds, a paper on Cloud Computing recently published by a quartet of UC Berkeley RAD Lab professors. I’ve been quite disappointed with publications on the subject of the latest buzzword taking the world by storm right now, so I was not expecting much when I first clicked on the link. The thing is, as I started reading through the Executive Summary it all sounded very familiar. The outline the give in the summary follows the same outline as a talk I gave in November last year at the ThoughtWorks London office for the London Java Community.

The only criticism I have is that they don’t put enough emphasis on one of my key reasons for why it’s suddenly taken off. Cloud computing is not a new idea – it’s an extension of the Utility Computing that John McCarthy talked about in 1961. Although they only make a passing remark in section 3, I think one of the most important reasons it’s taken off is that the services Amazon provide were the first that were not a “solution looking for a problem”. Earlier offerings by the likes of Sun, HP and Intel all created a solution that they tried to sell to clients. The problem was that there were remarkably few problems that their solutions solved. Amazon simply exposed services that they were using internally already. That’s not to say the other reasons they give are not valid, I totally agree with them. I think they just missed a good point.

One of the topics I only glanced over is covered cover quite well in section 6 – Cloud Computing Economics. They provide some interesting example cost calculations. Although the numbers are obviously US centric, they do provide a nice way for a company to approach making the old “build vs buy” comparison.

In summary, I highly recommend this paper for anyone who wants to get the head around what this Cloud stuff is all about and what they need to do to prepare for it.

Introducing ESCAPE

13 February 2009 3 comments

Whenever I talk to new clients about Continuous Integration, and especially about using Build Pipelines to extend their CI process to cover testing things like the deployment of their application, there is always one question that is guaranteed to pop up – how do I manage the configuration of my application in all these environments?

This is always a hard one to answer. In the last place I worked as a System Administrator we used Split-Horizon DNS as one of the ways to solve connecting to the correct host for a service. Our applications had hard coded hostnames for key services such as db.internal.domain, loghost.internal.domain and mailhost.internal.domain. Depending on which environment they ran in, when the did a DNS lookup they would get an answer that pointed them to the correct server providing that service for the environment they were physically running in. Combine this with tools like an LDAP Server in each of these environments containing the rest of the system configuration and life is easy. Or is it?

DNS and LDAP servers are relatively straight forward for experienced Sys Admins to understand and maintain, but they still can’t be described as easy to use, which is probably why so few people do it. This limits our options for fixing things down to two general categories – fix DNS and LDAP admin tools so they are easy to use, or find another way to solve the problem.

We chose the path of least resistance and went for the second option – creating ESCAPE. In the Unix tradition, it’s an app that takes one problem and solves it simply and well (at least in our opinion). It provides a RESTful interface for both the setting and getting of environment configuration. GET requests will retrieve configuration, whereas POST/PUT requests will create new entries or update them.

The URL scheme we’ve decided on is most easily demonstrated by constructing an example URL:

URL Value returned in the body
http://escape/ User interface. No API available here.
http://escape/environments/ A JSON list of all the available environment.
http://escape/environments/production/ A JSON list of all the applications in the “production” environment.
http://escape/environments/production/mywebapp All keys and values for the “mywebapp” application in the “production” environment.e.g:
key1=value1
key2=value2
http://escape/environments/production/mywebapp/thiskey The value of “thiskey” for the “mywebapp” application in the “production” environment.

As the tool is now usable we’ve happily released version 0.1. Currently we’re busy putting a lot of work into making the management interface understandable and intuitive to use. The closest thing we currently have to a roadmap is our ToDo list.

Please join us on the discussion group with your feedback.

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