Introducing ESCAPE

Chris Read — Fri, 13 Feb 2009 12:31:12 +0000

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.

Chris Read » Build Pipelines

Introducing ESCAPE