Virgo Buildpack Refreshed

I'm no longer leading the Virgo project, but I am still fond of Virgo, so I thought I would update the Virgo buildpack (previously mentioned in this blog) in my own time to re-base it on the current Java buildpack.

It now inherits all the benefits of the Java buildpack (more here):

• Ability to upgrade Virgo without changing the buildpack or the application - great when a security fix needs to be applied.
• Automatic calculation of JVM memory settings.
• Clean separation of components - Virgo is a new container (described here) and the other components including OpenJDK support are inherited for free.
• Helpful diagnostics including automatic JVM destruction on "out of memory" and debug logging of the buildpack's operations.

I decided to stick to the most general style of application layout that the previous version of the Virgo buildpack used. This consists of a pickup directory containing zero or more applications and, optionally, a repository/usr directory containing any additional dependencies of the application which are not provided by Virgo. This has the advantage that the detection criterion for Virgo (existence of the pickup directory) does not overlap with the detection criteria of the other containers inherited from the Java buildpack (Groovy, Play, Java Main, Spring Boot CLI, Tomcat) and so the Virgo buildpack is a functional superset of the Java buildpack.

There are two use cases that interest me. One is running Virgo on Cloud Foundry. The other is running Virgo as an Ubuntu Juju Charm - but more of that on another occasion.