14 Jan 2011

SBT builds with Hudson

We build our Lift applications with Hudson Jenkins, and we’re in the process of converting some projects from Maven to SBT.  This is mostly straight-forward but there are a couple of non-obvious things you might need to know.

Running SBT

There’s the start of a Hudson SBT plugin, but at the moment we’re running SBT from Hudson by simply shelling out to execute the SBT command.

To do this, install SBT somewhere (.hudson/tools/sbt for us) and then create a new free-style Hudson job and add a build step of “Execute Shell”.  We have:

/usr/lib/jvm/java-6-sun/bin/java -Dsbt.log.noformat=true -jar /home/hudson/.hudson/tools/sbt/sbt-launch-0.7.4.jar clean update test package

That’s it. Your project will build.

(The -Dsbt.log.noformat=true part turns off the SBT colour formatting which you want off otherwise your build file will contain weird formatting control characters).

Controlling the WAR name

By default the WAR filename will be something like foo-scala\_2.8.1-1.0.war, which is fine, except because of the way we deploy we wanted to drop the Scala version number.  That’s easy to do, and you can configure it in your SBT project file:

override def artifactID = "foo"

Adding build information to your MANIFEST.MF

In our apps we like to include the Hudson build number in the footer of every page. We do this by using the fact that Maven Hudson builds include the build number in the META-INF/MANIFEST file.  SBT doesn’t.

Fortunately, the fine Scala team at The Guardian have published an SBT plugin to add information to the MANIFEST.  The install details are in the README.  

Hudson sets the build number as an environment (shell) variable.  To pick these up via the plugin we just set them as -D parameters:

/usr/lib/jvm/java-6-sun/bin/java -DBUILD_NUMBER=$BUILD_NUMBER -DGIT_BRANCH=master -DJOB_NAME=$JOB_NAME -Dsbt.log.noformat=true -jar /home/hudson/.hudson/tools/sbt/sbt-launch-0.7.4.jar clean update test package

When that executes:

/usr/lib/jvm/java-6-sun/bin/java -DBUILD_NUMBER=212 -DGIT_BRANCH=master -DJOB_NAME=FooHudsonJob  -Dsbt.log.noformat=true -jar /home/hudson/.hudson/tools/sbt/sbt-launch-0.7.4.jar clean update test package

Our SBT project file picks up these System properties:

def revision = systemOptional[String]("GIT_BRANCH", "DEV").value
def build = systemOptional[String]("BUILD_NUMBER", "DEV").value
def versionName = systemOptional[String]("JOB_NAME", "DEV").value

The result is a WAR file with a META-INF/MANIFEST.MF file that looks something like this:

Manifest-Version: 1.0
Implementation-Title: foo-1.0
Title: foo-1.0
Implementation-Version: FooHudsonJob
Branch: master
Date: Fri Jan 07 14:41:51 UTC 2011 Build: 212

Test results

With what we have at the moment if a test fails, the build fails.  This is good.

What we don’t have is the nice graph of tests.  If you want that, take a look at  Christoph Henkelmann’s Blog:  How to build sbt projects with Hudson and integrate test results.

For us, the next step is adding in the Undercover code coverage reporting tool instead.