Hudson Default Ant

Most Hudson configuration is self-explanatory and easy to find in the web configuration. Many props go to the developers of Hudson because it is quite easy to setup and use. However, there are a couple of things that I've found lately that don't seem to be documented in the Hudson docs.

Configuring Ant

From the Hudson dashboard, click on
  Manage Hudson -> Configure System
or you can simply navigate to
  http://your-server-here/hudson/configure

Look for the section labeled "Ant" and add your Ant installations by clicking "Add" and providing a name and the absolute path for ANT_HOME. This couldn't be simpler.

Default Ant

When you are configuring a build, you can tell Hudson which Ant you want to use. You may either use one of the named Ant installations that you previously added, or Hudson gives you the option of using the "Default Ant."

For some reason, I was thinking that I had somehow set the only Ant installation that I added as the default (since it was indeed the only one). But, this was not the case, and my build failed with this console output:

FATAL: command execution failed.Maybe you need to configure the job to choose one of your Ant installations?
java.io.IOException: Cannot run program "ant" (in directory "/home/tomcat/hudson/jobs//workspace/build")

Then, I got to looking at how to set the default Ant, and I could not for the life of me find the setting anywhere. This is because, there is NO default that can be changed from within Hudson.

If you tell Hudson to use the default Ant for a build, then it will use whatever ant it finds on the PATH. Note that I did not say that Hudson will use whatever ANT_HOME points to. Hudson must be able to find the ant command on the PATH.

In our case, Hudson runs as the user 'tomcat.'

So, if I wanted to use the default Ant for a build, I would typically solve this by setting both the ANT_HOME and PATH environment variables for the tomcat user. I would set ANT_HOME to the Ant installation that I wish to use as default, and I would then add $ANT_HOME/bin to the PATH environment variable.

What I Actually Did

Since I really didn't care to go to all that trouble of setting environment variables, I just used the named Ant instance that I had already configured in Hudson. We do not have a default Ant available to Hudson, and it's not a problem.