Akom's Tech Ruminations

First, the custom fact. Important note here is that if you're on an older puppet (say, 3.7), you need to make sure that stringify_facts is false on both the puppet master and agents, and that you bounced both! This fact returns an array of hashes, and if stringify_facts is true, you'll get a very ugly string instead.

Here is a basic implementation of a fact that loads info about the installed JDK's - this is for linux only, obviously:

# Looks for install JDKs in /usr/lib/jvm and sets them as an array of hashes: { "path" => dirpath, "vendor" => vendor, "version" => version }
#
Facter.add("java_versions") do
  setcode do

    result = []

    if File.exists?('/usr/lib/jvm') or File.exists?('/usr/lib64/jvm')
      cmd = 'find /usr/lib*/jvm -type f -name javac | grep -v jre | grep -E "[0-9]\.[0-9]" | sort | sed "s/^\(.*java-\([0-9]\.[0-9]\)\.[0-9].*\)\/bin\/javac$/\2 \1/"'
      output = %x( #{cmd} ).split("\n")


      output.each { |line|
        lineparts = line.split(" ")
        version = lineparts[0]
        dirpath = lineparts[1]
        vendor = "sun"

        if dirpath.match(/openjdk/)
          vendor = "openjdk"
        end

        result.push({"path" => dirpath, "vendor" => vendor, "version" => version})
      }
    end

    result
  end
end  

 

I would add support for other JDK vendors but I didn't have any to test on. Of course it would be more proper to use some complicated combination of querying rpm and alternatives, but in my testing these were both entirely unpredictable.

Now, let's use the information in a template:

<toolchains>
    <% @java_versions.each do |java_info| %>

    <toolchain>
        <type>jdk</type>
        <provides>
            <version><%=java_info['version']%></version>
            <vendor><%=java_info['vendor']%></vendor>
        </provides>
        <configuration>
            <jdkHome><%=java_info['path']%></jdkHome>
        </configuration>
    </toolchain>
   
    <% end %>

</toolchains>