(#13205) Rotate array/string randomley based on fqdn, fqdn_rotate()

lib/puppet/parser/functions/fqdn_rotate.rb

@@ -0,0 +1,46 @@
+#
+# fqdn_rotate.rb
+#
+
+module Puppet::Parser::Functions
+  newfunction(:fqdn_rotate, :type => :rvalue, :doc => <<-EOS
+Rotates an array a random number of times based on a nodes fqdn.
+    EOS
+  ) do |arguments|
+
+    raise(Puppet::ParseError, "fqdn_rotate(): Wrong number of arguments " +
+      "given (#{arguments.size} for 1)") if arguments.size < 1
+
+    value = arguments[0]
+    klass = value.class
+    require 'digest/md5'
+
+    unless [Array, String].include?(klass)
+      raise(Puppet::ParseError, 'fqdn_rotate(): Requires either ' +
+        'array or string to work with')
+    end
+
+    result = value.clone
+
+    string = value.is_a?(String) ? true : false
+
+    # Check whether it makes sense to rotate ...
+    return result if result.size <= 1
+
+    # We turn any string value into an array to be able to rotate ...
+    result = string ? result.split('') : result
+
+    elements = result.size
+
+    srand(Digest::MD5.hexdigest([lookupvar('::fqdn'),arguments].join(':')).hex)
+    rand(elements).times {
+       result.push result.shift
+    }
+
+    result = string ? result.join : result
+
+    return result
+  end
+end
+
+# vim: set ts=2 sw=2 et :

spec/unit/puppet/parser/functions/fqdn_rotate_spec.rb

@@ -0,0 +1,40 @@
+#!/usr/bin/env rspec
+require 'spec_helper'
+
+describe "the fqdn_rotate function" do
+  before :all do
+    Puppet::Parser::Functions.autoloader.loadall
+  end
+
+  before :each do
+    @scope = Puppet::Parser::Scope.new
+  end
+
+  it "should exist" do
+    Puppet::Parser::Functions.function("fqdn_rotate").should == "function_fqdn_rotate"
+  end
+
+  it "should raise a ParseError if there is less than 1 arguments" do
+    lambda { @scope.function_fqdn_rotate([]) }.should( raise_error(Puppet::ParseError))
+  end
+
+  it "should rotate a string and the result should be the same size" do
+    @scope.expects(:lookupvar).with("::fqdn").returns("127.0.0.1")
+    result = @scope.function_fqdn_rotate(["asdf"])
+    result.size.should(eq(4))
+  end
+
+  it "should rotate a string to give the same results for one host" do
+    @scope.expects(:lookupvar).with("::fqdn").returns("127.0.0.1").twice 
+    @scope.function_fqdn_rotate(["abcdefg"]).should eql(@scope.function_fqdn_rotate(["abcdefg"]))
+  end
+
+  it "should rotate a string to give different values on different hosts" do
+     @scope.expects(:lookupvar).with("::fqdn").returns("127.0.0.1")
+     val1 = @scope.function_fqdn_rotate(["abcdefghijklmnopqrstuvwxyz01234567890987654321"])
+     @scope.expects(:lookupvar).with("::fqdn").returns("127.0.0.2")
+     val2 = @scope.function_fqdn_rotate(["abcdefghijklmnopqrstuvwxyz01234567890987654321"])
+     val1.should_not eql(val2)
+  end
+
+end