(#2886) seeded_rand: new function

seeded_rand is needed for repeatable randomness across nodes in a cluster

1 files changed, 22 insertions, 0 deletions

diff --git a/lib/puppet/parser/functions/seeded_rand.rb b/lib/puppet/parser/functions/seeded_rand.rb
new file mode 100644
index 0000000..44e27b8
--- /dev/null
+++ b/lib/puppet/parser/functions/seeded_rand.rb
@@ -0,0 +1,22 @@
+Puppet::Parser::Functions::newfunction(
+  :seeded_rand,
+  :arity => 2,
+  :type => :rvalue,
+  :doc => <<-EOS
+Usage: `seeded_rand(MAX, SEED)`. MAX must be a positive integer; SEED is any string.
+
+Generates a random whole number greater than or equal to 0 and less
+than MAX, using the value of SEED for repeatable randomness.  If SEED
+starts with "$fqdn:", this is behaves the same as `fqdn_rand`.
+
+EOS
+) do |args|
+  require 'digest/md5'
+
+  raise(ArgumentError, "seeded_rand(): first argument must be a positive integer") unless function_is_integer([args[0]]) and args[0].to_i > 0
+  raise(ArgumentError, "seeded_rand(): second argument must be a string") unless args[1].is_a? String
+
+  max = args[0].to_i
+  seed = Digest::MD5.hexdigest(args[1]).hex
+  Puppet::Util.deterministic_rand(seed,max)
+end