cronrand - stateful (between puppet runs) randomizer eg. for cron minutes for equal load distribution

1 files changed, 31 insertions, 0 deletions

diff --git a/cronrand.rb b/cronrand.rb
new file mode 100644
index 0000000..3dd6810
--- /dev/null
+++ b/cronrand.rb
@@ -0,0 +1,31 @@
+# vim: set ts=2 sw=2 et :
+# TODO: path should not be hardcoded here
+#
+# USAGE:
+# $minutes = cronrand("puppet-run", $fqdn, 59)
+# file { "puppet-cron":
+#   name => /etc/cron.d/puppet-run",
+#   content => "$minutes * * * * root /usr/sbin/puppetd --onetime --no-daemonize --logdest syslog > /dev/null 2>&1\n"
+# }
+# ---
+# minutes will be chosen random and saved for each $fqdn,
+# second puppet run on same host will create same content as first one.
+
+module Puppet::Parser::Functions
+  newfunction(:cronrand, :type => :rvalue) do |args|
+    job = args[0]
+    host = args[1]
+    minutes = (args[2].to_i < 60) ? args[2].to_i : 59
+    filename = "/etc/puppet/modules/puppet/state/cronminutes-#{job}-#{host}"
+    value = 0
+
+    if FileTest.exists?(filename)
+      File.open(filename, 'r') { |fd| value = fd.gets.chomp.to_i }
+    else
+      value = rand(minutes)
+      File.open(filename, 'w') { |fd| fd.puts value }
+    end
+    value
+  end
+end
+