The chef-client cookbook does a similar thing in its cron recipe:

  # Generate a uniformly distributed unique number to sleep.
  if node['chef_client']['splay'].to_i > 0
    checksum   = Digest::MD5.hexdigest(node['fqdn'] || 'unknown-hostname')
    sleep_time = checksum.to_s.hex % node['chef_client']['splay'].to_i
  else
    sleep_time = nil
  end

https://github.com/opscode-cookbooks/chef-client/blob/master...

This is random enough so you won't kill the server, and deterministic so the resource isn't always changing every Chef run.

No hash collisions, hostnames (in almost all practical environments) are never identical.

It's more or less random, but stable.