My custom puppet function changes values

[p]

Hi Everyone,

My custom puppet code changes values randomly. Why?

This code creates a random port for me based on the argument's hash. The idea is that this will create a TCP port for me based on the name of the argument I give it (for instance the FQDN) so that it is unique, above 1024 but below 65535. I don't want to have to worry about port numbers, it should just calculate the same every time.

module Puppet::Parser::Functions

  newfunction(:ip_port, :type => :rvalue) do |args|

    args[0].hash % 64511 + 1024

  end

end

I use it in a manifest this way:

$ip_port = ip_port('www.example.com')

The puppet agent runs every 30 minutes by default. It's a master/slave v3.8 setup. When I run it manually, the value always comes back the same. But when I leave it alone, at some point the value changes. I use this to create ports for haproxy. Thanks for your help.

Peter

[Trevor Vaughan]

Hi Peter,

Object.hash in Ruby provides the hash of the Object ID, not a consistent cryptographic hash of the string provided.

Try it in two different IRB sessions and you'll see what I mean. It will change between garbage collection runs and/or at every invocation of Puppet if done in cron.

Trevor

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[p]

Thanks, Trevor. I did and as you had predicted they are different.

[p]

Any suggestions on how I can get the hash of the string content itself so I can get this function to work? I really just don't want to manage ports anymore.

On Wednesday, May 18, 2016 at 7:35:55 AM UTC-7, Trevor Vaughan wrote:

[p]

I'm doing this instead:

module Puppet::Parser::Functions

  newfunction(:ip_port, :type => :rvalue) do |args|

    require 'zlib'

    Zlib.crc32(args[0]) % 64511 + 1024

  end

end

[Trevor Vaughan]

This should work in all versions of Ruby (YMMV)

'foo.bar.baz'.each_byte.map{|x| x}.join.to_i % 64511 + 1024

Trevor

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