Is there a way to calculate resource value based on input parameter in HOT?

Question

I need to automatically calculate one volume size based on another. Simplified example:

There is an input parameter

data_disk_size:
  type: number
  default: 50

And we want second volume to be: 100 if 1 < data_disk_size < 200; 200 if 200 < data_disk_size < 400; else 400

As i understood, conditions block would not help as it operates only with boolean values and available options are if and yaql. But i could not manage to use them together:

  instance_volume_2:
    type: OS::Cinder::Volume
    properties:
      ...
      size:
        if:
        - yaql:
            expression: $.data > 1 and $.data < 200
            data: {get_param: data_disk_size}
        - 100
        - 200 {only for test, there should be nested if}

It gives:

'ERROR: if.yaql: The function "yaql" is invalid in this context'

So the only remaining option is pure yaql, BUT it has no if operator!

What am i missing? Maybe there is simple way to do it?

Answer 1

I`ve found solution! Ugly, but working one :)

YAQL has no if, but has other logic operators, such as and/or. So value can be calculated this way:

instance_volume_2:
  type: OS::Cinder::Volume
    properties:
      ...
      size:
        yaql:
          expression: (($.data < 200 and 100) or ($.data < 400 and 200)) or 400
          data: {get_param: data_disk_size}