plugin for knife-vsphere to add extend disk, extra disk, and memory reservation during clone

knife-vsphere-plugin.rb

require 'rbvmomi'

class KnifeVspherePlugin
  ##
  # example json data
  # disk_num will default to 1
  # datastore will default to the first disks datastore
  # pass the below json as a string using the --cplugin-data option 
  # {"memory_reservation":200, "extend_disk":{"new_size_gb":11,"disk_num":1},"extra_disk":{"size":10,"datastore":"somedatastore"}}
  ##
  attr_accessor :data # rather than defining a data= method

  def customize_clone_spec(src_config, clone_spec)

    unless data.nil?
      json_data = JSON.parse(data)
      #add memory reservation if requested
      if json_data.key?('memory_reservation')
        puts "Memory Reservation  #{json_data['memory_reservation']}"
        clone_spec.config.memoryAllocation = {"reservation"=> json_data['memory_reservation']}

      end

      #extend 1st disk or a disk by number
      if json_data.key?('extend_disk')
        disk_num= json_data['extend_disk']['disk_num'] || 1
        new_disk_size = json_data['extend_disk']['new_size_gb']
        vmdk_size_kb = new_disk_size.to_i * 1024 * 1024

        src_config.hardware.device.each do |device|
          if device.class == RbVmomi::VIM::VirtualDisk
            if device.deviceInfo.label == "Hard disk #{disk_num}"
              puts "Disk #{disk_num} found !"
              puts "New disk size #{new_disk_size} GB"
              device.capacityInKB=vmdk_size_kb

              extend_disk_spec = RbVmomi::VIM::VirtualDeviceConfigSpec(
                device: device,
                operation: RbVmomi::VIM::VirtualDeviceConfigSpecOperation('edit')
              )
              clone_spec.config.deviceChange << extend_disk_spec

            end
          end

        end
      end


      #add another disk if requested

      if json_data.key?('extra_disk')

        #get number of disks on template that is being cloned
        disks =src_config.hardware.device.select do |device|
          device.is_a? RbVmomi::VIM::VirtualDisk
        end

        disk_number = disks.length+1
        #use same datatsore as first disk if not specified
        datastore = json_data['extra_disk']['datastore'] || src_config.datastoreUrl[0].name
        size = json_data['extra_disk']['size'].to_i * 1024 * 1024
        puts "Extra disk size #{json_data['extra_disk']['size']} GB "

        newdisk = RbVmomi::VIM::VirtualDeviceConfigSpec(
          operation: 'add',
          fileOperation: :create,
          device: RbVmomi::VIM.VirtualDisk(
            key: disk_number,
            backing: RbVmomi::VIM.VirtualDiskFlatVer2BackingInfo(
              fileName: "[#{datastore}]",
              diskMode: "persistent",
              thinProvisioned: false,
            ),
            controllerKey: 1000,
            unitNumber: disk_number,
            capacityInKB: size,
          )
        )
        clone_spec.config.deviceChange << newdisk

      end

    end

    #dump clone_spec for debugging
     Chef::Log.debug(YAML::dump(clone_spec))
    clone_spec
  end

end

plugin-json.json

{
  "memory_reservation": 200,
  "extend_disk": {
    "new_size_gb": 11,
    "disk_num": 1
  },
  "extra_disk": {
    "size": 10,
    "datastore": "somedatastore"
  }
}

Seems like new_size_gb is the total size after extending the disk. Changed the value to a larger one and it worked.
If the disk is 30GB, we have to use a number that is greater than 30. e.g.
--cplugin-data '{"extend_disk":{"new_size_gb":40,"disk_num":1},"extra_disk":{"size":15,"datastore":"Verify_003"}}'