5 The HAIZEA parameter in OpenNebula

The previous section showed how you can add an HAIZEA parameter to your OpenNebula VM template to request a simple advance reservation. The three Haizea options (start, duration, and preemptible) can take other values:

• start: This option specifies when the VM will start. Valid values are:
  • best_effort: The VM will be scheduled as soon as resources are available. If resources are not available right now, the request is put on a queue and it remains there until there are sufficient resources (requests are scheduled on a first-come-first-serve basis).
  • now: The VM will be scheduled right now. If resources are not available right now, the request is rejected.
  • Exact ISO timestamp: i.e., YYYY-MM-DD HH:MM:SS. The VM must start at exactly that time. If enough resources are not available at that time, the resource is not requested.
  • Relative ISO timestamp: For convenience's sake (and also for testing) this provides an easy way of specifying that a VM must start "at T time after the VM is submitted". The format would be +HH:MM:SS (the "+" is not ISO, but is used by Haizea to determine that it is a relative timestamp)
• duration: The duration of the lease. Possible values are:
  • unlimited: The lease will run forever, until explicitly stopped
  • ISO-formatted time: i.e., HH:MM:SS
• preemptible: This option can be either yes or no.
• group: This option can take on any string value, and allows you to schedule several VMs as a group (or, in Haizea terminology, as a single lease with multiple nodes). All OpenNebula VM templates with the same group name will be considered part of the same lease (i.e., all the VMs will be scheduled in a all-or-nothing fashion: all VMs must be able to start/stop at the same time). Future versions of OpenNebula will automatically manage this option, so users don't have to worry about manually setting this option in multiple VM templates (which can be error-prone).

Usually, you will want to use these options to create one of Haizea's supported lease types:

1 Advance reservations

When you need your VM available at a specific time, this is called an advance reservation, or AR. The VM we used above is an example of an AR:

HAIZEA = [
  start        = "+00:00:30",
  duration     = "00:01:00",
  preemptible  = "no"
]

Of course, instead of specifying that you want your VM to start after a certain amount of time has passed (30 seconds, in this case), you can also specify an exact start time:

HAIZEA = [
  start        = "2008-11-04 11:00:00",
  duration     = "03:00:00",
  preemptible  = "no"
]

NOTE: Haizea currently only supports non-preemptible ARs.

2 Best-effort provisioning

When you instruct Haizea to determine the start time on a best-effort basis, your request will be allocated resources as soon as they become available. Take into account that your request may be placed on a queue, and you'll have to wait until your turn is up. You can use the haizea-list-leases and haizea-show-queue to check on the state of your lease.

HAIZEA = [
  start        = "best_effort",
  duration     = "01:00:00",
  preemptible  = "yes"
]

A best-effort VM can be preemptible or non-preemptible. If you request a non-preemptible VM, you may still have to wait in the queue until you get your resources but, once you do, no one can take them from you.

3 Immediate provisioning

Sometimes, you need a VM right now or not at all. In that case, you can set the starting time to now.

HAIZEA = [
  start        = "now",
  duration     = "unlimited",
  preemptible  = "no"
]