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BalanceInstancesOS Heuristic

Table of Contents

Description

This heuristic aims to balance the hosts that are overloaded, by migrating the instances that are responsible for the increased utilization in the hosts, to hosts that aren't overloaded, till the hosts aren't overloaded anymore or that all possibilities are over. A host is considered overloaded when its total of used cpu divided by the total of cpu is greater than the provided cpu_ratio.

Algorithm

1. Select all hosts that are overloaded
2. If no overloaded hosts or If all overloaded hosts are equal to the all hosts given in the
infrastructure section, nothing can be done
3. For each overloaded host
    3.1 While selected_host is overloaded and still have instances to try to migrate:
        3.1.1 Selected instance with high utilization that wasn't migrated before.
        3.1.2 Look for a host that is less loaded and can recive this instance without exceed the cpu_ratio.
4. Migrate the all instances selected
5. Update the number of wait rounds for all migrated instances.

Configuration

To configure this heuristic you need to set two parameters in the heuristic section in the configuration file, thoose parameters are: moduleand class.

You can find an example of configuration file for this heuristic here.

Example of heuristic section in configuration file

load_balancer_balanceinstancesos.cfg

[heuristic]
# The filename for the module that is located in /loadbalancer/service/heuristic/
# without .py extension
module=instances
# The class name that is inside the given module, this class should implement BasicHeuristic
class=BalanceInstancesOS

Dependencies

  • Monasca In your Monasca you should ensure that you have the following metrics:

  • cpu.percent: Informs the percentage of cpu used by a host.

  • vm.cpu.utilization_norm_perc: Informs the normalized cpu utilization percentage for instances in the hosts

  • Hypervisor KVM Your hosts should provide use KVM as hypervisor to allow the collection of the capacity of the instances through the virsh command through ssh connection.