Workload Balance Migration Strategy

Synopsis

display name: Workload Balance Migration Strategy

goal: workload_balancing

[PoC]Workload balance using live migration

Description

It is a migration strategy based on the VM workload of physical servers. It generates solutions to move a workload whenever a server’s CPU or RAM utilization % is higher than the specified threshold. The VM to be moved should make the host close to average workload of all compute nodes.

Requirements

  • Hardware: compute node should use the same physical CPUs/RAMs

  • Software: Ceilometer component ceilometer-agent-compute running in each compute node, and Ceilometer API can report such telemetry “instance_cpu_usage” and “instance_ram_usage” successfully.

  • You must have at least 2 physical compute nodes to run this strategy.

Limitations

  • This is a proof of concept that is not meant to be used in production

  • We cannot forecast how many servers should be migrated. This is the reason why we only plan a single virtual machine migration at a time. So it’s better to use this algorithm with CONTINUOUS audits.

  • It assume that live migrations are possible

Requirements

None.

Metrics

The workload_balance strategy requires the following metrics:

metric

service name

plugins

comment

cpu_util

ceilometer

none

cpu_util has been removed since Stein.

memory.resident

ceilometer

none

Cluster data model

Default Watcher’s Compute cluster data model:

Nova cluster data model collector

The Nova cluster data model collector creates an in-memory representation of the resources exposed by the compute service.

Actions

Default Watcher’s actions:

action

description

migration

Migrates a server to a destination nova-compute host

This action will allow you to migrate a server to another compute destination host. Migration type ‘live’ can only be used for migrating active VMs. Migration type ‘cold’ can be used for migrating non-active VMs as well active VMs, which will be shut down while migrating.

The action schema is:

schema = Schema({
 'resource_id': str,  # should be a UUID
 'migration_type': str,  # choices -> "live", "cold"
 'destination_node': str,
 'source_node': str,
})

The resource_id is the UUID of the server to migrate. The source_node and destination_node parameters are respectively the source and the destination compute hostname (list of available compute hosts is returned by this command: nova service-list --binary nova-compute).

Note

Nova API version must be 2.56 or above if destination_node parameter is given.

Planner

Default Watcher’s planner:

Weight planner implementation

This implementation builds actions with parents in accordance with weights. Set of actions having a higher weight will be scheduled before the other ones. There are two config options to configure: action_weights and parallelization.

Limitations

  • This planner requires to have action_weights and parallelization configs tuned well.

Configuration

Strategy parameters are:

parameter

type

default Value

description

metrics

String

‘cpu_util’

Workload balance base on cpu or ram utilization. choice: [‘cpu_util’, ‘memory.resident’]

threshold

Number

25.0

Workload threshold for migration

period

Number

300

Aggregate time period of ceilometer

Efficacy Indicator

None

Algorithm

For more information on the Workload Balance Migration Strategy please refer to: https://specs.openstack.org/openstack/watcher-specs/specs/mitaka/implemented/workload-balance-migration-strategy.html

How to use it ?

$ openstack optimize audittemplate create \
  at1 workload_balancing --strategy workload_balance

$ openstack optimize audit create -a at1 -p threshold=26.0 \
        -p period=310 -p metrics=cpu_util