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Resolves unclear formatting of compute extensions documentation at http://nova.openstack.org/api_ext/index.html The rst extensions template has been updated to include extension name as top level hierarchy, and demote all other content. All existing documentation pages have been reformatted as per the updated template. The ext_aggreagates.rst file has also been added to index.rst. Amendments: - Author added to Authors file - Typo in ext_volumes.rst fixed Change-Id: Id67ef91a6e8eaaf4fba46abbd57759c77aaf8991
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The Host Aggregates Extension
About this Extension
This extension introduces the concept of aggregates into Nova. Host aggregates are different from zones and availability zones: while the former allows the partition of Nova deployments into logical groups for load balancing and instance distribution, the latter are for providing some form of physical isolation and redundancy from other availability zones (e.g. by using separate power supply and network gears). Availability zones do not necessarily mean geographic distribution whereas zones usually do. Host aggregates can be regarded as a mechanism to further partitioning an availability zone, i.e. into multiple groups of hosts that share common resources like storage and network. This enables a finer level of granularity in which to structure an entire OpenStack deployment. Aggregates allows higher availability of a single guest instance within an availability zone, it enables advanced VM placement strategies, and more importantly it enables hosts' zero-downtime upgrades (for example, via VM live migration across members of the aggregate, thus causing no disruption to guest instances).
You can use this extension when you have multiple Compute nodes installed (only XenServer/XCP via xenapi driver is currently supported), and you want to leverage the capabilities of the underlying hypervisor resource pools. For example, you want to enable VM live migration (i.e. VM migration within the pool) or enable host maintenance with zero-downtime for guest instances. Please, note that VM migration across pools (i.e. storage migration) is not yet supported in XenServer/XCP, but will be added when available. Bear in mind that the two migration techniques are not mutually exclusive and can be used in combination for a higher level of flexibility in your cloud management.
To find more about it, please read http://wiki.openstack.org/host-aggregates or quick-search for 'aggregates' on the Nova developer guide.
Pre-requisites depend on the kind of hypervisor support you are going to use. As for XenServer/XCP, the same requirements for resource pools apply.
To obtain current information the extensions available to you, issue an EXTENSION query on the OpenStack system where it is installed, such as http://example.com/v1.1/tenant/extensions.
Extension Overview
- Name
-
Host Aggregates
- Namespace
- Alias
-
OS-AGGREGATES
- Contact
-
Armando Migliaccio <armando.migliaccio@citrix.com>
- Status
-
Released
- Extension Version
-
v1.0 (2012-02-28)
- Dependencies
-
Compute API 1.1
- Doc Link (PDF)
- Doc Link (WADL)
- Short Description
-
This extension enables the use of hypervisor resource pools in Nova.
Sample Query Responses
As shown below, responses to an EXTENSION query in XML or JSON provide basic information about the extension.
Extension Query Response: XML:
<extension name="Aggregates" namespace="http://docs.openstack.org/compute/ext/aggregates/api/v1.1" alias="os-aggregates" updated="2012-01-12T00:00:00+00:00"><description>Admin-only aggregate administration</description></extension>Extension Query Response: JSON:
{"extension": {"updated": "2012-01-12T00:00:00+00:00", "name": "Aggregates", "links": [], "namespace": "http://docs.openstack.org/compute/ext/aggregates/api/v1.1", "alias": "os-aggregates", "description": "Admin-only aggregate administration"}}Document Change History
| Revision Date | Summary of Changes |
| 2012-02-28 | Initial draft |
| 2012-03-30 | Reformat of content |
Summary of Changes
This extension to the OpenStack Compute API allows the creation and management of host aggregates (i.e. pools of compute nodes).
This support is provided by the addition of new actions.
New Actions
When a new aggregate has been created, actions can be executed using:
POST /v1.1/<tenant-id>/os-aggregates/<aggregate-id>/action
Valid actions are:
set_metadata add_host remove_host
Normal response Code: 200
For example, to set metadata for an aggregate the following xml must be submitted:
{"set_metadata": {"metadata": {"foo_key": "foo_value"}}}
For example, to add a host to an aggregate, the following xml must be submitted:
{"add_host": {"host": "<host-id>"}}
For example, to remove a host from an aggregate, the following xml must be submitted:
{"remove_host": {"host": "<host-id>"}}
Error Response Code(s) conflict (409), badRequest (400), itemNotFound (404)
New Faults
None
New Headers
None
New Resources
None
New States
None
Changes to the Cloud Servers Specification
None