Bug #943178: aggregate extension lacks documentation
add rst docs for this extension. Change-Id: I74080c240a0a6911271674177ac08a113b4c50d1
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Armando Migliaccio
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doc/source/api_ext/ext_aggregates.rst
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doc/source/api_ext/ext_aggregates.rst
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About This Extension
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====================
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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).
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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.
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To find more about it, please read http://wiki.openstack.org/host-aggregates or quick-search for 'aggregates' on the Nova developer guide.
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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.
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To obtain current information the extensions available to you, issue an EXTENSION query on the OpenStack system where it is installed, such as http://mycloud.com/v1.1/tenant/extensions.
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Extension Overview
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------------------
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Name
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Host Aggregates
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Namespace
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http://docs.openstack.org/compute/ext/aggregates/api/v1.1
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Alias
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OS-AGGREGATES
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Contact
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Armando Migliaccio <armando.migliaccio@citrix.com>
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Status
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Released
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Extension Version
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v1.0 (2012-02-28)
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Dependencies
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Compute API 1.1
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Doc Link (PDF)
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http://
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Doc Link (WADL)
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http://
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Short Description
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This extension enables the use of hypervisor resource pools in Nova.
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Sample Query Responses
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----------------------
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As shown below, responses to an EXTENSION query in XML or JSON provide basic information about the extension.
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Extension Query Response: XML::
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<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>
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Extension Query Response: JSON::
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{"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"}}
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Document Change History
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-----------------------
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============= =====================================
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Revision Date Summary of Changes
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2012-02-28 Initial draft
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============= =====================================
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Summary of Changes
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==================
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This extension to the OpenStack Compute API allows the creation and management of host aggregates (i.e. pools of compute nodes).
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New Action
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----------
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When a new aggregate has been created, actions can be executed using:
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POST /v1.1/<tenant-id>/os-aggregates/<aggregate-id>/action
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Valid actions are:
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set_metadata
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add_host
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remove_host
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Normal response Code: 200
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For example, to set metadata for an aggregate the following xml must be submitted:
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{"set_metadata": {"metadata": {"foo_key": "foo_value"}}}
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For example, to add a host to an aggregate, the following xml must be submitted:
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{"add_host": {"host": "<host-id>"}}
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For example, to remove a host from an aggregate, the following xml must be submitted:
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{"remove_host": {"host": "<host-id>"}}
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Error Response Code(s) conflict (409), badRequest (400), itemNotFound (404)
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New Faults
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----------
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None
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New Headers
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-----------
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None
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New Resources
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-------------
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None
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New States
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----------
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None
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Changes to the Cloud Servers Specification
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------------------------------------------
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None
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65
doc/source/devref/aggregates.rst
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65
doc/source/devref/aggregates.rst
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..
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Copyright 2012 OpenStack, LLC
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Copyright 2012 Citrix Systems, Inc.
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All Rights Reserved.
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Licensed under the Apache License, Version 2.0 (the "License"); you may
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not use this file except in compliance with the License. You may obtain
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a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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License for the specific language governing permissions and limitations
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under the License.
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Host Aggregates
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===============
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This extension introduces the concept of aggregate 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).
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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.
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Design
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=======
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The OSAPI Admin API will be extended to support the following operations:
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* Aggregates
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* list aggregates: returns a list of all the host-aggregates (optionally filtered by availability zone)
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* create aggregate: creates an aggregate, takes a friendly name, etc. returns an id
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* show aggregate: shows the details of an aggregate (id, name, availability_zone, hosts and metadata)
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* update aggregate: updates the name and availability zone of an aggregate
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* set metadata: sets the metadata on an aggregate to the values supplied
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* delete aggregate: deletes an aggregate, it fails if the aggregate is not empty
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* add host: adds a host to the aggregate
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* remove host: removes a host from the aggregate, it fails if the host is not disabled or
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* Hosts
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* start host maintenance (or evacuate-host): disallow a host to serve API requests and migrate instances to other hosts of the aggregate
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* stop host maintenance: (or rebalance-host): put the host back into operational mode, migrating instances back onto that host
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Using the Nova CLI
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==================
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Using the nova command you can create, delete and manage aggregates. The following section outlines the list of available commands.
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Usage
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-----
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* aggregate-list Print a list of all aggregates.
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* aggregate-create <name> <availability_zone> Create a new aggregate with the specified details.
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* aggregate-delete <id> Delete the aggregate by its id.
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* aggregate-details <id> Show details of the specified aggregate.
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* aggregate-add-host <id> <host> Add the host to the specified aggregate.
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* aggregate-remove-host <id> <host> Remove the specified host from the specfied aggregate.
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* aggregate-set-metadata <id> <key=value> [<key=value> ...] Update the metadata associated with the aggregate.
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* aggregate-update <id> <name> [<availability_zone>] Update the aggregate's name and optionally availablity zone.
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* host-update --maintenance [enable | disable] Put/resume host into/from maintenance.
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