Add the exclusive machine scheduling docs.
Change-Id: Ic467677d485d3a86e4a3eea6092434055d47f424
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Paul Hummer
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Nova-LXD Exclusive Machine
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==========================
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As LXD is a system container format, it is possible to provision "bare metal"
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machines with nova-lxd without exposing the kernel and firmware to the tenant.
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This is done by means of host aggregates and flavor assignment. The instance
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will fill the entirety of the host, and no other instances will be assigned
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to it.
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This document describes the method used to achieve this exclusive machine
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scheduling. It is meant to serve as an example; the names of flavors and
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aggregates may be named as desired.
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Prerequisites
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-------------
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Exclusive machine scheduling requires two scheduler filters to be enabled in
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`scheduler_default_filters` in `nova.conf`, namely
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`AggregateInstanceExtraSpecsFilter` and `AggregateNumInstancesFilter`.
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If juju was used to install and manage the openstack environment, the following
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command will enable these filters::
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juju set nova-cloud-controller scheduler-default-filters="AggregateInstanceExtraSpecsFilter,AggregateNumInstancesFilter,RetryFilter,AvailabilityZoneFilter,CoreFilter,RamFilter,ComputeFilter,ComputeCapabilitiesFilter,ImagePropertiesFilter,ServerGroupAntiAffinityFilter,ServerGroupAffinityFilter"
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Host Aggregate
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--------------
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Each host designed to be exclusively available to a single instance must be
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added to a special host aggregate.
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In this example, the following is a nova host listing::
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user@openstack$ nova host-list
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+------------+-----------+----------+
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| host_name | service | zone |
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+------------+-----------+----------+
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| machine-9 | cert | internal |
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| machine-9 | scheduler | internal |
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| machine-9 | conductor | internal |
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| machine-12 | compute | nova |
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| machine-11 | compute | nova |
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| machine-10 | compute | nova |
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+------------+-----------+----------+
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Create the host aggregate itself. In this example, the aggregate is called
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"exclusive-machines"::
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user@openstack$ nova aggregate-create exclusive-machines
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+----+--------------------+-------------------+-------+----------+
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| 1 | exclusive-machines | - | | |
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+----+--------------------+-------------------+-------+----------+
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Two metadata properties are then set on the host aggregate itself::
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user@openstack$ nova aggregate-set-metadata 1 aggregate_instance_extra_specs:exclusive=true
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Metadata has been successfully updated for aggregate 1.
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+----+--------------------+-------------------+-------+-------------------------------------------------+
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| Id | Name | Availability Zone | Hosts | Metadata |
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+----+--------------------+-------------------+-------+-------------------------------------------------+
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| 1 | exclusive-machines | - | | 'aggregate_instance_extra_specs:exclusive=true' |
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+----+--------------------+-------------------+-------+-------------------------------------------------+
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user@openstack$ nova aggregate-set-metadata 1 max_instances_per_host=1
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Metadata has been successfully updated for aggregate 1.
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+----+--------------------+-------------------+-------+-----------------------------------------------------------------------------+
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| Id | Name | Availability Zone | Hosts | Metadata |
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+----+--------------------+-------------------+-------+-----------------------------------------------------------------------------+
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| 1 | exclusive-machines | - | | 'aggregate_instance_extra_specs:exclusive=true', 'max_instances_per_host=1' |
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+----+--------------------+-------------------+-------+-----------------------------------------------------------------------------
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The first aggregate metadata property is the link between the flavor (still to
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be created) and the compute hosts (still to be added to the aggregate). The
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second metadata property ensures that nova doesn't ever try to add another
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instance to this one in (e.g. if nova is configured to overcommit resources).
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Now the hosts must be added to the aggregate. Once they are added to the
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host aggregate, they will not be available for other flavors. This will be
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important in resource sizing efforts. To add the hosts::
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user@openstack$ nova aggregate-add-host exclusive-machines machine-10
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Host juju-serverstack-machine-10 has been successfully added for aggregate 1
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+----+--------------------+-------------------+--------------+-----------------------------------------------------------------------------+
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| Id | Name | Availability Zone | Hosts | Metadata |
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+----+--------------------+-------------------+--------------+-----------------------------------------------------------------------------+
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| 1 | exclusive-machines | - | 'machine-10' | 'aggregate_instance_extra_specs:exclusive=true', 'max_instances_per_host=1' |
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+----+--------------------+-------------------+--------------+-----------------------------------------------------------------------------+
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Exclusive machine flavors
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-------------------------
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When planning for exclusive machine flavors, there is still a small amount
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of various resources that will be needed for nova compute and lxd itself.
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In general, it's a safe bet that this can be quantified in 100MB of RAM,
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though specific hosts may need to be configured more closely to their
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use cases.
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In this example, `machine-10` has 4096MB of total memory, 2 CPUS, and 500GB
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of disk space. The flavor that is created will have a quantity of 3996MB of
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RAM, 2 CPUS, and 500GB of disk.::
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user@openstack$ nova flavor-create --is-public true e1.medium 100 3996 500 2
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+-----+-----------+-----------+------+-----------+------+-------+-------------+-----------+
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| ID | Name | Memory_MB | Disk | Ephemeral | Swap | VCPUs | RXTX_Factor | Is_Public |
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+-----+-----------+-----------+------+-----------+------+-------+-------------+-----------+
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| 100 | e1.medium | 3996 | 500 | 0 | | 2 | 1.0 | True |
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+-----+-----------+-----------+------+-----------+------+-------+-------------+-----------+
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The `e1.medium` flavor must now have some metadata set to link it with the
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`exclusive-machines` host aggregate.::
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user@openstack$ nova flavor-key 100 set exclusive=true
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Booting an exclusive instance
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-----------------------------
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Once the host aggregate and flavor have been created, exclusive machines
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can be provisioned by using the flavor `e1.medium`::
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user@openstack$ nova boot --flavor 100 --image $IMAGE exclusive
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The `exclusive` instance, once provisioned, will fill the entire host
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machine.
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@ -11,10 +11,9 @@ Contents:
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.. toctree::
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:maxdepth: 2
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readme
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installation
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usage
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contributing
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exclusive_machine
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Indices and tables
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==================
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@ -1 +0,0 @@
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.. include:: ../../README.rst
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