OpenStack - User contributions [en]

Blueprint-nova-cells-loadbalancing

2013-05-12T22:18:08Z

Matiu: Created page with "== Load balanced cells == === Rationale === In some situations the nova-cell process can become a bottle neck and not consume messages from the RPC system fast enough. === G..."

== Load balanced cells ==

=== Rationale ===
In some situations the nova-cell process can become a bottle neck and not consume messages from the RPC system fast enough.

=== Goal ===
This blueprint sets out to enable multiple 'nova-cell' consumers from a single RPC queue.

It should work all scenarios, for example:
* Global cell
:nova-api instances put messages in the queue, multiple nova-cell instances push those messages down to child cells
* Child cell
:incoming command messages come from a parent cell into our RPC queue, multiple 'nova-cell' workers consume and process these messages.

=== Concerns ===

Blueprint-spare-hosts

2013-03-21T22:25:48Z

Matiu: Created page with "== Specification for the spare-hosts blueprint == === Use cases === As an openstack administrator, when I set up a new cell, I need to set 10 or so hosts as spares before en..."

== Specification for the spare-hosts blueprint ==

=== Use cases ===

As an openstack administrator, when I set up a new cell, I need to set 10 or so hosts as spares before enabling the cell / openstack install.

This is primarily aimed at cells / openstack-installs, where all hosts are the same size and the scheduling model is to spread out the VMs as much as possible.

A spare host will be guaranteed not to have any VMs on it.

* When another host goes down, I can chassis swap it with a spare host.
* If a surprise VM building spree happens and we run out of space in the huddle, we can enable some hosts while new ones are being ordered/burnt in
* If a raid array shows signs of imminent failure, and there's not much room in the huddle, we can enable a spare and evacuate to it

==== Possible later additions ====

* A '''warning threshhold''', if the number of free machines is less than double the number of spares, a warning is emitted via the notifications system each time a host is activated.
* '''Queueing of migrations''', if a migration is waiting on a spare host to be enabled, it can be put in a new state 'waiting for host availability' rather than failing.==

=== Plan of action ===

==== Scheduler ====

1. When scheduler chooses a destination host, the list of hosts to be filtered will already have spares removed. We choose this way instead of writing a new filter, as the filtering code is currently already very slow

==== DB ====

1. We'll add an 'is_spare' column to the ComputeNode field, with an index to make filtering fast
2. In the API we'll add an optional parameter to the ''compute_node_get_all'' method, to either filter out, or only return spare hosts.
3. We'll add an API method to list the migrations headed towards or on the host. This is needed so we can guarantee that when a host is set to spare, it has zero VMs on it.

==== openstack api extension ====

We'll add an api extension with the following methods:

* list_spares(cell = None) - returns a list of host_names of spare machines. Takes an optional 'cell' argument, that would restrict the output to that of the single cell.
* reserve_spare(host_name=None, count=1, cell=None) - Sets the is_spare flag and disables the host. The box must have zero running VMs and no migrations heading towards it.
* If host_name is None, it spares the eligible host with the most available RAM that it can
* if host_name is None, count will make it spare the 'count' biggest hosts it finds (measured by available RAM)
* if cell is passed, and cells is enabled, it'll restrict the operation to that cell
* It will return a list of host_names that were set to spare
* release_spare(host_name=None, count=1, cell=None) - removes the is_spare flag and enables the host.
* host_name - restrict to one certain host
* count - if host_name is None, release 'count' of the smallest spares (by ram)
* cell - restrict to one cell

Scheduler Filters

2013-03-13T22:04:08Z

Matiu: Made it look nice

The nova scheduler has a bunch of filters. See here: http://docs.openstack.org/developer/nova/devref/filter_scheduler.htmlL

This is a quick summary of the filters in grizzly:

* '''affinity_filter''' - Don't put instances in a set on the same host
* '''aggregate_instance_extra_specs''' - Only build no hosts that support the desired instance type
* '''aggregate_multitenancy_isolation''' - This host is reserved for 'tenant_id'; only his vms can go here
* '''all_hosts_filter''' - All hosts are good, yippee!
* '''availability_zone_filter''' - Can only build in hosts that are in the desired 'availability_zone'
* '''compute_capabilities_filter''' - Check that vm's 'extra_specs' match hosts 'capabilities'
* '''compute_filter''' - Only build on active compute nodes
* '''core_filter''' - Only if we have enough cpu cores free
* '''disk_filter''' - Only if we have enough disk space free
* '''extra_specs_ops''' - NOT A FILTER - defines operators for compute_capabilities_filter, like >=
* '''image_props_filter''' - Checks the requirement of the VM image on architecture, hypervisor type, or virtual machine mode properties
* '''io_ops_filter''' - Don't build on hosts that are doing too much disk IO right now
* '''isolated_hosts_filter''' - Lets you specify a list of 'isolated' images and 'isolated' hosts. If image is in the list, host has to be in the list too, and vice versa.
* '''json_filter''' - Lets you make up your own filter using JSON in the configuration options
* '''num_instances_filter''' - Don't build if host has > X instances
* '''ram_filter''' - Don't build if there isn't enough free RAM
* '''retry_filter''' - Don't try to build if we already tried on this host
* '''trusted_filter''' - Only build in trusted compute pools
* '''type_filter''' - Only allow one instance type per host, eg. All VMs must be 512 MB size

Scheduler Filters

2013-03-13T22:00:58Z

Matiu: List of scheduler filters

The nova scheduler has a bunch of filters. See here: http://docs.openstack.org/developer/nova/devref/filter_scheduler.htmlL

This is a quick summary of the filters in grizzly:

* affinity_filter.py - Don't put instances in a set on the same host
* aggregate_instance_extra_specs.py - Only build no hosts that support the desired instance type
* aggregate_multitenancy_isolation.py - This host is reserved for 'tenant_id'; only his vms can go here
* all_hosts_filter.py - All hosts are good, yippee!
* availability_zone_filter.py - Can only build in hosts that are in the desired 'availability_zone'
* compute_capabilities_filter.py - Check that vm's 'extra_specs' match hosts 'capabilities'
* compute_filter.py - Only build on active compute nodes
* core_filter.py - Only if we have enough cpu cores free
* disk_filter.py - Only if we have enough disk space free
* extra_specs_ops.py - NOT A FILTER - defines operators for compute_capabilities_filter, like >=
* image_props_filter.py - Checks the requirement of the VM image on architecture, hypervisor type, or virtual machine mode properties
* io_ops_filter.py - Don't build on hosts that are doing too much disk IO right now
* isolated_hosts_filter.py - Lets you specify a list of 'isolated' images and 'isolated' hosts. If image is in the list, host has to be in the list too, and vice versa.
* json_filter.py - Lets you make up your own filter using JSON in the configuration options
* num_instances_filter.py - Don't build if host has > X instances
* ram_filter.py - Don't build if there isn't enough free RAM
* retry_filter.py - Don't try to build if we already tried on this host
* trusted_filter.py - Only build in trusted compute pools
* type_filter.py - Only allow one instance type per host, eg. All VMs must be 512 MB size

Nova

2013-03-13T21:59:14Z

Matiu: /* Other resources */

= [https://wiki.openstack.org Openstack] Compute ("Nova") =

{| border="1" cellpadding="2" cellspacing="0"
| Source code
|-
| Bug tracker
|-
| Blueprints
|-
| Developer doc
|}

== Related projects ==
* Python Nova client
* Compute API documentation

== Documentation ==
* [http://docs.openstack.org/api/openstack-compute/2/content/ Compute API (v2) specification]
* [http://docs.openstack.org/trunk/openstack-compute/admin/content/ Administration Guide]

== Other resources ==
* [[InstallInstructions/Nova|Install Instructions]]
* [[Nova/APIFeatureComparison | API feature comparison]]
* Configuring Nova: listing of nova.conf [[NovaConfigOptions|configuration options]]
* Details about [[HypervisorSupportMatrix|hypervisor support]]
* List of [[Scheduler Filters]]

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[[Category:Nova]]