openstack/nova
Code Issues Proposed changes
aabf8cc2d0
nova/doc/source/index.rst
Matt Riedemann ddd7273ac3 Add evacuate vs rebuild contributor doc 
People often get confused about the differences between
evacuate and rebuild operations, especially since the
conductor and compute methods are both called "rebuild_instance".
This change adds a contributor document which explains some
of the high and low level differences between the two operations.

Change-Id: I146fbc65237c4729ce3c28a4614589ba085dfce0
Closes-Bug: #1843439
2019-09-19 17:55:19 -04:00

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..
Copyright 2010-2012 United States Government as represented by the
Administrator of the National Aeronautics and Space Administration.
All Rights Reserved.
Licensed under the Apache License, Version 2.0 (the "License"); you may
not use this file except in compliance with the License. You may obtain
a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
License for the specific language governing permissions and limitations
under the License.
========================
OpenStack Compute (nova)
========================
What is nova?
=============
Nova is the OpenStack project that provides a way to provision compute
instances (aka virtual servers). Nova supports creating virtual machines,
baremetal servers (through the use of ironic), and has limited support for
system containers. Nova runs as a set of daemons on top of existing Linux
servers to provide that service.
It requires the following additional OpenStack services for basic function:
* :keystone-doc:`Keystone <>`: This provides identity and authentication for
all OpenStack services.
* :glance-doc:`Glance <>`: This provides the compute image repository. All
compute instances launch from glance images.
* :neutron-doc:`Neutron <>`: This is responsible for provisioning the virtual
or physical networks that compute instances connect to on boot.
* :placement-doc:`Placement <>`: This is responsible for tracking inventory of
resources available in a cloud and assisting in choosing which provider of
those resources will be used when creating a virtual machine.
It can also integrate with other services to include: persistent block
storage, encrypted disks, and baremetal compute instances.
For End Users
=============
As an end user of nova, you'll use nova to create and manage servers with
either tools or the API directly.
Tools for using Nova
--------------------
* :horizon-doc:`Horizon <user/launch-instances.html>`: The official web UI for
the OpenStack Project.
* :python-openstackclient-doc:`OpenStack Client <>`: The official CLI for
OpenStack Projects. You should use this as your CLI for most things, it
includes not just nova commands but also commands for most of the projects in
OpenStack.
* :python-novaclient-doc:`Nova Client <user/shell.html>`: For some very
advanced features (or administrative commands) of nova you may need to use
nova client. It is still supported, but the ``openstack`` cli is recommended.
Writing to the API
------------------
All end user (and some administrative) features of nova are exposed via a REST
API, which can be used to build more complicated logic or automation with
nova. This can be consumed directly, or via various SDKs. The following
resources will help you get started with consuming the API directly.
* `Compute API Guide <https://docs.openstack.org/api-guide/compute/>`_: The
concept guide for the API. This helps lay out the concepts behind the API to
make consuming the API reference easier.
* `Compute API Reference <https://docs.openstack.org/api-ref/compute/>`_:
The complete reference for the compute API, including all methods and
request / response parameters and their meaning.
* :doc:`Compute API Microversion History </reference/api-microversion-history>`:
The compute API evolves over time through `Microversions
<https://docs.openstack.org/api-guide/compute/microversions.html>`_. This
provides the history of all those changes. Consider it a "what's new" in the
compute API.
* :doc:`Block Device Mapping </user/block-device-mapping>`: One of the trickier
parts to understand is the Block Device Mapping parameters used to connect
specific block devices to computes. This deserves its own deep dive.
* :doc:`Metadata </user/metadata>`: Provide information to the guest instance
when it is created.
Nova can be configured to emit notifications over RPC.
* :ref:`Versioned Notifications <versioned_notification_samples>`: This
provides the list of existing versioned notifications with sample payloads.
For Operators
=============
Architecture Overview
---------------------
* :doc:`Nova architecture </user/architecture>`: An overview of how all the parts in
nova fit together.
Installation
------------
.. TODO(sdague): links to all the rest of the install guide pieces.
The detailed install guide for nova. A functioning nova will also require
having installed :keystone-doc:`keystone <install/>`, :glance-doc:`glance
<install/>`, :neutron-doc:`neutron <install/>`, and
:placement-doc:`placement <install/>`. Ensure that you follow their install
guides first.
.. toctree::
:maxdepth: 2
install/index
Deployment Considerations
-------------------------
There is information you might want to consider before doing your deployment,
especially if it is going to be a larger deployment. For smaller deployments
the defaults from the :doc:`install guide </install/index>` will be sufficient.
* **Compute Driver Features Supported**: While the majority of nova deployments use
libvirt/kvm, you can use nova with other compute drivers. Nova attempts to
provide a unified feature set across these, however, not all features are
implemented on all backends, and not all features are equally well tested.
* :doc:`Feature Support by Use Case </user/feature-classification>`: A view of
what features each driver supports based on what's important to some large
use cases (General Purpose Cloud, NFV Cloud, HPC Cloud).
* :doc:`Feature Support full list </user/support-matrix>`: A detailed dive through
features in each compute driver backend.
* :doc:`Cells v2 Planning </user/cellsv2-layout>`: For large deployments, Cells v2
allows sharding of your compute environment. Upfront planning is key to a
successful Cells v2 layout.
* :doc:`Running nova-api on wsgi <user/wsgi>`: Considerations for using a real
WSGI container instead of the baked-in eventlet web server.
Maintenance
-----------
Once you are running nova, the following information is extremely useful.
* :doc:`Admin Guide </admin/index>`: A collection of guides for administrating
nova.
* :doc:`Flavors </user/flavors>`: What flavors are and why they are used.
* :doc:`Upgrades </user/upgrade>`: How nova is designed to be upgraded for minimal
service impact, and the order you should do them in.
* :doc:`Quotas </user/quotas>`: Managing project quotas in nova.
* :doc:`Aggregates </user/aggregates>`: Aggregates are a useful way of grouping
hosts together for scheduling purposes.
* :doc:`Filter Scheduler </user/filter-scheduler>`: How the filter scheduler is
configured, and how that will impact where compute instances land in your
environment. If you are seeing unexpected distribution of compute instances
in your hosts, you'll want to dive into this configuration.
* :doc:`Exposing custom metadata to compute instances </admin/vendordata>`: How
and when you might want to extend the basic metadata exposed to compute
instances (either via metadata server or config drive) for your specific
purposes.
Reference Material
------------------
* :doc:`Nova CLI Command References </cli/index>`: the complete command reference
for all the daemons and admin tools that come with nova.
* :doc:`Configuration Guide <configuration/index>`: Information on configuring
the system, including role-based access control policy rules.
For Contributors
================
If you are new to Nova, this should help you start to understand what Nova
actually does, and why.
.. toctree::
:maxdepth: 1
contributor/index
There are also a number of technical references on both current and future
looking parts of our architecture. These are collected below.
.. toctree::
:maxdepth: 1
reference/index
.. # NOTE(mriedem): This is the section where we hide things that we don't
# actually want in the table of contents but sphinx build would fail if
# they aren't in the toctree somewhere. For example, we hide api/autoindex
# since that's already covered with modindex below.
.. toctree::
:hidden:
admin/index
admin/configuration/index
cli/index
configuration/index
contributor/development-environment
contributor/api
contributor/api-2
contributor/api-ref-guideline
contributor/blueprints
contributor/code-review
contributor/documentation
contributor/evacuate-vs-rebuild.rst
contributor/microversions
contributor/policies.rst
contributor/releasenotes
contributor/testing
contributor/testing/libvirt-numa
contributor/testing/serial-console
contributor/testing/zero-downtime-upgrade
contributor/testing/down-cell
contributor/testing/eventlet-profiling
contributor/how-to-get-involved
contributor/process
contributor/project-scope
contributor/ptl-guide
reference/api-microversion-history.rst
reference/conductor
reference/gmr
reference/i18n
reference/live-migration
reference/notifications
reference/policy-enforcement
reference/rpc
reference/scheduling
reference/scheduler-evolution
reference/services
reference/stable-api
reference/threading
reference/update-provider-tree
reference/upgrade-checks
reference/vm-states
reference/scheduler-hints-vs-flavor-extra-specs
reference/isolate-aggregates
user/index
user/aggregates
user/architecture
user/block-device-mapping
user/cells
user/cellsv2-layout
user/certificate-validation
user/feature-classification
user/filter-scheduler
user/flavors
user/manage-ip-addresses
user/quotas
user/support-matrix
user/upgrade
user/wsgi
Search
======
* :ref:`Nova document search <search>`: Search the contents of this document.
* `OpenStack wide search <https://docs.openstack.org>`_: Search the wider
set of OpenStack documentation, including forums.
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