100 lines
3.8 KiB
ReStructuredText
100 lines
3.8 KiB
ReStructuredText
========================
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Compute service overview
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========================
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.. todo:: Update a lot of the links in here.
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Use OpenStack Compute to host and manage cloud computing systems. OpenStack
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Compute is a major part of an Infrastructure-as-a-Service (IaaS) system. The
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main modules are implemented in Python.
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OpenStack Compute interacts with OpenStack Identity for authentication;
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OpenStack Image service for disk and server images; and OpenStack Dashboard for
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the user and administrative interface. Image access is limited by projects, and
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by users; quotas are limited per project (the number of instances, for
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example). OpenStack Compute can scale horizontally on standard hardware, and
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download images to launch instances.
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OpenStack Compute consists of the following areas and their components:
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``nova-api`` service
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Accepts and responds to end user compute API calls. The service supports the
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OpenStack Compute API. It enforces some policies and initiates most
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orchestration activities, such as running an instance.
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``nova-api-metadata`` service
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Accepts metadata requests from instances. The ``nova-api-metadata`` service
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is generally used when you run in multi-host mode with ``nova-network``
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installations. For details, see :ref:`metadata-service`
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in the Compute Administrator Guide.
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``nova-compute`` service
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A worker daemon that creates and terminates virtual machine instances through
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hypervisor APIs. For example:
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- XenAPI for XenServer/XCP
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- libvirt for KVM or QEMU
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- VMwareAPI for VMware
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Processing is fairly complex. Basically, the daemon accepts actions from the
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queue and performs a series of system commands such as launching a KVM
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instance and updating its state in the database.
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``nova-placement-api`` service
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Tracks the inventory and usage of each provider. For details, see
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:doc:`/user/placement`.
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``nova-scheduler`` service
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Takes a virtual machine instance request from the queue and determines on
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which compute server host it runs.
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``nova-conductor`` module
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Mediates interactions between the ``nova-compute`` service and the database.
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It eliminates direct accesses to the cloud database made by the
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``nova-compute`` service. The ``nova-conductor`` module scales horizontally.
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However, do not deploy it on nodes where the ``nova-compute`` service runs.
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For more information, see the ``conductor`` section in the
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:doc:`/configuration/config`.
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``nova-consoleauth`` daemon
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Authorizes tokens for users that console proxies provide. See
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``nova-novncproxy`` and ``nova-xvpvncproxy``. This service must be running
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for console proxies to work. You can run proxies of either type against a
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single nova-consoleauth service in a cluster configuration. For information,
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see :ref:`about-nova-consoleauth`.
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``nova-novncproxy`` daemon
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Provides a proxy for accessing running instances through a VNC connection.
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Supports browser-based novnc clients.
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``nova-spicehtml5proxy`` daemon
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Provides a proxy for accessing running instances through a SPICE connection.
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Supports browser-based HTML5 client.
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``nova-xvpvncproxy`` daemon
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Provides a proxy for accessing running instances through a VNC connection.
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Supports an OpenStack-specific Java client.
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The queue
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A central hub for passing messages between daemons. Usually implemented with
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`RabbitMQ <https://www.rabbitmq.com/>`__, also can be implemented with
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another AMQP message queue, such as `ZeroMQ <http://www.zeromq.org/>`__.
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SQL database
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Stores most build-time and run-time states for a cloud infrastructure,
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including:
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- Available instance types
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- Instances in use
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- Available networks
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- Projects
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Theoretically, OpenStack Compute can support any database that SQLAlchemy
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supports. Common databases are SQLite3 for test and development work, MySQL,
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MariaDB, and PostgreSQL.
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