OpenStack Compute
Use OpenStack Compute to host and manage cloud computing systems.
OpenStack Compute is a major part of an Infrastructure-as-a-Service
(IaaS) system. The main modules are implemented in Python.
OpenStack Compute interacts with OpenStack Identity for authentication,
OpenStack Image service for disk and server images, and OpenStack
dashboard for the user and administrative interface. Image access is
limited by projects, and by users; quotas are limited per project (the
number of instances, for example). OpenStack Compute can scale
horizontally on standard hardware, and download images to launch
instances.
OpenStack Compute consists of the following areas and their components:
- nova-api service
- Accepts and responds to end user compute API calls. The service
supports the OpenStack Compute API, the Amazon EC2 API, and a
special Admin API for privileged users to perform administrative
actions. It enforces some policies and initiates most orchestration
activities, such as running an instance.
- nova-api-metadata service
- Accepts metadata requests from instances. The nova-api-metadata
service is generally used when you run in multi-host mode with
nova-network installations. For details, see Metadata
service
in the OpenStack Cloud Administrator Guide.
- nova-compute service
A worker daemon that creates and terminates virtual machine
instances through hypervisor APIs. For example:
- XenAPI for XenServer/XCP
- libvirt for KVM or QEMU
- VMwareAPI for VMware
Processing is fairly complex. Basically, the daemon accepts actions
from the queue and performs a series of system commands such as
launching a KVM instance and updating its state in the database.
- nova-scheduler service
- Takes a virtual machine instance request from the queue and
determines on which compute server host it runs.
- nova-conductor module
- Mediates interactions between the nova-compute service and the
database. It eliminates direct accesses to the cloud database made
by the nova-compute service. The nova-conductor module scales
horizontally. However, do not deploy it on nodes where the
nova-compute service runs. For more information, see Configuration
Reference Guide.
- nova-cert module
- A server daemon that serves the Nova Cert service for X509
certificates. Used to generate certificates for
euca-bundle-image. Only needed for the EC2 API.
- nova-network worker daemon
- Similar to the nova-compute service, accepts networking tasks from
the queue and manipulates the network. Performs tasks such as
setting up bridging interfaces or changing IPtables rules.
- nova-consoleauth daemon
- Authorizes tokens for users that console proxies provide. See
nova-novncproxy and nova-xvpvncproxy. This service must be running
for console proxies to work. You can run proxies of either type
against a single nova-consoleauth service in a cluster
configuration. For information, see About
nova-consoleauth.
- nova-novncproxy daemon
- Provides a proxy for accessing running instances through a VNC
connection. Supports browser-based novnc clients.
- nova-spicehtml5proxy daemon
- Provides a proxy for accessing running instances through a SPICE
connection. Supports browser-based HTML5 client.
- nova-xvpvncproxy daemon
- Provides a proxy for accessing running instances through a VNC
connection. Supports an OpenStack-specific Java client.
- nova-cert daemon
- x509 certificates.
- euca2ools client
- A set of command-line interpreter commands for managing cloud
resources. Although it is not an OpenStack module, you can configure
nova-api to support this EC2 interface. For more information, see
the Eucalyptus 3.4
Documentation.
- nova client
- Enables users to submit commands as a tenant administrator or end
user.
- The queue
- A central hub for passing messages between daemons. Usually
implemented with RabbitMQ, but can be
implemented with an AMQP message queue, such as Apache
Qpid or Zero
MQ.
- SQL数据库
Stores most build-time and run-time states for a cloud
infrastructure, including:
- Available instance types
- Instances in use
- Available networks
- Projects
Theoretically, OpenStack Compute can support any database that
SQL-Alchemy supports. Common databases are SQLite3 for test and
development work, MySQL, and PostgreSQL.