Compute service overview
Update a lot of the links in here.
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:
Accepts and responds to end user compute API calls. The service supports the OpenStack Compute API. It enforces some policies and initiates most orchestration activities, such as running an instance.
Accepts metadata requests from instances. The
nova-api-metadataservice is generally used when you run in multi-host mode with
nova-networkinstallations. For details, see Metadata service in the OpenStack Administrator Guide.
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.
Tracks the inventory and usage of each provider. For details, see /user/placement.
Takes a virtual machine instance request from the queue and determines on which compute server host it runs.
Mediates interactions between the
nova-computeservice and the database. It eliminates direct accesses to the cloud database made by the
nova-conductormodule scales horizontally. However, do not deploy it on nodes where the
nova-computeservice runs. For more information, see Configuration Reference Guide.
Authorizes tokens for users that console proxies provide. See
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.
Provides a proxy for accessing running instances through a VNC connection. Supports browser-based novnc clients.
Provides a proxy for accessing running instances through a SPICE connection. Supports browser-based HTML5 client.
Provides a proxy for accessing running instances through a VNC connection. Supports an OpenStack-specific Java client.
- The queue
- SQL database
Stores most build-time and run-time states for a cloud infrastructure, including:
- Available instance types
- Instances in use
- Available networks
Theoretically, OpenStack Compute can support any database that SQLAlchemy supports. Common databases are SQLite3 for test and development work, MySQL, MariaDB, and PostgreSQL.