80 lines
3.5 KiB
ReStructuredText
80 lines
3.5 KiB
ReStructuredText
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.. _architecture:
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===================
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System Architecture
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===================
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High Level description
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======================
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An Ironic deployment will be composed of the following components:
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- A RESTful `API service`_, by which operators and other services may interact
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with the managed bare metal servers.
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- A `Manager service`_, which does the bulk of the work. Functionality is
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exposed via the `API service`_. The Manager and API services communicate via
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RPC.
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- A Database and `DB API`_ for storing the state of the Manager and Drivers.
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- One or more Deployment Agents, which provide local control over the
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hardware which is not available remotely to the Manager. A ramdisk should be
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built which contains one of these agents, eg. with `diskimage-builder`_.
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This ramdisk can be booted on-demand.
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- **NOTE:** The agent is never run inside a tenant instance.
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Drivers
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=======
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The internal driver API provides a consistent interface between the
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Manager service and the driver implementations. There are two types of drivers:
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- `ControlDrivers`_ manage the hardware, performing functions such as power
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on/off, toggle boot device, etc.
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- `DeployDrivers`_ handle the task of booting a temporary ramdisk, formatting
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drives, and putting a persistent image onto the hardware.
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- Driver implementations are loaded and instantiated via entrypoints when the
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`Manager service`_ starts. Each Node record stored in the database indicates
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which drivers should manage it. When a task is started on that node,
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information about the node and task is passed to the corresponding driver.
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In this way, heterogeneous hardware deployments can be managed by a single
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Manager service.
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In addition to the two types of drivers, there are three categories of driver
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functionality: core, common, and vendor:
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- :term:`Core functionality` represents the minimal API for that driver type, eg.
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power on/off for a ControlDriver.
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- :term:`Common functionality` represents an extended but supported API, and any
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driver which implements it must be consistent with all other driver
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implementations of that functionality. For example, if a driver supports
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enumerating PCI devices, it must return that list as well-structured JSON. In
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this case, Ironic may validate the API input's structure, but will pass it
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unaltered to the driver. This ensures compatibility for common features
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across drivers.
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- :term:`Vendor functionality` allows an excemption to the API contract when a vendor
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wishes to expose unique functionality provided by their hardware and is
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unable to do so within the core or common APIs. In this case, Ironic will
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neither store nor introspect the messages passed between the API and the
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driver.
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Default Drivers
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===============
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The default drivers, suitable for most deployments will be the `IPMIPowerDriver`_
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and the `PXEDeployDriver`_.
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Additionally, for test environments that do not have IPMI (eg., when mocking a
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deployment using virtual machines), an `SSHPowerDriver`_ is also supplied.
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.. _API service: api/ironic.api.controllers.v1
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.. _Manager service: api/ironic.manager.manager
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.. _DB API: api/ironic.db.api
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.. _ControlDrivers: api/ironic.drivers.base#ironic.drivers.base.ControlDriver
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.. _DeployDrivers: api/ironic.drivers.base#ironic.drivers.base.DeployDriver
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.. _IPMIPowerDriver: api/ironic.drivers.ipmi#ironic.drivers.ipmi.IPMIPowerDriver
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.. _PXEDeployDriver: api/ironic.drivers.pxe#ironic.drivers.pxe.PXEDeployDriver
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.. _SSHPowerDriver: api/ironic.drivers.ssh#ironic.drivers.ssh.SSHPowerDriver
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.. _diskimage-builder: https://github.com/stackforge/diskimage-builder
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