41e0e53b5c
Clarify wording in the architecture doc page that Ironic's API service is intended only for privileged (admin) users and privileged services in the control plane. Change-Id: I2e660401c7e2ebe2f6dc89673236107727462fcc
95 lines
3.9 KiB
ReStructuredText
95 lines
3.9 KiB
ReStructuredText
.. _architecture:
|
|
|
|
===================
|
|
System Architecture
|
|
===================
|
|
|
|
High Level description
|
|
======================
|
|
|
|
An Ironic deployment will be composed of the following components:
|
|
|
|
- An admin-only RESTful `API service`_, by which privileged users, such as
|
|
cloud operators and other services within the cloud control plane, may
|
|
interact with the managed bare metal servers.
|
|
- A `Conductor service`_, which does the bulk of the work. Functionality is
|
|
exposed via the `API service`_. The Conductor and API services communicate via
|
|
RPC.
|
|
- A Database and `DB API`_ for storing the state of the Conductor and Drivers.
|
|
- A Deployment Ramdisk or Deployment Agent, which provide control over the
|
|
hardware which is not available remotely to the Conductor. A ramdisk should be
|
|
built which contains one of these agents, eg. with `diskimage-builder`_.
|
|
This ramdisk can be booted on-demand.
|
|
|
|
- **NOTE:** The agent is never run inside a tenant instance.
|
|
|
|
Drivers
|
|
=======
|
|
|
|
The internal driver API provides a consistent interface between the
|
|
Conductor service and the driver implementations. A driver is defined by
|
|
a class inheriting from the `BaseDriver`_ class, defining certain interfaces;
|
|
each interface is an instance of the relevant driver module.
|
|
|
|
For example, a fake driver class might look like this::
|
|
|
|
class FakePower(base.PowerInterface):
|
|
def validate(self, task):
|
|
pass
|
|
|
|
def get_power_state(self, task):
|
|
return states.NOSTATE
|
|
|
|
def set_power_state(self, task, power_state):
|
|
pass
|
|
|
|
def reboot(self, task):
|
|
pass
|
|
|
|
class FakeDriver(base.BaseDriver):
|
|
def __init__(self):
|
|
self.power = FakePower()
|
|
|
|
|
|
There are three categories of driver interfaces:
|
|
|
|
- `Core` interfaces provide the essential functionality for Ironic within
|
|
OpenStack, and may be depended upon by other services. All drivers
|
|
must implement these interfaces. Presently, the Core interfaces are power and deploy.
|
|
- `Standard` interfaces provide functionality beyond the needs of OpenStack,
|
|
but which has been standardized across all drivers and becomes part of
|
|
Ironic's API. If a driver implements this interface, it must adhere to the
|
|
standard. This is presented to encourage vendors to work together with the
|
|
Ironic project and implement common features in a consistent way, thus
|
|
reducing the burden on consumers of the API.
|
|
Presently, the Standard interfaces are rescue and console.
|
|
- The `Vendor` interface allows an exemption to the API contract when a vendor
|
|
wishes to expose unique functionality provided by their hardware and is
|
|
unable to do so within the core or standard interfaces. In this case, Ironic
|
|
will merely relay the message from the API service to the appropriate driver.
|
|
|
|
|
|
Message Routing
|
|
===============
|
|
|
|
Each Conductor registers itself in the database upon start-up, and periodically
|
|
updates the timestamp of its record. Contained within this registration is a
|
|
list of the drivers which this Conductor instance supports. This allows all
|
|
services to maintain a consistent view of which Conductors and which drivers
|
|
are available at all times.
|
|
|
|
Based on their respective driver, all nodes are mapped across the set of
|
|
available Conductors using a `consistent hashing algorithm`_. Node-specific
|
|
tasks are dispatched from the API tier to the appropriate conductor using
|
|
conductor-specific RPC channels. As Conductor instances join or leave the
|
|
cluster, nodes may be remapped to different Conductors, thus triggering various
|
|
driver actions such as take-over or clean-up.
|
|
|
|
|
|
.. _API service: ../webapi/v1.html
|
|
.. _BaseDriver: ../api/ironic.drivers.base.html#ironic.drivers.base.BaseDriver
|
|
.. _Conductor service: ../api/ironic.conductor.manager.html
|
|
.. _DB API: ../api/ironic.db.api.html
|
|
.. _diskimage-builder: https://github.com/openstack/diskimage-builder
|
|
.. _consistent hashing algorithm: ../api/ironic.common.hash_ring.html
|