ironic/doc/source/dev/drivers.rst

Pluggable Drivers

Ironic supports a pluggable driver model. This allows contributors to easily add new drivers, and operators to use third-party drivers or write their own.

Drivers are loaded by the ironic-conductor service during initialization, by enumerating the python entrypoint "ironic.drivers" and attempting to load all drivers specified in the "enabled_drivers" configuration option. A complete list of drivers available on the system may be found by enumerating this entrypoint by running the following python script:

#!/usr/bin/env python

import pkg_resources as pkg
print [p.name for p in pkg.iter_entry_points("ironic.drivers") if not p.name.startswith("fake")]

A list of drivers enabled in a running Ironic service may be found by issuing the following command against that API end point:

ironic driver-list

Supported Drivers

For a list of supported drivers (those that are continuously tested on every upstream commit) please consult the wiki page:

https://wiki.openstack.org/wiki/Ironic/Drivers

Node Vendor Passthru

Drivers may implement a passthrough API, which is accessible via the /v1/nodes/<Node UUID or Name>/vendor_passthru?method={METHOD} endpoint. Beyond basic checking, Ironic does not introspect the message body and simply "passes it through" to the relevant driver.

A method:

• can support one or more HTTP methods (for example, GET, POST)
• is asynchronous or synchronous
  • For asynchronous methods, a 202 (Accepted) HTTP status code is returned to indicate that the request was received, accepted and is being acted upon. No body is returned in the response.
  • For synchronous methods, a 200 (OK) HTTP status code is returned to indicate that the request was fulfilled. The response may include a body.
• can require an exclusive lock on the node. This only occurs if the method doesn't specify require_exclusive_lock=False in the decorator. If an exclusive lock is held on the node, other requests for the node will be delayed and may fail with an HTTP 409 (Conflict) error code.

This endpoint exposes a node's driver directly, and as such, it is expressly not part of Ironic's standard REST API. There is only a single HTTP endpoint exposed, and the semantics of the message body are determined solely by the driver. Ironic makes no guarantees about backwards compatibility; this is solely up to the discretion of each driver's author.

To get information about all the methods available via the vendor_passthru endpoint for a particular node, you can issue an HTTP GET request:

GET /v1/nodes/<Node UUID or name>/vendor_passthru/methods

The response's JSON body will contain information for each method, such as the method's name, a description, the HTTP methods supported, and whether it's asynchronous or synchronous.

Driver Vendor Passthru

Drivers may implement an API for requests not related to any node, at /v1/drivers/<driver name>/vendor_passthru?method={METHOD}.

A method:

• can support one or more HTTP methods (for example, GET, POST)
• is asynchronous or synchronous
  • For asynchronous methods, a 202 (Accepted) HTTP status code is returned to indicate that the request was received, accepted and is being acted upon. No body is returned in the response.
  • For synchronous methods, a 200 (OK) HTTP status code is returned to indicate that the request was fulfilled. The response may include a body.

Note

Unlike methods in Node Vendor Passthru, a request does not lock any resource, so it will not delay other requests and will not fail with an HTTP 409 (Conflict) error code.

Ironic makes no guarantees about the semantics of the message BODY sent to this endpoint. That is left up to each driver's author.

To get information about all the methods available via the driver vendor_passthru endpoint, you can issue an HTTP GET request:

GET /v1/drivers/<driver name>/vendor_passthru/methods

The response's JSON body will contain information for each method, such as the method's name, a description, the HTTP methods supported, and whether it's asynchronous or synchronous.