[openstack-dev] [Ironic] ironic-discoverd status update
dtantsur at redhat.com
Thu Dec 11 14:35:00 UTC 2014
As you know I actively promote ironic-discoverd project  as one of
the means to do hardware inspection for Ironic (see e.g. spec ), so I
decided it's worth to give some updates to the community from time to
time. This email is purely informative, you may safely skip it, if
you're not interested.
The discoverd project (I usually skip the "ironic-" part when talking
about it) solves the problem of populating information about a node in
Ironic database without help of any vendor-specific tool. This
information usually includes Nova scheduling properties (CPU, RAM, disk
size) and MAC's for ports.
Introspection is done by booting a ramdisk on a node, collecting data
there and posting it back to discoverd HTTP API. Thus actually discoverd
consists of 2 components: the service  and the ramdisk . The
service handles 2 major tasks:
* Processing data posted by the ramdisk, i.e. finding the node in Ironic
database and updating node properties with new data.
* Managing iptables so that the default PXE environment for
introspection does not interfere with Neutron
The project was born from a series of patches to Ironic itself after we
discovered that this change is going to be too intrusive. Discoverd was
actively tested as part of Instack  and it's RPM is a part of Juno
RDO. After the Paris summit, we agreed on bringing it closer to the
Ironic upstream, and now discoverd is hosted on StackForge and tracks
bugs on Launchpad.
The basic feature of discoverd: supply Ironic with properties required
for scheduling, is pretty finished as of the latest stable series 0.2.
However, more features are planned for release 1.0.0 this January .
They go beyond the bare minimum of finding out CPU, RAM, disk size and
An interesting feature of discoverd is support for plugins, which I
prefer to call hooks. It's possible to hook into the introspection data
processing chain in 2 places:
* Before any data processing. This opens opportunity to adopt discoverd
to ramdisks that have different data format. The only requirement is
that the ramdisk posts a JSON object.
* After a node is found in Ironic database and ports are created for
MAC's, but before any actual data update. This gives an opportunity to
alter, which properties discoverd is going to update.
Actually, even the default logic of update Node.properties is contained
in a plugin - see SchedulerHook in ironic_discoverd/plugins/standard.py
. This plugability opens wide opportunities for integrating with 3rd
party ramdisks and CMDB's (which as we know Ironic is not ;).
Some people have found it limiting that the introspection requires power
credentials (IPMI user name and password) to be already set. The recent
set of patches  introduces a possibility to request manual power on
of the machine and update IPMI credentials via the ramdisk to the
expected values. Note that support of this feature in the reference
ramdisk  is not ready yet. Also note that this scenario is only
possible when using discoverd directly via it's API, not via Ironic API
like in .
Discoverd terribly lacks reviews. Out team is very small and
self-approving is not a rare case. I'm even not against fast-tracking
any existing Ironic core to a discoverd core after a couple of
meaningful reviews :)
And of course patches are welcome, especially plugins for integration
with existing systems doing similar things and CMDB's. Patches are
accepted via usual Gerrit workflow. Ideas are accepted as Launchpad
blueprints (we do not follow the Gerrit spec process right now).
Finally, please comment on the Ironic spec , I'd like to know what
More information about the OpenStack-dev