[openstack-dev] [Ironic] ironic-discoverd status update

Zhou, Zhenzan zhenzan.zhou at intel.com
Mon Jan 5 08:31:37 UTC 2015

Hi, Dmitry

I think this is a good project. 
I got one question: what is the relationship with ironic-python-agent? 

Zhou Zhenzan

-----Original Message-----
From: Dmitry Tantsur [mailto:dtantsur at redhat.com] 
Sent: Thursday, December 11, 2014 10:35 PM
To: OpenStack Development Mailing List (not for usage questions)
Subject: [openstack-dev] [Ironic] ironic-discoverd status update

Hi all!

As you know I actively promote ironic-discoverd project [1] as one of the means to do hardware inspection for Ironic (see e.g. spec [2]), 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 [1] and the ramdisk [3]. 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 [4] 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 [5]. 
They go beyond the bare minimum of finding out CPU, RAM, disk size and NIC MAC's.


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
[6]. 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 [7] 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 [3] 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 [2].

Get Involved

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 [2], I'd like to know what you think.


[1] https://pypi.python.org/pypi/ironic-discoverd
[2] https://review.openstack.org/#/c/135605/
[4] https://github.com/agroup/instack-undercloud/
[5] https://bugs.launchpad.net/ironic-discoverd/+milestone/1.0.0

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