Merge "Promote iPXE to separate boot interface"

specs/approved/ipxe-boot-interface.rst

@@ -0,0 +1,208 @@
+..
+ This work is licensed under a Creative Commons Attribution 3.0 Unported
+ License.
+
+ http://creativecommons.org/licenses/by/3.0/legalcode
+
+=======================================
+Promote iPXE to separate boot interface
+=======================================
+
+https://bugs.launchpad.net/ironic/+bug/1628069
+
+The iPXE boot should be promoted to a separate boot driver interface.
+This will simplify the code base and allow to not force global PXE *vs* iPXE
+conductor setting.
+
+
+Problem description
+===================
+
+Currently setting PXE or iPXE is enforced per-conductor, and taking
+into account the possibility of node take-over, this choice is effectively
+global for the whole Ironic installation.
+
+Due to this the current code of ``PXEBoot`` interface is riddled
+with constructs of:
+
+.. code-block:: python
+
+   if CONF.pxe.ixpe_enabled ...
+
+Recently added or proposed changes (like ``CONF.pxe.ipxe_use_swift`` option)
+make the logic there even more complicated.
+
+Proposed change
+===============
+
+It is proposed to implement a separate iPXE boot interface,
+which will use the new way of serving iPXE boot scripts and boot config files
+directly from Ironic API as outlined in `dynamic iPXE configuration`_ spec.
+
+The new interface will get a separate ``[ipxe]`` config section,
+where all ``[pxe]ipxe_*`` options should be moved following proper deprecation
+policy for config options.
+Current iPXE-related behavior of ``PXEBoot`` interface should
+be deprecated and eventually removed.
+
+Alternatives
+------------
+
+Continue mixing PXE and iPXE in single driver interface
+and setting iPXE *vs* PXE globally.
+
+Data model impact
+-----------------
+
+None
+
+State Machine Impact
+--------------------
+
+None
+
+REST API impact
+---------------
+
+None
+
+
+Client (CLI) impact
+-------------------
+
+None
+
+"ironic" CLI
+~~~~~~~~~~~~
+
+None
+
+"openstack baremetal" CLI
+~~~~~~~~~~~~~~~~~~~~~~~~~
+
+None
+
+RPC API impact
+--------------
+
+None
+
+Driver API impact
+-----------------
+
+None
+
+Nova driver impact
+------------------
+
+None
+
+Ramdisk impact
+--------------
+
+None
+
+Security impact
+---------------
+
+None
+
+Other end user impact
+---------------------
+
+None
+
+Scalability impact
+------------------
+
+None
+
+Performance Impact
+------------------
+
+None
+
+Other deployer impact
+---------------------
+
+* A new config section ``[ipxe]`` will be added, with most of the
+  ipxe_* options copied from current ``[pxe]`` section (with ``ipxe_`` removed
+  from option names).
+  By the virtue of ``oslo_config`` library, the new options will be backward
+  compatible with old, deprecated ones, using their values when not set
+  explicitly.
+
+* This change has no immediate effect. Enabling it is a conscious choice of
+  the operator:
+
+  + a driver utilizing this new ``iPXEBoot`` boot interface must be composed
+  + such driver must be assigned to the node
+
+
+Developer impact
+----------------
+
+None
+
+
+Implementation
+==============
+
+Assignee(s)
+-----------
+
+Primary assignee:
+  pshchelo (Pavlo Shchelokovskyy)
+
+Work Items
+----------
+
+* create a new ``iPXEBoot`` boot interface
+
+  - identify and refactor code that is common for ``PXEBoot`` and
+    ``iPXEBoot`` interfaces
+
+* register this driver as entry point for ``ironic.hardware.interfaces.boot``
+
+  - add it to list of boot interfaces enabled by default in ironic config
+    (``[DEFAULT]enabled_boot_interfaces`` config option)
+
+* add appropriate documentation
+
+Dependencies
+============
+
+* `Dynamic iPXE configuration`_
+* `Driver composition reform`_
+
+Testing
+=======
+
+No specific coverage seems to be needed apart from enabling a driver that
+uses this new proposed boot interface at least on one gate job.
+
+Upgrades and Backwards Compatibility
+====================================
+
+The feature has no immediate effect on existing installation as it must
+be manually enabled first by enabling the interface and composing an
+appropriate driver with this boot interface.
+
+Existing drivers do not depend on this feature in any way.
+
+It is also proposed to deprecate and eventually remove iPXE capabilities
+from the PXEBoot interface.
+
+Chain-loading an iPXE-capable boot-loader will still be supported by
+iPXEBoot driver to support older/dumber/buggy hardware.
+
+Documentation Impact
+====================
+
+Document new driver interface and its usage.
+
+References
+==========
+
+.. _dynamic iPXE configuration: http://specs.openstack.org/openstack/ironic-specs/specs/not-implemented/ipxe-dynamic-config.html
+.. _Driver composition reform: http://specs.openstack.org/openstack/ironic-specs/specs/not-implemented/driver-composition-reform.html

specs/not-implemented/ipxe-boot-interface.rst

@@ -0,0 +1 @@
+../approved/ipxe-boot-interface.rst