Add a flag to always perform persistent boot on PXE interface

With the proposal to solve the bug that PXE interface should
be using non-persistent boot for cleaning/deploying phases as
default(commit: c7091fb8e2898e526f8ce242f50096a2cabeb1fa), it's
necessary to create a flag to enable persistent behavior when
you set the boot device.
This flag will override a non-persistent behavior in the
cleaning and deploy process.

Change-Id: I1f47393c17a3f5319fffd963ec0a016b41865c5d
Closes-Bug: 1703945
Co-Authored-By: Stenio Araujo <steniaraujo@lsd.ufcg.edu.br>

doc/source/admin/drivers.rst

@@ -13,6 +13,14 @@ nodes, and runs processes inside of a ramdisk.
 
 For more information on this, see :ref:`IPA`.
 
+PXE Boot Interface
+------------------
+
+.. toctree::
+  :maxdepth: 1
+
+  drivers/pxe
+
 IPMITool driver
 ---------------
 

doc/source/admin/drivers/pxe.rst

@@ -0,0 +1,26 @@
+.. pxe:
+
+==============================
+Configuring PXE boot interface
+==============================
+
+Enable persistent boot device for deploy/clean operation
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Ironic uses non-persistent boot for cleaning/deploying phases as default,
+in PXE interface. For some drivers, a persistent change is far more
+costly than a non-persistent one, so this can bring performance improvements.
+
+Enable persistent boot device on node
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+1. Set the flag ``force_persistent_boot_device`` to ``True`` in the node's ``driver_info``::
+
+    $ openstack baremetal node set --driver-info force_persistent_boot_device=True <node>
+
+  .. note::
+     It's recommended to check if the node's state has not changed as there
+     is no way of locking the node between these commands.
+
+Once the flag is present, the next cleaning and deploy steps will be done
+with persistent boot for that node.

ironic/drivers/modules/pxe.py

@@ -21,6 +21,7 @@ from ironic_lib import metrics_utils
 from ironic_lib import utils as ironic_utils
 from oslo_log import log as logging
 from oslo_utils import fileutils
+from oslo_utils import strutils
 
 from ironic.common import boot_devices
 from ironic.common import dhcp_factory
@@ -493,8 +494,11 @@ class PXEBoot(base.BootInterface):
 
         pxe_utils.create_pxe_config(task, pxe_options,
                                     pxe_config_template)
+        persistent = strutils.bool_from_string(
+            node.driver_info.get('force_persistent_boot_device',
+                                 False))
         manager_utils.node_set_boot_device(task, boot_devices.PXE,
-                                           persistent=False)
+                                           persistent=persistent)
 
         if CONF.pxe.ipxe_enabled and CONF.pxe.ipxe_use_swift:
             pxe_info.pop('deploy_kernel', None)

ironic/tests/unit/drivers/modules/test_pxe.py

@@ -1199,6 +1199,21 @@ class PXEBootTestCase(db_base.DbTestCase):
                                                          boot_devices.DISK,
                                                          persistent=True)
 
+    @mock.patch.object(manager_utils, 'node_set_boot_device', autospec=True)
+    @mock.patch.object(pxe_utils, 'clean_up_pxe_config', autospec=True)
+    def test_is_force_persistent_boot_device_enabled(
+            self, clean_up_pxe_config_mock, set_boot_device_mock):
+        with task_manager.acquire(self.context, self.node.uuid) as task:
+            task.node.instance_info['capabilities'] = {'boot_option': 'local'}
+            task.driver.boot.prepare_instance(task)
+            clean_up_pxe_config_mock.assert_called_once_with(task)
+            driver_info = task.node.driver_info
+            driver_info['force_persistent _boot_device'] = True
+            task.node.driver_info = driver_info
+            set_boot_device_mock.assert_called_once_with(task,
+                                                         boot_devices.DISK,
+                                                         persistent=True)
+
     @mock.patch.object(manager_utils, 'node_set_boot_device', autospec=True)
     @mock.patch.object(pxe_utils, 'clean_up_pxe_config', autospec=True)
     def test_prepare_instance_localboot_active(self, clean_up_pxe_config_mock,

releasenotes/notes/flag_always_reboot-62468a7058b58823.yaml

@@ -0,0 +1,9 @@
+---
+features:
+  - |
+    Adds a boolean flag called ``force_persistent_boot_device`` into
+    a node's ``driver_info`` to enable persistent behavior when you
+    set the boot device during deploy and cleaning operations. This
+    flag will override a non-persistent behavior in the cleaning and
+    deploy process.
+    For more information, see https://bugs.launchpad.net/ironic/+bug/1703945.