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docs: host migration behaviour with disable-migration flag #184

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069cecf
add docs for host migration behaviour with disable-migration flag
H-M-Quang-Ngo Mar 24, 2026
ed9546c
improve how the flag usage is mentioned
H-M-Quang-Ngo Mar 26, 2026
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16 changes: 15 additions & 1 deletion explanation/maintenance-mode.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -78,7 +78,20 @@ Apply

* Audit action plan

* Execute the watcher audit action plan.
* Execute the Watcher audit action plan. By default, the plan will live migrate active
instances and cold migrate inactive instances off the node.

* Operators can control migration behavior using the ``--disable-migration`` flag:

* ``--disable-migration=live``: Disable live migration. All instances (active and
inactive) will be cold migrated.
* ``--disable-migration=cold``: Disable cold migration. Active instances will be
live migrated; inactive instances will be ignored.
* ``--disable-migration=both`` (or ``--disable-migration`` without a value): Disable
all migration. Active instances will be stopped; inactive instances will be ignored.

* This is based on the `Watcher Host Maintenance strategy`_ which supports
``disable_live_migration`` and ``disable_cold_migration`` parameters.

Verify
^^^^^^
Expand Down Expand Up @@ -283,6 +296,7 @@ Once all roles on the node meet these conditions, the node is considered to be o
**Maintenance** mode.

.. LINKS
.. _Watcher Host Maintenance strategy: https://docs.openstack.org/watcher/latest/strategies/host_maintenance.html
.. _ceph administration tool: https://docs.ceph.com/en/reef/man/8/ceph/
.. _kubectl drain: https://kubernetes.io/docs/reference/kubectl/generated/kubectl_drain/
.. _kubectl cordon: https://kubernetes.io/docs/reference/kubectl/generated/kubectl_cordon/
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47 changes: 45 additions & 2 deletions how-to/operations/maintenance-mode.rst
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Expand Up @@ -28,7 +28,7 @@ Before enabling maintenance mode, perform a dry run to check for potential issue

.. code:: text

sunbeam cluster maintenance enable <node> --dry-run
sunbeam cluster maintenance enable <node> [--disable-migration[=live|cold|both]] --dry-run

Continue to run operations to enable maintenance mode for <node>:
0: change_nova_service_state state=disabled resource=<node>
Expand All @@ -41,7 +41,7 @@ If no issues are reported, enable maintenance mode:

.. code:: text

sunbeam cluster maintenance enable <node>
sunbeam cluster maintenance enable <node> [--disable-migration[=live|cold|both]]

Continue to run operations to enable maintenance mode for <node>:
0: change_nova_service_state state=disabled resource=<node>
Expand All @@ -61,6 +61,49 @@ If no issues are reported, enable maintenance mode:
Enable maintenance for node: <node>


Controlling migration behavior
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

By default, enabling maintenance mode will live migrate active instances and cold
migrate inactive instances. The ``--disable-migration`` flag allows operators to
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@hemanthnakkina hemanthnakkina Mar 24, 2026

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The option should also be provided in Usage section

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@H-M-Quang-Ngo H-M-Quang-Ngo Mar 24, 2026

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Hi @hemanthnakkina , thanks for the review!

I'm a bit confused here, because it is already in Usage section. The hierarchy is Usage -> Enabling Maintenance Mode -> Controlling migration behavior

I intentionally placed it after the basic enable flow so the simple happy path is provided first, with the optional flag documented as a follow-up. Do you think this structure works, or would you prefer something different?

I attach this image for clearer visualization:

image

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@hemanthnakkina hemanthnakkina Mar 25, 2026

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I mean [ --disable-migration ] should be specified as optional parameter in commands during --dry-run since the output varies based on the this flag

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@H-M-Quang-Ngo H-M-Quang-Ngo Mar 26, 2026

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@hemanthnakkina , thanks, I added in ed9546c

control this behavior during maintenance.

.. note::

If ``--disable-migration`` is not specified, the default behavior is unchanged.

To disable live migration (cold migrate both active and inactive instances):

.. code:: text

sunbeam cluster maintenance enable <node> --disable-migration=live

To disable cold migration (live migrate active instances, ignore inactive instances):

.. code:: text

sunbeam cluster maintenance enable <node> --disable-migration=cold

To disable all migration (only stop active instances, ignore inactive instances):

.. code:: text

sunbeam cluster maintenance enable <node> --disable-migration=both

Or equivalently, without specifying a value:

.. code:: text

sunbeam cluster maintenance enable <node> --disable-migration

The ``--disable-migration`` flag can be combined with ``--dry-run`` to preview the
effect before applying:

.. code:: text

sunbeam cluster maintenance enable <node> --disable-migration=live --dry-run


Disabling Maintenance Mode
~~~~~~~~~~~~~~~~~~~~~~~~~~

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