Merge "Allow dynamic enable/disable of SRR capability"

specs/pike/srr-capability-dynamic-toggle.rst

@@ -0,0 +1,145 @@
+..
+ This work is licensed under a Creative Commons Attribution 3.0 Unported
+ License.
+
+ http://creativecommons.org/licenses/by/3.0/legalcode
+
+==============================================
+Allow dynamic enable/disable of SRR capability
+==============================================
+
+Include the URL of your launchpad blueprint:
+
+https://blueprints.launchpad.net/nova-powervm/+spec/srr-capability-dynamic-toggle
+
+Currently to enable or disable the SRR capability on the VM we need to have
+the VM in shutoff state. We should be able to toggle this field dynamically
+so that the shutdown of a VM is not needed.
+
+Problem description
+===================
+
+The simplified remote restart (SRR) capability governs whether a VM can be
+rebuilt (remote restarted) on a different host when the host on which the
+VM resides is down. Currently this attribute can be changed only when the VM
+is in shut-off state. This blueprint addresses that by enabling toggle
+of simplified remote restart capability dynamically (while the VM is still
+active).
+
+
+Use Cases
+---------
+
+The end user would like to :
+- Enable the srr capability on the VM without shutting it down so that any
+workloads on the VM are unaffected.
+- Disable the srr capability for a VM which need not be rebuilt to another
+host while the VM is still up and running.
+
+
+Proposed change
+===============
+The SRR capability is a VM level attribute and can be changed using
+the resize operation. In case of a resize operation for an active VM
+- Check if the hypervisor supports dynamic toggle of srr capability.
+- If it is supported proceed with updating of srr capability if it has been
+changed.
+- Throw a warning if update of srr capability is not supported.
+
+
+Alternatives
+------------
+
+None
+
+
+Security impact
+---------------
+
+None
+
+
+End user impact
+---------------
+
+None
+
+
+Performance Impact
+------------------
+
+The change is srr capability is not likely to happen very frequently so this
+should not have a major impact. When the change happens the impact on the
+performance of any other component (the VM, the compute service, the REST
+service, etc.) should be negligible.
+
+
+Deployer impact
+---------------
+
+End user will be able to dynamically the toggle the srr capability for the
+VM. The changes can be utilized immediately once they are deployed.
+
+
+Developer impact
+----------------
+
+None
+
+Implementation
+==============
+
+Assignee(s)
+-----------
+
+
+Primary assignee:
+  manasmandlekar
+
+Other contributors:
+  shyvenug
+
+Work Items
+----------
+NA
+
+Dependencies
+============
+
+Need to work with PowerVM platform team to ensure that the srr toggle
+capability is exposed for the Compute driver to consume.
+
+
+Testing
+=======
+
+The testing of the change requires full Openstack environment with
+Compute resources configured.
+- Ensure srr state for VM can be toggled when it is up and running.
+- Ensure srr state for VM can be toggled when it is shut-off.
+- Perform rebuild operations to ensure that the capability is indeed
+getting utilized.
+
+
+Documentation Impact
+====================
+
+None
+
+
+References
+==========
+
+None
+
+
+History
+=======
+
+.. list-table:: Revisions
+   :header-rows: 1
+
+   * - Release Name
+     - Description
+   * - Pike
+     - Introduced