TELCODOCS#2230: Coordinating reboots for configuration changes

Author: sr1kar99

edge_computing/policygenerator_for_ztp/ztp-configuring-managed-clusters-policygenerator.adoc

@@ -55,6 +55,8 @@ include::modules/ztp-customizing-a-managed-site-using-pgt.adoc[leveloffset=+1]
 
 include::modules/ztp-monitoring-policy-deployment-progress.adoc[leveloffset=+1]
 
+include::modules/ztp-coordinating-reboots-for-config-changes.adoc[leveloffset=+1]
+
 include::modules/ztp-validating-the-generation-of-configuration-policy-crs.adoc[leveloffset=+1]
 
 include::modules/ztp-restarting-policies-reconciliation.adoc[leveloffset=+1]

modules/ztp-coordinating-reboots-for-config-changes.adoc

@@ -0,0 +1,58 @@
+// Module included in the following assemblies:
+//
+// * scalability_and_performance/ztp_far_edge/ztp-configuring-managed-clusters-policies.adoc
+ifeval::["{context}" == "ztp-configuring-managed-clusters-policygenerator"]
+:ztp:
+endif::[]
+
+:_mod-docs-content-type: PROCEDURE
+[id="ztp-coordinating-reboots-for-config-changes_{context}"]
+ifdef::ztp[]
+= Coordinating reboots for configuration changes
+endif::ztp[]
+ifndef::ztp[]
+= Coordinating reboots for tuned profile changes
+endif::ztp[]
+
+You can use {cgu-operator-full} to coordinate reboots across a fleet of spoke clusters when configuration changes require a reboot.
+
+ifdef::ztp[]
+The following types of configuration changes typically require a reboot:
+
+* Updates to tuning profiles that modify kernel parameters or system behavior.node-tuning-operator
+* Kubelet configuration updates.
+* Node-level changes delivered through `MachineConfig`, such as `sysctl` settings or system service changes.
+endif::ztp[]
+
+ifndef::ztp[]
+These configuration changes include updates to tuning profiles that modify kernel parameters or system behavior.
+endif::ztp[]
+
+{cgu-operator} ensures that only nodes with a degraded tuned profile, indicating a reboot is needed, are rebooted.
+
+Instead of rebooting nodes after each individual change, you can apply all configuration updates through policies and then trigger a single, coordinated reboot. 
+
+.Prerequisites
+
+* You have installed the {oc-first}.
+* You have logged in to the hub cluster as a user with `cluster-admin` privileges.
+* You have deployed and configured {cgu-operator}.
+
+.Procedure
+
+. Create the configuration policies and policy bindings for the tuning or configuration changes.
+
+. Create a reboot policy on the hub cluster. This policy checks for degraded tuned profiles that indicate a reboot is needed.
+
+. Create and apply the `ClusterGroupUpgrade` (CGU) custom resource (CR). In the `spec.managedPolicies` list, include all relevant configuration policies first, followed by the reboot policy and the optional `mcp-validator` policy.
++
+After you apply the CGU custom resource, {cgu-operator} rolls out the configuration policies in order. When all policies are compliant, {cgu-operator} applies the reboot policy. This triggers a reboot of all nodes in the specified `MachineConfigPool`.
+
+.Verification
+
+* Confirm that all nodes in the `MachineConfigPool` have rebooted.
+* Verify that the `MachineConfigPool` reaches the `Updated` state.
+
+ifeval::["{context}" == "ztp-configuring-managed-clusters-policygenerator"]
+:!ztp:
+endif::[]

scalability_and_performance/using-node-tuning-operator.adoc

@@ -15,6 +15,8 @@ include::modules/accessing-an-example-cluster-node-tuning-operator-specification
 
 include::modules/cluster-node-tuning-operator-default-profiles-set.adoc[leveloffset=+1]
 
+include::modules/ztp-coordinating-reboots-for-config-changes.adoc[leveloffset=+1]
+
 include::modules/cluster-node-tuning-operator-verify-profiles.adoc[leveloffset=+1]
 
 include::modules/custom-tuning-specification.adoc[leveloffset=+1]