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docs(refactor): moves drain cleaner content #9647

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Feb 8, 2024
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docs(refactor): moves drain cleaner content #9647

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docs(drain cleaner): moves drain cleaner content plus some edits
PaulRMellor Feb 6, 2024
237ca81
docs(drain cleaner): rolling updates change
PaulRMellor Feb 6, 2024
f97a6b6
docs(review): edits to doc from review by JS
PaulRMellor Feb 7, 2024
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docs(drain cleaner): rolling updates change 
Signed-off-by: prmellor <pmellor@redhat.com>
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@PaulRMellor
PaulRMellor committed Feb 6, 2024
commit 237ca81d15f32e7572fb2701febc4e451fb2bbe0
26 changes: 11 additions & 15 deletions documentation/modules/upgrading/con-upgrade-cluster.adoc
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Expand Up @@ -47,18 +47,12 @@ In a highly available environment, the Cluster Operator maintains a minimum numb

== Rolling pods using the Strimzi Drain Cleaner

You can use the xref:assembly-drain-cleaner-{context}[Strimzi Drain Cleaner] to evict nodes during an upgrade.
The Strimzi Drain Cleaner annotates pods with a rolling update pod annotation.
This informs the Cluster Operator to perform a rolling update of an evicted pod.
When using the Strimzi Drain Cleaner to evict nodes during upgrade, it annotates pods with a rolling update pod annotation to inform the Cluster Operator to perform a rolling update of an evicted pod.
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A pod disruption budget allows only a specified number of pods to be unavailable at a given time.
During planned maintenance of Kafka broker pods, a pod disruption budget ensures Kafka continues to run in a highly available environment.

You specify a pod disruption budget using a `template` customization for a Kafka component.
By default, pod disruption budgets allow only a single pod to be unavailable at a given time.

In order to use the Drain Cleaner to roll pods, you set `maxUnavailable` to `0` (zero).
Reducing the pod disruption budget to zero prevents voluntary disruptions, so pods must be evicted manually.
A pod disruption budget limits the number of unavailable pods and ensures Kafka's availability during planned maintenance.
By default, the budget permits only one pod to be unavailable at a given time.
To be able to use the Drain Cleaner to roll Kafka pods, you must set `maxUnavailable` to `0` (zero) in the template configuration of the `Kafka` resource.
Reducing the pod disruption budget to zero prevents Kubernetes from evicting pods automatically, so pods must be evicted through Strimzi Drain Cleaner.

.Specifying a pod disruption budget
[source,yaml,subs=attributes+]
Expand All @@ -77,6 +71,8 @@ spec:
# ...
----

For more information, see xref:assembly-drain-cleaner-{context}[].

== Rolling pods manually while keeping topics available

During an upgrade, you can trigger a manual rolling update of pods through the Cluster Operator.
Expand All @@ -89,13 +85,13 @@ You then add a pod annotation to make the update.
Here, the annotation updates a Kafka broker.

.Performing a manual rolling update on a Kafka broker pod
[source,shell,subs="+quotes,attributes"]
[source,shell,subs="+quotes"]
----
kubectl annotate pod _<cluster_name>_-kafka-_<index>_ strimzi.io/manual-rolling-update=true
kubectl annotate pod <cluster_name>-kafka-<index> strimzi.io/manual-rolling-update=true
----

You replace _<cluster_name>_ with the name of the cluster.
Kafka broker pods are named _<cluster-name>_-kafka-_<index>_, where _<index>_ starts at zero and ends at the total number of replicas minus one.
You replace <cluster_name> with the name of the cluster.
Kafka broker pods are named <cluster-name>-kafka-<index>, where <index> starts at zero and ends at the total number of replicas minus one.
For example, `my-cluster-kafka-0`.

[role="_additional-resources"]
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