Added v0.0.30 upgrade guide

docs/UPGRADE_v0.0.30.md

@@ -0,0 +1,85 @@
+# Upgrade guide v0.0.30
+
+This guide illustrates, step by step, how to migrate to `v0.0.30` from previous versions. 
+
+This release ships outstanding changes that make the Galera recovery process notably more robust. For making this possible, the `v0.0.30` operator relies some functionality available in both the `init` and `agent` containers used for Galera, so they both need to be updated to `v0.0.30` as detailed in further steps.
+
+- Uninstall you current `mariadb-operator` for preventing conflicts:
+```bash
+helm uninstall mariadb-operator
+```
+Alternatively, you may only downscale and delete the webhook configurations:
+```bash
+kubectl scale deployment mariadb-operator --replicas=0
+kubectl scale deployment mariadb-operator-webhook --replicas=0
+kubectl delete validatingwebhookconfiguration mariadb-operator-webhook
+kubectl delete mutatingwebhookconfiguration mariadb-operator-webhook
+```
+
+- Upgrade CRDs to `v0.0.30`:
+> [!IMPORTANT]  
+> Helm does not handle CRD upgrades. See [helm docs](https://helm.sh/docs/chart_best_practices/custom_resource_definitions/#some-caveats-and-explanations).
+
+```bash
+kubectl replace -f https://github.com/mariadb-operator/mariadb-operator/releases/download/helm-chart-0.30.0/crds.yaml
+```
+
+- If you are using Galera, apply the following changes in the `MariaDB` resources:
+
+Update the `init` and `agent` containers to `v0.0.30`:
+```diff
+apiVersion: k8s.mariadb.com/v1alpha1
+kind: MariaDB
+metadata:
+  name: mariadb
+spec:
+  galera:
+    agent:
+-      image: docker-registry3.mariadb.com/mariadb-operator/mariadb-operator:v0.0.29
++      image: docker-registry3.mariadb.com/mariadb-operator/mariadb-operator:v0.0.30
+    initContainer:
+-      image: docker-registry3.mariadb.com/mariadb-operator/mariadb-operator:v0.0.29
++      image: docker-registry3.mariadb.com/mariadb-operator/mariadb-operator:v0.0.30
+```
+
+`podSyncTimeout` and `podRecoveryTimeout` defaults have been bumped to `5m`, make sure you bump them as well to at least `5m`:
+
+```diff
+apiVersion: k8s.mariadb.com/v1alpha1
+kind: MariaDB
+metadata:
+  name: mariadb
+spec:
+  galera:
+    recovery:
+-      podRecoveryTimeout: 3m
++      podRecoveryTimeout: 5m
+-      podSyncTimeout: 3m
++      podSyncTimeout: 5m
+```
+
+`minClusterSize` defaults to `1` replica now, which means that the recovery process will only be triggered when all the `Pods` are down. This is the recommended setting now, as it fits better the new recovery process:
+
+```diff
+apiVersion: k8s.mariadb.com/v1alpha1
+kind: MariaDB
+metadata:
+  name: mariadb
+spec:
+  galera:
+    recovery:
+-      minClusterSize: "50%"
++      minClusterSize: 1
+```
+ 
+-  Upgrade `mariadb-operator` to `v0.0.30`:
+```bash 
+helm repo update mariadb-operator
+helm upgrade --install mariadb-operator mariadb-operator/mariadb-operator --version 0.30.0 
+```
+
+- If you previously decided to downscale the operator, make sure you upscale it back:
+```bash
+kubectl scale deployment mariadb-operator -n default --replicas=1
+kubectl scale deployment mariadb-operator-webhook -n default --replicas=1
+```