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cybozu-go · Sep 6, 2023 · 282b34c · 282b34c
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diff --git a/change-pvc-template.html b/change-pvc-template.html
@@ -182,6 +182,77 @@ <h3 id="metrics-1"><a class="header" href="#metrics-1">Metrics</a></h3>
 If fails to volume size changed, the metrics in <code>moco_cluster_volume_resized_errors_total</code> is incremented after each reconcile,
 so users can notice anomalies by monitoring this metrics.</p>
 <p>See the <a href="./metrics.html">metrics documentation</a> for more details.</p>
+<h2 id="volume-reduction"><a class="header" href="#volume-reduction">Volume reduction</a></h2>
+<p>MOCO supports PVC reduction, but unlike PVC expansion, the user must perform the operation manually.</p>
+<p>The steps are as follows:</p>
+<ol>
+<li>The user modifies the <code>.spec.volumeClaimTemplates</code> of the MySQLCluster and sets a smaller volume size.</li>
+<li>MOCO updates the <code>.spec.volumeClaimTemplates</code> of the StatefulSet. This does not propagate to existing Pods, PVCs, or PVs.</li>
+<li>The user manually deletes the MySQL Pod &amp; PVC.</li>
+<li>Wait for the Pod &amp; PVC to be recreated by the statefulset-controller, and for MOCO to clone the data.</li>
+<li>Once the cluster becomes Healthy, the user deletes the next Pod and PVC.</li>
+<li>It is completed when all Pods and PVCs are recreated.</li>
+</ol>
+<h3 id="1-the-user-modifies-the-specvolumeclaimtemplates-of-the-mysqlcluster-and-sets-a-smaller-volume-size"><a class="header" href="#1-the-user-modifies-the-specvolumeclaimtemplates-of-the-mysqlcluster-and-sets-a-smaller-volume-size">1. The user modifies the <code>.spec.volumeClaimTemplates</code> of the MySQLCluster and sets a smaller volume size</a></h3>
+<p>For example, the user modifies the <code>.spec.volumeClaimTemplates</code> of the MySQLCluster as follows:</p>
+<pre><code class="language-diff">  apiVersion: moco.cybozu.com/v1beta2
+  kind: MySQLCluster
+  metadata:
+    namespace: default
+    name: test
+  spec:
+    replicas: 3
+    podTemplate:
+      spec:
+        containers:
+        - name: mysqld
+          image: quay.io/cybozu/mysql:8.0.30
+    volumeClaimTemplates:
+    - metadata:
+        name: mysql-data
+      spec:
+        accessModes: [ &quot;ReadWriteOnce&quot; ]
+        resources:
+          requests:
+-           storage: 1Gi
++           storage: 500Mi
+</code></pre>
+<h3 id="2-moco-updates-the-specvolumeclaimtemplates-of-the-statefulset-this-does-not-propagate-to-existing-pods-pvcs-or-pvs"><a class="header" href="#2-moco-updates-the-specvolumeclaimtemplates-of-the-statefulset-this-does-not-propagate-to-existing-pods-pvcs-or-pvs">2. MOCO updates the <code>.spec.volumeClaimTemplates</code> of the StatefulSet. This does not propagate to existing Pods, PVCs, or PVs</a></h3>
+<p>The moco-controller will update the <code>.spec.volumeClaimTemplates</code> of the StatefulSet.
+The actual modification of the StatefulSet's <code>.spec.volumeClaimTemplates</code> is not allowed,
+so this change is achieved by recreating the StatefulSet.
+At this time, only the recreation of StatefulSet is performed, without deleting the Pods and PVCs.</p>
+<h3 id="3-the-user-manually-deletes-the-mysql-pod--pvc"><a class="header" href="#3-the-user-manually-deletes-the-mysql-pod--pvc">3. The user manually deletes the MySQL Pod &amp; PVC</a></h3>
+<p>The user manually deletes the PVC and Pod.
+Use the following command to delete them:</p>
+<pre><code class="language-console">$ kubectl delete --wait=false pvc &lt;pvc-name&gt;
+$ kubectl delete --grace-period=1 &lt;pod-name&gt;
+</code></pre>
+<h3 id="4-wait-for-the-pod--pvc-to-be-recreated-by-the-statefulset-controller-and-for-moco-to-clone-the-data"><a class="header" href="#4-wait-for-the-pod--pvc-to-be-recreated-by-the-statefulset-controller-and-for-moco-to-clone-the-data">4. Wait for the Pod &amp; PVC to be recreated by the statefulset-controller, and for MOCO to clone the data</a></h3>
+<p>The statefulset-controller recreates Pods and PVCs, creating a new PVC with a reduced size.
+Once the MOCO successfully starts a Pod, it begins cloning the data.</p>
+<pre><code class="language-console">$ kubectl get mysqlcluster,po,pvc
+NAME                                AVAILABLE   HEALTHY   PRIMARY   SYNCED REPLICAS   ERRANT REPLICAS   LAST BACKUP
+mysqlcluster.moco.cybozu.com/test   True        False     0         2                                   &lt;no value&gt;
+
+NAME              READY   STATUS     RESTARTS   AGE
+pod/moco-test-0   3/3     Running    0          2m14s
+pod/moco-test-1   3/3     Running    0          114s
+pod/moco-test-2   0/3     Init:1/2   0          7s
+
+NAME                                           STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS   AGE
+persistentvolumeclaim/mysql-data-moco-test-0   Bound    pvc-03c73525-0d6d-49de-b68a-f8af4c4c7faa   1Gi        RWO            standard       2m14s
+persistentvolumeclaim/mysql-data-moco-test-1   Bound    pvc-73c26baa-3432-4c85-b5b6-875ffd2456d9   1Gi        RWO            standard       114s
+persistentvolumeclaim/mysql-data-moco-test-2   Bound    pvc-779b5b3c-3efc-4048-a549-a4bd2d74ed4e   500Mi      RWO            standard       7s
+</code></pre>
+<h3 id="5-once-the-cluster-becomes-healthy-the-user-deletes-the-next-pod-and-pvc"><a class="header" href="#5-once-the-cluster-becomes-healthy-the-user-deletes-the-next-pod-and-pvc">5. Once the cluster becomes Healthy, the user deletes the next Pod and PVC</a></h3>
+<p>The user waits until the MySQLCluster state becomes Healthy, and then deletes the next Pod and PVC.</p>
+<pre><code class="language-console">$ kubectl get mysqlcluster
+NAME                                AVAILABLE   HEALTHY   PRIMARY   SYNCED REPLICAS   ERRANT REPLICAS   LAST BACKUP
+mysqlcluster.moco.cybozu.com/test   True        True      1         3                                   &lt;no value&gt;
+</code></pre>
+<h3 id="6-it-is-completed-when-all-pods-and-pvcs-are-recreated"><a class="header" href="#6-it-is-completed-when-all-pods-and-pvcs-are-recreated">6. It is completed when all Pods and PVCs are recreated</a></h3>
+<p>Repeat steps 3 to 5 until all Pods and PVCs are recreated.</p>
 <h2 id="references"><a class="header" href="#references">References</a></h2>
 <ul>
 <li><a href="./designdoc/support_apply_pvc_template_changes.html">Design document</a></li>

diff --git a/print.html b/print.html
@@ -1039,6 +1039,77 @@ <h3 id="metrics-2"><a class="header" href="#metrics-2">Metrics</a></h3>
 If fails to volume size changed, the metrics in <code>moco_cluster_volume_resized_errors_total</code> is incremented after each reconcile,
 so users can notice anomalies by monitoring this metrics.</p>
 <p>See the <a href="./metrics.html">metrics documentation</a> for more details.</p>
+<h2 id="volume-reduction"><a class="header" href="#volume-reduction">Volume reduction</a></h2>
+<p>MOCO supports PVC reduction, but unlike PVC expansion, the user must perform the operation manually.</p>
+<p>The steps are as follows:</p>
+<ol>
+<li>The user modifies the <code>.spec.volumeClaimTemplates</code> of the MySQLCluster and sets a smaller volume size.</li>
+<li>MOCO updates the <code>.spec.volumeClaimTemplates</code> of the StatefulSet. This does not propagate to existing Pods, PVCs, or PVs.</li>
+<li>The user manually deletes the MySQL Pod &amp; PVC.</li>
+<li>Wait for the Pod &amp; PVC to be recreated by the statefulset-controller, and for MOCO to clone the data.</li>
+<li>Once the cluster becomes Healthy, the user deletes the next Pod and PVC.</li>
+<li>It is completed when all Pods and PVCs are recreated.</li>
+</ol>
+<h3 id="1-the-user-modifies-the-specvolumeclaimtemplates-of-the-mysqlcluster-and-sets-a-smaller-volume-size"><a class="header" href="#1-the-user-modifies-the-specvolumeclaimtemplates-of-the-mysqlcluster-and-sets-a-smaller-volume-size">1. The user modifies the <code>.spec.volumeClaimTemplates</code> of the MySQLCluster and sets a smaller volume size</a></h3>
+<p>For example, the user modifies the <code>.spec.volumeClaimTemplates</code> of the MySQLCluster as follows:</p>
+<pre><code class="language-diff">  apiVersion: moco.cybozu.com/v1beta2
+  kind: MySQLCluster
+  metadata:
+    namespace: default
+    name: test
+  spec:
+    replicas: 3
+    podTemplate:
+      spec:
+        containers:
+        - name: mysqld
+          image: quay.io/cybozu/mysql:8.0.30
+    volumeClaimTemplates:
+    - metadata:
+        name: mysql-data
+      spec:
+        accessModes: [ &quot;ReadWriteOnce&quot; ]
+        resources:
+          requests:
+-           storage: 1Gi
++           storage: 500Mi
+</code></pre>
+<h3 id="2-moco-updates-the-specvolumeclaimtemplates-of-the-statefulset-this-does-not-propagate-to-existing-pods-pvcs-or-pvs"><a class="header" href="#2-moco-updates-the-specvolumeclaimtemplates-of-the-statefulset-this-does-not-propagate-to-existing-pods-pvcs-or-pvs">2. MOCO updates the <code>.spec.volumeClaimTemplates</code> of the StatefulSet. This does not propagate to existing Pods, PVCs, or PVs</a></h3>
+<p>The moco-controller will update the <code>.spec.volumeClaimTemplates</code> of the StatefulSet.
+The actual modification of the StatefulSet's <code>.spec.volumeClaimTemplates</code> is not allowed,
+so this change is achieved by recreating the StatefulSet.
+At this time, only the recreation of StatefulSet is performed, without deleting the Pods and PVCs.</p>
+<h3 id="3-the-user-manually-deletes-the-mysql-pod--pvc"><a class="header" href="#3-the-user-manually-deletes-the-mysql-pod--pvc">3. The user manually deletes the MySQL Pod &amp; PVC</a></h3>
+<p>The user manually deletes the PVC and Pod.
+Use the following command to delete them:</p>
+<pre><code class="language-console">$ kubectl delete --wait=false pvc &lt;pvc-name&gt;
+$ kubectl delete --grace-period=1 &lt;pod-name&gt;
+</code></pre>
+<h3 id="4-wait-for-the-pod--pvc-to-be-recreated-by-the-statefulset-controller-and-for-moco-to-clone-the-data"><a class="header" href="#4-wait-for-the-pod--pvc-to-be-recreated-by-the-statefulset-controller-and-for-moco-to-clone-the-data">4. Wait for the Pod &amp; PVC to be recreated by the statefulset-controller, and for MOCO to clone the data</a></h3>
+<p>The statefulset-controller recreates Pods and PVCs, creating a new PVC with a reduced size.
+Once the MOCO successfully starts a Pod, it begins cloning the data.</p>
+<pre><code class="language-console">$ kubectl get mysqlcluster,po,pvc
+NAME                                AVAILABLE   HEALTHY   PRIMARY   SYNCED REPLICAS   ERRANT REPLICAS   LAST BACKUP
+mysqlcluster.moco.cybozu.com/test   True        False     0         2                                   &lt;no value&gt;
+
+NAME              READY   STATUS     RESTARTS   AGE
+pod/moco-test-0   3/3     Running    0          2m14s
+pod/moco-test-1   3/3     Running    0          114s
+pod/moco-test-2   0/3     Init:1/2   0          7s
+
+NAME                                           STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS   AGE
+persistentvolumeclaim/mysql-data-moco-test-0   Bound    pvc-03c73525-0d6d-49de-b68a-f8af4c4c7faa   1Gi        RWO            standard       2m14s
+persistentvolumeclaim/mysql-data-moco-test-1   Bound    pvc-73c26baa-3432-4c85-b5b6-875ffd2456d9   1Gi        RWO            standard       114s
+persistentvolumeclaim/mysql-data-moco-test-2   Bound    pvc-779b5b3c-3efc-4048-a549-a4bd2d74ed4e   500Mi      RWO            standard       7s
+</code></pre>
+<h3 id="5-once-the-cluster-becomes-healthy-the-user-deletes-the-next-pod-and-pvc"><a class="header" href="#5-once-the-cluster-becomes-healthy-the-user-deletes-the-next-pod-and-pvc">5. Once the cluster becomes Healthy, the user deletes the next Pod and PVC</a></h3>
+<p>The user waits until the MySQLCluster state becomes Healthy, and then deletes the next Pod and PVC.</p>
+<pre><code class="language-console">$ kubectl get mysqlcluster
+NAME                                AVAILABLE   HEALTHY   PRIMARY   SYNCED REPLICAS   ERRANT REPLICAS   LAST BACKUP
+mysqlcluster.moco.cybozu.com/test   True        True      1         3                                   &lt;no value&gt;
+</code></pre>
+<h3 id="6-it-is-completed-when-all-pods-and-pvcs-are-recreated"><a class="header" href="#6-it-is-completed-when-all-pods-and-pvcs-are-recreated">6. It is completed when all Pods and PVCs are recreated</a></h3>
+<p>Repeat steps 3 to 5 until all Pods and PVCs are recreated.</p>
 <h2 id="references"><a class="header" href="#references">References</a></h2>
 <ul>
 <li><a href="./designdoc/support_apply_pvc_template_changes.html">Design document</a></li>

diff --git a/searchindex.js b/searchindex.js
diff --git a/searchindex.json b/searchindex.json