Avoid updating immutable fields.

org.jdrupes.vmoperator.manager/src/org/jdrupes/vmoperator/manager/PvcReconciler.java

@@ -18,6 +18,7 @@
 
 package org.jdrupes.vmoperator.manager;
 
+import com.google.gson.JsonObject;
 import freemarker.core.ParseException;
 import freemarker.template.Configuration;
 import freemarker.template.MalformedTemplateNameException;
@@ -25,6 +26,7 @@ import freemarker.template.TemplateException;
 import freemarker.template.TemplateNotFoundException;
 import io.kubernetes.client.custom.V1Patch;
 import io.kubernetes.client.openapi.ApiException;
+import io.kubernetes.client.util.generic.dynamic.DynamicKubernetesObject;
 import io.kubernetes.client.util.generic.dynamic.Dynamics;
 import io.kubernetes.client.util.generic.options.ListOptions;
 import io.kubernetes.client.util.generic.options.PatchOptions;
@@ -41,6 +43,7 @@ import org.jdrupes.vmoperator.common.K8sV1PvcStub;
 import org.jdrupes.vmoperator.manager.events.VmChannel;
 import org.jdrupes.vmoperator.manager.events.VmDefChanged;
 import org.jdrupes.vmoperator.util.DataPath;
+import org.jdrupes.vmoperator.util.GsonPtr;
 import org.yaml.snakeyaml.LoaderOptions;
 import org.yaml.snakeyaml.Yaml;
 import org.yaml.snakeyaml.constructor.SafeConstructor;
@@ -179,9 +182,13 @@ import org.yaml.snakeyaml.constructor.SafeConstructor;
         var pvcDef = Dynamics.newFromYaml(
             new Yaml(new SafeConstructor(new LoaderOptions())), out.toString());
 
-        // Do apply changes
+        // Apply changes
         var pvcStub
             = K8sV1PvcStub.get(channel.client(), vmDef.namespace(), pvcName);
+        var pvc = pvcStub.model();
+        if (pvc.isEmpty()
+            || !"Bound".equals(pvc.get().getStatus().getPhase())) {
+            // Does not exist or isn't bound, use apply
             PatchOptions opts = new PatchOptions();
             opts.setForce(true);
             opts.setFieldManager("kubernetes-java-kubectl-apply");
@@ -191,5 +198,35 @@ import org.yaml.snakeyaml.constructor.SafeConstructor;
                 logger.warning(
                     () -> "Could not patch pvc for " + pvcStub.name());
             }
+            return;
+        }
+
+        // If bound, use json merge, omitting immutable fields
+        var spec = GsonPtr.to(pvcDef.getRaw()).to("spec");
+        spec.removeExcept("volumeAttributesClassName", "resources");
+        spec.access("resources").ifPresent(p -> p.removeExcept("requests"));
+        PatchOptions opts = new PatchOptions();
+        opts.setFieldManager("kubernetes-java-kubectl-apply");
+        if (pvcStub.patch(V1Patch.PATCH_FORMAT_JSON_MERGE_PATCH,
+            new V1Patch(channel.client().getJSON().serialize(pvcDef)), opts)
+            .isEmpty()) {
+            logger.warning(
+                () -> "Could not patch pvc for " + pvcStub.name());
+        }
+    }
+
+    @SuppressWarnings("PMD.AvoidLiteralsInIfCondition")
+    private void removeImmutable(DynamicKubernetesObject pvcDef) {
+        var spec = GsonPtr.to(pvcDef.getRaw()).to("spec").get(JsonObject.class);
+        for (var itr = spec.entrySet().iterator(); itr.hasNext();) {
+            var entry = itr.next();
+            if ("volumeAttributesClassName".equals(entry.getKey())) {
+                continue;
+            }
+            if ("resources".equals(entry.getKey())) {
+                continue;
+            }
+            itr.remove();
+        }
     }
 }

org.jdrupes.vmoperator.util/src/org/jdrupes/vmoperator/util/GsonPtr.java

@@ -23,6 +23,7 @@ import com.google.gson.JsonElement;
 import com.google.gson.JsonObject;
 import com.google.gson.JsonPrimitive;
 import java.math.BigInteger;
+import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
 import java.util.Optional;
@@ -62,7 +63,8 @@ public class GsonPtr {
      * @param selectors the selectors
      * @return the Gson pointer
      */
-    @SuppressWarnings({ "PMD.ShortMethodName", "PMD.PreserveStackTrace" })
+    @SuppressWarnings({ "PMD.ShortMethodName", "PMD.PreserveStackTrace",
+        "PMD.AvoidDuplicateLiterals" })
     public GsonPtr to(Object... selectors) {
         JsonElement element = position;
         for (Object sel : selectors) {
@@ -91,6 +93,42 @@ public class GsonPtr {
         return new GsonPtr(element);
     }
 
+    /**
+     * Create a new instance pointing to the {@link JsonElement} 
+     * selected by the given selectors. If a selector of type 
+     * {@link String} denotes a non-existant member of a
+     * {@link JsonObject} the result is empty.
+     *
+     * @param selectors the selectors
+     * @return the Gson pointer
+     */
+    @SuppressWarnings({ "PMD.ShortMethodName", "PMD.PreserveStackTrace" })
+    public Optional<GsonPtr> access(Object... selectors) {
+        JsonElement element = position;
+        for (Object sel : selectors) {
+            if (element instanceof JsonObject obj
+                && sel instanceof String member) {
+                element = obj.get(member);
+                if (element == null) {
+                    return Optional.empty();
+                }
+                continue;
+            }
+            if (element instanceof JsonArray arr
+                && sel instanceof Integer index) {
+                try {
+                    element = arr.get(index);
+                } catch (IndexOutOfBoundsException e) {
+                    throw new IllegalStateException("Selected array index"
+                        + " may not be empty.");
+                }
+                continue;
+            }
+            throw new IllegalStateException("Invalid selection");
+        }
+        return Optional.of(new GsonPtr(element));
+    }
+
     /**
      * Returns {@link JsonElement} that the pointer points to.
      *
@@ -336,4 +374,22 @@ public class GsonPtr {
         return this;
     }
 
+    /**
+     * Removes all properties except the specified ones.
+     *
+     * @param properties the properties
+     */
+    public void removeExcept(String... properties) {
+        if (!position.isJsonObject()) {
+            return;
+        }
+        for (var itr = ((JsonObject) position).entrySet().iterator();
+                itr.hasNext();) {
+            var entry = itr.next();
+            if (Arrays.asList(properties).contains(entry.getKey())) {
+                continue;
+            }
+            itr.remove();
+        }
+    }
 }