Fix UnsupportedOperationException from ReadOnlyVersion in storeMetadataUpdate

Author: misyel

internal/venice-common/src/main/java/com/linkedin/venice/meta/ReadOnlyStore.java

@@ -1588,6 +1588,12 @@ public Version getVersion(int versionNumber) {
     return version;
   }
 
+  @Override
+  public void setVersionTargetRegionPromoted(int versionNumber, boolean targetRegionPromoted) {
+    // Delegate to the mutable store to bypass ReadOnlyVersion, which throws on setters.
+    this.delegate.setVersionTargetRegionPromoted(versionNumber, targetRegionPromoted);
+  }
+
   @Override
   @Nonnull
   public Version getVersionOrThrow(int versionNumber) throws StoreVersionNotFoundException {

internal/venice-common/src/main/java/com/linkedin/venice/meta/Store.java

@@ -288,6 +288,13 @@ default IntSet getVersionNumbers() {
 
   void updateVersionStatus(int versionNumber, VersionStatus status);
 
+  default void setVersionTargetRegionPromoted(int versionNumber, boolean targetRegionPromoted) {
+    Version version = getVersion(versionNumber);
+    if (version != null) {
+      version.setTargetRegionPromoted(targetRegionPromoted);
+    }
+  }
+
   int peekNextVersionNumber();
 
   /**

services/venice-controller/src/main/java/com/linkedin/venice/controller/VeniceHelixAdmin.java

@@ -6682,9 +6682,13 @@ private void internalUpdateStore(String clusterName, String storeName, UpdateSto
 
       if (targetRegionPromoted.orElse(false)) {
         storeMetadataUpdate(clusterName, storeName, (store, resources) -> {
-          Version futureVersion = store.getVersion(store.getLargestUsedVersionNumber());
+          int futureVersionNum = store.getLargestUsedVersionNumber();
+          Version futureVersion = store.getVersion(futureVersionNum);
           if (futureVersion != null && !futureVersion.isTargetRegionPromoted()) {
-            futureVersion.setTargetRegionPromoted(true);
+            // Use store.setVersionTargetRegionPromoted rather than futureVersion.setTargetRegionPromoted
+            // because storeMetadataUpdate may provide a ReadOnlyStore whose getVersion() wraps versions
+            // in ReadOnlyVersion (setters throw). The store-level method bypasses that wrapper.
+            store.setVersionTargetRegionPromoted(futureVersionNum, true);
           }
           return store;
         });