Fix a bug where changes to GWC layers won't be propagated to other pods.

src/gwc/backends/pgconfig/src/main/java/org/geoserver/cloud/gwc/backend/pgconfig/CachingTileLayerInfoRepository.java

@@ -20,6 +20,10 @@
 import java.util.Set;
 import java.util.stream.Stream;
 
+/**
+ * {@link TileLayerInfoRepository} decorator cache {@link TileLayerInfo}s on demand, alleviating the
+ * load on the delegate, especially under load.
+ */
 @RequiredArgsConstructor
 @Slf4j(topic = "org.geoserver.cloud.gwc.backend.pgconfig.caching")
 public class CachingTileLayerInfoRepository implements TileLayerInfoRepository {

src/gwc/backends/pgconfig/src/main/java/org/geoserver/cloud/gwc/backend/pgconfig/PgconfigTileLayerInfoRepository.java

@@ -11,7 +11,6 @@
 import org.geoserver.cloud.backend.pgconfig.catalog.repository.LoggingTemplate;
 import org.geoserver.gwc.layer.CatalogConfiguration;
 import org.geoserver.gwc.layer.GeoServerTileLayerInfo;
-import org.geoserver.gwc.layer.TileLayerCatalog;
 import org.geoserver.platform.resource.ResourceStore;
 import org.springframework.dao.DataAccessException;
 import org.springframework.dao.EmptyResultDataAccessException;
@@ -26,8 +25,8 @@
 import java.util.stream.Stream;
 
 /**
- * Implementation of {@link TileLayerCatalog} for {@link CatalogConfiguration} to manage {@link
- * GeoServerTileLayerInfo}s directly from the database instead of going through {@link
+ * Implementation of {@link TileLayerInfoRepository} for {@link CatalogConfiguration} to manage
+ * {@link GeoServerTileLayerInfo}s directly from the database instead of going through {@link
  * ResourceStore}.
  *
  * @since 1.7

src/gwc/backends/pgconfig/src/main/java/org/geoserver/cloud/gwc/backend/pgconfig/TileLayerInfoRepository.java

@@ -10,6 +10,11 @@
 import java.util.Set;
 import java.util.stream.Stream;
 
+/**
+ * {@code TileLayerInfoRepository} defines CRUD operations on {@link TileLayerInfo}.
+ *
+ * @see PgconfigTileLayerCatalog
+ */
 public interface TileLayerInfoRepository {
 
     void add(TileLayerInfo pgInfo) throws DataAccessException;

src/gwc/core/pom.xml

@@ -45,5 +45,15 @@
       <artifactId>gs-web-gwc</artifactId>
       <optional>true</optional>
     </dependency>
+    <dependency>
+      <groupId>org.xmlunit</groupId>
+      <artifactId>xmlunit-core</artifactId>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>org.xmlunit</groupId>
+      <artifactId>xmlunit-assertj</artifactId>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
 </project>

src/gwc/core/src/main/java/org/geoserver/cloud/gwc/config/core/DefaultTileLayerCatalogConfiguration.java

@@ -6,7 +6,6 @@
 
 import org.geoserver.GeoServerConfigurationLock;
 import org.geoserver.catalog.Catalog;
-import org.geoserver.cloud.gwc.event.TileLayerEvent;
 import org.geoserver.cloud.gwc.repository.CachingTileLayerCatalog;
 import org.geoserver.cloud.gwc.repository.CloudCatalogConfiguration;
 import org.geoserver.cloud.gwc.repository.GeoServerTileLayerConfiguration;
@@ -16,8 +15,10 @@
 import org.geoserver.gwc.config.GWCConfigPersister;
 import org.geoserver.gwc.config.GWCInitializer;
 import org.geoserver.gwc.layer.CatalogConfiguration;
+import org.geoserver.gwc.layer.GeoServerTileLayer;
 import org.geoserver.gwc.layer.TileLayerCatalog;
 import org.geoserver.platform.resource.ResourceStore;
+import org.geowebcache.config.TileLayerConfiguration;
 import org.geowebcache.grid.GridSetBroker;
 import org.springframework.beans.factory.annotation.Qualifier;
 import org.springframework.cache.CacheManager;
@@ -29,7 +30,6 @@
 import org.springframework.web.context.WebApplicationContext;
 
 import java.util.Optional;
-import java.util.function.Consumer;
 
 /**
  * @since 1.0
@@ -57,6 +57,20 @@ DefaultGwcInitializer gwcInitializer(
         return new DefaultGwcInitializer(configPersister, blobStore, geoseverTileLayers, lock);
     }
 
+    /**
+     * In vanilla GeoServer, {@link CatalogConfiguration} is the {@link TileLayerConfiguration}
+     * contributed to the app context to serve {@code TileLayer}s ({@link GeoServerTileLayer}) out
+     * of the GeoServer {@link Catalog} by means of a {@link TileLayerCatalog}.
+     *
+     * <p>Here we contribute a different {@code TileLayerConfiguration} for the same purpose, {@link
+     * GeoServerTileLayerConfiguration}, which is a distributed-event aware decorator over the
+     * actual {@link CloudCatalogConfiguration} implementation of {@code TileLayerCatalog}.
+     *
+     * <p>Since the {@code CloudCatalogConfiguration} isn't hence a spring bean, in order to avoid
+     * registering as a delegate to {@link TileLayerDispatcher}, {@link TileLayerEvents} will need
+     * to be relayed from {@code GeoServerTileLayerConfiguration} to {@link
+     * CloudCatalogConfiguration#onTileLayerEventEvict()}.
+     */
     @SuppressWarnings("java:S6830")
     @Bean(name = "gwcCatalogConfiguration")
     GeoServerTileLayerConfiguration gwcCatalogConfiguration( //
@@ -66,8 +80,12 @@ GeoServerTileLayerConfiguration gwcCatalogConfiguration( //
             ApplicationEventPublisher eventPublisher) {
 
         var config = new CloudCatalogConfiguration(catalog, tld, gsb);
-        Consumer<TileLayerEvent> gwcEventPublisher = eventPublisher::publishEvent;
-        return new GeoServerTileLayerConfiguration(config, gwcEventPublisher);
+        var eventAwareConfig =
+                new GeoServerTileLayerConfiguration(config, eventPublisher::publishEvent);
+        // tell GeoServerTileLayerConfiguration to relay TileLayerEvents to
+        // CloudCatalogConfiguration, since it's not a spring bean can't listen itself.
+        eventAwareConfig.setEventListener(config::onTileLayerEventEvict);
+        return eventAwareConfig;
     }
 
     @Primary

src/gwc/core/src/main/java/org/geoserver/cloud/gwc/event/TileLayerEvent.java

@@ -41,11 +41,6 @@ public TileLayerEvent(
         this.name = layerName;
     }
 
-    public static TileLayerEvent ofId(
-            @NonNull Object source, @NonNull Type eventType, @NonNull String layerId) {
-        return new TileLayerEvent(source, eventType, layerId, layerId);
-    }
-
     public static TileLayerEvent created(
             @NonNull Object source, @NonNull String publishedId, @NonNull String layerName) {
         return valueOf(source, Type.CREATED, publishedId, layerName, null);
@@ -77,8 +72,20 @@ private static TileLayerEvent valueOf(
 
     @Override
     public String toString() {
-        return "%s[%s id: %s, name: %s]"
-                .formatted(getClass().getSimpleName(), getEventType(), getPublishedId(), getName());
+        if (null == getOldName())
+            return "%s[%s id: %s, name: %s]"
+                    .formatted(
+                            getClass().getSimpleName(),
+                            getEventType(),
+                            getPublishedId(),
+                            getName());
+        return "%s[%s id: %s, name: %s, oldname: %s]"
+                .formatted(
+                        getClass().getSimpleName(),
+                        getEventType(),
+                        getPublishedId(),
+                        getName(),
+                        getOldName());
     }
 
     protected @Override String getObjectId() {