Fix 1158 (#1160)

Author: wind57

docs/src/main/asciidoc/discovery-client.adoc

@@ -131,8 +131,23 @@ Spring Cloud Kubernetes can also watch the Kubernetes service catalog for change
 milliseconds (by default it is `30000`). The heartbeat event will contain the target references (and their namespaces of the addresses of all endpoints
 (for the exact details of what will get returned you can take a look inside `KubernetesCatalogWatch`). This is an implementation detail, and listeners of the heartbeat event
 should not rely on the details. Instead, they should see if there are differences between two subsequent heartbeats via `equals` method. We will take care to return a correct implementation that adheres to the equals contract.
-The endpoints will be queried in either all namespaces (enabled via `spring.cloud.kubernetes.discovery.all-namespaces=true`), or
-we will use: xref:property-source-config.adoc#namespace-resolution[Namespace Resolution].
+The endpoints will be queried in either :
+
+ - all namespaces (enabled via `spring.cloud.kubernetes.discovery.all-namespaces=true`)
+
+ - specific namespaces (enabled via `spring.cloud.kubernetes.discovery.namespaces`), for example:
+
+```
+spring:
+  cloud:
+    kubernetes:
+      discovery:
+        namespaces:
+          - namespace-a
+          - namespace-b
+```
+
+- we will use: xref:property-source-config.adoc#namespace-resolution[Namespace Resolution] if the above two paths are not taken.
 
 In order to enable this functionality you need to add
 `@EnableScheduling` on a configuration class in your application.

spring-cloud-kubernetes-fabric8-config/src/main/java/org/springframework/cloud/kubernetes/fabric8/config/Fabric8ConfigContext.java

@@ -27,6 +27,6 @@
  *
  * @author wind57
  */
-final record Fabric8ConfigContext(KubernetesClient client, NormalizedSource normalizedSource, String namespace,
+record Fabric8ConfigContext(KubernetesClient client, NormalizedSource normalizedSource, String namespace,
 		Environment environment) {
 }

spring-cloud-kubernetes-fabric8-discovery/src/main/java/org/springframework/cloud/kubernetes/fabric8/discovery/Fabric8EndpointSliceV1CatalogWatch.java

@@ -16,6 +16,7 @@
 
 package org.springframework.cloud.kubernetes.fabric8.discovery;
 
+import java.util.ArrayList;
 import java.util.List;
 import java.util.function.Function;
 import java.util.stream.Stream;
@@ -44,23 +45,25 @@ final class Fabric8EndpointSliceV1CatalogWatch
 	public List<EndpointNameAndNamespace> apply(Fabric8CatalogWatchContext context) {
 		// take only pods that have endpoints
 		List<EndpointSlice> endpointSlices;
+		KubernetesClient client = context.kubernetesClient();
+
 		if (context.properties().allNamespaces()) {
 			LOG.debug(() -> "discovering endpoints in all namespaces");
-
-			// can't use try with resources here as it will close the client
-			KubernetesClient client = context.kubernetesClient();
 			endpointSlices = client.discovery().v1().endpointSlices().inAnyNamespace()
 					.withLabels(context.properties().serviceLabels()).list().getItems();
 		}
+		else if (!context.properties().namespaces().isEmpty()) {
+			LOG.debug(() -> "discovering endpoints in " + context.properties().namespaces());
+			List<EndpointSlice> inner = new ArrayList<>(context.properties().namespaces().size());
+			context.properties().namespaces()
+					.forEach(namespace -> inner.addAll(endpointSlices(context, namespace, client)));
+			endpointSlices = inner;
+		}
 		else {
 			String namespace = Fabric8Utils.getApplicationNamespace(context.kubernetesClient(), null, "catalog-watcher",
 					context.namespaceProvider());
-			LOG.debug(() -> "fabric8 catalog watcher will use namespace : " + namespace);
-
-			// can't use try with resources here as it will close the client
-			KubernetesClient client = context.kubernetesClient();
-			endpointSlices = client.discovery().v1().endpointSlices().inNamespace(namespace)
-					.withLabels(context.properties().serviceLabels()).list().getItems();
+			LOG.debug(() -> "discovering endpoints in namespace : " + namespace);
+			endpointSlices = endpointSlices(context, namespace, client);
 		}
 
 		Stream<ObjectReference> references = endpointSlices.stream().map(EndpointSlice::getEndpoints)
@@ -70,4 +73,10 @@ public List<EndpointNameAndNamespace> apply(Fabric8CatalogWatchContext context)
 
 	}
 
+	private List<EndpointSlice> endpointSlices(Fabric8CatalogWatchContext context, String namespace,
+			KubernetesClient client) {
+		return client.discovery().v1().endpointSlices().inNamespace(namespace)
+				.withLabels(context.properties().serviceLabels()).list().getItems();
+	}
+
 }

spring-cloud-kubernetes-fabric8-discovery/src/main/java/org/springframework/cloud/kubernetes/fabric8/discovery/Fabric8EndpointsCatalogWatch.java

@@ -16,6 +16,7 @@
 
 package org.springframework.cloud.kubernetes.fabric8.discovery;
 
+import java.util.ArrayList;
 import java.util.List;
 import java.util.Objects;
 import java.util.function.Function;
@@ -44,25 +45,25 @@ final class Fabric8EndpointsCatalogWatch
 
 	@Override
 	public List<EndpointNameAndNamespace> apply(Fabric8CatalogWatchContext context) {
-		// take only pods that have endpoints
 		List<Endpoints> endpoints;
+		KubernetesClient client = context.kubernetesClient();
+
 		if (context.properties().allNamespaces()) {
 			LOG.debug(() -> "discovering endpoints in all namespaces");
-
-			// can't use try with resources here as it will close the client
-			KubernetesClient client = context.kubernetesClient();
 			endpoints = client.endpoints().inAnyNamespace().withLabels(context.properties().serviceLabels()).list()
 					.getItems();
 		}
+		else if (!context.properties().namespaces().isEmpty()) {
+			LOG.debug(() -> "discovering endpoints in " + context.properties().namespaces());
+			List<Endpoints> inner = new ArrayList<>(context.properties().namespaces().size());
+			context.properties().namespaces().forEach(namespace -> inner.addAll(endpoints(context, namespace, client)));
+			endpoints = inner;
+		}
 		else {
 			String namespace = Fabric8Utils.getApplicationNamespace(context.kubernetesClient(), null, "catalog-watcher",
 					context.namespaceProvider());
-			LOG.debug(() -> "fabric8 catalog watcher will use namespace : " + namespace);
-
-			// can't use try with resources here as it will close the client
-			KubernetesClient client = context.kubernetesClient();
-			endpoints = client.endpoints().inNamespace(namespace).withLabels(context.properties().serviceLabels())
-					.list().getItems();
+			LOG.debug(() -> "discovering endpoints in namespace : " + namespace);
+			endpoints = endpoints(context, namespace, client);
 		}
 
 		/**
@@ -82,4 +83,9 @@ public List<EndpointNameAndNamespace> apply(Fabric8CatalogWatchContext context)
 		return Fabric8CatalogWatchContext.state(references);
 	}
 
+	private List<Endpoints> endpoints(Fabric8CatalogWatchContext context, String namespace, KubernetesClient client) {
+		return client.endpoints().inNamespace(namespace).withLabels(context.properties().serviceLabels()).list()
+				.getItems();
+	}
+
 }

spring-cloud-kubernetes-fabric8-discovery/src/main/java/org/springframework/cloud/kubernetes/fabric8/discovery/KubernetesCatalogWatch.java

@@ -84,6 +84,12 @@ public void catalogServicesWatch() {
 
 	@PostConstruct
 	void postConstruct() {
+		stateGenerator = stateGenerator();
+	}
+
+	Function<Fabric8CatalogWatchContext, List<EndpointNameAndNamespace>> stateGenerator() {
+
+		Function<Fabric8CatalogWatchContext, List<EndpointNameAndNamespace>> localStateGenerator;
 
 		if (context.properties().useEndpointSlices()) {
 			// can't use try with resources here as it will close the client
@@ -99,14 +105,16 @@ void postConstruct() {
 				throw new IllegalArgumentException("EndpointSlices are not supported on the cluster");
 			}
 			else {
-				stateGenerator = new Fabric8EndpointSliceV1CatalogWatch();
+				localStateGenerator = new Fabric8EndpointSliceV1CatalogWatch();
 			}
 		}
 		else {
-			stateGenerator = new Fabric8EndpointsCatalogWatch();
+			localStateGenerator = new Fabric8EndpointsCatalogWatch();
 		}
 
-		LOG.debug(() -> "stateGenerator is of type: " + stateGenerator.getClass().getSimpleName());
+		LOG.debug(() -> "stateGenerator is of type: " + localStateGenerator.getClass().getSimpleName());
+
+		return localStateGenerator;
 	}
 
 }