feat: add label selector to metrics call

examples/examples-release-latest/src/main/java/io/kubernetes/client/examples/MetricsExample.java

@@ -64,5 +64,22 @@ public static void main(String[] args) throws IOException, ApiException {
         System.out.println();
       }
     }
+
+      for (PodMetrics item : metrics.getPodMetrics("default", "foo=bar").getItems()) {
+          System.out.println(item.getMetadata().getName());
+          System.out.println("------------------------------");
+          if (item.getContainers() == null) {
+              continue;
+          }
+          for (ContainerMetrics container : item.getContainers()) {
+              System.out.println(container.getName());
+              System.out.println("-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-");
+              for (String key : container.getUsage().keySet()) {
+                  System.out.println("\t" + key);
+                  System.out.println("\t" + container.getUsage().get(key));
+              }
+              System.out.println();
+          }
+      }
   }
 }

util/src/main/java/io/kubernetes/client/Metrics.java

@@ -20,8 +20,17 @@
 import io.kubernetes.client.openapi.ApiException;
 import io.kubernetes.client.openapi.Configuration;
 import io.kubernetes.client.util.generic.GenericKubernetesApi;
+import io.kubernetes.client.util.generic.KubernetesApiResponse;
+import io.kubernetes.client.util.generic.options.ListOptions;
+
+import javax.annotation.Nullable;
 
 public class Metrics {
+  private static final String API_GROUP = "metrics.k8s.io";
+  private static final String API_VERSION = "v1beta1";
+  private static final String PODS = "pods";
+  private static final String NODES = "nodes";
+
   private ApiClient apiClient;
 
   /** Simple Metrics API constructor, uses default configuration */
@@ -61,17 +70,37 @@ public NodeMetricsList getNodeMetrics() throws ApiException {
         new GenericKubernetesApi<>(
             NodeMetrics.class,
             NodeMetricsList.class,
-            "metrics.k8s.io",
-            "v1beta1",
-            "nodes",
+            Metrics.API_GROUP,
+            Metrics.API_VERSION,
+            Metrics.NODES,
             apiClient);
     return metricsClient.list().throwsApiException().getObject();
   }
 
   public PodMetricsList getPodMetrics(String namespace) throws ApiException {
+    return getPodMetrics(namespace, null);
+  }
+
+  /**
+   * Obtain Pod Metrics in the given Namespace with an optional label selector.
+   * @param namespace     The Namespace to look in.
+   * @param labelSelector The label selector, optional.  Use comma-delimited for multiple labels.
+   * @return  PodMetricList, never null.
+   * @throws ApiException   If the ApiClient cannot complete the request.
+   */
+  public PodMetricsList getPodMetrics(String namespace, @Nullable String labelSelector) throws ApiException {
     GenericKubernetesApi<PodMetrics, PodMetricsList> metricsClient =
-        new GenericKubernetesApi<>(
-            PodMetrics.class, PodMetricsList.class, "metrics.k8s.io", "v1beta1", "pods", apiClient);
-    return metricsClient.list(namespace).throwsApiException().getObject();
+            new GenericKubernetesApi<>(
+                    PodMetrics.class, PodMetricsList.class, Metrics.API_GROUP, Metrics.API_VERSION, Metrics.PODS, apiClient);
+    final KubernetesApiResponse<PodMetricsList> response;
+    if (labelSelector == null || labelSelector.trim().isEmpty()) {
+        response = metricsClient.list(namespace);
+    } else {
+        final ListOptions listOptions = new ListOptions();
+        listOptions.setLabelSelector(labelSelector);
+        response = metricsClient.list(namespace, listOptions);
+    }
+
+    return response.throwsApiException().getObject();
   }
 }

util/src/test/java/io/kubernetes/client/MetricsTest.java

@@ -14,8 +14,7 @@
 
 import static com.github.tomakehurst.wiremock.client.WireMock.*;
 import static com.github.tomakehurst.wiremock.core.WireMockConfiguration.options;
-import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.failBecauseExceptionWasNotThrown;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 import com.github.tomakehurst.wiremock.junit5.WireMockExtension;
 import io.kubernetes.client.openapi.ApiClient;
@@ -49,12 +48,7 @@ void getPodMetricsThrowsAPIExceptionWhenServerReturnsError() {
                     .withStatus(503)
                     .withHeader("Content-Type", "text/plain")
                     .withBody("Service Unavailable")));
-    try {
-      metrics.getPodMetrics(namespace);
-      failBecauseExceptionWasNotThrown(ApiException.class);
-    } catch (ApiException ex) {
-      assertThat(ex.getCode()).isEqualTo(503);
-    }
+      assertThrows(ApiException.class, () -> metrics.getPodMetrics(namespace));
   }
 
   @Test
@@ -67,11 +61,6 @@ void getNodeMetricsThrowsAPIExceptionWhenServerReturnsError() {
                     .withStatus(503)
                     .withHeader("Content-Type", "text/plain")
                     .withBody("Service Unavailable")));
-    try {
-      metrics.getNodeMetrics();
-      failBecauseExceptionWasNotThrown(ApiException.class);
-    } catch (ApiException ex) {
-      assertThat(ex.getCode()).isEqualTo(503);
-    }
+      assertThrows(ApiException.class, metrics::getNodeMetrics);
   }
 }