Allow using non default context

Author: omarkhammassi

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

@@ -97,15 +97,19 @@ public static ApiClient defaultClient() throws IOException {
    *     cannot be read.
    */
   public static ClientBuilder standard() throws IOException {
-    return standard(true);
+    return standard(true, null);
   }
 
-  public static ClientBuilder standard(boolean persistConfig) throws IOException {
+  public static ClientBuilder standard(String context) throws IOException {
+    return standard(true, context);
+  }
+
+  public static ClientBuilder standard(boolean persistConfig, String context) throws IOException {
     final File kubeConfig = findConfigFromEnv();
-    ClientBuilder clientBuilderEnv = getClientBuilder(persistConfig, kubeConfig);
+    ClientBuilder clientBuilderEnv = getClientBuilder(persistConfig, kubeConfig, context);
     if (clientBuilderEnv != null) return clientBuilderEnv;
     final File config = findConfigInHomeDir();
-    ClientBuilder clientBuilderHomeDir = getClientBuilder(persistConfig, config);
+    ClientBuilder clientBuilderHomeDir = getClientBuilder(persistConfig, config, context);
     if (clientBuilderHomeDir != null) return clientBuilderHomeDir;
     final File clusterCa = new File(SERVICEACCOUNT_CA_PATH);
     if (clusterCa.exists()) {
@@ -114,14 +118,14 @@ public static ClientBuilder standard(boolean persistConfig) throws IOException {
     return new ClientBuilder();
   }
 
-  private static ClientBuilder getClientBuilder(boolean persistConfig, File kubeConfig)
+  private static ClientBuilder getClientBuilder(boolean persistConfig, File kubeConfig, String context)
       throws IOException {
     if (kubeConfig != null) {
       try (BufferedReader kubeConfigReader =
           new BufferedReader(
               new InputStreamReader(
                   new FileInputStream(kubeConfig), StandardCharsets.UTF_8.name()))) {
-        KubeConfig kc = KubeConfig.loadKubeConfig(kubeConfigReader);
+        KubeConfig kc = KubeConfig.loadKubeConfig(kubeConfigReader, context);
         if (persistConfig) {
           kc.setPersistConfig(new FilePersister(kubeConfig));
         }

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

@@ -81,20 +81,36 @@ public static void registerAuthenticator(Authenticator auth) {
     registerAuthenticator(new OpenIDConnectAuthenticator());
   }
 
-  /** Load a Kubernetes config from a Reader */
   public static KubeConfig loadKubeConfig(Reader input) {
+    return loadKubeConfig(input, null);
+  }
+
+  /**
+   * Load a Kubernetes config from a Reader.
+   *
+   * @param input
+   * @param context if null will use current-context
+   * @return KubeConfig object
+   */
+  public static KubeConfig loadKubeConfig(Reader input, String context) {
     Yaml yaml = new Yaml(new SafeConstructor());
     Object config = yaml.load(input);
     Map<String, Object> configMap = (Map<String, Object>) config;
 
-    String currentContext = (String) configMap.get("current-context");
     ArrayList<Object> contexts = (ArrayList<Object>) configMap.get("contexts");
     ArrayList<Object> clusters = (ArrayList<Object>) configMap.get("clusters");
     ArrayList<Object> users = (ArrayList<Object>) configMap.get("users");
     Object preferences = configMap.get("preferences");
 
     KubeConfig kubeConfig = new KubeConfig(contexts, clusters, users);
-    kubeConfig.setContext(currentContext);
+
+    if (context != null) {
+      kubeConfig.setContext(context);
+    } else {
+      String currentContext = (String) configMap.get("current-context");
+      kubeConfig.setContext(currentContext);
+    }
+
     kubeConfig.setPreferences(preferences);
 
     return kubeConfig;

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

@@ -317,4 +317,18 @@ public void testDetectsServerNotSet() {
           ClientBuilder.kubeconfig(kubeConfigWithoutServer);
         });
   }
+
+  @Test
+  public void testKubeConfigWithContext() throws Exception {
+      String path =
+              withEnvironmentVariable("HOME", HOME_PATH)
+                      .and("KUBECONFIG", KUBECONFIG_FILE_PATH)
+                      .execute(
+                              () -> {
+                                  final ApiClient client = ClientBuilder.standard("foo-second-context").build();
+                                  return client.getBasePath();
+                              });
+      assertEquals("http://kubeconfig.second.dir.com", path);
+  }
+
 }

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

@@ -491,4 +491,30 @@ public void testExecCredentialsCertificate() throws Exception {
     assertEquals("key", kc.getCredentials().get(KubeConfig.CRED_CLIENT_KEY_DATA_KEY));
     assertNull(kc.getCredentials().get(KubeConfig.CRED_TOKEN_KEY));
   }
+
+  private static final String KUBECONFIG_WITH_MULTIPLE_CONTEXTS =
+          "apiVersion: v1\n" +
+                  "clusters:\n" +
+                  "  - cluster:\n" +
+                  "      server: http://kubeconfig.dir.com\n" +
+                  "    name: foo\n" +
+                  "  - cluster:\n" +
+                  "      server: http://kubeconfig.second.dir.com\n" +
+                  "    name: foo-second-cluster\n" +
+                  "contexts:\n" +
+                  "  - context:\n" +
+                  "      cluster: foo\n" +
+                  "    name: foo-context\n" +
+                  "    name: foo-context  \n" +
+                  "   - context:\n" +
+                  "      cluster: foo-second-cluster\n" +
+                  "    name: foo-second-context\n" +
+                  "current-context: foo-context\n";
+
+  @Test
+  public void testConfigWithContext() throws Exception {
+    String expectedContext = "foo-second-context";
+    KubeConfig kc = KubeConfig.loadKubeConfig(new StringReader(KUBECONFIG_WITH_MULTIPLE_CONTEXTS), expectedContext);
+    assertEquals(expectedContext, kc.getCurrentContext());
+  }
 }

util/src/test/resources/kubeconfig

@@ -3,8 +3,14 @@ clusters:
   - cluster:
       server: http://kubeconfig.dir.com
     name: foo
+  - cluster:
+      server: http://kubeconfig.second.dir.com
+    name: foo-second-cluster
 contexts:
   - context:
       cluster: foo
     name: foo-context
+   - context:
+      cluster: foo-second-cluster
+    name: foo-second-context
 current-context: foo-context