Fix issue with DNS resolution (#118)

* Fix issue with DNS resolution

* Address comments

Author: foxish

resource-managers/kubernetes/core/src/main/scala/org/apache/spark/deploy/kubernetes/KubernetesClientBuilder.scala

@@ -22,6 +22,8 @@ import com.google.common.base.Charsets
 import com.google.common.io.Files
 import io.fabric8.kubernetes.client.{Config, ConfigBuilder, DefaultKubernetesClient}
 
+import org.apache.spark.deploy.kubernetes.constants._
+
 private[spark] object KubernetesClientBuilder {
   private val API_SERVER_TOKEN = new File(Config.KUBERNETES_SERVICE_ACCOUNT_TOKEN_PATH)
   private val CA_CERT_FILE = new File(Config.KUBERNETES_SERVICE_ACCOUNT_CA_CRT_PATH)
@@ -33,11 +35,10 @@ private[spark] object KubernetesClientBuilder {
    * into the pod's disk space.
    */
   def buildFromWithinPod(
-      kubernetesMaster: String,
       kubernetesNamespace: String): DefaultKubernetesClient = {
     var clientConfigBuilder = new ConfigBuilder()
       .withApiVersion("v1")
-      .withMasterUrl(kubernetesMaster)
+      .withMasterUrl(KUBERNETES_MASTER_INTERNAL_URL)
       .withNamespace(kubernetesNamespace)
 
     if (CA_CERT_FILE.isFile) {

resource-managers/kubernetes/core/src/main/scala/org/apache/spark/deploy/kubernetes/constants.scala

@@ -67,4 +67,5 @@ package object constants {
   // Miscellaneous
   private[spark] val DRIVER_CONTAINER_NAME = "spark-kubernetes-driver"
   private[spark] val KUBERNETES_SUBMIT_SSL_NAMESPACE = "kubernetes.submit"
+  private[spark] val KUBERNETES_MASTER_INTERNAL_URL = "https://kubernetes.default.svc"
 }

resource-managers/kubernetes/core/src/main/scala/org/apache/spark/scheduler/cluster/kubernetes/KubernetesClusterSchedulerBackend.scala

@@ -44,7 +44,6 @@ private[spark] class KubernetesClusterSchedulerBackend(
   private val EXECUTOR_MODIFICATION_LOCK = new Object
   private val runningExecutorPods = new scala.collection.mutable.HashMap[String, Pod]
 
-  private val kubernetesMaster = "https://kubernetes"
   private val executorDockerImage = conf.get(EXECUTOR_DOCKER_IMAGE)
   private val kubernetesNamespace = conf.get(KUBERNETES_NAMESPACE)
   private val executorPort = conf.getInt("spark.executor.port", DEFAULT_STATIC_PORT)
@@ -77,7 +76,7 @@ private[spark] class KubernetesClusterSchedulerBackend(
     ThreadUtils.newDaemonCachedThreadPool("kubernetes-executor-requests"))
 
   private val kubernetesClient = KubernetesClientBuilder
-    .buildFromWithinPod(kubernetesMaster, kubernetesNamespace)
+    .buildFromWithinPod(kubernetesNamespace)
 
   private val driverPod = try {
     kubernetesClient.pods().inNamespace(kubernetesNamespace).

resource-managers/kubernetes/integration-tests/src/test/scala/org/apache/spark/deploy/kubernetes/integrationtest/minikube/Minikube.scala

@@ -76,7 +76,7 @@ private[spark] object Minikube extends Logging {
 
   def getDockerEnv: Map[String, String] = synchronized {
     assert(MINIKUBE_EXECUTABLE_DEST.exists(), EXPECTED_DOWNLOADED_MINIKUBE_MESSAGE)
-    executeMinikube("docker-env")
+    executeMinikube("docker-env", "--shell", "bash")
         .filter(_.startsWith("export"))
         .map(_.replaceFirst("export ", "").split('='))
         .map(arr => (arr(0), arr(1).replaceAllLiterally("\"", "")))