Make spark master configurable

docs/quickstart/kubernetes.md

@@ -56,7 +56,7 @@ Get `zeppelin-server.yaml` from github repository or find it from Zeppelin distr
 $ curl -s -O https://raw.githubusercontent.com/apache/zeppelin/master/k8s/zeppelin-server.yaml
 
 # or get it from Zeppelin distribution package.
-$ ls <zeppelin-distribution/k8s/zeppelin-server.yaml
+$ ls <zeppelin-distribution>/k8s/zeppelin-server.yaml
 ```
 
 Start zeppelin on kubernetes cluster,
@@ -113,7 +113,7 @@ And then start your spark interpreter
 sc.parallelize(1 to 100).count
 ...
 ```
-Spark executors will be automatically created in your Kubernetes cluster.
+While `master` property of SparkInterpreter starts with `k8s://` (default `k8s://https://kubernetes.default.svc` when Zeppelin started using zeppelin-server.yaml), Spark executors will be automatically created in your Kubernetes cluster.
 Spark UI is accessible by clicking `SPARK JOB` on the Paragraph. 
 
 Check [here](https://spark.apache.org/docs/latest/running-on-kubernetes.html) to know more about Running Spark on Kubernetes.

k8s/zeppelin-server.yaml

@@ -110,6 +110,8 @@ spec:
         configMapKeyRef:
           name: zeppelin-server-conf
           key: serviceDomain
+    - name: MASTER   # default value of master property for spark interpreter.
+      value: k8s://https://kubernetes.default.svc
   - name: zeppelin-server-gateway
     image: nginx:1.14.0
     command: [ "/bin/sh", "-c" ]

zeppelin-plugins/launcher/k8s-standard/src/main/java/org/apache/zeppelin/interpreter/launcher/K8sRemoteInterpreterProcess.java

@@ -267,7 +267,9 @@ public class K8sRemoteInterpreterProcess extends RemoteInterpreterProcess {
     if (isSpark()) {
       int webUiPort = 4040;
       k8sProperties.put("zeppelin.k8s.spark.container.image", sparkImage);
-      envs.put("SPARK_SUBMIT_OPTIONS", envs.getOrDefault("SPARK_SUBMIT_OPTIONS", "") + buildSparkSubmitOptions());
+      if (isSparkOnKubernetes(properties)) {
+        envs.put("SPARK_SUBMIT_OPTIONS", envs.getOrDefault("SPARK_SUBMIT_OPTIONS", "") + buildSparkSubmitOptions());
+      }
       envs.put("SPARK_HOME", envs.getOrDefault("SPARK_HOME", "/spark"));
 
       // configure interpreter property "zeppelin.spark.uiWebUrl" if not defined, to enable spark ui through reverse proxy
@@ -290,6 +292,15 @@ public class K8sRemoteInterpreterProcess extends RemoteInterpreterProcess {
     return "spark".equalsIgnoreCase(interpreterGroupName);
   }
 
+  boolean isSparkOnKubernetes(Properties interpreteProperties) {
+    String propertySparkMaster = (String) interpreteProperties.getOrDefault("master", "");
+    if (propertySparkMaster.startsWith("k8s://")) {
+      return true;
+    } else {
+      return false;
+    }
+  }
+
   @VisibleForTesting
   String buildSparkSubmitOptions() {
     StringBuilder options = new StringBuilder();

zeppelin-plugins/launcher/k8s-standard/src/test/java/org/apache/zeppelin/interpreter/launcher/K8sRemoteInterpreterProcessTest.java

@@ -154,6 +154,7 @@ public class K8sRemoteInterpreterProcessTest {
 
     Properties properties = new Properties();
     properties.put("my.key1", "v1");
+    properties.put("master", "k8s://http://api");
     HashMap<String, String> envs = new HashMap<String, String>();
     envs.put("MY_ENV1", "V1");
     envs.put("SPARK_SUBMIT_OPTIONS", "my options");