[SPARK-11859][MESOS] SparkContext accepts invalid Master URLs in the form zk://host:port for a multi-master Mesos cluster using ZooKeeper

* According to below doc and validation logic in [SparkSubmit.scala](https://github.com/apache/spark/blob/master/core/src/main/scala/org/apache/spark/deploy/SparkSubmit.scala#L231), master URL for a mesos cluster should always start with `mesos://`

http://spark.apache.org/docs/latest/running-on-mesos.html
`The Master URLs for Mesos are in the form mesos://host:5050 for a single-master Mesos cluster, or mesos://zk://host:2181 for a multi-master Mesos cluster using ZooKeeper.`

* However, [SparkContext.scala](https://github.com/apache/spark/blob/master/core/src/main/scala/org/apache/spark/SparkContext.scala#L2749) fails the validation and can receive master URL in the form `zk://host:port`

* For the master URLs in the form `zk:host:port`, the valid form should be `mesos://zk://host:port`

* This PR restrict the validation in `SparkContext.scala`, and now only mesos master URLs prefixed with `mesos://` can be accepted.

* This PR also updated corresponding unit test.

Author: toddwan <tawan0109@outlook.com>

Closes #9886 from toddwan/S11859.

2 files changed, 15 insertions, 6 deletions

diff --git a/core/src/main/scala/org/apache/spark/SparkContext.scala b/core/src/main/scala/org/apache/spark/SparkContext.scala
index b030d3c71d..8a62b71c3f 100644
--- a/core/src/main/scala/org/apache/spark/SparkContext.scala
+++ b/core/src/main/scala/org/apache/spark/SparkContext.scala
@@ -2708,15 +2708,14 @@ object SparkContext extends Logging {
         scheduler.initialize(backend)
         (backend, scheduler)
 
-      case mesosUrl @ MESOS_REGEX(_) =>
+      case MESOS_REGEX(mesosUrl) =>
         MesosNativeLibrary.load()
         val scheduler = new TaskSchedulerImpl(sc)
         val coarseGrained = sc.conf.getBoolean("spark.mesos.coarse", defaultValue = true)
-        val url = mesosUrl.stripPrefix("mesos://") // strip scheme from raw Mesos URLs
         val backend = if (coarseGrained) {
-          new CoarseMesosSchedulerBackend(scheduler, sc, url, sc.env.securityManager)
+          new CoarseMesosSchedulerBackend(scheduler, sc, mesosUrl, sc.env.securityManager)
         } else {
-          new MesosSchedulerBackend(scheduler, sc, url)
+          new MesosSchedulerBackend(scheduler, sc, mesosUrl)
         }
         scheduler.initialize(backend)
         (backend, scheduler)
@@ -2727,6 +2726,11 @@ object SparkContext extends Logging {
         scheduler.initialize(backend)
         (backend, scheduler)
 
+      case zkUrl if zkUrl.startsWith("zk://") =>
+        logWarning("Master URL for a multi-master Mesos cluster managed by ZooKeeper should be " +
+          "in the form mesos://zk://host:port. Current Master URL will stop working in Spark 2.0.")
+        createTaskScheduler(sc, "mesos://" + zkUrl)
+
       case _ =>
         throw new SparkException("Could not parse Master URL: '" + master + "'")
     }
@@ -2745,8 +2749,8 @@ private object SparkMasterRegex {
   val LOCAL_CLUSTER_REGEX = """local-cluster\[\s*([0-9]+)\s*,\s*([0-9]+)\s*,\s*([0-9]+)\s*]""".r
   // Regular expression for connecting to Spark deploy clusters
   val SPARK_REGEX = """spark://(.*)""".r
-  // Regular expression for connection to Mesos cluster by mesos:// or zk:// url
-  val MESOS_REGEX = """(mesos|zk)://.*""".r
+  // Regular expression for connection to Mesos cluster by mesos:// or mesos://zk:// url
+  val MESOS_REGEX = """mesos://(.*)""".r
   // Regular expression for connection to Simr cluster
   val SIMR_REGEX = """simr://(.*)""".r
 }
diff --git a/core/src/test/scala/org/apache/spark/SparkContextSchedulerCreationSuite.scala b/core/src/test/scala/org/apache/spark/SparkContextSchedulerCreationSuite.scala
index e5a14a69ef..d18e0782c0 100644
--- a/core/src/test/scala/org/apache/spark/SparkContextSchedulerCreationSuite.scala
+++ b/core/src/test/scala/org/apache/spark/SparkContextSchedulerCreationSuite.scala
@@ -175,6 +175,11 @@ class SparkContextSchedulerCreationSuite
   }
 
   test("mesos with zookeeper") {
+    testMesos("mesos://zk://localhost:1234,localhost:2345",
+      classOf[MesosSchedulerBackend], coarse = false)
+  }
+
+  test("mesos with zookeeper and Master URL starting with zk://") {
     testMesos("zk://localhost:1234,localhost:2345", classOf[MesosSchedulerBackend], coarse = false)
   }
 }