For SPARK-1082, Use Curator for ZK interaction in standalone cluster

Author: Raymond Liu <raymond.liu@intel.com>

Closes #611 from colorant/curator and squashes the following commits:

7556aa1 [Raymond Liu] Address review comments
af92e1f [Raymond Liu] Fix coding style
964f3c2 [Raymond Liu] Ignore NodeExists exception
6df2966 [Raymond Liu] Rewrite zookeeper client code with curator

core/pom.xml

@@ -55,8 +55,8 @@
             <artifactId>avro-ipc</artifactId>
         </dependency>
         <dependency>
-            <groupId>org.apache.zookeeper</groupId>
-            <artifactId>zookeeper</artifactId>
+            <groupId>org.apache.curator</groupId>
+            <artifactId>curator-recipes</artifactId>
         </dependency>
         <dependency>
             <groupId>org.eclipse.jetty</groupId>

core/src/main/scala/org/apache/spark/deploy/master/LeaderElectionAgent.scala

@@ -30,6 +30,7 @@ import org.apache.spark.deploy.master.MasterMessages.ElectedLeader
  * [[org.apache.spark.deploy.master.MasterMessages.RevokedLeadership RevokedLeadership]]
  */
 private[spark] trait LeaderElectionAgent extends Actor {
+  //TODO: LeaderElectionAgent does not necessary to be an Actor anymore, need refactoring.
   val masterActor: ActorRef
 }
 

core/src/main/scala/org/apache/spark/deploy/master/MasterMessages.scala

@@ -28,10 +28,6 @@ private[master] object MasterMessages {
 
   case object RevokedLeadership
 
-  // Actor System to LeaderElectionAgent
-
-  case object CheckLeader
-
   // Actor System to Master
 
   case object CheckForWorkerTimeOut

core/src/main/scala/org/apache/spark/deploy/master/SparkCuratorUtil.scala

@@ -0,0 +1,53 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.deploy.master
+
+import org.apache.spark.{SparkConf, Logging}
+import org.apache.curator.framework.{CuratorFramework, CuratorFrameworkFactory}
+import org.apache.curator.retry.ExponentialBackoffRetry
+import org.apache.zookeeper.KeeperException
+
+
+object SparkCuratorUtil extends Logging {
+
+  val ZK_CONNECTION_TIMEOUT_MILLIS = 15000
+  val ZK_SESSION_TIMEOUT_MILLIS = 60000
+  val RETRY_WAIT_MILLIS = 5000
+  val MAX_RECONNECT_ATTEMPTS = 3
+
+  def newClient(conf: SparkConf): CuratorFramework = {
+    val ZK_URL = conf.get("spark.deploy.zookeeper.url")
+    val zk = CuratorFrameworkFactory.newClient(ZK_URL,
+      ZK_SESSION_TIMEOUT_MILLIS, ZK_CONNECTION_TIMEOUT_MILLIS,
+      new ExponentialBackoffRetry(RETRY_WAIT_MILLIS, MAX_RECONNECT_ATTEMPTS))
+    zk.start()
+    zk
+  }
+
+  def mkdir(zk: CuratorFramework, path: String) {
+    if (zk.checkExists().forPath(path) == null) {
+      try {
+        zk.create().creatingParentsIfNeeded().forPath(path)
+      } catch {
+        case nodeExist: KeeperException.NodeExistsException =>
+          // do nothing, ignore node existing exception.
+        case e: Exception => throw e
+      }
+    }
+  }
+}