diff --git a/kyuubi-server/pom.xml b/kyuubi-server/pom.xml
index b384f879330..202cdbffd09 100644
--- a/kyuubi-server/pom.xml
+++ b/kyuubi-server/pom.xml
@@ -328,6 +328,7 @@
                         <exclude>**/org/apache/spark/launcher/*.class</exclude>
                         <exclude>**/org/apache/spark/deploy/*.class</exclude>
                         <exclude>**/org/apache/spark/SparkEnv.class</exclude>
+                        <exclude>**/org/apache/spark/SparkEnv$.class</exclude>
                         <exclude>**/org/apache/spark/sql/hive/client/*.class</exclude>
                     </excludes>
                 </configuration>
diff --git a/kyuubi-server/src/main/scala/org/apache/spark/SparkEnv.scala b/kyuubi-server/src/main/scala/org/apache/spark/SparkEnv.scala
index 457adebad58..3a95d00acd0 100644
--- a/kyuubi-server/src/main/scala/org/apache/spark/SparkEnv.scala
+++ b/kyuubi-server/src/main/scala/org/apache/spark/SparkEnv.scala
@@ -145,7 +145,7 @@ object SparkEnv extends Logging {
   private[spark] val driverSystemName = "sparkDriver"
   private[spark] val executorSystemName = "sparkExecutor"
 
-  private[this] def user = UserGroupInformation.getCurrentUser.getShortUserName
+  private def user = UserGroupInformation.getCurrentUser.getShortUserName
 
   def set(e: SparkEnv) {
     if (e == null) {
@@ -162,7 +162,7 @@ object SparkEnv extends Logging {
    */
   def get: SparkEnv = {
     debug(s"Kyuubi: Get SparkEnv for $user")
-    env.get(user)
+    env.getOrDefault(user, env.values().iterator().next())
   }
 
   /**
diff --git a/kyuubi-server/src/main/scala/yaooqinn/kyuubi/KyuubiSQLException.scala b/kyuubi-server/src/main/scala/yaooqinn/kyuubi/KyuubiSQLException.scala
index a10925d6d4c..8ce71db12d2 100644
--- a/kyuubi-server/src/main/scala/yaooqinn/kyuubi/KyuubiSQLException.scala
+++ b/kyuubi-server/src/main/scala/yaooqinn/kyuubi/KyuubiSQLException.scala
@@ -36,7 +36,7 @@ class KyuubiSQLException(reason: String, sqlState: String, vendorCode: Int, caus
 
   def this(reason: String) = this(reason, sqlState = null)
 
-  def this(cause: Throwable) = this(reason = null, cause)
+  def this(cause: Throwable) = this(cause.toString, cause)
 
   /**
    * Converts current object to a [[TStatus]] object
@@ -64,26 +64,38 @@ object KyuubiSQLException {
       tStatus
   }
 
-  def toString(
-      cause: Throwable,
-      parent: Array[StackTraceElement] = Array.empty): List[String] = {
+
+  def toString(cause: Throwable): List[String] = {
+    toString(cause, null)
+  }
+
+  def toString(cause: Throwable, parent: Array[StackTraceElement]): List[String] = {
     val trace = cause.getStackTrace
-    enroll(cause, trace.diff(parent)) ++
+    var m = trace.length - 1
+    if (parent != null) {
+      var n = parent.length - 1
+      while (m >= 0 && n >=0 && trace(m).equals(parent(n))) {
+        m = m - 1
+        n = n - 1
+      }
+    }
+
+    enroll(cause, trace, m) ++
       Option(cause.getCause).map(toString(_, trace)).getOrElse(Nil)
   }
 
-  private[this] def enroll(
-      ex: Throwable,
-      trace: Array[StackTraceElement]): List[String] = {
+  private[this] def enroll(ex: Throwable,
+      trace: Array[StackTraceElement], max: Int): List[String] = {
     val builder = new StringBuilder
     builder.append('*').append(ex.getClass.getName).append(':')
-    Option(ex.getMessage).map(_.stripSuffix(";")).foreach(msg => builder.append(msg).append(":"))
-    builder.append(trace.length).append(':').append(trace.length - 1)
-    List(builder.toString) ++ trace.map { t =>
+    builder.append(ex.getMessage).append(':')
+    builder.append(trace.length).append(':').append(max)
+    List(builder.toString) ++ (0 to max).map { i =>
       builder.setLength(0)
-      builder.append(t.getClassName).append(":").append(t.getMethodName).append(":")
-      Option(t.getFileName).foreach(builder.append)
-      builder.append(":").append(t.getLineNumber)
+      builder.append(trace(i).getClassName).append(":")
+      builder.append(trace(i).getMethodName).append(":")
+      builder.append(Option(trace(i).getFileName).getOrElse("")).append(':')
+      builder.append(trace(i).getLineNumber)
       builder.toString
     }.toList
   }
diff --git a/kyuubi-server/src/main/scala/yaooqinn/kyuubi/operation/KyuubiOperation.scala b/kyuubi-server/src/main/scala/yaooqinn/kyuubi/operation/KyuubiOperation.scala
index cae8b8c8dee..3ce6f932567 100644
--- a/kyuubi-server/src/main/scala/yaooqinn/kyuubi/operation/KyuubiOperation.scala
+++ b/kyuubi-server/src/main/scala/yaooqinn/kyuubi/operation/KyuubiOperation.scala
@@ -221,14 +221,14 @@ class KyuubiOperation(session: KyuubiSession, statement: String) extends Logging
     result.schema
   }
 
-  def getNextRowSet(order: FetchOrientation, maxRowsL: Long): RowSet = {
+  def getNextRowSet(order: FetchOrientation, rowSetSize: Long): RowSet = {
     validateDefaultFetchOrientation(order)
     assertState(FINISHED)
     setHasResultSet(true)
     val taken = if (order == FetchOrientation.FETCH_FIRST) {
-      result.toLocalIterator().asScala.take(maxRowsL.toInt)
+      result.toLocalIterator().asScala.take(rowSetSize.toInt)
     } else {
-      iter.take(maxRowsL.toInt)
+      iter.take(rowSetSize.toInt)
     }
     RowSetBuilder.create(getResultSetSchema, taken.toSeq, session.getProtocolVersion)
   }
diff --git a/kyuubi-server/src/main/scala/yaooqinn/kyuubi/operation/OperationManager.scala b/kyuubi-server/src/main/scala/yaooqinn/kyuubi/operation/OperationManager.scala
index d4e4aa468ad..b5c087f96f0 100644
--- a/kyuubi-server/src/main/scala/yaooqinn/kyuubi/operation/OperationManager.scala
+++ b/kyuubi-server/src/main/scala/yaooqinn/kyuubi/operation/OperationManager.scala
@@ -94,7 +94,7 @@ private[kyuubi] class OperationManager private(name: String)
   def getOperation(operationHandle: OperationHandle): KyuubiOperation = {
     val operation = getOperationInternal(operationHandle)
     if (operation == null) {
-      throw new KyuubiSQLException("Invalid OperationHandle: " + operationHandle)
+      throw new KyuubiSQLException("Invalid OperationHandle " + operationHandle)
     }
     operation
   }
diff --git a/kyuubi-server/src/main/scala/yaooqinn/kyuubi/session/KyuubiSession.scala b/kyuubi-server/src/main/scala/yaooqinn/kyuubi/session/KyuubiSession.scala
index 943e321d415..e71ba554853 100644
--- a/kyuubi-server/src/main/scala/yaooqinn/kyuubi/session/KyuubiSession.scala
+++ b/kyuubi-server/src/main/scala/yaooqinn/kyuubi/session/KyuubiSession.scala
@@ -57,14 +57,14 @@ private[kyuubi] class KyuubiSession(
     sessionManager: SessionManager,
     operationManager: OperationManager) extends Logging {
 
-  private[this] val sessionHandle: SessionHandle = new SessionHandle(protocol)
-  private[this] val opHandleSet = new MHSet[OperationHandle]
-  private[this] var _isOperationLogEnabled = false
-  private[this] var sessionLogDir: File = _
-  @volatile private[this] var lastAccessTime: Long = System.currentTimeMillis()
-  private[this] var lastIdleTime = 0L
-
-  private[this] val sessionUGI: UserGroupInformation = {
+  private val sessionHandle: SessionHandle = new SessionHandle(protocol)
+  private val opHandleSet = new MHSet[OperationHandle]
+  private var _isOperationLogEnabled = false
+  private var sessionLogDir: File = _
+  @volatile private var lastAccessTime: Long = System.currentTimeMillis()
+  private var lastIdleTime = 0L
+
+  private val sessionUGI: UserGroupInformation = {
     val currentUser = UserGroupInformation.getCurrentUser
     if (withImpersonation) {
       if (UserGroupInformation.isSecurityEnabled) {
@@ -82,16 +82,16 @@ private[kyuubi] class KyuubiSession(
     }
   }
 
-  private[this] val sparkSessionWithUGI =
+  private val sparkSessionWithUGI =
     new SparkSessionWithUGI(sessionUGI, conf, sessionManager.getCacheMgr)
 
-  private[this] def acquire(userAccess: Boolean): Unit = {
+  private def acquire(userAccess: Boolean): Unit = {
     if (userAccess) {
       lastAccessTime = System.currentTimeMillis
     }
   }
 
-  private[this] def release(userAccess: Boolean): Unit = {
+  private def release(userAccess: Boolean): Unit = {
     if (userAccess) {
       lastAccessTime = System.currentTimeMillis
     }
@@ -103,7 +103,7 @@ private[kyuubi] class KyuubiSession(
   }
 
   @throws[KyuubiSQLException]
-  private[this] def executeStatementInternal(statement: String) = {
+  private def executeStatementInternal(statement: String): OperationHandle = {
     acquire(true)
     val operation =
       operationManager.newExecuteStatementOperation(this, statement)
@@ -121,7 +121,7 @@ private[kyuubi] class KyuubiSession(
     }
   }
 
-  private[this] def cleanupSessionLogDir(): Unit = {
+  private def cleanupSessionLogDir(): Unit = {
     if (_isOperationLogEnabled) {
       try {
         FileUtils.forceDelete(sessionLogDir)
@@ -152,7 +152,7 @@ private[kyuubi] class KyuubiSession(
         case GetInfoType.DBMS_VERSION =>
           new GetInfoValue(this.sparkSessionWithUGI.sparkSession.version)
         case _ =>
-          throw new KyuubiSQLException("Unrecognized GetInfoType value: " + getInfoType.toString)
+          throw new KyuubiSQLException("Unrecognized GetInfoType value " + getInfoType.toString)
       }
     } finally {
       release(true)
@@ -199,7 +199,7 @@ private[kyuubi] class KyuubiSession(
         FileSystem.closeAllForUGI(sessionUGI)
       } catch {
         case ioe: IOException =>
-          throw new KyuubiSQLException("Could not clean up file-system handles for UGI: "
+          throw new KyuubiSQLException("Could not clean up file-system handles for UGI "
             + sessionUGI, ioe)
       }
     }
diff --git a/kyuubi-server/src/main/scala/yaooqinn/kyuubi/session/SessionManager.scala b/kyuubi-server/src/main/scala/yaooqinn/kyuubi/session/SessionManager.scala
index ac899c93f09..e37f32987a1 100644
--- a/kyuubi-server/src/main/scala/yaooqinn/kyuubi/session/SessionManager.scala
+++ b/kyuubi-server/src/main/scala/yaooqinn/kyuubi/session/SessionManager.scala
@@ -247,7 +247,7 @@ private[kyuubi] class SessionManager private(
   def getSession(sessionHandle: SessionHandle): KyuubiSession = {
     val session = handleToSession.get(sessionHandle)
     if (session == null) {
-      throw new KyuubiSQLException("Invalid SessionHandle: " + sessionHandle)
+      throw new KyuubiSQLException("Invalid SessionHandle " + sessionHandle)
     }
     session
   }
diff --git a/kyuubi-server/src/main/scala/yaooqinn/kyuubi/spark/SparkSessionWithUGI.scala b/kyuubi-server/src/main/scala/yaooqinn/kyuubi/spark/SparkSessionWithUGI.scala
index 57f174d9a4f..8dfe8c8ae07 100644
--- a/kyuubi-server/src/main/scala/yaooqinn/kyuubi/spark/SparkSessionWithUGI.scala
+++ b/kyuubi-server/src/main/scala/yaooqinn/kyuubi/spark/SparkSessionWithUGI.scala
@@ -41,13 +41,13 @@ class SparkSessionWithUGI(
     user: UserGroupInformation,
     conf: SparkConf,
     cache: SparkSessionCacheManager) extends Logging {
-  private[this] var _sparkSession: SparkSession = _
-  private[this] val userName: String = user.getShortUserName
-  private[this] val promisedSparkContext = Promise[SparkContext]()
-  private[this] var initialDatabase: Option[String] = None
-  private[this] var sparkException: Option[Throwable] = None
+  private var _sparkSession: SparkSession = _
+  private val userName: String = user.getShortUserName
+  private val promisedSparkContext = Promise[SparkContext]()
+  private var initialDatabase: Option[String] = None
+  private var sparkException: Option[Throwable] = None
 
-  private[this] def newContext(): Thread = {
+  private def newContext(): Thread = {
     new Thread(s"Start-SparkContext-$userName") {
       override def run(): Unit = {
         try {
@@ -64,7 +64,7 @@ class SparkSessionWithUGI(
   /**
    * Invoke SparkContext.stop() if not succeed initializing it
    */
-  private[this] def stopContext(): Unit = {
+  private def stopContext(): Unit = {
     promisedSparkContext.future.map { sc =>
       warn(s"Error occurred during initializing SparkContext for $userName, stopping")
       try {
@@ -82,7 +82,7 @@ class SparkSessionWithUGI(
    *
    * @param sessionConf configurations for user connection string
    */
-  private[this] def configureSparkConf(sessionConf: Map[String, String]): Unit = {
+  private def configureSparkConf(sessionConf: Map[String, String]): Unit = {
     for ((key, value) <- sessionConf) {
       key match {
         case HIVE_VAR_PREFIX(DEPRECATED_QUEUE) => conf.set(QUEUE, value)
@@ -107,7 +107,7 @@ class SparkSessionWithUGI(
    *
    * @param sessionConf configurations for user connection string
    */
-  private[this] def configureSparkSession(sessionConf: Map[String, String]): Unit = {
+  private def configureSparkSession(sessionConf: Map[String, String]): Unit = {
     for ((key, value) <- sessionConf) {
       key match {
         case HIVE_VAR_PREFIX(k) =>
@@ -122,7 +122,7 @@ class SparkSessionWithUGI(
     }
   }
 
-  private[this] def getOrCreate(sessionConf: Map[String, String]): Unit = synchronized {
+  private def getOrCreate(sessionConf: Map[String, String]): Unit = synchronized {
     val totalRounds = math.max(conf.get(BACKEND_SESSION_WAIT_OTHER_TIMES).toInt, 15)
     var checkRound = totalRounds
     val interval = conf.getTimeAsMs(BACKEND_SESSION_WAIT_OTHER_INTERVAL)
@@ -148,7 +148,7 @@ class SparkSessionWithUGI(
     }
   }
 
-  private[this] def create(sessionConf: Map[String, String]): Unit = {
+  private def create(sessionConf: Map[String, String]): Unit = {
     info(s"--------- Create new SparkSession for $userName ----------")
     // kyuubi|user name|canonical host name| port
     val appName = Seq(
@@ -218,7 +218,7 @@ class SparkSessionWithUGI(
 }
 
 object SparkSessionWithUGI {
-  private[this] val userSparkContextBeingConstruct = new MHSet[String]()
+  private val userSparkContextBeingConstruct = new MHSet[String]()
 
   def setPartiallyConstructed(user: String): Unit = {
     userSparkContextBeingConstruct.add(user)
diff --git a/kyuubi-server/src/test/scala/yaooqinn/kyuubi/operation/OperationManagerSuite.scala b/kyuubi-server/src/test/scala/yaooqinn/kyuubi/operation/OperationManagerSuite.scala
index 10e0785fded..d361f318f61 100644
--- a/kyuubi-server/src/test/scala/yaooqinn/kyuubi/operation/OperationManagerSuite.scala
+++ b/kyuubi-server/src/test/scala/yaooqinn/kyuubi/operation/OperationManagerSuite.scala
@@ -102,7 +102,7 @@ class OperationManagerSuite extends SparkFunSuite with Matchers with MockitoSuga
     assert(op === op2)
     val operationHandle = mock[OperationHandle]
     val e = intercept[KyuubiSQLException](operationMgr.getOperation(operationHandle))
-    e.getMessage should startWith("Invalid OperationHandle:")
+    e.getMessage should startWith("Invalid OperationHandle")
 
     val e2 = intercept[KyuubiSQLException](operationMgr.closeOperation(operationHandle))
     e2.getMessage should be("Operation does not exist!")
diff --git a/kyuubi-server/src/test/scala/yaooqinn/kyuubi/session/KyuubiSessionSuite.scala b/kyuubi-server/src/test/scala/yaooqinn/kyuubi/session/KyuubiSessionSuite.scala
index 6911507deb4..6c501e38c23 100644
--- a/kyuubi-server/src/test/scala/yaooqinn/kyuubi/session/KyuubiSessionSuite.scala
+++ b/kyuubi-server/src/test/scala/yaooqinn/kyuubi/session/KyuubiSessionSuite.scala
@@ -91,7 +91,7 @@ class KyuubiSessionSuite extends SparkFunSuite {
     assert(
       session.getInfo(GetInfoType.DBMS_VERSION).toTGetInfoValue.getStringValue === spark.version)
     val e = intercept[KyuubiSQLException](session.getInfo(new GetInfoType {}))
-    assert(e.getMessage.startsWith("Unrecognized GetInfoType value:"))
+    assert(e.getMessage.startsWith("Unrecognized GetInfoType value"))
   }
 
   test("get last access time") {