diff --git a/rsc/src/main/java/org/apache/livy/rsc/ContextLauncher.java b/rsc/src/main/java/org/apache/livy/rsc/ContextLauncher.java
index c59136d55..07fe7883d 100644
--- a/rsc/src/main/java/org/apache/livy/rsc/ContextLauncher.java
+++ b/rsc/src/main/java/org/apache/livy/rsc/ContextLauncher.java
@@ -397,11 +397,11 @@ public void run() {
               fail(new IOException(String.format("Child process exited with code %d.", exitCode)));
             }
           } catch (InterruptedException ie) {
-            LOG.warn("Waiting thread interrupted, killing child process.");
+            LOG.error("Waiting thread interrupted, killing child process.", ie);
             Thread.interrupted();
             child.destroy();
           } catch (Exception e) {
-            LOG.warn("Exception while waiting for child process.", e);
+            LOG.error("Exception while waiting for child process.", e);
           } finally {
             RSCClientFactory.childProcesses().decrementAndGet();
           }
@@ -436,7 +436,7 @@ public void detach() {
       try {
         monitor.join(conf.getTimeAsMs(CLIENT_SHUTDOWN_TIMEOUT));
       } catch (InterruptedException ie) {
-        LOG.debug("Interrupted before driver thread was finished.");
+        LOG.error("Interrupted before driver thread was finished.", ie);
       }
     }
 
diff --git a/rsc/src/main/java/org/apache/livy/rsc/driver/SparkEntries.java b/rsc/src/main/java/org/apache/livy/rsc/driver/SparkEntries.java
index 6726bb1ab..e6f2efb2c 100644
--- a/rsc/src/main/java/org/apache/livy/rsc/driver/SparkEntries.java
+++ b/rsc/src/main/java/org/apache/livy/rsc/driver/SparkEntries.java
@@ -85,7 +85,7 @@ public SparkSession sparkSession() {
               LOG.info("Created Spark session.");
             }
           } catch (Exception e) {
-            LOG.warn("SparkSession is not supported", e);
+            LOG.error("SparkSession is not supported", e);
             throw e;
           }
         }
diff --git a/rsc/src/main/java/org/apache/livy/rsc/rpc/Rpc.java b/rsc/src/main/java/org/apache/livy/rsc/rpc/Rpc.java
index 5fce16410..c761d6936 100644
--- a/rsc/src/main/java/org/apache/livy/rsc/rpc/Rpc.java
+++ b/rsc/src/main/java/org/apache/livy/rsc/rpc/Rpc.java
@@ -315,7 +315,7 @@ private void handleCall(ChannelHandlerContext ctx, Object msg, Class<?> handleCl
       }
       writeMessage(MessageType.REPLY, payload);
     } catch (InvocationTargetException ite) {
-      LOG.debug(String.format("[%s] Error in RPC handler.", name()), ite.getCause());
+      LOG.warn(String.format("[%s] Error in RPC handler.", name()), ite.getCause());
       writeMessage(MessageType.ERROR, Utils.stackTraceAsString(ite.getCause()));
     }
   }
diff --git a/server/src/main/scala/org/apache/livy/utils/SparkYarnApp.scala b/server/src/main/scala/org/apache/livy/utils/SparkYarnApp.scala
index dd551c20b..8d61ed28c 100644
--- a/server/src/main/scala/org/apache/livy/utils/SparkYarnApp.scala
+++ b/server/src/main/scala/org/apache/livy/utils/SparkYarnApp.scala
@@ -272,6 +272,7 @@ class SparkYarnApp private[utils] (
         }
       } catch {
         case e: Exception =>
+          error("Get application info error ", e)
           appIdPromise.failure(e)
           throw e
       }
@@ -329,6 +330,7 @@ class SparkYarnApp private[utils] (
         } catch {
           // This exception might be thrown during app is starting up. It's transient.
           case e: ApplicationAttemptNotFoundException =>
+            debug("Encountered ApplicationAttemptNotFoundException. ", e)
           // Workaround YARN-4411: No enum constant FINAL_SAVING from getApplicationAttemptReport()
           case e: IllegalArgumentException =>
             if (e.getMessage.contains("FINAL_SAVING")) {
diff --git a/thriftserver/server/src/main/scala/org/apache/livy/thriftserver/LivyThriftSessionManager.scala b/thriftserver/server/src/main/scala/org/apache/livy/thriftserver/LivyThriftSessionManager.scala
index 03e10c35a..0a2c8f7a0 100644
--- a/thriftserver/server/src/main/scala/org/apache/livy/thriftserver/LivyThriftSessionManager.scala
+++ b/thriftserver/server/src/main/scala/org/apache/livy/thriftserver/LivyThriftSessionManager.scala
@@ -100,7 +100,8 @@ class LivyThriftSessionManager(val server: LivyThriftServer, val livyConf: LivyC
     } else {
       future.value match {
         case Some(Success(session)) => session
-        case Some(Failure(e)) => throw Option(e.getCause).getOrElse(e)
+        // It can`t be e.getCause because we need know the specific reason!
+        case Some(Failure(e)) => e
         case None => throw new RuntimeException("Future cannot be None when it is completed")
       }
     }