From f479c99c616c4a62956e7175e57005ac1c9fc4e9 Mon Sep 17 00:00:00 2001
From: Hossein <hossein@databricks.com>
Date: Tue, 28 Jul 2015 18:05:51 -0700
Subject: [PATCH 1/5] Wrting exception cause message in JVM

---
 .../scala/org/apache/spark/api/r/RBackendHandler.scala    | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/core/src/main/scala/org/apache/spark/api/r/RBackendHandler.scala b/core/src/main/scala/org/apache/spark/api/r/RBackendHandler.scala
index a5de10fe89c42..10a60c3f4e4c1 100644
--- a/core/src/main/scala/org/apache/spark/api/r/RBackendHandler.scala
+++ b/core/src/main/scala/org/apache/spark/api/r/RBackendHandler.scala
@@ -69,8 +69,11 @@ private[r] class RBackendHandler(server: RBackend)
             case e: Exception =>
               logError(s"Removing $objId failed", e)
               writeInt(dos, -1)
+              writeString(dos, s"Removing $objId failed: ${e.getMessage}")
           }
-        case _ => dos.writeInt(-1)
+        case _ =>
+          dos.writeInt(-1)
+          writeString(dos, "Unknown error")
       }
     } else {
       handleMethodCall(isStatic, objId, methodName, numArgs, dis, dos)
@@ -148,6 +151,9 @@ private[r] class RBackendHandler(server: RBackend)
       case e: Exception =>
         logError(s"$methodName on $objId failed", e)
         writeInt(dos, -1)
+        // Writing the error message of the cause for the exception. This will be returned
+        // to user in the R process.
+        writeString(dos, e.getCause.getMessage)
     }
   }
 

From 2af75d5e9e4dfbe1c6a629ff408b6a9998b2b133 Mon Sep 17 00:00:00 2001
From: Hossein <hossein@databricks.com>
Date: Tue, 28 Jul 2015 18:06:21 -0700
Subject: [PATCH 2/5] Reading error message in case of failure and stoping with
 that message

---
 R/pkg/R/backend.R | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/R/pkg/R/backend.R b/R/pkg/R/backend.R
index 2fb6fae55f28c..49162838b8d1a 100644
--- a/R/pkg/R/backend.R
+++ b/R/pkg/R/backend.R
@@ -110,6 +110,8 @@ invokeJava <- function(isStatic, objId, methodName, ...) {
 
   # TODO: check the status code to output error information
   returnStatus <- readInt(conn)
-  stopifnot(returnStatus == 0)
+  if (returnStatus != 0) {
+    stop(readString(conn))
+  }
   readObject(conn)
 }

From 5cf17f0305ed27e45161fec6f62c613f319b9b5b Mon Sep 17 00:00:00 2001
From: Hossein <hossein@databricks.com>
Date: Tue, 28 Jul 2015 18:06:59 -0700
Subject: [PATCH 3/5] Adding unit test for error messages from SQLContext

---
 R/pkg/inst/tests/test_sparkSQL.R | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/R/pkg/inst/tests/test_sparkSQL.R b/R/pkg/inst/tests/test_sparkSQL.R
index 62fe48a5d6c7b..756d47fa521ec 100644
--- a/R/pkg/inst/tests/test_sparkSQL.R
+++ b/R/pkg/inst/tests/test_sparkSQL.R
@@ -1000,6 +1000,11 @@ test_that("crosstab() on a DataFrame", {
   expect_identical(expected, ordered)
 })
 
+test_that("SQL error message is returned from JVM", {
+  retError <- tryCatch(sql(sqlContext, "select * from blah"), error = function(e) e)
+  expect_equal(grepl("Table Not Found: blah", retError), TRUE)
+})
+
 unlink(parquetPath)
 unlink(jsonPath)
 unlink(jsonPathNa)

From 4a8005c33604f5e3a73653c047ec8d401edb6df8 Mon Sep 17 00:00:00 2001
From: Hossein <hossein@databricks.com>
Date: Wed, 29 Jul 2015 18:05:39 -0700
Subject: [PATCH 4/5] Returning stack track of causing exception from
 RBackendHandler

---
 .../main/scala/org/apache/spark/api/r/RBackendHandler.scala   | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/core/src/main/scala/org/apache/spark/api/r/RBackendHandler.scala b/core/src/main/scala/org/apache/spark/api/r/RBackendHandler.scala
index 10a60c3f4e4c1..83b9aa49b37a1 100644
--- a/core/src/main/scala/org/apache/spark/api/r/RBackendHandler.scala
+++ b/core/src/main/scala/org/apache/spark/api/r/RBackendHandler.scala
@@ -73,7 +73,7 @@ private[r] class RBackendHandler(server: RBackend)
           }
         case _ =>
           dos.writeInt(-1)
-          writeString(dos, "Unknown error")
+          writeString(dos, s"Error: unknown method $methodName")
       }
     } else {
       handleMethodCall(isStatic, objId, methodName, numArgs, dis, dos)
@@ -153,7 +153,7 @@ private[r] class RBackendHandler(server: RBackend)
         writeInt(dos, -1)
         // Writing the error message of the cause for the exception. This will be returned
         // to user in the R process.
-        writeString(dos, e.getCause.getMessage)
+        writeString(dos, Utils.exceptionString(e.getCause))
     }
   }
 

From 4f643c9aea187c4876b895d6f0a92bfff93fd818 Mon Sep 17 00:00:00 2001
From: Hossein <hossein@databricks.com>
Date: Thu, 30 Jul 2015 11:53:28 -0700
Subject: [PATCH 5/5] Not logging exceptions in RBackendHandler

---
 .../src/main/scala/org/apache/spark/api/r/RBackendHandler.scala | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/core/src/main/scala/org/apache/spark/api/r/RBackendHandler.scala b/core/src/main/scala/org/apache/spark/api/r/RBackendHandler.scala
index 83b9aa49b37a1..14dac4ed28ce3 100644
--- a/core/src/main/scala/org/apache/spark/api/r/RBackendHandler.scala
+++ b/core/src/main/scala/org/apache/spark/api/r/RBackendHandler.scala
@@ -149,7 +149,7 @@ private[r] class RBackendHandler(server: RBackend)
       }
     } catch {
       case e: Exception =>
-        logError(s"$methodName on $objId failed", e)
+        logError(s"$methodName on $objId failed")
         writeInt(dos, -1)
         // Writing the error message of the cause for the exception. This will be returned
         // to user in the R process.