SPARK-1053. Don't require SPARK_YARN_APP_JAR

It looks this just requires taking out the checks.

I verified that, with the patch, I was able to run spark-shell through yarn without setting the environment variable.

Author: Sandy Ryza <sandy@cloudera.com>

Closes #553 from sryza/sandy-spark-1053 and squashes the following commits:

b037676 [Sandy Ryza] SPARK-1053.  Don't require SPARK_YARN_APP_JAR

3 files changed, 5 insertions, 8 deletions

diff --git a/yarn/common/src/main/scala/org/apache/spark/deploy/yarn/ClientArguments.scala b/yarn/common/src/main/scala/org/apache/spark/deploy/yarn/ClientArguments.scala
index 1419f215c7..fe37168e5a 100644
--- a/yarn/common/src/main/scala/org/apache/spark/deploy/yarn/ClientArguments.scala
+++ b/yarn/common/src/main/scala/org/apache/spark/deploy/yarn/ClientArguments.scala
@@ -108,7 +108,7 @@ class ClientArguments(val args: Array[String], val sparkConf: SparkConf) {
           args = tail
 
         case Nil =>
-          if (userJar == null || userClass == null) {
+          if (userClass == null) {
             printUsageAndExit(1)
           }
 
@@ -129,7 +129,7 @@ class ClientArguments(val args: Array[String], val sparkConf: SparkConf) {
     System.err.println(
       "Usage: org.apache.spark.deploy.yarn.Client [options] \n" +
       "Options:\n" +
-      "  --jar JAR_PATH             Path to your application's JAR file (required)\n" +
+      "  --jar JAR_PATH             Path to your application's JAR file (required in yarn-standalone mode)\n" +
       "  --class CLASS_NAME         Name of your application's main class (required)\n" +
       "  --args ARGS                Arguments to be passed to your application's main class.\n" +
       "                             Mutliple invocations are possible, each will be passed in order.\n" +
diff --git a/yarn/common/src/main/scala/org/apache/spark/deploy/yarn/ClientBase.scala b/yarn/common/src/main/scala/org/apache/spark/deploy/yarn/ClientBase.scala
index 2db5744be1..24520bd21b 100644
--- a/yarn/common/src/main/scala/org/apache/spark/deploy/yarn/ClientBase.scala
+++ b/yarn/common/src/main/scala/org/apache/spark/deploy/yarn/ClientBase.scala
@@ -68,7 +68,8 @@ trait ClientBase extends Logging {
   def validateArgs() = {
     Map(
       (System.getenv("SPARK_JAR") == null) -> "Error: You must set SPARK_JAR environment variable!",
-      (args.userJar == null) -> "Error: You must specify a user jar!",
+      ((args.userJar == null && args.amClass == classOf[ApplicationMaster].getName) ->
+          "Error: You must specify a user jar when running in standalone mode!"),
       (args.userClass == null) -> "Error: You must specify a user class!",
       (args.numWorkers <= 0) -> "Error: You must specify at least 1 worker!",
       (args.amMemory <= YarnAllocationHandler.MEMORY_OVERHEAD) -> ("Error: AM memory size must be" +
diff --git a/yarn/common/src/main/scala/org/apache/spark/scheduler/cluster/YarnClientSchedulerBackend.scala b/yarn/common/src/main/scala/org/apache/spark/scheduler/cluster/YarnClientSchedulerBackend.scala
index 22e55e0c60..e7130d2407 100644
--- a/yarn/common/src/main/scala/org/apache/spark/scheduler/cluster/YarnClientSchedulerBackend.scala
+++ b/yarn/common/src/main/scala/org/apache/spark/scheduler/cluster/YarnClientSchedulerBackend.scala
@@ -44,10 +44,6 @@ private[spark] class YarnClientSchedulerBackend(
   override def start() {
     super.start()
 
-    val userJar = System.getenv("SPARK_YARN_APP_JAR")
-    if (userJar == null)
-      throw new SparkException("env SPARK_YARN_APP_JAR is not set")
-
     val driverHost = conf.get("spark.driver.host")
     val driverPort = conf.get("spark.driver.port")
     val hostport = driverHost + ":" + driverPort
@@ -55,7 +51,7 @@ private[spark] class YarnClientSchedulerBackend(
     val argsArrayBuf = new ArrayBuffer[String]()
     argsArrayBuf += (
       "--class", "notused",
-      "--jar", userJar,
+      "--jar", null,
       "--args", hostport,
       "--master-class", "org.apache.spark.deploy.yarn.WorkerLauncher"
     )