[SPARK-19038][YARN] Avoid overwriting keytab configuration in yarn-client

## What changes were proposed in this pull request?

Because yarn#client will reset the `spark.yarn.keytab` configuration to point to the location in distributed file, so if user still uses the old `SparkConf` to create `SparkSession` with Hive enabled, it will read keytab from the path in distributed cached. This is OK for yarn cluster mode, but in yarn client mode where driver is running out of container, it will be failed to fetch the keytab.

So here we should avoid reseting this configuration in the `yarn#client` and only overwriting it for AM, so using `spark.yarn.keytab` could get correct keytab path no matter running in client (keytab in local fs) or cluster (keytab in distributed cache) mode.

## How was this patch tested?

Verified in security cluster.

Author: jerryshao <sshao@hortonworks.com>

Closes #16923 from jerryshao/SPARK-19038.

1 files changed, 6 insertions, 3 deletions

diff --git a/resource-managers/yarn/src/main/scala/org/apache/spark/deploy/yarn/Client.scala b/resource-managers/yarn/src/main/scala/org/apache/spark/deploy/yarn/Client.scala
index a00234c2b4..fa99cd3b64 100644
--- a/resource-managers/yarn/src/main/scala/org/apache/spark/deploy/yarn/Client.scala
+++ b/resource-managers/yarn/src/main/scala/org/apache/spark/deploy/yarn/Client.scala
@@ -100,6 +100,7 @@ private[spark] class Client(
   private var principal: String = null
   private var keytab: String = null
   private var credentials: Credentials = null
+  private var amKeytabFileName: String = null
 
   private val launcherBackend = new LauncherBackend() {
     override def onStopRequest(): Unit = {
@@ -471,7 +472,7 @@ private[spark] class Client(
       logInfo("To enable the AM to login from keytab, credentials are being copied over to the AM" +
         " via the YARN Secure Distributed Cache.")
       val (_, localizedPath) = distribute(keytab,
-        destName = sparkConf.get(KEYTAB),
+        destName = Some(amKeytabFileName),
         appMasterOnly = true)
       require(localizedPath != null, "Keytab file already distributed.")
     }
@@ -708,6 +709,9 @@ private[spark] class Client(
       // Save Spark configuration to a file in the archive.
       val props = new Properties()
       sparkConf.getAll.foreach { case (k, v) => props.setProperty(k, v) }
+      // Override spark.yarn.key to point to the location in distributed cache which will be used
+      // by AM.
+      Option(amKeytabFileName).foreach { k => props.setProperty(KEYTAB.key, k) }
       confStream.putNextEntry(new ZipEntry(SPARK_CONF_FILE))
       val writer = new OutputStreamWriter(confStream, StandardCharsets.UTF_8)
       props.store(writer, "Spark configuration.")
@@ -995,8 +999,7 @@ private[spark] class Client(
       val f = new File(keytab)
       // Generate a file name that can be used for the keytab file, that does not conflict
       // with any user file.
-      val keytabFileName = f.getName + "-" + UUID.randomUUID().toString
-      sparkConf.set(KEYTAB.key, keytabFileName)
+      amKeytabFileName = f.getName + "-" + UUID.randomUUID().toString
       sparkConf.set(PRINCIPAL.key, principal)
     }
     // Defensive copy of the credentials