From 7093afd8746cc120875eb27053bad692482d2aab Mon Sep 17 00:00:00 2001
From: bibinchundatt <bibinchundatt@apache.org>
Date: Fri, 28 Sep 2018 12:32:37 +0530
Subject: [PATCH] YARN-8829. Cluster metrics can fail with
 IndexOutOfBoundsException. Contributed by Akshay Agarwal.

---
 .../router/clientrm/FederationClientInterceptor.java     | 2 +-
 .../router/clientrm/TestFederationClientInterceptor.java | 9 +++++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-router/src/main/java/org/apache/hadoop/yarn/server/router/clientrm/FederationClientInterceptor.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-router/src/main/java/org/apache/hadoop/yarn/server/router/clientrm/FederationClientInterceptor.java
index 3d9b3946f4e..797b1aa8b71 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-router/src/main/java/org/apache/hadoop/yarn/server/router/clientrm/FederationClientInterceptor.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-router/src/main/java/org/apache/hadoop/yarn/server/router/clientrm/FederationClientInterceptor.java
@@ -654,7 +654,7 @@ public class FederationClientInterceptor
           exceptions.put(subClusterId, ioe);
         }
       }
-      if (results.isEmpty()) {
+      if (results.isEmpty() && !clusterIds.isEmpty()) {
         SubClusterId subClusterId = clusterIds.get(0);
         IOException ioe = exceptions.get(subClusterId);
         if (ioe != null) {
diff --git a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-router/src/test/java/org/apache/hadoop/yarn/server/router/clientrm/TestFederationClientInterceptor.java b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-router/src/test/java/org/apache/hadoop/yarn/server/router/clientrm/TestFederationClientInterceptor.java
index 8f19ecc46e1..c49fe4e8320 100644
--- a/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-router/src/test/java/org/apache/hadoop/yarn/server/router/clientrm/TestFederationClientInterceptor.java
+++ b/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-router/src/test/java/org/apache/hadoop/yarn/server/router/clientrm/TestFederationClientInterceptor.java
@@ -22,6 +22,7 @@ import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
 
+import java.util.Map;
 import org.apache.hadoop.yarn.api.protocolrecords.GetApplicationReportRequest;
 import org.apache.hadoop.yarn.api.protocolrecords.GetApplicationReportResponse;
 import org.apache.hadoop.yarn.api.protocolrecords.GetClusterMetricsRequest;
@@ -412,5 +413,13 @@ public class TestFederationClientInterceptor extends BaseRouterClientRMTest {
         interceptor.getClusterMetrics(GetClusterMetricsRequest.newInstance());
     Assert.assertEquals(subClusters.size(),
         response.getClusterMetrics().getNumNodeManagers());
+
+    ClientMethod remoteMethod = new ClientMethod("getClusterMetrics",
+        new Class[] {GetClusterMetricsRequest.class},
+        new Object[] {GetClusterMetricsRequest.newInstance()});
+    Map<SubClusterId, GetClusterMetricsResponse> clusterMetrics =interceptor.
+        invokeConcurrent(new ArrayList<>(), remoteMethod,
+            GetClusterMetricsResponse.class);
+    Assert.assertEquals(true, clusterMetrics.isEmpty());
   }
 }