From 0fbd3d42fdb9bcd6f8f2508fa4b8b5de81cf1ba6 Mon Sep 17 00:00:00 2001
From: David Mollitor <dmollitor@apache.org>
Date: Tue, 27 Jul 2021 12:02:31 -0400
Subject: [PATCH] TEZ-4321: Do Not Wrap Singleton Collections

---
 .../apache/tez/dag/app/dag/impl/BroadcastEdgeManager.java   | 6 ++----
 .../apache/tez/dag/app/dag/impl/OneToOneEdgeManager.java    | 3 +--
 .../tez/dag/app/dag/impl/OneToOneEdgeManagerOnDemand.java   | 3 +--
 .../java/org/apache/tez/dag/app/TestMockDAGAppMaster.java   | 3 +--
 4 files changed, 5 insertions(+), 10 deletions(-)

diff --git a/tez-dag/src/main/java/org/apache/tez/dag/app/dag/impl/BroadcastEdgeManager.java b/tez-dag/src/main/java/org/apache/tez/dag/app/dag/impl/BroadcastEdgeManager.java
index ca510f7fc4..867403fcd5 100644
--- a/tez-dag/src/main/java/org/apache/tez/dag/app/dag/impl/BroadcastEdgeManager.java
+++ b/tez-dag/src/main/java/org/apache/tez/dag/app/dag/impl/BroadcastEdgeManager.java
@@ -53,8 +53,7 @@ public int getNumSourceTaskPhysicalOutputs(int sourceTaskIndex) {
   public void routeDataMovementEventToDestination(DataMovementEvent event,
       int sourceTaskIndex, int sourceOutputIndex, 
       Map<Integer, List<Integer>> destinationTaskAndInputIndices) {
-    List<Integer> inputIndices = 
-        Collections.unmodifiableList(Collections.singletonList(sourceTaskIndex));
+    List<Integer> inputIndices = Collections.singletonList(sourceTaskIndex);
     // for each task make the i-th source task as the i-th physical input
     for (int i=0; i<getContext().getDestinationVertexNumTasks(); ++i) {
       destinationTaskAndInputIndices.put(i, inputIndices);
@@ -93,8 +92,7 @@ public EventRouteMetadata routeInputSourceTaskFailedEventToDestination(
   @Override
   public void routeInputSourceTaskFailedEventToDestination(int sourceTaskIndex,
       Map<Integer, List<Integer>> destinationTaskAndInputIndices) {
-    List<Integer> inputIndices = 
-        Collections.unmodifiableList(Collections.singletonList(sourceTaskIndex));
+    List<Integer> inputIndices = Collections.singletonList(sourceTaskIndex);
     // for each task make the i-th source task as the i-th physical input
     for (int i=0; i<getContext().getDestinationVertexNumTasks(); ++i) {
       destinationTaskAndInputIndices.put(i, inputIndices);
diff --git a/tez-dag/src/main/java/org/apache/tez/dag/app/dag/impl/OneToOneEdgeManager.java b/tez-dag/src/main/java/org/apache/tez/dag/app/dag/impl/OneToOneEdgeManager.java
index f9bacbf034..8a6008a496 100644
--- a/tez-dag/src/main/java/org/apache/tez/dag/app/dag/impl/OneToOneEdgeManager.java
+++ b/tez-dag/src/main/java/org/apache/tez/dag/app/dag/impl/OneToOneEdgeManager.java
@@ -32,8 +32,7 @@
 
 public class OneToOneEdgeManager extends EdgeManagerPlugin {
 
-  final List<Integer> destinationInputIndices =
-      Collections.unmodifiableList(Collections.singletonList(0));
+  final List<Integer> destinationInputIndices = Collections.singletonList(0);
   final AtomicBoolean stateChecked = new AtomicBoolean(false);
 
   public OneToOneEdgeManager(EdgeManagerPluginContext context) {
diff --git a/tez-dag/src/main/java/org/apache/tez/dag/app/dag/impl/OneToOneEdgeManagerOnDemand.java b/tez-dag/src/main/java/org/apache/tez/dag/app/dag/impl/OneToOneEdgeManagerOnDemand.java
index e2dbf457cf..464d87df59 100644
--- a/tez-dag/src/main/java/org/apache/tez/dag/app/dag/impl/OneToOneEdgeManagerOnDemand.java
+++ b/tez-dag/src/main/java/org/apache/tez/dag/app/dag/impl/OneToOneEdgeManagerOnDemand.java
@@ -34,8 +34,7 @@
 
 public class OneToOneEdgeManagerOnDemand extends EdgeManagerPluginOnDemand {
 
-  final List<Integer> destinationInputIndices =
-      Collections.unmodifiableList(Collections.singletonList(0));
+  final List<Integer> destinationInputIndices = Collections.singletonList(0);
   final AtomicBoolean stateChecked = new AtomicBoolean(false);
  
   final EventRouteMetadata commonRouteMeta = 
diff --git a/tez-dag/src/test/java/org/apache/tez/dag/app/TestMockDAGAppMaster.java b/tez-dag/src/test/java/org/apache/tez/dag/app/TestMockDAGAppMaster.java
index 5dca6940ea..aa5d3b9535 100644
--- a/tez-dag/src/test/java/org/apache/tez/dag/app/TestMockDAGAppMaster.java
+++ b/tez-dag/src/test/java/org/apache/tez/dag/app/TestMockDAGAppMaster.java
@@ -300,8 +300,7 @@ public void testBasicEvents() throws Exception {
   }
   
   public static class LegacyEdgeTestEdgeManager extends EdgeManagerPlugin {
-    List<Integer> destinationInputIndices = 
-        Collections.unmodifiableList(Collections.singletonList(0));
+    List<Integer> destinationInputIndices = Collections.singletonList(0);
     public LegacyEdgeTestEdgeManager(EdgeManagerPluginContext context) {
       super(context);
     }