From 462561654bb37dc1d453bfe15c3e75c274bbfb02 Mon Sep 17 00:00:00 2001
From: Eric Badger <ebadger@verizonmedia.com>
Date: Tue, 9 Feb 2021 19:01:38 +0000
Subject: [PATCH] MAPREDUCE-7319. Log list of mappers at trace level in
 ShuffleHandler audit log. Contributed by Jim Brennan.

---
 .../java/org/apache/hadoop/mapred/ShuffleHandler.java    | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-shuffle/src/main/java/org/apache/hadoop/mapred/ShuffleHandler.java b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-shuffle/src/main/java/org/apache/hadoop/mapred/ShuffleHandler.java
index 62be3a08e8..1d5b475ea7 100644
--- a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-shuffle/src/main/java/org/apache/hadoop/mapred/ShuffleHandler.java
+++ b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-shuffle/src/main/java/org/apache/hadoop/mapred/ShuffleHandler.java
@@ -1170,8 +1170,13 @@ protected void populateHeaders(List<String> mapIds, String jobId,
         StringBuilder sb = new StringBuilder("shuffle for ");
         sb.append(jobId).append(" reducer ").append(reduce);
         sb.append(" length ").append(contentLength);
-        sb.append(" mappers: ").append(mapIds);
-        AUDITLOG.debug(sb.toString());
+        if (AUDITLOG.isTraceEnabled()) {
+          // For trace level logging, append the list of mappers
+          sb.append(" mappers: ").append(mapIds);
+          AUDITLOG.trace(sb.toString());
+        } else {
+          AUDITLOG.debug(sb.toString());
+        }
       }
     }