MAPREDUCE-6808. Log map attempts as part of shuffle handler audit log (Contributed by Gergő Pásztor via Daniel Templeton)

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-shuffle/src/main/java/org/apache/hadoop/mapred/ShuffleHandler.java

@@ -947,7 +947,7 @@ public class ShuffleHandler extends AuxiliaryService {
       // to turn it on please enable this audit log
       // on log4j.properties by uncommenting the setting
       if (AUDITLOG.isDebugEnabled()) {
-        AUDITLOG.debug("shuffle for " + jobQ.get(0) +
+        AUDITLOG.debug("shuffle for " + jobQ.get(0) + " mappers: " + mapIds +
                          " reducer " + reduceQ.get(0));
       }
       int reduceId;