MAPREDUCE-5649. Reduce cannot use more than 2G memory for the final merge. Contributed by Gera Shegalov

(cherry picked from commit 7dc3c1203d)

(cherry picked from commit 87c2d915f1)
(cherry picked from commit 1da62ba736f5f161a18a52b7ca0d212786f3848c)

hadoop-mapreduce-project/CHANGES.txt

@@ -35,6 +35,9 @@ Release 2.6.1 - UNRELEASED
     MAPREDUCE-6324. Fixed MapReduce uber jobs to not fail the udpate of AM-RM
     tokens when they roll-over. (Jason Lowe via vinodkv)
 
+    MAPREDUCE-5649. Reduce cannot use more than 2G memory for the final merge
+    (Gera Shegalov via jlowe)
+
 Release 2.6.0 - 2014-11-18
 
   INCOMPATIBLE CHANGES

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/task/reduce/MergeManagerImpl.java

@@ -93,8 +93,10 @@ public class MergeManagerImpl<K, V> implements MergeManager<K, V> {
   
   Set<CompressAwarePath> onDiskMapOutputs = new TreeSet<CompressAwarePath>();
   private final OnDiskMerger onDiskMerger;
-  
-  private final long memoryLimit;
+
+  @VisibleForTesting
+  final long memoryLimit;
+
   private long usedMemory;
   private long commitMemory;
   private final long maxSingleShuffleLimit;
@@ -167,11 +169,10 @@ public class MergeManagerImpl<K, V> implements MergeManager<K, V> {
     }
 
     // Allow unit tests to fix Runtime memory
-    this.memoryLimit = 
-      (long)(jobConf.getLong(MRJobConfig.REDUCE_MEMORY_TOTAL_BYTES,
-          Math.min(Runtime.getRuntime().maxMemory(), Integer.MAX_VALUE))
-        * maxInMemCopyUse);
- 
+    this.memoryLimit = (long)(jobConf.getLong(
+        MRJobConfig.REDUCE_MEMORY_TOTAL_BYTES,
+        Runtime.getRuntime().maxMemory()) * maxInMemCopyUse);
+
     this.ioSortFactor = jobConf.getInt(MRJobConfig.IO_SORT_FACTOR, 100);
 
     final float singleShuffleMemoryLimitPercent =
@@ -201,7 +202,7 @@ public class MergeManagerImpl<K, V> implements MergeManager<K, V> {
 
     if (this.maxSingleShuffleLimit >= this.mergeThreshold) {
       throw new RuntimeException("Invalid configuration: "
-          + "maxSingleShuffleLimit should be less than mergeThreshold"
+          + "maxSingleShuffleLimit should be less than mergeThreshold "
           + "maxSingleShuffleLimit: " + this.maxSingleShuffleLimit
           + "mergeThreshold: " + this.mergeThreshold);
     }
@@ -667,24 +668,26 @@ public class MergeManagerImpl<K, V> implements MergeManager<K, V> {
     }
   }
 
+  @VisibleForTesting
+  final long getMaxInMemReduceLimit() {
+    final float maxRedPer =
+        jobConf.getFloat(MRJobConfig.REDUCE_INPUT_BUFFER_PERCENT, 0f);
+    if (maxRedPer > 1.0 || maxRedPer < 0.0) {
+      throw new RuntimeException(maxRedPer + ": "
+          + MRJobConfig.REDUCE_INPUT_BUFFER_PERCENT
+          + " must be a float between 0 and 1.0");
+    }
+    return (long)(memoryLimit * maxRedPer);
+  }
+
   private RawKeyValueIterator finalMerge(JobConf job, FileSystem fs,
                                        List<InMemoryMapOutput<K,V>> inMemoryMapOutputs,
                                        List<CompressAwarePath> onDiskMapOutputs
                                        ) throws IOException {
-    LOG.info("finalMerge called with " + 
-             inMemoryMapOutputs.size() + " in-memory map-outputs and " + 
-             onDiskMapOutputs.size() + " on-disk map-outputs");
-    
-    final float maxRedPer =
-      job.getFloat(MRJobConfig.REDUCE_INPUT_BUFFER_PERCENT, 0f);
-    if (maxRedPer > 1.0 || maxRedPer < 0.0) {
-      throw new IOException(MRJobConfig.REDUCE_INPUT_BUFFER_PERCENT +
-                            maxRedPer);
-    }
-    int maxInMemReduce = (int)Math.min(
-        Runtime.getRuntime().maxMemory() * maxRedPer, Integer.MAX_VALUE);
-    
-
+    LOG.info("finalMerge called with " +
+        inMemoryMapOutputs.size() + " in-memory map-outputs and " +
+        onDiskMapOutputs.size() + " on-disk map-outputs");
+    final long maxInMemReduce = getMaxInMemReduceLimit();
     // merge config params
     Class<K> keyClass = (Class<K>)job.getMapOutputKeyClass();
     Class<V> valueClass = (Class<V>)job.getMapOutputValueClass();

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/test/java/org/apache/hadoop/mapreduce/task/reduce/TestMergeManager.java

@@ -260,4 +260,33 @@ public class TestMergeManager {
     }
 
   }
+
+  @Test
+  public void testLargeMemoryLimits() throws Exception {
+    final JobConf conf = new JobConf();
+    // Xmx in production
+    conf.setLong(MRJobConfig.REDUCE_MEMORY_TOTAL_BYTES,
+        8L * 1024 * 1024 * 1024);
+
+    // M1 = Xmx fraction for map outputs
+    conf.setFloat(MRJobConfig.SHUFFLE_INPUT_BUFFER_PERCENT, 1.0f);
+
+    // M2 = max M1 fraction for a single maple output
+    conf.setFloat(MRJobConfig.SHUFFLE_MEMORY_LIMIT_PERCENT, 0.95f);
+
+    // M3 = M1 fraction at which in memory merge is triggered
+    conf.setFloat(MRJobConfig.SHUFFLE_MERGE_PERCENT, 1.0f);
+
+    // M4 = M1 fraction of map outputs remaining in memory for a reduce
+    conf.setFloat(MRJobConfig.REDUCE_INPUT_BUFFER_PERCENT, 1.0f);
+
+    final MergeManagerImpl<Text, Text> mgr = new MergeManagerImpl<Text, Text>(
+        null, conf, mock(LocalFileSystem.class), null, null, null, null, null,
+        null, null, null, null, null, new MROutputFiles());
+    assertTrue("Large shuffle area unusable: " + mgr.memoryLimit,
+        mgr.memoryLimit > Integer.MAX_VALUE);
+    final long maxInMemReduce = mgr.getMaxInMemReduceLimit();
+    assertTrue("Large in-memory reduce area unusable: " + maxInMemReduce,
+        maxInMemReduce > Integer.MAX_VALUE);
+  }
 }