HDFS-7475. Make TestLazyPersistFiles#testLazyPersistBlocksAreSaved deterministic. (Contributed by Xiaoyu Yao)

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -567,6 +567,9 @@ Release 2.7.0 - UNRELEASED
     HDFS-5578. [JDK8] Fix Javadoc errors caused by incorrect or illegal tags
     in doc comments. (Andrew Purtell via wheat9)
 
+    HDFS-7475. Make TestLazyPersistFiles#testLazyPersistBlocksAreSaved
+    deterministic. (Xiaoyu Yao via Arpit Agarwal)
+
 Release 2.6.1 - UNRELEASED
 
   INCOMPATIBLE CHANGES

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/LazyPersistTestCase.java

@@ -50,6 +50,8 @@
 import java.util.Arrays;
 import java.util.EnumSet;
 import java.util.List;
+import java.util.HashSet;
+import java.util.Set;
 import java.util.UUID;
 
 import static org.apache.hadoop.fs.CreateFlag.CREATE;
@@ -131,6 +133,48 @@ protected final LocatedBlocks ensureFileReplicasOnStorageType(
     return locatedBlocks;
   }
 
+  /**
+   * Make sure at least one non-transient volume has a saved copy of the replica.
+   * An infinite loop is used to ensure the async lazy persist tasks are completely
+   * done before verification. Caller of ensureLazyPersistBlocksAreSaved expects
+   * either a successful pass or timeout failure.
+   */
+  protected final void ensureLazyPersistBlocksAreSaved(
+      LocatedBlocks locatedBlocks) throws IOException, InterruptedException {
+    final String bpid = cluster.getNamesystem().getBlockPoolId();
+    List<? extends FsVolumeSpi> volumes =
+      cluster.getDataNodes().get(0).getFSDataset().getVolumes();
+    final Set<Long> persistedBlockIds = new HashSet<Long>();
+
+    while (persistedBlockIds.size() < locatedBlocks.getLocatedBlocks().size()) {
+      // Take 1 second sleep before each verification iteration
+      Thread.sleep(1000);
+
+      for (LocatedBlock lb : locatedBlocks.getLocatedBlocks()) {
+        for (FsVolumeSpi v : volumes) {
+          if (v.isTransientStorage()) {
+            continue;
+          }
+
+          FsVolumeImpl volume = (FsVolumeImpl) v;
+          File lazyPersistDir = volume.getBlockPoolSlice(bpid).getLazypersistDir();
+
+          long blockId = lb.getBlock().getBlockId();
+          File targetDir =
+            DatanodeUtil.idToBlockDir(lazyPersistDir, blockId);
+          File blockFile = new File(targetDir, lb.getBlock().getBlockName());
+          if (blockFile.exists()) {
+            // Found a persisted copy for this block and added to the Set
+            persistedBlockIds.add(blockId);
+          }
+        }
+      }
+    }
+
+    // We should have found a persisted copy for each located block.
+    assertThat(persistedBlockIds.size(), is(locatedBlocks.getLocatedBlocks().size()));
+  }
+
   protected final void makeRandomTestFile(Path path, long length,
       boolean isLazyPersist, long seed) throws IOException {
     DFSTestUtil.createFile(fs, path, isLazyPersist, BUFFER_LENGTH, length,

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/TestLazyPersistFiles.java

@@ -304,37 +304,7 @@ public void testLazyPersistBlocksAreSaved()
 
     // Make sure that there is a saved copy of the replica on persistent
     // storage.
-    final String bpid = cluster.getNamesystem().getBlockPoolId();
+    ensureLazyPersistBlocksAreSaved(locatedBlocks);
-    List<? extends FsVolumeSpi> volumes =
-        cluster.getDataNodes().get(0).getFSDataset().getVolumes();
-
-    final Set<Long> persistedBlockIds = new HashSet<Long>();
-
-    // Make sure at least one non-transient volume has a saved copy of
-    // the replica.
-    for (FsVolumeSpi v : volumes) {
-      if (v.isTransientStorage()) {
-        continue;
-      }
-
-      FsVolumeImpl volume = (FsVolumeImpl) v;
-      File lazyPersistDir = volume.getBlockPoolSlice(bpid).getLazypersistDir();
-
-      for (LocatedBlock lb : locatedBlocks.getLocatedBlocks()) {
-        File targetDir = DatanodeUtil.idToBlockDir(lazyPersistDir, lb.getBlock().getBlockId());
-        File blockFile = new File(targetDir, lb.getBlock().getBlockName());
-        if (blockFile.exists()) {
-          // Found a persisted copy for this block!
-          boolean added = persistedBlockIds.add(lb.getBlock().getBlockId());
-          assertThat(added, is(true));
-        } else {
-          LOG.error(blockFile + " not found");
-        }
-      }
-    }
-
-    // We should have found a persisted copy for each located block.
-    assertThat(persistedBlockIds.size(), is(locatedBlocks.getLocatedBlocks().size()));
   }
 
   /**