HDFS-12316. Verify HDFS snapshot deletion doesn't crash the ongoing file writes.

(cherry picked from commit 4230872dd66d748172903b1522885b03f34bbf9b)

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/snapshot/TestOpenFilesWithSnapshot.java

@@ -23,7 +23,11 @@ import java.util.EnumSet;
 import java.util.HashSet;
 import java.util.Random;
 import java.util.Set;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.atomic.AtomicBoolean;
 
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.FSDataOutputStream;
 import org.apache.hadoop.fs.Path;
@@ -38,12 +42,15 @@ import org.apache.hadoop.hdfs.protocol.HdfsConstants;
 import org.apache.hadoop.hdfs.server.namenode.NameNode;
 import org.apache.hadoop.hdfs.server.namenode.NameNodeAdapter;
 import org.apache.hadoop.hdfs.server.protocol.NamenodeProtocols;
+import org.apache.hadoop.util.Time;
 import org.junit.After;
 import org.junit.Assert;
 import org.junit.Before;
 import org.junit.Test;
 
 public class TestOpenFilesWithSnapshot {
+  private static final Log LOG =
+      LogFactory.getLog(TestOpenFilesWithSnapshot.class.getName());
   private final Configuration conf = new Configuration();
   MiniDFSCluster cluster = null;
   DistributedFileSystem fs = null;
@@ -622,6 +629,108 @@ public class TestOpenFilesWithSnapshot {
     hbaseOutputStream.close();
   }
 
+  /**
+   * Test client writing to open files are not interrupted when snapshots
+   * that captured open files get deleted.
+   */
+  @Test (timeout = 240000)
+  public void testOpenFileWritingAcrossSnapDeletion() throws Exception {
+    final Path snapRootDir = new Path("/level_0_A");
+    final String flumeFileName = "flume.log";
+    final String hbaseFileName = "hbase.log";
+    final String snap1Name = "snap_1";
+    final String snap2Name = "snap_2";
+    final String snap3Name = "snap_3";
+
+    // Create files and open streams
+    final Path flumeFile = new Path(snapRootDir, flumeFileName);
+    FSDataOutputStream flumeOut = fs.create(flumeFile, false,
+        8000, (short)3, 1048576);
+    flumeOut.close();
+    final Path hbaseFile = new Path(snapRootDir, hbaseFileName);
+    FSDataOutputStream hbaseOut = fs.create(hbaseFile, false,
+        8000, (short)3, 1048576);
+    hbaseOut.close();
+
+    final AtomicBoolean writerError = new AtomicBoolean(false);
+    final CountDownLatch startLatch = new CountDownLatch(1);
+    final CountDownLatch deleteLatch = new CountDownLatch(1);
+    Thread t = new Thread(new Runnable() {
+      @Override
+      public void run() {
+        try {
+          FSDataOutputStream flumeOutputStream = fs.append(flumeFile, 8000);
+          FSDataOutputStream hbaseOutputStream = fs.append(hbaseFile, 8000);
+          byte[] bytes = new byte[(int) (1024 * 0.2)];
+          Random r = new Random(Time.now());
+
+          for (int i = 0; i < 200000; i++) {
+            r.nextBytes(bytes);
+            flumeOutputStream.write(bytes);
+            if (hbaseOutputStream != null) {
+              hbaseOutputStream.write(bytes);
+            }
+            if (i == 50000) {
+              startLatch.countDown();
+            } else if (i == 100000) {
+              deleteLatch.countDown();
+            } else if (i == 150000) {
+              hbaseOutputStream.hsync();
+              fs.delete(hbaseFile, true);
+              try {
+                hbaseOutputStream.close();
+              } catch (Exception e) {
+                // since the file is deleted before the open stream close,
+                // it might throw FileNotFoundException. Ignore the
+                // expected exception.
+              }
+              hbaseOutputStream = null;
+            } else if (i % 5000 == 0) {
+              LOG.info("Write pos: " + flumeOutputStream.getPos()
+                  + ", size: " + fs.getFileStatus(flumeFile).getLen()
+                  + ", loop: " + (i + 1));
+            }
+          }
+        } catch (Exception e) {
+          LOG.warn("Writer error: " + e);
+          writerError.set(true);
+        }
+      }
+    });
+    t.start();
+
+    startLatch.await();
+    final Path snap1Dir = SnapshotTestHelper.createSnapshot(
+        fs, snapRootDir, snap1Name);
+    final Path flumeS1Path = new Path(snap1Dir, flumeFileName);
+    LOG.info("Snap1 file status: " + fs.getFileStatus(flumeS1Path));
+    LOG.info("Current file status: " + fs.getFileStatus(flumeFile));
+
+    deleteLatch.await();
+    LOG.info("Snap1 file status: " + fs.getFileStatus(flumeS1Path));
+    LOG.info("Current file status: " + fs.getFileStatus(flumeFile));
+
+    // Verify deletion of snapshot which had the under construction file
+    // captured is not truncating the under construction file and the thread
+    // writing to the same file not crashing on newer block allocations.
+    LOG.info("Deleting " + snap1Name);
+    fs.deleteSnapshot(snapRootDir, snap1Name);
+
+    // Verify creation and deletion of snapshot newer than the oldest
+    // snapshot is not crashing the thread writing to under construction file.
+    SnapshotTestHelper.createSnapshot(fs, snapRootDir, snap2Name);
+    SnapshotTestHelper.createSnapshot(fs, snapRootDir, snap3Name);
+    fs.deleteSnapshot(snapRootDir, snap3Name);
+    fs.deleteSnapshot(snapRootDir, snap2Name);
+    SnapshotTestHelper.createSnapshot(fs, snapRootDir, "test");
+
+    t.join();
+    Assert.assertFalse("Client encountered writing error!", writerError.get());
+
+    restartNameNode();
+    cluster.waitActive();
+  }
+
   private void restartNameNode() throws Exception {
     cluster.triggerBlockReports();
     NameNode nameNode = cluster.getNameNode();