HDFS-11988. Verify HDFS Snapshots with open files captured are consistent across truncates and appends to current version file.

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

@@ -30,6 +30,7 @@ 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.FileChecksum;
 import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.hdfs.DFSConfigKeys;
 import org.apache.hadoop.hdfs.DFSOutputStream;
@@ -731,6 +732,117 @@ public class TestOpenFilesWithSnapshot {
     cluster.waitActive();
   }
 
+  /**
+   * Verify snapshots with open files captured are safe even when the
+   * 'current' version of the file is truncated and appended later.
+   */
+  @Test (timeout = 120000)
+  public void testOpenFilesSnapChecksumWithTrunkAndAppend() throws Exception {
+    conf.setBoolean(DFSConfigKeys.DFS_NAMENODE_SNAPSHOT_CAPTURE_OPENFILES,
+        true);
+    // Construct the directory tree
+    final Path dir = new Path("/A/B/C");
+    fs.mkdirs(dir);
+
+    // String constants
+    final Path hbaseSnapRootDir = dir;
+    final String hbaseFileName = "hbase.wal";
+    final String hbaseSnap1Name = "hbase_snap_s1";
+    final String hbaseSnap2Name = "hbase_snap_s2";
+    final String hbaseSnap3Name = "hbase_snap_s3";
+    final String hbaseSnap4Name = "hbase_snap_s4";
+
+    // Create files and open a stream
+    final Path hbaseFile = new Path(dir, hbaseFileName);
+    createFile(hbaseFile);
+    final FileChecksum hbaseWALFileCksum0 =
+        fs.getFileChecksum(hbaseFile);
+    FSDataOutputStream hbaseOutputStream = fs.append(hbaseFile);
+
+    // Create Snapshot S1
+    final Path hbaseS1Dir = SnapshotTestHelper.createSnapshot(
+        fs, hbaseSnapRootDir, hbaseSnap1Name);
+    final Path hbaseS1Path = new Path(hbaseS1Dir, hbaseFileName);
+    final FileChecksum hbaseFileCksumS1 = fs.getFileChecksum(hbaseS1Path);
+
+    // Verify if Snap S1 checksum is same as the current version one
+    Assert.assertEquals("Live and snap1 file checksum doesn't match!",
+        hbaseWALFileCksum0, fs.getFileChecksum(hbaseS1Path));
+
+    int newWriteLength = (int) (BLOCKSIZE * 1.5);
+    byte[] buf = new byte[newWriteLength];
+    Random random = new Random();
+    random.nextBytes(buf);
+    writeToStream(hbaseOutputStream, buf);
+
+    // Create Snapshot S2
+    final Path hbaseS2Dir = SnapshotTestHelper.createSnapshot(
+        fs, hbaseSnapRootDir, hbaseSnap2Name);
+    final Path hbaseS2Path = new Path(hbaseS2Dir, hbaseFileName);
+    final FileChecksum hbaseFileCksumS2 = fs.getFileChecksum(hbaseS2Path);
+
+    // Verify if the s1 checksum is still the same
+    Assert.assertEquals("Snap file checksum has changed!",
+        hbaseFileCksumS1, fs.getFileChecksum(hbaseS1Path));
+    // Verify if the s2 checksum is different from the s1 checksum
+    Assert.assertNotEquals("Snap1 and snap2 file checksum should differ!",
+        hbaseFileCksumS1, hbaseFileCksumS2);
+
+    newWriteLength = (int) (BLOCKSIZE * 2.5);
+    buf = new byte[newWriteLength];
+    random.nextBytes(buf);
+    writeToStream(hbaseOutputStream, buf);
+
+    // Create Snapshot S3
+    final Path hbaseS3Dir = SnapshotTestHelper.createSnapshot(
+        fs, hbaseSnapRootDir, hbaseSnap3Name);
+    final Path hbaseS3Path = new Path(hbaseS3Dir, hbaseFileName);
+    FileChecksum hbaseFileCksumS3 = fs.getFileChecksum(hbaseS3Path);
+
+    // Record the checksum for the before truncate current file
+    hbaseOutputStream.close();
+    final FileChecksum hbaseFileCksumBeforeTruncate =
+        fs.getFileChecksum(hbaseFile);
+    Assert.assertEquals("Snap3 and before truncate file checksum should match!",
+        hbaseFileCksumBeforeTruncate, hbaseFileCksumS3);
+
+    // Truncate the current file and record the after truncate checksum
+    long currentFileLen = fs.getFileStatus(hbaseFile).getLen();
+    boolean fileTruncated = fs.truncate(hbaseFile, currentFileLen / 2);
+    Assert.assertTrue("File truncation failed!", fileTruncated);
+    final FileChecksum hbaseFileCksumAfterTruncate =
+        fs.getFileChecksum(hbaseFile);
+
+    Assert.assertNotEquals("Snap3 and after truncate checksum shouldn't match!",
+        hbaseFileCksumS3, hbaseFileCksumAfterTruncate);
+
+    // Append more data to the current file
+    hbaseOutputStream = fs.append(hbaseFile);
+    newWriteLength = (int) (BLOCKSIZE * 5.5);
+    buf = new byte[newWriteLength];
+    random.nextBytes(buf);
+    writeToStream(hbaseOutputStream, buf);
+
+    // Create Snapshot S4
+    final Path hbaseS4Dir = SnapshotTestHelper.createSnapshot(
+        fs, hbaseSnapRootDir, hbaseSnap4Name);
+    final Path hbaseS4Path = new Path(hbaseS4Dir, hbaseFileName);
+    final FileChecksum hbaseFileCksumS4 = fs.getFileChecksum(hbaseS4Path);
+
+    // Record the checksum for the current file after append
+    hbaseOutputStream.close();
+    final FileChecksum hbaseFileCksumAfterAppend =
+        fs.getFileChecksum(hbaseFile);
+
+    Assert.assertEquals("Snap4 and after append file checksum should match!",
+        hbaseFileCksumAfterAppend, hbaseFileCksumS4);
+
+    // Recompute checksum for S3 path and verify it has not changed
+    hbaseFileCksumS3 = fs.getFileChecksum(hbaseS3Path);
+    Assert.assertEquals("Snap3 and before truncate file checksum should match!",
+        hbaseFileCksumBeforeTruncate, hbaseFileCksumS3);
+  }
+
   private void restartNameNode() throws Exception {
     cluster.triggerBlockReports();
     NameNode nameNode = cluster.getNameNode();