HDFS-8150. Make getFileChecksum fail for blocks under construction (Contributed by J.Andreina)

(cherry picked from commit def9136e02)

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

@@ -428,6 +428,9 @@ Release 2.8.0 - UNRELEASED
     HDFS-7728. Avoid updating quota usage while loading edits.
     (Jing Zhao via wheat9)
 
+    HDFS-8150. Make getFileChecksum fail for blocks under construction
+    (J.Andreina via vinayakumarb)
+
 Release 2.7.1 - UNRELEASED
 
   INCOMPATIBLE CHANGES

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSClient.java

@@ -1871,6 +1871,10 @@ public MD5MD5CRC32FileChecksum getFileChecksum(String src, long length)
     if (null == blockLocations) {
       throw new FileNotFoundException("File does not exist: " + src);
     }
+    if (blockLocations.isUnderConstruction()) {
+      throw new IOException("Fail to get checksum, since file " + src
+          + " is under construction.");
+    }
     List<LocatedBlock> locatedblocks = blockLocations.getLocatedBlocks();
     final DataOutputBuffer md5out = new DataOutputBuffer();
     int bytesPerCRC = -1;
@@ -1890,6 +1894,10 @@ public MD5MD5CRC32FileChecksum getFileChecksum(String src, long length)
         if (null == blockLocations) {
           throw new FileNotFoundException("File does not exist: " + src);
         }
+        if (blockLocations.isUnderConstruction()) {
+          throw new IOException("Fail to get checksum, since file " + src
+              + " is under construction.");
+        }
         locatedblocks = blockLocations.getLocatedBlocks();
         refetchBlocks = false;
       }

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestGetFileChecksum.java

@@ -17,7 +17,12 @@
  */
 package org.apache.hadoop.hdfs;
 
+import static org.junit.Assert.fail;
+
+import java.io.IOException;
+
 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.junit.After;
@@ -67,6 +72,20 @@ public void testGetFileChecksum(final Path foo, final int appendLength)
     }
   }
 
+  @Test
+  public void testGetFileChecksumForBlocksUnderConstruction() {
+    try {
+      FSDataOutputStream file = dfs.create(new Path("/testFile"));
+      file.write("Performance Testing".getBytes());
+      dfs.getFileChecksum(new Path("/testFile"));
+      fail("getFileChecksum should fail for files "
+          + "with blocks under construction");
+    } catch (IOException ie) {
+      Assert.assertTrue(ie.getMessage().contains(
+          "Fail to get checksum, since file /testFile "
+              + "is under construction."));
+    }
+  }
   @Test
   public void testGetFileChecksum() throws Exception {
     testGetFileChecksum(new Path("/foo"), BLOCKSIZE / 4);

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

@@ -18,6 +18,7 @@
 package org.apache.hadoop.hdfs.server.namenode.snapshot;
 
 import java.io.ByteArrayOutputStream;
+import java.io.IOException;
 import java.io.PrintStream;
 
 import org.apache.hadoop.fs.FSDataOutputStream;
@@ -32,6 +33,8 @@
 import static org.hamcrest.CoreMatchers.not;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertThat;
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
 
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.FSDataInputStream;
@@ -111,8 +114,16 @@ public void testSnapshotfileLength() throws Exception {
     // Append to the file.
     FSDataOutputStream out = hdfs.append(file1);
     // Nothing has been appended yet. All checksums should still be equal.
-    assertThat("file and snapshot checksums (open for append) are not equal",
-        hdfs.getFileChecksum(file1), is(snapChksum1));
+    // HDFS-8150:Fetching checksum for file under construction should fail
+    try {
+      hdfs.getFileChecksum(file1);
+      fail("getFileChecksum should fail for files "
+          + "with blocks under construction");
+    } catch (IOException ie) {
+      assertTrue(ie.getMessage().contains(
+          "Fail to get checksum, since file " + file1
+              + " is under construction."));
+    }
     assertThat("snapshot checksum (post-open for append) has changed",
         hdfs.getFileChecksum(file1snap1), is(snapChksum1));
     try {
@@ -122,8 +133,6 @@ public void testSnapshotfileLength() throws Exception {
       assertThat("Wrong data size in snapshot.",
           dataFromSnapshot.length, is(origLen));
       // Verify that checksum didn't change
-      assertThat("snapshot file checksum (pre-close) has changed",
-          hdfs.getFileChecksum(file1), is(snapChksum1));
       assertThat("snapshot checksum (post-append) has changed",
           hdfs.getFileChecksum(file1snap1), is(snapChksum1));
     } finally {