HDFS-10225. DataNode hot swap drives should disallow storage type changes. Contributed by Lei (Eddy) Xu.

(cherry picked from commit 132deb4cac)

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java

@@ -625,7 +625,7 @@ static class ChangedVolumes {
    * @param newVolumes a comma separated string that specifies the data volumes.
    * @return changed volumes.
    * @throws IOException if none of the directories are specified in the
-   * configuration.
+   * configuration, or the storage type of a directory is changed.
    */
   @VisibleForTesting
   ChangedVolumes parseChangedVolumes(String newVolumes) throws IOException {
@@ -637,6 +637,12 @@ ChangedVolumes parseChangedVolumes(String newVolumes) throws IOException {
       throw new IOException("No directory is specified.");
     }
 
+    // Use the existing StorageLocation to detect storage type changes.
+    Map<String, StorageLocation> existingLocations = new HashMap<>();
+    for (StorageLocation loc : getStorageLocations(this.conf)) {
+      existingLocations.put(loc.getFile().getCanonicalPath(), loc);
+    }
+
     ChangedVolumes results = new ChangedVolumes();
     results.newLocations.addAll(locations);
 
@@ -650,6 +656,12 @@ ChangedVolumes parseChangedVolumes(String newVolumes) throws IOException {
         if (location.getFile().getCanonicalPath().equals(
             dir.getRoot().getCanonicalPath())) {
           sl.remove();
+          StorageLocation old = existingLocations.get(
+              location.getFile().getCanonicalPath());
+          if (old != null &&
+              old.getStorageType() != location.getStorageType()) {
+            throw new IOException("Changing storage type is not allowed.");
+          }
           results.unchangedLocations.add(location);
           found = true;
           break;

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestDataNodeHotSwapVolumes.java

@@ -27,6 +27,7 @@
 import org.apache.hadoop.fs.FileStatus;
 import org.apache.hadoop.fs.FileSystem;
 import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.fs.StorageType;
 import org.apache.hadoop.hdfs.BlockMissingException;
 import org.apache.hadoop.hdfs.DFSConfigKeys;
 import org.apache.hadoop.hdfs.DFSTestUtil;
@@ -255,6 +256,27 @@ public void testParseChangedVolumesFailures() throws IOException {
     }
   }
 
+  @Test
+  public void testParseStorageTypeChanges() throws IOException {
+    startDFSCluster(1, 1);
+    DataNode dn = cluster.getDataNodes().get(0);
+    Configuration conf = dn.getConf();
+    List<StorageLocation> oldLocations = DataNode.getStorageLocations(conf);
+
+    // Change storage type of an existing StorageLocation
+    String newLoc = String.format("[%s]%s", StorageType.SSD,
+        oldLocations.get(1).getUri());
+    String newDataDirs = oldLocations.get(0).toString() + "," + newLoc;
+
+    try {
+      dn.parseChangedVolumes(newDataDirs);
+      fail("should throw IOE because storage type changes.");
+    } catch (IOException e) {
+      GenericTestUtils.assertExceptionContains(
+          "Changing storage type is not allowed", e);
+    }
+  }
+
   /** Add volumes to the first DataNode. */
   private void addVolumes(int numNewVolumes)
       throws ReconfigurationException, IOException {