HADOOP-17999. No-op implementation of setWriteChecksum and setVerifyChecksum in ViewFileSystem. Contributed by Abhishek Das. (#3639)

(cherry picked from commit 54a1d78e16533e286455de62a545ee75cbc1eff5)

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/viewfs/ViewFileSystem.java

@@ -776,13 +776,9 @@ public class ViewFileSystem extends FileSystem {
   }
 
   @Override
-  public void setVerifyChecksum(final boolean verifyChecksum) { 
-    List<InodeTree.MountPoint<FileSystem>> mountPoints = 
-        fsState.getMountPoints();
-    Map<String, FileSystem> fsMap = initializeMountedFileSystems(mountPoints);
-    for (InodeTree.MountPoint<FileSystem> mount : mountPoints) {
-      fsMap.get(mount.src).setVerifyChecksum(verifyChecksum);
-    }
+  public void setVerifyChecksum(final boolean verifyChecksum) {
+    // This is a file system level operations, however ViewFileSystem
+    // points to many file systems. Noop for ViewFileSystem.
   }
 
   /**
@@ -874,13 +870,9 @@ public class ViewFileSystem extends FileSystem {
   }
 
   @Override
-  public void setWriteChecksum(final boolean writeChecksum) { 
-    List<InodeTree.MountPoint<FileSystem>> mountPoints = 
-        fsState.getMountPoints();
-    Map<String, FileSystem> fsMap = initializeMountedFileSystems(mountPoints);
-    for (InodeTree.MountPoint<FileSystem> mount : mountPoints) {
-      fsMap.get(mount.src).setWriteChecksum(writeChecksum);
-    }
+  public void setWriteChecksum(final boolean writeChecksum) {
+    // This is a file system level operations, however ViewFileSystem
+    // points to many file systems. Noop for ViewFileSystem.
   }
 
   @Override

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/fs/viewfs/TestViewFileSystemDelegation.java

@@ -83,12 +83,6 @@ public class TestViewFileSystemDelegation { //extends ViewFileSystemTestSetup {
     assertEquals(new URI("fs2:/").getAuthority(), fs2.getUri().getAuthority());
   }
   
-  @Test
-  public void testVerifyChecksum() throws Exception {
-    checkVerifyChecksum(false);
-    checkVerifyChecksum(true);
-  }
-
   /**
    * Tests that ViewFileSystem dispatches calls for every ACL method through the
    * mount table to the correct underlying FileSystem with all Path arguments
@@ -144,12 +138,6 @@ public class TestViewFileSystemDelegation { //extends ViewFileSystemTestSetup {
     verify(mockFs2).getAclStatus(mockFsPath2);
   }
 
-  void checkVerifyChecksum(boolean flag) {
-    viewFs.setVerifyChecksum(flag);
-    assertEquals(flag, fs1.getVerifyChecksum());
-    assertEquals(flag, fs2.getVerifyChecksum());
-  }
-
   static class FakeFileSystem extends LocalFileSystem {
     boolean verifyChecksum = true;
     URI uri;

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/fs/viewfs/ViewFileSystemBaseTest.java

@@ -1129,4 +1129,47 @@ abstract public class ViewFileSystemBaseTest {
     // viewfs inner cache is disabled
     assertEquals(cacheSize + 2, TestFileUtil.getCacheSize());
   }
+
+  @Test
+  public void testTargetFileSystemLazyInitializationForChecksumMethods()
+      throws Exception {
+    final String clusterName = "cluster" + new Random().nextInt();
+    Configuration config = new Configuration(conf);
+    config.setBoolean(CONFIG_VIEWFS_ENABLE_INNER_CACHE, false);
+    config.setClass("fs.othermockfs.impl",
+        TestChRootedFileSystem.MockFileSystem.class, FileSystem.class);
+    ConfigUtil.addLink(config, clusterName, "/user",
+        URI.create("othermockfs://mockauth1/mockpath"));
+    ConfigUtil.addLink(config, clusterName,
+        "/mock", URI.create("othermockfs://mockauth/mockpath"));
+
+    final int cacheSize = TestFileUtil.getCacheSize();
+    ViewFileSystem viewFs = (ViewFileSystem) FileSystem.get(
+        new URI("viewfs://" + clusterName + "/"), config);
+
+    // As no inner file system instance has been initialized,
+    // cache size will remain the same
+    // cache is disabled for viewfs scheme, so the viewfs:// instance won't
+    // go in the cache even after the initialization
+    assertEquals(cacheSize, TestFileUtil.getCacheSize());
+
+    // This is not going to initialize any filesystem instance
+    viewFs.setVerifyChecksum(true);
+
+    // Cache size will remain the same
+    assertEquals(cacheSize, TestFileUtil.getCacheSize());
+
+    // This resolve path will initialize the file system corresponding
+    // to the mount table entry of the path "/user"
+    viewFs.getFileChecksum(
+        new Path(String.format("viewfs://%s/%s", clusterName, "/user")));
+
+    // Cache size will increase by 1.
+    assertEquals(cacheSize + 1, TestFileUtil.getCacheSize());
+
+    viewFs.close();
+    // Initialized FileSystem instances will not be removed from cache as
+    // viewfs inner cache is disabled
+    assertEquals(cacheSize + 1, TestFileUtil.getCacheSize());
+  }
 }