HDFS-16972. Delete a snapshot may deleteCurrentFile. (#5532)

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FsImageValidation.java

@@ -77,6 +77,12 @@ public class FsImageValidation {
 
   static final String FS_IMAGE = "FS_IMAGE";
 
+  static String getEnv(String property) {
+    final String value = System.getenv().get(property);
+    LOG.info("ENV: {} = {}", property, value);
+    return value;
+  }
+
   static FsImageValidation newInstance(String... args) {
     final String f = Cli.parse(args);
     if (f == null) {
@@ -302,10 +308,7 @@ public class FsImageValidation {
     static String parse(String... args) {
       final String f;
       if (args == null || args.length == 0) {
-        f = System.getenv().get(FS_IMAGE);
-        if (f != null) {
-          println("Environment variable %s = %s", FS_IMAGE, f);
-        }
+        f = getEnv(FS_IMAGE);
       } else if (args.length == 1) {
         f = args[0];
       } else {

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/INode.java

@@ -49,6 +49,7 @@ import java.io.PrintWriter;
 import java.io.StringWriter;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 
 /**
  * We keep an in-memory representation of the file/block hierarchy.
@@ -1016,6 +1017,8 @@ public abstract class INode implements INodeAttributes, Diff.Element<byte[]> {
     /** Used to collect quota usage delta */
     private final QuotaDelta quotaDelta;
 
+    private Snapshot snapshotToBeDeleted = null;
+
     /**
      * @param bsps
      *      block storage policy suite to calculate intended storage type
@@ -1037,6 +1040,36 @@ public abstract class INode implements INodeAttributes, Diff.Element<byte[]> {
       this.quotaDelta = new QuotaDelta();
     }
 
+    /**
+     * Set the snapshot to be deleted
+     * for {@link FSEditLogOpCodes#OP_DELETE_SNAPSHOT}.
+     *
+     * @param snapshot the snapshot to be deleted
+     */
+    public void setSnapshotToBeDeleted(Snapshot snapshot) {
+      this.snapshotToBeDeleted = Objects.requireNonNull(
+          snapshot, "snapshot == null");
+    }
+
+    /**
+     * For {@link FSEditLogOpCodes#OP_DELETE_SNAPSHOT},
+     * return the snapshot to be deleted.
+     * For other ops, return {@link Snapshot#CURRENT_STATE_ID}.
+     */
+    public int getSnapshotIdToBeDeleted() {
+      return Snapshot.getSnapshotId(snapshotToBeDeleted);
+    }
+
+    public int getSnapshotIdToBeDeleted(int snapshotId, INode inode) {
+      final int snapshotIdToBeDeleted = getSnapshotIdToBeDeleted();
+      if (snapshotId != snapshotIdToBeDeleted) {
+        LOG.warn("Snapshot changed: current = {}, original = {}, inode: {}",
+            Snapshot.getSnapshotString(snapshotId), snapshotToBeDeleted,
+            inode.toDetailString());
+      }
+      return snapshotIdToBeDeleted;
+    }
+
     public BlockStoragePolicySuite storagePolicySuite() {
       return bsps;
     }
@@ -1054,8 +1087,11 @@ public abstract class INode implements INodeAttributes, Diff.Element<byte[]> {
      * removedUCFiles but a new quotaDelta.
      */
     public ReclaimContext getCopy() {
-      return new ReclaimContext(bsps, collectedBlocks, removedINodes,
+      final ReclaimContext that = new ReclaimContext(
+          bsps, collectedBlocks, removedINodes,
           removedUCFiles);
+      that.snapshotToBeDeleted = this.snapshotToBeDeleted;
+      return that;
     }
   }
 

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/INodeReference.java

@@ -35,32 +35,48 @@ import org.apache.hadoop.hdfs.server.namenode.visitor.NamespaceVisitor;
 import org.apache.hadoop.security.AccessControlException;
 
 /**
- * An anonymous reference to an inode.
- *
+ * A reference to an inode.
+ * <p>
  * This class and its subclasses are used to support multiple access paths.
  * A file/directory may have multiple access paths when it is stored in some
- * snapshots and it is renamed/moved to other locations.
- * 
+ * snapshots, and it is renamed/moved to other locations.
+ * <p>
  * For example,
- * (1) Suppose we have /abc/foo, say the inode of foo is inode(id=1000,name=foo)
- * (2) create snapshot s0 for /abc
+ * (1) Suppose we have /abc/foo and the inode is inode(id=1000,name=foo).
+ *     Suppose foo is created after snapshot s0,
+ *     i.e. foo is not in s0 and inode(id=1000,name=foo)
+ *     is in the create-list of /abc for the s0 diff entry.
+ * (2) Create snapshot s1, s2 for /abc, i.e. foo is in s1 and s2.
+ *     Suppose sDst is the last snapshot /xyz.
  * (3) mv /abc/foo /xyz/bar, i.e. inode(id=1000,name=...) is renamed from "foo"
  *     to "bar" and its parent becomes /xyz.
- * 
- * Then, /xyz/bar and /abc/.snapshot/s0/foo are two different access paths to
- * the same inode, inode(id=1000,name=bar).
- *
+ * <p>
+ * Then, /xyz/bar, /abc/.snapshot/s1/foo and /abc/.snapshot/s2/foo
+ * are different access paths to the same inode, inode(id=1000,name=bar).
+ * Inside the inode tree, /abc/.snapshot/s1/foo and /abc/.snapshot/s2/foo
+ * indeed have the same resolved path,
+ * but /xyz/bar has a different resolved path.
+ * <p>
  * With references, we have the following
- * - /abc has a child ref(id=1001,name=foo).
- * - /xyz has a child ref(id=1002) 
- * - Both ref(id=1001,name=foo) and ref(id=1002) point to another reference,
- *   ref(id=1003,count=2).
- * - Finally, ref(id=1003,count=2) points to inode(id=1000,name=bar).
- * 
- * Note 1: For a reference without name, e.g. ref(id=1002), it uses the name
- *         of the referred inode.
+ * - The source /abc/foo inode(id=1000,name=foo) is replaced with
+ *   a WithName(name=foo,lastSnapshot=s2) and then it is moved
+ *   to the delete-list of /abc for the s2 diff entry.
+ *   The replacement also replaces inode(id=1000,name=foo)
+ *   in the create-list of /abc for the s0 diff entry with the WithName.
+ *   The same as before, /abc/foo is in s1 and s2, but not in s0.
+ * - The destination /xyz adds a child DstReference(dstSnapshot=sDst).
+ *   DstReference is added to the create-list of /xyz for the sDst diff entry.
+ *   /xyz/bar is not in sDst.
+ * - Both WithName and DstReference point to another reference WithCount(count=2).
+ * - Finally, WithCount(count=2) points to inode(id=1000,name=bar)
+ *   Note that the inode name is changed to "bar".
+ * <p>
+ * Note 1: References other than WithName use the name of the referred inode,
+ *         i.e. WithCount and DstReference do not have their own name.
  * Note 2: getParent() always returns the parent in the current state, e.g.
  *         inode(id=1000,name=bar).getParent() returns /xyz but not /abc.
+ * Note 3: {@link INodeReference#getId()} returns the id the referred inode,
+ *         e.g. all WithName, DstReference and WithCount above return id=1000.
  */
 public abstract class INodeReference extends INode {
   /** Assert the relationship this node and the references. */
@@ -409,9 +425,9 @@ public abstract class INodeReference extends INode {
       final StringBuilder b = new StringBuilder("[");
       if (!withNameList.isEmpty()) {
         final Iterator<WithName> i = withNameList.iterator();
-        b.append(i.next().getFullPathAndObjectString());
+        b.append(i.next().getNameDetails());
         for(; i.hasNext();) {
-          b.append(", ").append(i.next().getFullPathAndObjectString());
+          b.append(", ").append(i.next().getNameDetails());
         }
       }
       b.append("]");
@@ -548,7 +564,9 @@ public abstract class INodeReference extends INode {
 
     /**
      * The id of the last snapshot in the src tree when this WithName node was 
-     * generated. When calculating the quota usage of the referred node, only 
+     * generated, i.e. this reference is in that snapshot.
+     * <p>
+     * When calculating the quota usage of the referred node, only
      * the files/dirs existing when this snapshot was taken will be counted for 
      * this WithName node and propagated along its ancestor path.
      */
@@ -564,6 +582,11 @@ public abstract class INodeReference extends INode {
       INodeReferenceValidation.add(this, WithName.class);
     }
 
+    String getNameDetails() {
+      return getClass().getSimpleName() + "[" + getLocalName()
+          + ", lastSnapshot=" + lastSnapshotId + "]";
+    }
+
     @Override
     void assertReferences() {
       final INode ref= getReferredINode();
@@ -673,7 +696,7 @@ public abstract class INodeReference extends INode {
         reclaimContext.quotaDelta().setCounts(old);
       }
     }
-    
+
     @Override
     public void destroyAndCollectBlocks(ReclaimContext reclaimContext) {
       int snapshot = getSelfSnapshot();
@@ -727,7 +750,8 @@ public abstract class INodeReference extends INode {
   
   public static class DstReference extends INodeReference {
     /**
-     * Record the latest snapshot of the dst subtree before the rename. For
+     * Record the latest snapshot of the dst subtree before the rename,
+     * i.e. this reference is NOT in that snapshot.  For
      * later operations on the moved/renamed files/directories, if the latest
      * snapshot is after this dstSnapshot, changes will be recorded to the
      * latest snapshot. Otherwise changes will be recorded to the snapshot
@@ -752,6 +776,11 @@ public abstract class INodeReference extends INode {
       INodeReferenceValidation.add(this, DstReference.class);
     }
 
+    String getDstDetails() {
+      return getClass().getSimpleName() + "[" + getLocalName()
+          + ", dstSnapshot=" + dstSnapshotId + "]";
+    }
+
     @Override
     void assertReferences() {
       final INode ref = getReferredINode();
@@ -794,7 +823,27 @@ public abstract class INodeReference extends INode {
         getReferredINode().cleanSubtree(reclaimContext, snapshot, prior);
       }
     }
-    
+
+    /**
+     * When dstSnapshotId >= snapshotToBeDeleted,
+     * this reference is not in snapshotToBeDeleted.
+     * This reference should not be destroyed.
+     *
+     * @param context to {@link ReclaimContext#getSnapshotIdToBeDeleted()}
+     */
+    private boolean shouldDestroy(ReclaimContext context) {
+      final int snapshotToBeDeleted = context.getSnapshotIdToBeDeleted();
+      if (dstSnapshotId < snapshotToBeDeleted) {
+        return true;
+      }
+      LOG.warn("Try to destroy a DstReference with dstSnapshotId = {}"
+          + " >= snapshotToBeDeleted = {}", dstSnapshotId, snapshotToBeDeleted);
+      LOG.warn("    dstRef: {}", toDetailString());
+      final INode r = getReferredINode().asReference().getReferredINode();
+      LOG.warn("  referred: {}", r.toDetailString());
+      return false;
+    }
+
     /**
      * {@inheritDoc}
      * <br>
@@ -808,6 +857,10 @@ public abstract class INodeReference extends INode {
      */
     @Override
     public void destroyAndCollectBlocks(ReclaimContext reclaimContext) {
+      if (!shouldDestroy(reclaimContext)) {
+        return;
+      }
+
       // since we count everything of the subtree for the quota usage of a
       // dst reference node, here we should just simply do a quota computation.
       // then to avoid double counting, we pass a different QuotaDelta to other

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/snapshot/DirectorySnapshottableFeature.java

@@ -266,6 +266,8 @@ public class DirectorySnapshottableFeature extends DirectoryWithSnapshotFeature
       final Snapshot snapshot = snapshotsByNames.get(i);
       int prior = Snapshot.findLatestSnapshot(snapshotRoot, snapshot.getId());
       snapshotManager.assertPrior(snapshotRoot, snapshotName, prior);
+
+      reclaimContext.setSnapshotToBeDeleted(snapshot);
       snapshotRoot.cleanSubtree(reclaimContext, snapshot.getId(), prior);
       // remove from snapshotsByNames after successfully cleaning the subtree
       snapshotsByNames.remove(i);

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/snapshot/FileWithSnapshotFeature.java

@@ -122,9 +122,12 @@ public class FileWithSnapshotFeature implements INode.Feature {
   public void cleanFile(INode.ReclaimContext reclaimContext,
       final INodeFile file, final int snapshotId, int priorSnapshotId,
       byte storagePolicyId) {
+    final int snapshotToBeDeleted
+        = reclaimContext.getSnapshotIdToBeDeleted(snapshotId, file);
     if (snapshotId == Snapshot.CURRENT_STATE_ID) {
       // delete the current file while the file has snapshot feature
-      if (!isCurrentFileDeleted()) {
+      if (!isCurrentFileDeleted()
+          && snapshotToBeDeleted == Snapshot.CURRENT_STATE_ID) {
         file.recordModification(priorSnapshotId);
         deleteCurrentFile();
       }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/snapshot/Snapshot.java

@@ -94,6 +94,12 @@ public class Snapshot implements Comparable<byte[]> {
     return s == null ? CURRENT_STATE_ID : s.getId();
   }
 
+  public static String getSnapshotString(int snapshot) {
+    return snapshot == CURRENT_STATE_ID? "<CURRENT_STATE>"
+        : snapshot == NO_SNAPSHOT_ID? "<NO_SNAPSHOT>"
+        : "Snapshot #" + snapshot;
+  }
+
   /**
    * Compare snapshot with IDs, where null indicates the current status thus
    * is greater than any non-null snapshot.

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

@@ -53,8 +53,8 @@ public class TestFsImageValidation {
       final int errorCount = FsImageValidation.newInstance().run();
       Assert.assertEquals("Error Count: " + errorCount, 0, errorCount);
     } catch (HadoopIllegalArgumentException e) {
-      LOG.warn("The environment variable {} is not set: {}",
-          FsImageValidation.FS_IMAGE, e);
+      LOG.warn("The environment variable " + FsImageValidation.FS_IMAGE
+          + " is not set", e);
     }
   }
 

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

@@ -17,9 +17,12 @@
  */
 package org.apache.hadoop.hdfs.server.namenode.snapshot;
 
+import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.FileStatus;
 import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.FsShell;
 import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.fs.TrashPolicyDefault;
 import org.apache.hadoop.fs.UnresolvedLinkException;
 import org.apache.hadoop.hdfs.DFSClient;
 import org.apache.hadoop.hdfs.DFSTestUtil;
@@ -42,12 +45,19 @@ import org.apache.hadoop.metrics2.impl.MetricsSystemImpl;
 import org.apache.hadoop.security.UserGroupInformation;
 import org.apache.hadoop.test.GenericTestUtils;
 import org.apache.hadoop.util.GSet;
+import org.apache.log4j.Appender;
+import org.apache.log4j.Layout;
+import org.apache.log4j.LogManager;
+import org.apache.log4j.PatternLayout;
+import org.apache.log4j.WriterAppender;
 import org.junit.Assert;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import java.io.*;
 import java.util.*;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicInteger;
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
@@ -61,18 +71,18 @@ public class SnapshotTestHelper {
   /** Disable the logs that are not very useful for snapshot related tests. */
   public static void disableLogs() {
     final String[] lognames = {
+        "org.eclipse.jetty",
+        "org.apache.hadoop.ipc",
+        "org.apache.hadoop.net",
+        "org.apache.hadoop.security",
+
+        "org.apache.hadoop.hdfs.server.blockmanagement",
         "org.apache.hadoop.hdfs.server.common.Util",
-        "org.apache.hadoop.hdfs.server.blockmanagement.BlockReportLeaseManager",
+        "org.apache.hadoop.hdfs.server.datanode",
         "org.apache.hadoop.hdfs.server.namenode.FileJournalManager",
         "org.apache.hadoop.hdfs.server.namenode.NNStorageRetentionManager",
         "org.apache.hadoop.hdfs.server.namenode.FSImageFormatProtobuf",
         "org.apache.hadoop.hdfs.server.namenode.FSEditLog",
-        "org.apache.hadoop.hdfs.server.datanode.BlockPoolSliceScanner",
-        "org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.BlockPoolSlice",
-        "org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetImpl",
-        "org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetAsyncDiskService",
-        "org.apache.hadoop.hdfs.server.datanode.fsdataset.impl" +
-            ".RamDiskAsyncLazyPersistService",
     };
     for(String n : lognames) {
       GenericTestUtils.disableLog(LoggerFactory.getLogger(n));
@@ -105,6 +115,198 @@ public class SnapshotTestHelper {
     GenericTestUtils.disableLog(Server.LOG);
   }
 
+  static class MyCluster {
+    private final MiniDFSCluster cluster;
+    private final FSNamesystem fsn;
+    private final FSDirectory fsdir;
+    private final DistributedFileSystem hdfs;
+    private final FsShell shell = new FsShell();
+
+    private final Path snapshotDir = new Path("/");
+    private final AtomicInteger snapshotCount = new AtomicInteger();
+    private final AtomicInteger trashMoveCount = new AtomicInteger();
+    private final AtomicInteger printTreeCount = new AtomicInteger();
+    private final AtomicBoolean printTree = new AtomicBoolean();
+
+    MyCluster(Configuration conf) throws Exception {
+      cluster = new MiniDFSCluster.Builder(conf)
+          .numDataNodes(1)
+          .format(true)
+          .build();
+      fsn = cluster.getNamesystem();
+      fsdir = fsn.getFSDirectory();
+
+      cluster.waitActive();
+      hdfs = cluster.getFileSystem();
+      hdfs.allowSnapshot(snapshotDir);
+      createSnapshot();
+
+      shell.setConf(cluster.getConfiguration(0));
+      runShell("-mkdir", "-p", ".Trash");
+    }
+
+    void setPrintTree(boolean print) {
+      printTree.set(print);
+    }
+
+    boolean getPrintTree() {
+      return printTree.get();
+    }
+
+    Path getTrashPath(Path p) throws Exception {
+      final Path trash = hdfs.getTrashRoot(p);
+      final Path resolved = hdfs.resolvePath(p);
+      return new Path(trash, "Current/" + resolved.toUri().getPath());
+    }
+
+    int runShell(String... argv) {
+      return shell.run(argv);
+    }
+
+    String createSnapshot()
+        throws Exception {
+      final String name = "s" + snapshotCount.getAndIncrement();
+      SnapshotTestHelper.createSnapshot(hdfs, snapshotDir, name);
+      return name;
+    }
+
+    void deleteSnapshot(String snapshotName) throws Exception {
+      LOG.info("Before delete snapshot " + snapshotName);
+      hdfs.deleteSnapshot(snapshotDir, snapshotName);
+    }
+
+    boolean assertExists(Path path) throws Exception {
+      if (path == null) {
+        return false;
+      }
+      if (!hdfs.exists(path)) {
+        final String err = "Path not found: " + path;
+        printFs(err);
+        throw new AssertionError(err);
+      }
+      return true;
+    }
+
+    void printFs(String label) {
+      final PrintStream out = System.out;
+      out.println();
+      out.println();
+      out.println("XXX " + printTreeCount.getAndIncrement() + ": " + label);
+      if (printTree.get()) {
+        fsdir.getRoot().dumpTreeRecursively(out);
+      }
+    }
+
+    void shutdown() {
+      LOG.info("snapshotCount: {}", snapshotCount);
+      cluster.shutdown();
+    }
+
+    Path mkdirs(String dir) throws Exception {
+      return mkdirs(new Path(dir));
+    }
+
+    Path mkdirs(Path dir) throws Exception {
+      final String label = "mkdirs " + dir;
+      LOG.info(label);
+      hdfs.mkdirs(dir);
+      Assert.assertTrue(label, hdfs.exists(dir));
+      return dir;
+    }
+
+    Path createFile(String file) throws Exception {
+      return createFile(new Path(file));
+    }
+
+    Path createFile(Path file) throws Exception {
+      final String label = "createFile " + file;
+      LOG.info(label);
+      DFSTestUtil.createFile(hdfs, file, 0, (short)1, 0L);
+      Assert.assertTrue(label, hdfs.exists(file));
+      return file;
+    }
+
+    String rename(Path src, Path dst) throws Exception {
+      assertExists(src);
+      final String snapshot = createSnapshot();
+
+      final String label = "rename " + src + " -> " + dst;
+      final boolean renamed = hdfs.rename(src, dst);
+      LOG.info("{}: success? {}", label, renamed);
+      Assert.assertTrue(label, renamed);
+      return snapshot;
+    }
+
+    Path moveToTrash(Path path, boolean printFs) throws Exception {
+      return moveToTrash(path.toString(), printFs);
+    }
+
+    Path moveToTrash(String path, boolean printFs) throws Exception {
+      final Log4jRecorder recorder = Log4jRecorder.record(
+          LoggerFactory.getLogger(TrashPolicyDefault.class));
+      runShell("-rm", "-r", path);
+      final String label = "moveToTrash-" + trashMoveCount.getAndIncrement() + " " + path;
+      if (printFs) {
+        printFs(label);
+      } else {
+        LOG.info(label);
+      }
+      final String recorded = recorder.getRecorded();
+      LOG.info("Recorded: {}", recorded);
+
+      final String pattern = " to trash at: ";
+      final int i = recorded.indexOf(pattern);
+      if (i > 0) {
+        final String sub = recorded.substring(i + pattern.length());
+        return new Path(sub.trim());
+      }
+      return null;
+    }
+  }
+
+  /** Records log messages from a Log4j logger. */
+  public static final class Log4jRecorder {
+    static Log4jRecorder record(org.slf4j.Logger logger) {
+      return new Log4jRecorder(toLog4j(logger), getLayout());
+    }
+
+    static org.apache.log4j.Logger toLog4j(org.slf4j.Logger logger) {
+      return LogManager.getLogger(logger.getName());
+    }
+
+    static Layout getLayout() {
+      final org.apache.log4j.Logger root
+          = org.apache.log4j.Logger.getRootLogger();
+      Appender a = root.getAppender("stdout");
+      if (a == null) {
+        a = root.getAppender("console");
+      }
+      return a == null? new PatternLayout() : a.getLayout();
+    }
+
+    private final StringWriter stringWriter = new StringWriter();
+    private final WriterAppender appender;
+    private final org.apache.log4j.Logger logger;
+
+    private Log4jRecorder(org.apache.log4j.Logger logger, Layout layout) {
+      this.appender = new WriterAppender(layout, stringWriter);
+      this.logger = logger;
+      this.logger.addAppender(this.appender);
+    }
+
+    public String getRecorded() {
+      return stringWriter.toString();
+    }
+
+    public void stop() {
+      logger.removeAppender(appender);
+    }
+
+    public void clear() {
+      stringWriter.getBuffer().setLength(0);
+    }
+  }
+
   private SnapshotTestHelper() {
     // Cannot be instantinatied
   }

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

@@ -0,0 +1,394 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.hdfs.server.namenode.snapshot;
+
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.CommonConfigurationKeys;
+import org.apache.hadoop.fs.Path;
+import org.junit.After;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.concurrent.ThreadLocalRandom;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.function.Function;
+
+/**
+ * Testing snapshots with FsShell move-to-trash feature.
+ */
+public class TestFsShellMoveToTrashWithSnapshots {
+  static {
+    SnapshotTestHelper.disableLogs();
+  }
+
+  private static final Logger LOG =
+      LoggerFactory.getLogger("XXX");
+
+  private static final String TMP = ".tmp";
+  private static final String WAREHOUSE_DIR = "/warehouse/sub/";
+  private static final String TO_BE_REMOVED = "TMP/";
+
+  private static SnapshotTestHelper.MyCluster cluster;
+
+  @Before
+  public void setUp() throws Exception {
+    final Configuration conf = new Configuration();
+    conf.setInt(CommonConfigurationKeys.FS_TRASH_INTERVAL_KEY, 100);
+    cluster = new SnapshotTestHelper.MyCluster(conf);
+  }
+
+  @After
+  public void tearDown() throws Exception {
+    if (cluster != null) {
+      cluster.shutdown();
+      cluster = null;
+    }
+  }
+
+  static class MyDirs {
+    private final Path base;
+    private final boolean[] moved;
+    private final List<Integer> renames = new ArrayList<>();
+
+    MyDirs(Path base, int depth) {
+      this.base = base;
+      this.moved = new boolean[depth];
+
+      for (int i = 0; i < depth; i++) {
+        renames.add(i);
+      }
+      Collections.shuffle(renames);
+    }
+
+    int depth() {
+      return moved.length;
+    }
+
+    DeleteSnapshotOp rename() throws Exception {
+      final int i = renames.remove(renames.size() - 1);
+      final String snapshot = cluster.rename(getSubPath(i + 1), getSubPath(i));
+      moved[i] = true;
+      return new DeleteSnapshotOp(snapshot);
+    }
+
+    Path getSubPath(int n) {
+      if (n == 0) {
+        return base;
+      }
+      final StringBuilder b = new StringBuilder();
+      for (int i = 0; i < n; i++) {
+        if (!moved[i]) {
+          b.append(TO_BE_REMOVED);
+        }
+        b.append("dir").append(i).append("/");
+      }
+      return new Path(base, b.toString());
+    }
+
+    Path getPath() {
+      return getSubPath(moved.length);
+    }
+  }
+
+  static class MyFile {
+    private final Path tmp;
+    private Path dst;
+    private Path trash;
+
+    MyFile(String filePath) {
+      this.tmp = new Path(filePath + TMP);
+    }
+
+    @Override
+    public String toString() {
+      return "MyFile{" +
+          "tmp=" + tmp +
+          ", dst=" + dst +
+          ", trash=" + trash +
+          '}';
+    }
+
+    synchronized Path getPath() {
+      return trash != null ? trash
+          : dst != null ? dst
+          : tmp;
+    }
+
+    synchronized String moveFromTmp2Dst(Path dstDir) throws Exception {
+      final String tmpName = tmp.getName();
+      dst = new Path(dstDir, tmpName.substring(0, tmpName.length() - 4));
+      final String snapshot = cluster.rename(tmp, dst);
+      trash = cluster.getTrashPath(dst);
+      return snapshot;
+    }
+  }
+
+  MyFile createTmp(String filePath) throws Exception {
+    final MyFile f = new MyFile(filePath);
+    cluster.createFile(f.tmp);
+    return f;
+  }
+
+  DeleteSnapshotOp moveFromTmp2Dst(MyFile file, Path dstDir) throws Exception {
+    final String snapshot = file.moveFromTmp2Dst(dstDir);
+    return new DeleteSnapshotOp(snapshot);
+  }
+
+  List<MyFile> runTestMoveToTrashWithShell(
+      Path dbDir, Path tmpDir, int numFiles)
+      throws Exception {
+    return runTestMoveToTrashWithShell(dbDir, tmpDir, numFiles, 4, null);
+  }
+
+  List<MyFile> runTestMoveToTrashWithShell(
+      Path dbDir, Path tmpDir, int numFiles, int depth, Integer randomSleepMaxMs)
+      throws Exception {
+    LOG.info("dbDir={}", dbDir);
+    LOG.info("tmpDir={}", tmpDir);
+    LOG.info("numFiles={}, depth={}, randomSleepMaxMs={}", numFiles, depth, randomSleepMaxMs);
+    cluster.setPrintTree(numFiles < 10);
+
+    final List<Op> ops = new ArrayList<>();
+    createSnapshot(ops);
+
+    //swap sub1 and sub2
+    Path sub1 = cluster.mkdirs(new Path(dbDir, "sub1"));
+    Path sub2 = cluster.mkdirs(new Path(sub1, "sub2"));
+
+    ops.add(new DeleteSnapshotOp(cluster.rename(sub2, dbDir)));
+    sub2 = new Path(dbDir, "sub2");
+    ops.add(new DeleteSnapshotOp(cluster.rename(sub1, sub2)));
+    sub1 = new Path(sub2, "sub1");
+
+    final MyDirs dirs = new MyDirs(sub1, depth);
+    cluster.mkdirs(dirs.getPath());
+    final List<MyFile> buckets = new ArrayList<>();
+
+    for (int i = 0; i < dirs.depth() / 2; i++) {
+      ops.add(dirs.rename());
+    }
+    final int offset = numFiles / 4;
+    for (int i = 0; i < numFiles; i++) {
+      final String bucket = tmpDir + String.format("/bucket_%04d", i);
+      createSnapshot(ops);
+      buckets.add(createTmp(bucket));
+      if (i >= offset) {
+        final int j = i - offset;
+        ops.add(moveFromTmp2Dst(buckets.get(j), dirs.getPath()));
+      }
+      if (randomSleepMaxMs != null) {
+        Thread.sleep(ThreadLocalRandom.current().nextInt(randomSleepMaxMs));
+      }
+    }
+
+    for (int i = dirs.depth() / 2; i < dirs.depth(); i++) {
+      ops.add(dirs.rename());
+    }
+
+    ops.add(new DeleteSnapshotOp(cluster.rename(dirs.getSubPath(1), sub2)));
+    ops.add(new DeleteSnapshotOp(cluster.rename(sub1, dbDir)));
+    sub1 = new Path(dbDir, "sub1");
+    ops.add(new DeleteSnapshotOp(cluster.rename(sub2, sub1)));
+    sub2 = new Path(sub1, "sub2");
+    ops.add(new DeleteSnapshotOp(cluster.rename(sub2, new Path(sub1, "sub1"))));
+    ops.add(new DeleteSnapshotOp(cluster.rename(sub1, new Path(dbDir, "sub2"))));
+
+    final MoveToTrashOp m = new MoveToTrashOp(dbDir);
+    m.trashPath.thenAccept(p -> updateTrashPath(p, buckets));
+    ops.add(m);
+
+    LOG.info("ops count: {}", ops.size());
+    while (!ops.isEmpty()) {
+      runOneOp(ops);
+    }
+    cluster.printFs("END");
+    return buckets;
+  }
+
+  static Path removeSubstring(Path p) {
+    if (p == null) {
+      return null;
+    }
+    return new Path(p.toUri().getPath().replace(TO_BE_REMOVED, ""));
+  }
+
+  void updateTrashPath(String trashPathPrefix, List<MyFile> files) {
+    final String commonPrefix;
+    final int j = trashPathPrefix.lastIndexOf('/');
+    commonPrefix = trashPathPrefix.substring(0, j + 1);
+
+    for (MyFile f : files) {
+      final String original = f.trash.toUri().getPath();
+      if (!original.startsWith(trashPathPrefix)) {
+        Assert.assertTrue(original.startsWith(commonPrefix));
+
+        final int i = original.indexOf('/', commonPrefix.length());
+        final String suffix = original.substring(i + 1);
+        f.trash = new Path(trashPathPrefix, suffix);
+      }
+    }
+  }
+
+  @Test(timeout = 300_000)
+  public void test100tasks20files() throws Exception {
+    runMultipleTasks(100, 20);
+  }
+
+  @Test(timeout = 300_000)
+  public void test10tasks200files() throws Exception {
+    runMultipleTasks(10, 200);
+  }
+
+  void runMultipleTasks(int numTasks, int filesPerTask) throws Exception {
+    final List<Future<List<MyFile>>> futures = new ArrayList<>();
+    final List<MyFile> buckets = new ArrayList<>();
+
+    final ExecutorService executor = Executors.newFixedThreadPool(10);
+    try {
+      for (int i = 0; i < numTasks; i++) {
+        final String db = "db" + i;
+        final String tmp = "tmp" + i;
+        futures.add(executor.submit(() -> {
+          final Path dbDir = cluster.mkdirs(WAREHOUSE_DIR + db);
+          final Path tmpDir = cluster.mkdirs(WAREHOUSE_DIR + tmp);
+          return runTestMoveToTrashWithShell(dbDir, tmpDir, filesPerTask, 4, 100);
+        }));
+      }
+
+      for (Future<List<MyFile>> f : futures) {
+        buckets.addAll(f.get());
+      }
+    } finally {
+      executor.shutdown();
+    }
+    assertExists(buckets, f -> removeSubstring(f.getPath()));
+  }
+
+  @Test(timeout = 100_000)
+  public void test4files() throws Exception {
+    final Path dbDir = cluster.mkdirs(WAREHOUSE_DIR + "db");
+    final Path tmpDir = cluster.mkdirs(WAREHOUSE_DIR + "tmp");
+    final List<MyFile> buckets = runTestMoveToTrashWithShell(
+        dbDir, tmpDir, 4, 2, null);
+    assertExists(buckets, f -> removeSubstring(f.getPath()));
+  }
+
+  @Test(timeout = 300_000)
+  public void test200files() throws Exception {
+    final Path dbDir = cluster.mkdirs(WAREHOUSE_DIR + "db");
+    final Path tmpDir = cluster.mkdirs(WAREHOUSE_DIR + "tmp");
+    final List<MyFile> buckets = runTestMoveToTrashWithShell(
+        dbDir, tmpDir, 200);
+    assertExists(buckets, f -> removeSubstring(f.getPath()));
+  }
+
+  @Test(timeout = 300_000)
+  public void test50files10times() throws Exception {
+    final Path tmpDir = cluster.mkdirs(WAREHOUSE_DIR + "tmp");
+    final List<MyFile> buckets = new ArrayList<>();
+    for (int i = 0; i < 10; i++) {
+      final Path dbDir = cluster.mkdirs(WAREHOUSE_DIR + "db");
+      buckets.addAll(runTestMoveToTrashWithShell(dbDir, tmpDir, 50));
+    }
+    cluster.setPrintTree(true);
+    cluster.printFs("test_10files_10times");
+    assertExists(buckets, f -> removeSubstring(f.getPath()));
+  }
+
+  static void createSnapshot(List<Op> ops) throws Exception {
+    if (ThreadLocalRandom.current().nextBoolean()) {
+      ops.add(new DeleteSnapshotOp(cluster.createSnapshot()));
+    }
+  }
+
+  void runOneOp(List<Op> ops) throws Exception {
+    Collections.shuffle(ops);
+
+    final Op op = ops.remove(ops.size() - 1);
+    if (op instanceof MoveToTrashOp) {
+      createSnapshot(ops);
+    }
+    op.execute();
+  }
+
+  static abstract class Op {
+    private final AtomicBoolean executed = new AtomicBoolean();
+
+    final void execute() throws Exception {
+      if (executed.compareAndSet(false, true)) {
+        executeImpl();
+      }
+    }
+
+    final boolean isExecuted() {
+      return executed.get();
+    }
+
+    abstract void executeImpl() throws Exception;
+  }
+
+  static class MoveToTrashOp extends Op {
+    private final Path path;
+    private final CompletableFuture<String> trashPath = new CompletableFuture<>();
+
+    MoveToTrashOp(Path path) {
+      this.path = path;
+    }
+
+    @Override
+    public void executeImpl() throws Exception {
+      final Path p = cluster.moveToTrash(path, true);
+      LOG.info("MoveToTrash: {} -> {}", path, p);
+      trashPath.complete(p.toUri().getPath());
+    }
+  }
+
+  static class DeleteSnapshotOp extends Op {
+    private final String name;
+
+    DeleteSnapshotOp(String name) {
+      this.name = name;
+    }
+
+    @Override
+    void executeImpl() throws Exception {
+      cluster.deleteSnapshot(name);
+    }
+  }
+
+  void assertExists(List<MyFile> files, Function<MyFile, Path> getPath)
+      throws Exception {
+    for (MyFile f : files) {
+      final Path p = getPath.apply(f);
+      final boolean exists = cluster.assertExists(p);
+      if (cluster.getPrintTree()) {
+        LOG.info("{} exists? {}, {}", p, exists, f);
+      }
+    }
+  }
+}