MAPREDUCE-5197. Add a service for checkpointing task state.

Contributed by Carlo Curino


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1551726 13f79535-47bb-0310-9956-ffa450edef68

hadoop-mapreduce-project/CHANGES.txt

@@ -71,6 +71,9 @@ Trunk (Unreleased)
     MAPREDUCE-5014. Extend Distcp to accept a custom CopyListing.
     (Srikanth Sundarrajan via amareshwari)
 
+    MAPREDUCE-5197. Add a service for checkpointing task state.
+    (Carlo Curino via cdouglas)
+
   BUG FIXES
 
     MAPREDUCE-4272. SortedRanges.Range#compareTo is not spec compliant.

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/checkpoint/CheckpointID.java

@@ -0,0 +1,30 @@
+/**
+ * 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.mapreduce.checkpoint;
+
+import org.apache.hadoop.io.Writable;
+
+/**
+ * This class represent the identified (memento) for a checkpoint. It is allowed
+ * to contain small amount of metadata about a checkpoint and must provide
+ * sufficient information to the corresponding CheckpointService to locate and
+ * retrieve the data contained in the checkpoint.
+ */
+public interface CheckpointID extends Writable {
+
+}

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/checkpoint/CheckpointNamingService.java

@@ -0,0 +1,31 @@
+/**
+ * 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.mapreduce.checkpoint;
+
+/**
+ * This class represent a naming service for checkpoints.
+ */
+public interface CheckpointNamingService {
+
+  /**
+   * Generate a new checkpoint Name
+   * @return the checkpoint name
+   */
+  public String getNewName();
+
+}

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/checkpoint/CheckpointService.java

@@ -0,0 +1,100 @@
+/**
+ * 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.mapreduce.checkpoint;
+
+import java.io.IOException;
+import java.nio.channels.ReadableByteChannel;
+import java.nio.channels.WritableByteChannel;
+
+/**
+ * The CheckpointService provides a simple API to store and retrieve the state of a task.
+ *
+ * Checkpoints are atomic, single-writer, write-once, multiple-readers,
+ * ready-many type of objects. This is provided by releasing the CheckpointID
+ * for a checkpoint only upon commit of the checkpoint, and by preventing a
+ * checkpoint to be re-opened for writes.
+ *
+ * Non-functional properties such as durability, availability, compression,
+ * garbage collection, quotas are left to the implementation.
+ *
+ * This API is envisioned as the basic building block for a checkpoint service,
+ * on top of which richer interfaces can be layered (e.g., frameworks providing
+ * object-serialization, checkpoint metadata and provenance, etc.)
+ *
+ */
+public interface CheckpointService {
+
+  public interface CheckpointWriteChannel extends WritableByteChannel { }
+  public interface CheckpointReadChannel extends ReadableByteChannel { }
+
+  /**
+   * This method creates a checkpoint and provide a channel to write to it. The
+   * name/location of the checkpoint are unknown to the user as of this time, in
+   * fact, the CheckpointID is not released to the user until commit is called.
+   * This makes enforcing atomicity of writes easy.
+   * @return a channel that can be used to write to the checkpoint
+   * @throws IOException
+   * @throws InterruptedException
+   */
+  public CheckpointWriteChannel create()
+    throws IOException, InterruptedException;
+
+  /**
+   * Used to finalize and existing checkpoint. It returns the CheckpointID that
+   * can be later used to access (read-only) this checkpoint. This guarantees
+   * atomicity of the checkpoint.
+   * @param ch the CheckpointWriteChannel to commit
+   * @return a CheckpointID
+   * @throws IOException
+   * @throws InterruptedException
+   */
+  public CheckpointID commit(CheckpointWriteChannel ch)
+    throws IOException, InterruptedException;
+
+  /**
+   * Dual to commit, it aborts the current checkpoint. Garbage collection
+   * choices are left to the implementation. The CheckpointID is not generated
+   * nor released to the user so the checkpoint is not accessible.
+   * @param ch the CheckpointWriteChannel to abort
+   * @throws IOException
+   * @throws InterruptedException
+   */
+  public void abort(CheckpointWriteChannel ch)
+      throws IOException, InterruptedException;
+
+  /**
+   * Given a CheckpointID returns a reading channel.
+   * @param id CheckpointID for the checkpoint to be opened
+   * @return a CheckpointReadChannel
+   * @throws IOException
+   * @throws InterruptedException
+   */
+  public CheckpointReadChannel open(CheckpointID id)
+    throws IOException, InterruptedException;
+
+  /**
+   * It discards an existing checkpoint identified by its CheckpointID.
+   * @param  id CheckpointID for the checkpoint to be deleted
+   * @return a boolean confirming success of the deletion
+   * @throws IOException
+   * @throws InterruptedException
+   */
+  public boolean delete(CheckpointID id)
+    throws IOException, InterruptedException;
+
+}

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/checkpoint/FSCheckpointID.java

@@ -0,0 +1,72 @@
+/**
+ * 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.mapreduce.checkpoint;
+
+import java.io.DataInput;
+import java.io.DataOutput;
+import java.io.IOException;
+
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.io.Text;
+
+/**
+ * A FileSystem based checkpoint ID contains reference to the Path
+ * where the checkpoint has been saved.
+ */
+public class FSCheckpointID implements CheckpointID {
+
+  private Path path;
+
+  public FSCheckpointID(){
+  }
+
+  public FSCheckpointID(Path path) {
+    this.path = path;
+  }
+
+  public Path getPath() {
+    return path;
+  }
+
+  @Override
+  public String toString() {
+    return path.toString();
+  }
+
+  @Override
+  public void write(DataOutput out) throws IOException {
+    Text.writeString(out, path.toString());
+  }
+
+  @Override
+  public void readFields(DataInput in) throws IOException {
+    this.path = new Path(Text.readString(in));
+  }
+
+  @Override
+  public boolean equals(Object other) {
+    return other instanceof FSCheckpointID
+      && path.equals(((FSCheckpointID)other).path);
+  }
+
+  @Override
+  public int hashCode() {
+    return path.hashCode();
+  }
+
+}

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/checkpoint/FSCheckpointService.java

@@ -0,0 +1,193 @@
+/**
+ * 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.mapreduce.checkpoint;
+
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.nio.channels.Channels;
+import java.nio.channels.ReadableByteChannel;
+import java.nio.channels.WritableByteChannel;
+
+import org.apache.hadoop.fs.FSDataInputStream;
+import org.apache.hadoop.fs.FSDataOutputStream;
+import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.Path;
+
+/**
+ * A FileSystem based CheckpointService.
+ */
+public class FSCheckpointService implements CheckpointService {
+
+  private final Path base;
+  private final FileSystem fs;
+  private final CheckpointNamingService namingPolicy;
+  private final short replication;
+
+  public FSCheckpointService(FileSystem fs, Path base,
+      CheckpointNamingService namingPolicy, short replication) {
+    this.fs = fs;
+    this.base = base;
+    this.namingPolicy = namingPolicy;
+    this.replication = replication;
+  }
+
+  public CheckpointWriteChannel create()
+      throws IOException {
+
+    String name = namingPolicy.getNewName();
+
+    Path p = new Path(name);
+    if (p.isUriPathAbsolute()) {
+      throw new IOException("Checkpoint cannot be an absolute path");
+    }
+    return createInternal(new Path(base, p));
+  }
+
+  CheckpointWriteChannel createInternal(Path name) throws IOException {
+
+    //create a temp file, fail if file exists
+    return new FSCheckpointWriteChannel(name, fs.create(tmpfile(name),
+          replication));
+  }
+
+  private static class FSCheckpointWriteChannel
+      implements CheckpointWriteChannel {
+    private boolean isOpen = true;
+    private final Path finalDst;
+    private final WritableByteChannel out;
+
+    FSCheckpointWriteChannel(Path finalDst, FSDataOutputStream out) {
+      this.finalDst = finalDst;
+      this.out = Channels.newChannel(out);
+    }
+
+    public int write(ByteBuffer b) throws IOException {
+      return out.write(b);
+    }
+
+    public Path getDestination() {
+      return finalDst;
+    }
+
+    @Override
+    public void close() throws IOException {
+      isOpen=false;
+      out.close();
+    }
+
+    @Override
+    public boolean isOpen() {
+      return isOpen;
+    }
+
+  }
+
+  @Override
+  public CheckpointReadChannel open(CheckpointID id)
+      throws IOException, InterruptedException {
+      if (!(id instanceof FSCheckpointID)) {
+        throw new IllegalArgumentException(
+            "Mismatched checkpoint type: " + id.getClass());
+      }
+      return new FSCheckpointReadChannel(
+          fs.open(((FSCheckpointID) id).getPath()));
+  }
+
+  private static class FSCheckpointReadChannel
+      implements CheckpointReadChannel {
+
+    private boolean isOpen = true;
+    private final ReadableByteChannel in;
+
+    FSCheckpointReadChannel(FSDataInputStream in){
+      this.in = Channels.newChannel(in);
+    }
+
+    @Override
+    public int read(ByteBuffer bb) throws IOException {
+      return in.read(bb);
+    }
+
+    @Override
+    public void close() throws IOException {
+      isOpen = false;
+      in.close();
+    }
+
+    @Override
+    public boolean isOpen() {
+      return isOpen;
+    }
+
+  }
+
+  @Override
+  public CheckpointID commit(CheckpointWriteChannel ch)
+      throws IOException, InterruptedException {
+    if (ch.isOpen()) {
+      ch.close();
+    }
+    FSCheckpointWriteChannel hch = (FSCheckpointWriteChannel)ch;
+    Path dst = hch.getDestination();
+    if (!fs.rename(tmpfile(dst), dst)) {
+      // attempt to clean up
+      abort(ch);
+      throw new IOException("Failed to promote checkpoint" +
+      		 tmpfile(dst) + " -> " + dst);
+    }
+    return new FSCheckpointID(hch.getDestination());
+  }
+
+  @Override
+  public void abort(CheckpointWriteChannel ch) throws IOException {
+    if (ch.isOpen()) {
+      ch.close();
+    }
+    FSCheckpointWriteChannel hch = (FSCheckpointWriteChannel)ch;
+    Path tmp = tmpfile(hch.getDestination());
+    try {
+      if (!fs.delete(tmp, false)) {
+        throw new IOException("Failed to delete checkpoint during abort");
+      }
+    } catch (FileNotFoundException e) {
+      // IGNORE
+    }
+  }
+
+  @Override
+  public boolean delete(CheckpointID id) throws IOException,
+      InterruptedException {
+    if (!(id instanceof FSCheckpointID)) {
+      throw new IllegalArgumentException(
+          "Mismatched checkpoint type: " + id.getClass());
+    }
+    Path tmp = ((FSCheckpointID)id).getPath();
+    try {
+      return fs.delete(tmp, false);
+    } catch (FileNotFoundException e) {
+      // IGNORE
+    }
+    return true;
+  }
+
+  static final Path tmpfile(Path p) {
+    return new Path(p.getParent(), p.getName() + ".tmp");
+  }
+
+}

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/checkpoint/RandomNameCNS.java

@@ -0,0 +1,32 @@
+/**
+ * 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.mapreduce.checkpoint;
+
+import org.apache.commons.lang.RandomStringUtils;
+
+/**
+ * Simple naming service that generates a random checkpoint name.
+ */
+public class RandomNameCNS implements CheckpointNamingService {
+
+  @Override
+  public String getNewName() {
+    return "checkpoint_" + RandomStringUtils.randomAlphanumeric(8);
+  }
+
+}

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/checkpoint/SimpleNamingService.java

@@ -0,0 +1,39 @@
+/**
+ * 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.mapreduce.checkpoint;
+
+/**
+ * A naming service that simply returns the name it has been initialized with.
+ */
+public class SimpleNamingService implements CheckpointNamingService{
+
+  final String name;
+
+  public SimpleNamingService(String name){
+    this.name = name;
+  }
+
+  /**
+   * Generate a new checkpoint Name
+   * @return the checkpoint name
+   */
+  public String getNewName(){
+    return "checkpoint_" + name;
+  }
+
+}

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/test/java/org/apache/hadoop/mapreduce/checkpoint/TestFSCheckpointID.java

@@ -0,0 +1,48 @@
+/**
+ * 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.mapreduce.checkpoint;
+
+import java.io.IOException;
+
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.io.DataInputBuffer;
+import org.apache.hadoop.io.DataOutputBuffer;
+import org.junit.Test;
+
+public class TestFSCheckpointID {
+
+  @Test
+  public void testFSCheckpointIDSerialization() throws IOException {
+
+    Path inpath = new Path("/tmp/blah");
+    FSCheckpointID cidin = new FSCheckpointID(inpath);
+    DataOutputBuffer out = new DataOutputBuffer();
+    cidin.write(out);
+    out.close();
+
+    FSCheckpointID cidout = new FSCheckpointID(null);
+    DataInputBuffer in = new DataInputBuffer();
+    in.reset(out.getData(), 0, out.getLength());
+    cidout.readFields(in);
+    in.close();
+
+    assert cidin.equals(cidout);
+
+  }
+
+}

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/test/java/org/apache/hadoop/mapreduce/checkpoint/TestFSCheckpointService.java

@@ -0,0 +1,102 @@
+/**
+ * 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.mapreduce.checkpoint;
+
+import java.nio.ByteBuffer;
+
+import java.util.Arrays;
+import java.util.Random;
+
+import org.apache.hadoop.fs.FSDataOutputStream;
+import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.io.DataOutputBuffer;
+import org.apache.hadoop.mapreduce.checkpoint.CheckpointService.CheckpointWriteChannel;
+import org.junit.Test;
+import static org.junit.Assert.*;
+import static org.mockito.Mockito.*;
+import org.mockito.*;
+
+public class TestFSCheckpointService {
+
+  private final int BUFSIZE = 1024;
+
+  @Test
+  public void testCheckpointCreate() throws Exception {
+    checkpointCreate(ByteBuffer.allocate(BUFSIZE));
+  }
+
+  @Test
+  public void testCheckpointCreateDirect() throws Exception {
+    checkpointCreate(ByteBuffer.allocateDirect(BUFSIZE));
+  }
+
+  public void checkpointCreate(ByteBuffer b) throws Exception {
+    int WRITES = 128;
+    FileSystem fs = mock(FileSystem.class);
+    DataOutputBuffer dob = new DataOutputBuffer();
+    FSDataOutputStream hdfs = spy(new FSDataOutputStream(dob, null));
+    @SuppressWarnings("resource") // backed by array
+    DataOutputBuffer verif = new DataOutputBuffer();
+    when(fs.create(isA(Path.class), eq((short)1))).thenReturn(hdfs);
+    when(fs.rename(isA(Path.class), isA(Path.class))).thenReturn(true);
+
+    Path base = new Path("/chk");
+    Path finalLoc = new Path("/chk/checkpoint_chk0");
+    Path tmp = FSCheckpointService.tmpfile(finalLoc);
+
+    FSCheckpointService chk = new FSCheckpointService(fs, base,
+        new SimpleNamingService("chk0"), (short) 1);
+    CheckpointWriteChannel out = chk.create();
+
+    Random r = new Random();
+
+    final byte[] randBytes = new byte[BUFSIZE];
+    for (int i = 0; i < WRITES; ++i) {
+      r.nextBytes(randBytes);
+      int s = r.nextInt(BUFSIZE - 1);
+      int e = r.nextInt(BUFSIZE - s) + 1;
+      verif.write(randBytes, s, e);
+      b.clear();
+      b.put(randBytes).flip();
+      b.position(s).limit(b.position() + e);
+      out.write(b);
+    }
+    verify(fs, never()).rename(any(Path.class), eq(finalLoc));
+    CheckpointID cid = chk.commit(out);
+    verify(hdfs).close();
+    verify(fs).rename(eq(tmp), eq(finalLoc));
+
+    assertArrayEquals(Arrays.copyOfRange(verif.getData(), 0, verif.getLength()),
+        Arrays.copyOfRange(dob.getData(), 0, dob.getLength()));
+  }
+
+  @Test
+  public void testDelete() throws Exception {
+    FileSystem fs = mock(FileSystem.class);
+    Path chkloc = new Path("/chk/chk0");
+    when(fs.delete(eq(chkloc), eq(false))).thenReturn(true);
+    Path base = new Path("/otherchk");
+    FSCheckpointID id = new FSCheckpointID(chkloc);
+    FSCheckpointService chk = new FSCheckpointService(fs, base,
+        new SimpleNamingService("chk0"), (short) 1);
+    assertTrue(chk.delete(id));
+    verify(fs).delete(eq(chkloc), eq(false));
+  }
+
+}