HDFS-10251. Ozone: Shutdown cleanly. Contributed by Anu Engineer

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/ozone/container/common/helpers/KeyUtils.java

@@ -19,8 +19,11 @@
 
 import com.google.common.base.Preconditions;
 import org.apache.hadoop.hdfs.ozone.protocol.proto.ContainerProtos;
+import org.apache.hadoop.ozone.container.common.impl.KeyManagerImpl;
 import org.apache.hadoop.ozone.container.common.utils.ContainerCache;
 import org.apache.hadoop.ozone.container.common.utils.LevelDBStore;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import java.io.File;
 import java.io.IOException;
@@ -71,6 +74,27 @@ public static LevelDBStore getDB(ContainerData container,
     return db;
   }
 
+  /**
+   * Shutdown all DB Handles.
+   *
+   * @param cache - Cache for DB Handles.
+   * @throws IOException
+   */
+  @SuppressWarnings("unchecked")
+  public static void shutdownCache(ContainerCache cache)  {
+    Logger log = LoggerFactory.getLogger(KeyManagerImpl.class);
+    LevelDBStore[] handles = new LevelDBStore[cache.values().size()];
+    cache.values().toArray(handles);
+    Preconditions.checkState(handles.length == cache.values().size());
+    for (LevelDBStore db : handles) {
+      try {
+        db.close();
+      } catch (IOException ex) {
+        log.error("error closing db. error {}", ex);
+      }
+    }
+  }
+
   /**
    * Returns successful keyResponse.
    * @param msg - Request.

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/ozone/container/common/impl/ChunkManagerImpl.java

@@ -146,4 +146,15 @@ public void deleteChunk(Pipeline pipeline, String keyName, ChunkInfo info)
       containerManager.readUnlock();
     }
   }
+
+  /**
+   * Shutdown the chunkManager.
+   *
+   * In the chunkManager we haven't acquired any resources, so nothing to do
+   * here. This call is made with containerManager Writelock held.
+   */
+  @Override
+  public void shutdown() {
+    Preconditions.checkState(this.containerManager.hasWriteLock());
+  }
 }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/ozone/container/common/impl/ContainerManagerImpl.java

@@ -385,8 +385,9 @@ public ContainerData readContainer(String containerName) throws IOException {
    * @throws IOException
    */
   @Override
-  public void shutdown() throws IOException {
+  public void shutdown() {
-
+    Preconditions.checkState(this.hasWriteLock());
+    this.containerMap.clear();
   }
 
 

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/ozone/container/common/impl/KeyManagerImpl.java

@@ -142,4 +142,13 @@ public List<KeyData> listKey(Pipeline pipeline, String prefix, String
     // TODO :
     return null;
   }
+
+  /**
+   * Shutdown keyManager.
+   */
+  @Override
+  public void shutdown() {
+    Preconditions.checkState(this.containerManager.hasWriteLock());
+    KeyUtils.shutdownCache(containerCache);
+  }
 }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/ozone/container/common/interfaces/ChunkManager.java

@@ -65,4 +65,9 @@ void deleteChunk(Pipeline pipeline, String keyName, ChunkInfo info) throws
 
   // TODO : Support list operations.
 
+  /**
+   * Shutdown the chunkManager.
+   */
+  void shutdown();
+
 }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/ozone/container/common/interfaces/ContainerManager.java

@@ -94,7 +94,7 @@ void listContainer(String prevKey, long count, List<ContainerData> data)
    *
    * @throws IOException
    */
-  void shutdown() throws IOException;
+  void shutdown();
 
   /**
    * Sets the Chunk Manager.

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/ozone/container/common/interfaces/KeyManager.java

@@ -29,13 +29,15 @@
 public interface KeyManager {
   /**
    * Puts or overwrites a key.
+   *
    * @param pipeline - Pipeline.
-   * @param data - Key Data.
+   * @param data     - Key Data.
    */
   void putKey(Pipeline pipeline, KeyData data) throws IOException;
 
   /**
    * Gets an existing key.
+   *
    * @param data - Key Data.
    * @return Key Data.
    */
@@ -43,21 +45,26 @@ public interface KeyManager {
 
   /**
    * Deletes an existing Key.
-   * @param pipeline  - Pipeline.
+   *
-   * @param keyName Key Data.
+   * @param pipeline - Pipeline.
+   * @param keyName  Key Data.
    */
   void deleteKey(Pipeline pipeline, String keyName) throws IOException;
 
   /**
    * List keys in a container.
+   *
    * @param pipeline - pipeline.
-   * @param prefix - Prefix in needed.
+   * @param prefix   - Prefix in needed.
-   * @param prevKey - Key to Start from, EMPTY_STRING to begin.
+   * @param prevKey  - Key to Start from, EMPTY_STRING to begin.
-   * @param count - Number of keys to return.
+   * @param count    - Number of keys to return.
    * @return List of Keys that match the criteria.
    */
   List<KeyData> listKey(Pipeline pipeline, String prefix, String prevKey, int
       count);
 
-
+  /**
+   * Shutdown keyManager.
+   */
+  void shutdown();
 }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/ozone/container/common/transport/server/XceiverServer.java

@@ -78,7 +78,7 @@ public void start() throws Exception {
    *
    * @throws Exception
    */
-  public void stop() throws Exception {
+  public void stop() {
     if (bossGroup != null) {
       bossGroup.shutdownGracefully();
     }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/ozone/container/common/utils/ContainerCache.java

@@ -92,20 +92,4 @@ public void putDB(String containerName, LevelDBStore db) {
       lock.unlock();
     }
   }
-
-  /**
-   * Remove an entry from the cache.
-   *
-   * @param containerName - Name of the container.
-   */
-  public void removeDB(String containerName) {
-    Preconditions.checkNotNull(containerName);
-    Preconditions.checkState(!containerName.isEmpty());
-    lock.lock();
-    try {
-      this.remove(containerName);
-    } finally {
-      lock.unlock();
-    }
-  }
 }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/ozone/container/ozoneimpl/OzoneContainer.java

@@ -100,10 +100,48 @@ public void start() throws Exception {
 
   /**
    * Stops the ozone container.
-   * @throws Exception
+   *
+   * Shutdown logic is not very obvious from the following code.
+   * if you need to  modify the logic, please keep these comments in mind.
+   * Here is the shutdown sequence.
+   *
+   * 1. We shutdown the network ports.
+   *
+   * 2. Now we need to wait for all requests in-flight to finish.
+   *
+   * 3. The container manager lock is a read-write lock with "Fairness" enabled.
+   *
+   * 4. This means that the waiting threads are served in a "first-come-first
+   * -served" manner. Please note that this applies to waiting threads only.
+   *
+   * 5. Since write locks are exclusive, if we are waiting to get a lock it
+   * implies that we are waiting for in-flight operations to complete.
+   *
+   * 6. if there are other write operations waiting on the reader-writer lock,
+   * fairness guarantees that they will proceed before the shutdown lock
+   * request.
+   *
+   * 7. Since all operations either take a reader or writer lock of container
+   * manager, we are guaranteed that we are the last operation since we have
+   * closed the network port, and we wait until close is successful.
+   *
+   * 8. We take the writer lock and call shutdown on each of the managers in
+   * reverse order. That is chunkManager, keyManager and containerManager is
+   * shutdown.
+   *
    */
-  public void stop() throws  Exception {
+  public void stop() {
+    LOG.info("Attempting to stop container services.");
     server.stop();
+    try {
+      this.manager.writeLock();
+      this.chunkManager.shutdown();
+      this.keyManager.shutdown();
+      this.manager.shutdown();
+      LOG.info("container services shutdown complete.");
+    } finally {
+      this.manager.writeUnlock();
+    }
   }
 
   /**