/**
 * 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.yarn.nodelabels;

import java.io.IOException;
import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.locks.ReentrantReadWriteLock;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.fs.FSDataOutputStream;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.yarn.api.records.NodeId;
import org.apache.hadoop.yarn.api.records.NodeLabel;
import org.apache.hadoop.yarn.exceptions.YarnException;
import org.apache.hadoop.yarn.server.api.protocolrecords.AddToClusterNodeLabelsRequest;
import org.apache.hadoop.yarn.server.api.protocolrecords.ReplaceLabelsOnNodeRequest;
import org.apache.hadoop.yarn.server.api.protocolrecords.impl.pb.AddToClusterNodeLabelsRequestPBImpl;
import org.apache.hadoop.yarn.server.api.protocolrecords.impl.pb.ReplaceLabelsOnNodeRequestPBImpl;

public class NonAppendableFSNodeLabelStore extends FileSystemNodeLabelsStore {
  protected static final Log
      LOG = LogFactory.getLog(NonAppendableFSNodeLabelStore.class);

  @Override
  public void close() throws IOException {
  }


  @Override
  public void recover() throws YarnException,
      IOException {
    Path newMirrorPath = new Path(fsWorkingPath, MIRROR_FILENAME + ".new");
    Path oldMirrorPath = new Path(fsWorkingPath, MIRROR_FILENAME);
    loadFromMirror(newMirrorPath, oldMirrorPath);
    
    // if new mirror exists, remove old mirror and rename new mirror
    if (fs.exists(newMirrorPath)) {
      // remove old mirror
      try {
        fs.delete(oldMirrorPath, false);
      } catch (IOException e) {
        // do nothing
        if (LOG.isDebugEnabled()) {
          LOG.debug("Exception while removing old mirror", e);
        }
      }
      
      // rename new to old
      fs.rename(newMirrorPath, oldMirrorPath);
    }

    LOG.info("Node label store recover is completed");
  }
  
  @Override
  public void updateNodeToLabelsMappings(
      Map<NodeId, Set<String>> nodeToLabels) throws IOException {
    writeNewMirror();
  }

  @Override
  public void storeNewClusterNodeLabels(List<NodeLabel> labels)
      throws IOException {
    writeNewMirror();
  }

  @Override
  public void removeClusterNodeLabels(Collection<String> labels)
      throws IOException {
    writeNewMirror();
  }

  private void writeNewMirror() throws IOException {
    ReentrantReadWriteLock.ReadLock readLock = mgr.readLock;
    try {
      // Acquire readlock to make sure we get cluster node labels and
      // node-to-labels mapping atomically.
      readLock.lock();
      List<NodeLabel> nodeLabels = mgr.getClusterNodeLabels();
      Map<NodeId, Set<String>> nodeToLabels = mgr.getNodeLabels();
      
      // Write mirror to mirror.new.tmp file
      Path newTmpPath = new Path(fsWorkingPath, MIRROR_FILENAME + ".new.tmp"); 
      FSDataOutputStream os = fs
          .create(newTmpPath, true);
      ((AddToClusterNodeLabelsRequestPBImpl) AddToClusterNodeLabelsRequest
          .newInstance(nodeLabels)).getProto().writeDelimitedTo(os);

      ((ReplaceLabelsOnNodeRequestPBImpl) ReplaceLabelsOnNodeRequest
          .newInstance(nodeToLabels)).getProto().writeDelimitedTo(os);
      
      os.close();
      
      // Rename mirror.new.tmp to mirror.new (will remove .new if it's existed)
      Path newPath = new Path(fsWorkingPath, MIRROR_FILENAME + ".new"); 
      if (fs.exists(newPath)) {
        fs.delete(newPath, false);
      }
      fs.rename(newTmpPath, newPath);
      
      // Remove existing mirror and rename mirror.new to mirror
      Path mirrorPath = new Path(fsWorkingPath, MIRROR_FILENAME);
      if (fs.exists(mirrorPath)) {
        fs.delete(mirrorPath, false);
      }
      fs.rename(newPath, mirrorPath);
    } finally {
      readLock.unlock();
    }
  }
}