content: /*
   * Copyright 1999-2012 Alibaba Group.
   *  
   * Licensed 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 com.alibaba.cobar.mysql.bio.executor;
  
  import java.io.IOException;
  import java.nio.ByteBuffer;
  import java.util.concurrent.ConcurrentMap;
  import java.util.concurrent.Executor;
  import java.util.concurrent.atomic.AtomicBoolean;
  import java.util.concurrent.locks.Condition;
  import java.util.concurrent.locks.ReentrantLock;
  
  import org.apache.log4j.Logger;
  
  import com.alibaba.cobar.config.ErrorCode;
  import com.alibaba.cobar.exception.UnknownPacketException;
  import com.alibaba.cobar.mysql.bio.Channel;
  import com.alibaba.cobar.mysql.bio.MySQLChannel;
  import com.alibaba.cobar.net.mysql.BinaryPacket;
  import com.alibaba.cobar.net.mysql.ErrorPacket;
  import com.alibaba.cobar.net.mysql.OkPacket;
  import com.alibaba.cobar.route.RouteResultsetNode;
  import com.alibaba.cobar.server.ServerConnection;
  import com.alibaba.cobar.server.session.BlockingSession;
  
  /**
   * 事务回滚执行器
   * 
   * @author xianmao.hexm
   */
  public final class RollbackExecutor extends NodeExecutor {
      private static final Logger LOGGER = Logger.getLogger(RollbackExecutor.class);
  
      private int nodeCount;
      private AtomicBoolean isFail = new AtomicBoolean(false);
      private final ReentrantLock lock = new ReentrantLock();
      private final Condition taskFinished = lock.newCondition();
  
      @Override
      public void terminate() throws InterruptedException {
          final ReentrantLock lock = this.lock;
          lock.lock();
          try {
              while (nodeCount > 0) {
                  taskFinished.await();
              }
          } finally {
              lock.unlock();
          }
      }
  
      private void decrementCountToZero() {
          final ReentrantLock lock = this.lock;
          lock.lock();
          try {
              nodeCount = 0;
              taskFinished.signalAll();
          } finally {
              lock.unlock();
          }
      }
  
      /**
       * @param finish how many tasks finished
       * @return is this last task
       */
      private boolean decrementCountBy(int finished) {
          ReentrantLock lock = this.lock;
          lock.lock();
          try {
              boolean last = (nodeCount -= finished) <= 0;
              taskFinished.signalAll();
              return last;
          } finally {
              lock.unlock();
          }
      }
  
      /**
       * 事务回滚
       */
      public void rollback(final BlockingSession session) {
          final ServerConnection source = session.getSource();
          final ConcurrentMap<RouteResultsetNode, Channel> target = session.getTarget();
          final int initNodeCount = target.size();
          if (initNodeCount <= 0) {
              ByteBuffer buffer = source.allocate();
              source.write(source.writeToBuffer(OkPacket.OK, buffer));
              return;
          }
  
          // 初始化
          final ReentrantLock lock = this.lock;
          lock.lock();
          try {
              this.isFail.set(false);
              this.nodeCount = initNodeCount;
          } finally {
              lock.unlock();
          }
  
          if (source.isClosed()) {
              decrementCountToZero();
              return;
          }
  
          // 执行
          Executor committer = source.getProcessor().getCommitter();
  
          int started = 0;
          for (RouteResultsetNode rrn : target.keySet()) {
              final MySQLChannel mc = (MySQLChannel) target.get(rrn);
              if (mc != null) {
                  mc.setRunning(true);
                  committer.execute(new Runnable() {
                      @Override
                      public void run() {
                          _rollback(mc, session);
                      }
                  });
                  ++started;
              }
          }
  
          if (started < initNodeCount) {
              decrementCountBy(initNodeCount - started);
          }
      }
  
      private void _rollback(MySQLChannel mc, BlockingSession session) {
          final ServerConnection source = session.getSource();
          if (isFail.get() || source.isClosed()) {
              mc.setRunning(false);
              try {
                  throw new Exception("other task fails, rollback failed channel");
              } catch (Exception e) {
                  handleException(mc, session, e);
              }
              return;
          }
          try {
              BinaryPacket bin = mc.rollback();
              switch (bin.data[0]) {
              case OkPacket.FIELD_COUNT:
                  mc.setRunning(false);
                  if (decrementCountBy(1)) {
                      try {
                          if (isFail.get()) { // some other tasks failed
                              session.clear();
                              source.writeErrMessage(ErrorCode.ER_YES, "rollback error!");
                          } else { // all tasks are successful
                              session.release();
                              ByteBuffer buffer = source.allocate();
                              source.write(bin.write(buffer, source));
                          }
                      } catch (Exception e) {
                          LOGGER.warn("exception happens in success notification: " + source, e);
                      }
                  }
                  break;
              case ErrorPacket.FIELD_COUNT:
                  isFail.set(true);
                  if (decrementCountBy(1)) {
                      try {
                          session.clear();
                          LOGGER.warn(mc.getErrLog("rollback", mc.getErrMessage(bin), source));
                          ByteBuffer buffer = source.allocate();
                          source.write(bin.write(buffer, source));
                      } catch (Exception e) {
                          LOGGER.warn("exception happens in failure notification: " + source, e);
                      }
                  }
                  break;
              default:
                  throw new UnknownPacketException(bin.toString());
              }
          } catch (IOException e) {
              mc.close();
              handleException(mc, session, e);
          } catch (RuntimeException e) {
              mc.close();
              handleException(mc, session, e);
          }
      }
  
      private void handleException(Channel mc, BlockingSession session, Exception e) {
          isFail.set(true);
          if (decrementCountBy(1)) {
              try {
                  session.clear();
                  ServerConnection source = session.getSource();
                  LOGGER.warn(new StringBuilder().append(source).append(mc).append("rollback").toString(), e);
                  String msg = e.getMessage();
                  source.writeErrMessage(ErrorCode.ER_YES, msg == null ? e.getClass().getSimpleName() : msg);
              } catch (Exception e2) {
                  LOGGER.warn("exception happens in failure notification: " + session.getSource(), e2);
              }
          }
      }
  
  }
  