/**
    *
    * 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.hbase.regionserver;
  
  import java.io.IOException;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.DroppedSnapshotException;
  import org.apache.hadoop.hbase.RemoteExceptionHandler;
  import org.apache.hadoop.hbase.master.TableLockManager.TableLock;
  import org.apache.hadoop.hbase.security.User;
  import org.apache.hadoop.hbase.util.Bytes;
  import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
  import org.apache.hadoop.util.StringUtils;
  
  import com.google.common.base.Preconditions;
  
  /**
   * Handles processing region splits. Put in a queue, owned by HRegionServer.
   */
  @InterfaceAudience.Private
  class SplitRequest implements Runnable {
    private static final Log LOG = LogFactory.getLog(SplitRequest.class);
    private final HRegion parent;
    private final byte[] midKey;
    private final HRegionServer server;
    private final User user;
    private TableLock tableLock;
  
    SplitRequest(Region region, byte[] midKey, HRegionServer hrs, User user) {
      Preconditions.checkNotNull(hrs);
      this.parent = (HRegion)region;
      this.midKey = midKey;
      this.server = hrs;
      this.user = user;
    }
  
    @Override
    public String toString() {
      return "regionName=" + parent + ", midKey=" + Bytes.toStringBinary(midKey);
    }
  
    private void doSplitting(User user) {
      boolean success = false;
      server.metricsRegionServer.incrSplitRequest();
      long startTime = EnvironmentEdgeManager.currentTime();
      SplitTransactionImpl st = new SplitTransactionImpl(parent, midKey);
      try {
        //acquire a shared read lock on the table, so that table schema modifications
        //do not happen concurrently
        tableLock = server.getTableLockManager().readLock(parent.getTableDesc().getTableName()
            , "SPLIT_REGION:" + parent.getRegionInfo().getRegionNameAsString());
        try {
          tableLock.acquire();
        } catch (IOException ex) {
          tableLock = null;
          throw ex;
        }
  
        // If prepare does not return true, for some reason -- logged inside in
        // the prepare call -- we are not ready to split just now. Just return.
        if (!st.prepare()) return;
        try {
          st.execute(this.server, this.server, user);
          success = true;
        } catch (Exception e) {
          if (this.server.isStopping() || this.server.isStopped()) {
            LOG.info(
                "Skip rollback/cleanup of failed split of "
                    + parent.getRegionInfo().getRegionNameAsString() + " because server is"
                    + (this.server.isStopping() ? " stopping" : " stopped"), e);
            return;
          }
          if (e instanceof DroppedSnapshotException) {
            server.abort("Replay of WAL required. Forcing server shutdown", e);
            return;
          }
          try {
            LOG.info("Running rollback/cleanup of failed split of " +
              parent.getRegionInfo().getRegionNameAsString() + "; " + e.getMessage(), e);
            if (st.rollback(this.server, this.server)) {
             LOG.info("Successful rollback of failed split of " +
               parent.getRegionInfo().getRegionNameAsString());
           } else {
             this.server.abort("Abort; we got an error after point-of-no-return");
           }
         } catch (RuntimeException ee) {
           String msg = "Failed rollback of failed split of " +
             parent.getRegionInfo().getRegionNameAsString() + " -- aborting server";
           // If failed rollback, kill this server to avoid having a hole in table.
           LOG.info(msg, ee);
           this.server.abort(msg + " -- Cause: " + ee.getMessage());
         }
         return;
       }
     } catch (IOException ex) {
       LOG.error("Split failed " + this, RemoteExceptionHandler.checkIOException(ex));
       server.checkFileSystem();
     } finally {
       if (this.parent.getCoprocessorHost() != null) {
         try {
           this.parent.getCoprocessorHost().postCompleteSplit();
         } catch (IOException io) {
           LOG.error("Split failed " + this,
               RemoteExceptionHandler.checkIOException(io));
         }
       }
       if (parent.shouldForceSplit()) {
         parent.clearSplit();
       }
       releaseTableLock();
       long endTime = EnvironmentEdgeManager.currentTime();
       // Update regionserver metrics with the split transaction total running time
       server.metricsRegionServer.updateSplitTime(endTime - startTime);
       if (success) {
         server.metricsRegionServer.incrSplitSuccess();
         // Log success
         LOG.info("Region split, hbase:meta updated, and report to master. Parent="
             + parent.getRegionInfo().getRegionNameAsString() + ", new regions: "
             + st.getFirstDaughter().getRegionNameAsString() + ", "
             + st.getSecondDaughter().getRegionNameAsString() + ". Split took "
             + StringUtils.formatTimeDiff(EnvironmentEdgeManager.currentTime(), startTime));
       }
       // Always log the split transaction journal
       LOG.info("Split transaction journal:\n\t" + StringUtils.join("\n\t", st.getJournal()));
     }
   }
 
   @Override
   public void run() {
     if (this.server.isStopping() || this.server.isStopped()) {
       LOG.debug("Skipping split because server is stopping=" +
         this.server.isStopping() + " or stopped=" + this.server.isStopped());
       return;
     }
     doSplitting(user);
   }
 
   protected void releaseTableLock() {
     if (this.tableLock != null) {
       try {
         this.tableLock.release();
       } catch (IOException ex) {
         LOG.error("Could not release the table lock (something is really wrong). "
            + "Aborting this server to avoid holding the lock forever.");
         this.server.abort("Abort; we got an error when releasing the table lock "
                          + "on " + parent.getRegionInfo().getRegionNameAsString());
       }
     }
   }
 }