/**
    * 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.coordination;
  
  import static org.apache.hadoop.hbase.executor.EventType.RS_ZK_REGION_SPLIT;
  import static org.apache.hadoop.hbase.executor.EventType.RS_ZK_REGION_SPLITTING;
  import static org.apache.hadoop.hbase.executor.EventType.RS_ZK_REQUEST_REGION_SPLIT;
  
  import java.io.IOException;
  import java.util.List;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.hbase.CoordinatedStateManager;
  import org.apache.hadoop.hbase.HRegionInfo;
  import org.apache.hadoop.hbase.RegionTransition;
  import org.apache.hadoop.hbase.ServerName;
  import org.apache.hadoop.hbase.coordination.SplitTransactionCoordination;
  import org.apache.hadoop.hbase.executor.EventType;
  import org.apache.hadoop.hbase.regionserver.HRegion;
  import org.apache.hadoop.hbase.regionserver.Region;
  import org.apache.hadoop.hbase.regionserver.RegionServerServices;
  import org.apache.hadoop.hbase.zookeeper.ZKAssign;
  import org.apache.hadoop.hbase.zookeeper.ZKUtil;
  import org.apache.hadoop.hbase.zookeeper.ZooKeeperWatcher;
  import org.apache.zookeeper.KeeperException;
  import org.apache.zookeeper.data.Stat;
  
  public class ZKSplitTransactionCoordination implements SplitTransactionCoordination {
  
    private CoordinatedStateManager coordinationManager;
    private final ZooKeeperWatcher watcher;
  
    private static final Log LOG = LogFactory.getLog(ZKSplitTransactionCoordination.class);
  
    public ZKSplitTransactionCoordination(CoordinatedStateManager coordinationProvider,
        ZooKeeperWatcher watcher) {
      this.coordinationManager = coordinationProvider;
      this.watcher = watcher;
    }
  
    /**
     * Creates a new ephemeral node in the PENDING_SPLIT state for the specified region. Create it
     * ephemeral in case regionserver dies mid-split.
     * <p>
     * Does not transition nodes from other states. If a node already exists for this region, an
     * Exception will be thrown.
     * @param parent region to be created as offline
     * @param serverName server event originates from
     * @param hri_a daughter region
     * @param hri_b daughter region
     * @throws IOException
     */
  
    @Override
    public void startSplitTransaction(HRegion parent, ServerName serverName, HRegionInfo hri_a,
        HRegionInfo hri_b) throws IOException {
  
      HRegionInfo region = parent.getRegionInfo();
      try {
  
        LOG.debug(watcher.prefix("Creating ephemeral node for " + region.getEncodedName()
            + " in PENDING_SPLIT state"));
        byte[] payload = HRegionInfo.toDelimitedByteArray(hri_a, hri_b);
        RegionTransition rt =
            RegionTransition.createRegionTransition(RS_ZK_REQUEST_REGION_SPLIT,
              region.getRegionName(), serverName, payload);
        String node = ZKAssign.getNodeName(watcher, region.getEncodedName());
        if (!ZKUtil.createEphemeralNodeAndWatch(watcher, node, rt.toByteArray())) {
          throw new IOException("Failed create of ephemeral " + node);
        }
  
      } catch (KeeperException e) {
        throw new IOException("Failed creating PENDING_SPLIT znode on "
            + parent.getRegionInfo().getRegionNameAsString(), e);
      }
  
    }
  
    /**
     * Transitions an existing ephemeral node for the specified region which is currently in the begin
     * state to be in the end state. Master cleans up the final SPLIT znode when it reads it (or if we
     * crash, zk will clean it up).
     * <p>
     * Does not transition nodes from other states. If for some reason the node could not be
     * transitioned, the method returns -1. If the transition is successful, the version of the node
     * after transition is returned.
     * <p>
     * This method can fail and return false for three different reasons:
     * <ul>
    * <li>Node for this region does not exist</li>
    * <li>Node for this region is not in the begin state</li>
    * <li>After verifying the begin state, update fails because of wrong version (this should never
    * actually happen since an RS only does this transition following a transition to the begin
    * state. If two RS are conflicting, one would fail the original transition to the begin state and
    * not this transition)</li>
    * </ul>
    * <p>
    * Does not set any watches.
    * <p>
    * This method should only be used by a RegionServer when splitting a region.
    * @param parent region to be transitioned to opened
    * @param a Daughter a of split
    * @param b Daughter b of split
    * @param serverName server event originates from
    * @param std split transaction details
    * @param beginState the expected current state the znode should be
    * @param endState the state to be transition to
    * @return version of node after transition, -1 if unsuccessful transition
    * @throws IOException
    */
 
   private int transitionSplittingNode(HRegionInfo parent, HRegionInfo a, HRegionInfo b,
       ServerName serverName, SplitTransactionDetails std, final EventType beginState,
       final EventType endState) throws IOException {
     ZkSplitTransactionDetails zstd = (ZkSplitTransactionDetails) std;
     byte[] payload = HRegionInfo.toDelimitedByteArray(a, b);
     try {
       return ZKAssign.transitionNode(watcher, parent, serverName, beginState, endState,
         zstd.getZnodeVersion(), payload);
     } catch (KeeperException e) {
       throw new IOException(
           "Failed transition of splitting node " + parent.getRegionNameAsString(), e);
     }
   }
 
   /**
    * Wait for the splitting node to be transitioned from pending_split to splitting by master.
    * That's how we are sure master has processed the event and is good with us to move on. If we
    * don't get any update, we periodically transition the node so that master gets the callback. If
    * the node is removed or is not in pending_split state any more, we abort the split.
    */
   @Override
   public void waitForSplitTransaction(final RegionServerServices services, Region parent,
       HRegionInfo hri_a, HRegionInfo hri_b, SplitTransactionDetails sptd) throws IOException {
     ZkSplitTransactionDetails zstd = (ZkSplitTransactionDetails) sptd;
 
     // After creating the split node, wait for master to transition it
     // from PENDING_SPLIT to SPLITTING so that we can move on. We want master
     // knows about it and won't transition any region which is splitting.
     try {
       int spins = 0;
       Stat stat = new Stat();
       ServerName expectedServer = coordinationManager.getServer().getServerName();
       String node = parent.getRegionInfo().getEncodedName();
       while (!(coordinationManager.getServer().isStopped() || services.isStopping())) {
         if (spins % 5 == 0) {
           LOG.debug("Still waiting for master to process " + "the pending_split for " + node);
           SplitTransactionDetails temp = getDefaultDetails();
           transitionSplittingNode(parent.getRegionInfo(), hri_a, hri_b, expectedServer, temp,
             RS_ZK_REQUEST_REGION_SPLIT, RS_ZK_REQUEST_REGION_SPLIT);
         }
         Thread.sleep(100);
         spins++;
         byte[] data = ZKAssign.getDataNoWatch(watcher, node, stat);
         if (data == null) {
           throw new IOException("Data is null, splitting node " + node + " no longer exists");
         }
         RegionTransition rt = RegionTransition.parseFrom(data);
         EventType et = rt.getEventType();
         if (et == RS_ZK_REGION_SPLITTING) {
           ServerName serverName = rt.getServerName();
           if (!serverName.equals(expectedServer)) {
             throw new IOException("Splitting node " + node + " is for " + serverName + ", not us "
                 + expectedServer);
           }
           byte[] payloadOfSplitting = rt.getPayload();
           List<HRegionInfo> splittingRegions =
               HRegionInfo.parseDelimitedFrom(payloadOfSplitting, 0, payloadOfSplitting.length);
           assert splittingRegions.size() == 2;
           HRegionInfo a = splittingRegions.get(0);
           HRegionInfo b = splittingRegions.get(1);
           if (!(hri_a.equals(a) && hri_b.equals(b))) {
             throw new IOException("Splitting node " + node + " is for " + a + ", " + b
                 + ", not expected daughters: " + hri_a + ", " + hri_b);
           }
           // Master has processed it.
           zstd.setZnodeVersion(stat.getVersion());
           return;
         }
         if (et != RS_ZK_REQUEST_REGION_SPLIT) {
           throw new IOException("Splitting node " + node + " moved out of splitting to " + et);
         }
       }
       // Server is stopping/stopped
       throw new IOException("Server is " + (services.isStopping() ? "stopping" : "stopped"));
     } catch (Exception e) {
       if (e instanceof InterruptedException) {
         Thread.currentThread().interrupt();
       }
       throw new IOException("Failed getting SPLITTING znode on " +
         parent.getRegionInfo().getRegionNameAsString(), e);
     }
   }
 
   /**
    * Finish off split transaction, transition the zknode
    * @param services Used to online/offline regions.
    * @param a daughter region
    * @param b daughter region
    * @param std split transaction details
    * @param parent
    * @throws IOException If thrown, transaction failed. Call
    *  {@link org.apache.hadoop.hbase.regionserver.SplitTransaction#rollback(
    *  Server, RegionServerServices)}
    */
   @Override
   public void completeSplitTransaction(final RegionServerServices services, Region a, Region b,
       SplitTransactionDetails std, Region parent) throws IOException {
     ZkSplitTransactionDetails zstd = (ZkSplitTransactionDetails) std;
     // Tell master about split by updating zk. If we fail, abort.
     if (coordinationManager.getServer() != null) {
       try {
         zstd.setZnodeVersion(transitionSplittingNode(parent.getRegionInfo(), a.getRegionInfo(),
           b.getRegionInfo(), coordinationManager.getServer().getServerName(), zstd,
           RS_ZK_REGION_SPLITTING, RS_ZK_REGION_SPLIT));
 
         int spins = 0;
         // Now wait for the master to process the split. We know it's done
         // when the znode is deleted. The reason we keep tickling the znode is
         // that it's possible for the master to miss an event.
         do {
           if (spins % 10 == 0) {
             LOG.debug("Still waiting on the master to process the split for "
                 + parent.getRegionInfo().getEncodedName());
           }
           Thread.sleep(100);
           // When this returns -1 it means the znode doesn't exist
           zstd.setZnodeVersion(transitionSplittingNode(parent.getRegionInfo(), a.getRegionInfo(),
             b.getRegionInfo(), coordinationManager.getServer().getServerName(), zstd,
             RS_ZK_REGION_SPLIT, RS_ZK_REGION_SPLIT));
           spins++;
         } while (zstd.getZnodeVersion() != -1 && !coordinationManager.getServer().isStopped()
             && !services.isStopping());
       } catch (Exception e) {
         if (e instanceof InterruptedException) {
           Thread.currentThread().interrupt();
         }
         throw new IOException("Failed telling master about split", e);
       }
     }
 
     // Leaving here, the splitdir with its dross will be in place but since the
     // split was successful, just leave it; it'll be cleaned when parent is
     // deleted and cleaned up.
   }
 
   @Override
   public void clean(final HRegionInfo hri) {
     try {
       // Only delete if its in expected state; could have been hijacked.
       if (!ZKAssign.deleteNode(coordinationManager.getServer().getZooKeeper(),
         hri.getEncodedName(), RS_ZK_REQUEST_REGION_SPLIT, coordinationManager.getServer()
             .getServerName())) {
         ZKAssign.deleteNode(coordinationManager.getServer().getZooKeeper(), hri.getEncodedName(),
           RS_ZK_REGION_SPLITTING, coordinationManager.getServer().getServerName());
       }
     } catch (KeeperException.NoNodeException e) {
       LOG.info("Failed cleanup zk node of " + hri.getRegionNameAsString(), e);
     } catch (KeeperException e) {
       coordinationManager.getServer().abort("Failed cleanup of " + hri.getRegionNameAsString(), e);
     }
   }
 
   /**
    * ZK-based implementation. Has details about whether the state transition should be reflected in
    * ZK, as well as expected version of znode.
    */
   public static class ZkSplitTransactionDetails implements
       SplitTransactionCoordination.SplitTransactionDetails {
     private int znodeVersion;
 
     public ZkSplitTransactionDetails() {
     }
 
     /**
      * @return znode current version
      */
     public int getZnodeVersion() {
       return znodeVersion;
     }
 
     /**
      * @param znodeVersion znode new version
      */
     public void setZnodeVersion(int znodeVersion) {
       this.znodeVersion = znodeVersion;
     }
   }
 
   @Override
   public SplitTransactionDetails getDefaultDetails() {
     ZkSplitTransactionDetails zstd = new ZkSplitTransactionDetails();
     zstd.setZnodeVersion(-1);
     return zstd;
   }
 
   @Override
   public int processTransition(HRegionInfo p, HRegionInfo hri_a, HRegionInfo hri_b, ServerName sn,
       SplitTransactionDetails std) throws IOException {
     return transitionSplittingNode(p, hri_a, hri_b, sn, std, RS_ZK_REQUEST_REGION_SPLIT,
       RS_ZK_REGION_SPLITTING);
 
   }
 }