/**
    * 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.zookeeper;
  
  import java.io.EOFException;
  import java.io.IOException;
  import java.net.ConnectException;
  import java.net.NoRouteToHostException;
  import java.net.SocketException;
  import java.net.SocketTimeoutException;
  import java.rmi.UnknownHostException;
  import java.util.ArrayList;
  import java.util.List;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.hbase.HConstants;
  import org.apache.hadoop.hbase.HRegionInfo;
  import org.apache.hadoop.hbase.NotAllMetaRegionsOnlineException;
  import org.apache.hadoop.hbase.ServerName;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.client.HConnection;
  import org.apache.hadoop.hbase.client.RegionReplicaUtil;
  import org.apache.hadoop.hbase.client.RetriesExhaustedException;
  import org.apache.hadoop.hbase.exceptions.DeserializationException;
  import org.apache.hadoop.hbase.ipc.FailedServerException;
  import org.apache.hadoop.hbase.ipc.ServerNotRunningYetException;
  import org.apache.hadoop.hbase.master.RegionState;
  import org.apache.hadoop.hbase.protobuf.ProtobufUtil;
  import org.apache.hadoop.hbase.protobuf.generated.AdminProtos;
  import org.apache.hadoop.hbase.protobuf.generated.AdminProtos.AdminService;
  import org.apache.hadoop.hbase.protobuf.generated.HBaseProtos;
  import org.apache.hadoop.hbase.protobuf.generated.ZooKeeperProtos;
  import org.apache.hadoop.hbase.protobuf.generated.ZooKeeperProtos.MetaRegionServer;
  import org.apache.hadoop.hbase.regionserver.RegionServerStoppedException;
  import org.apache.hadoop.hbase.util.Bytes;
  import org.apache.hadoop.hbase.util.Pair;
  import org.apache.hadoop.ipc.RemoteException;
  import org.apache.zookeeper.KeeperException;
  
  import com.google.common.base.Stopwatch;
  import com.google.protobuf.InvalidProtocolBufferException;
  
  /**
   * Utility class to perform operation (get/wait for/verify/set/delete) on znode in ZooKeeper
   * which keeps hbase:meta region server location.
   *
   * Stateless class with a bunch of static methods. Doesn't manage resources passed in
   * (e.g. HConnection, ZooKeeperWatcher etc).
   *
   * Meta region location is set by <code>RegionServerServices</code>.
   * This class doesn't use ZK watchers, rather accesses ZK directly.
   *
   * This class it stateless. The only reason it's not made a non-instantiable util class
   * with a collection of static methods is that it'd be rather hard to mock properly in tests.
   *
   * TODO: rewrite using RPC calls to master to find out about hbase:meta.
   */
  @InterfaceAudience.Private
  public class MetaTableLocator {
    private static final Log LOG = LogFactory.getLog(MetaTableLocator.class);
  
    // only needed to allow non-timeout infinite waits to stop when cluster shuts down
    private volatile boolean stopped = false;
  
    /**
     * Checks if the meta region location is available.
     * @return true if meta region location is available, false if not
     */
    public boolean isLocationAvailable(ZooKeeperWatcher zkw) {
      return getMetaRegionLocation(zkw) != null;
    }
  
    /**
     * @param zkw ZooKeeper watcher to be used
     * @return meta table regions and their locations.
     */
    public List<Pair<HRegionInfo, ServerName>> getMetaRegionsAndLocations(ZooKeeperWatcher zkw) {
      return getMetaRegionsAndLocations(zkw, HRegionInfo.DEFAULT_REPLICA_ID);
    }
  
    /**
     * 
    * @param zkw
    * @param replicaId
    * @return meta table regions and their locations.
    */
   public List<Pair<HRegionInfo, ServerName>> getMetaRegionsAndLocations(ZooKeeperWatcher zkw,
       int replicaId) {
     ServerName serverName = getMetaRegionLocation(zkw, replicaId);
     List<Pair<HRegionInfo, ServerName>> list = new ArrayList<Pair<HRegionInfo, ServerName>>();
     list.add(new Pair<HRegionInfo, ServerName>(RegionReplicaUtil.getRegionInfoForReplica(
         HRegionInfo.FIRST_META_REGIONINFO, replicaId), serverName));
     return list;
   }
 
   /**
    * @param zkw ZooKeeper watcher to be used
    * @return List of meta regions
    */
   public List<HRegionInfo> getMetaRegions(ZooKeeperWatcher zkw) {
     return getMetaRegions(zkw, HRegionInfo.DEFAULT_REPLICA_ID);
   }
 
   /**
    * 
    * @param zkw
    * @param replicaId
    * @return List of meta regions
    */
   public List<HRegionInfo> getMetaRegions(ZooKeeperWatcher zkw, int replicaId) {
     List<Pair<HRegionInfo, ServerName>> result;
     result = getMetaRegionsAndLocations(zkw, replicaId);
     return getListOfHRegionInfos(result);
   }
 
   private List<HRegionInfo> getListOfHRegionInfos(
       final List<Pair<HRegionInfo, ServerName>> pairs) {
     if (pairs == null || pairs.isEmpty()) return null;
     List<HRegionInfo> result = new ArrayList<HRegionInfo>(pairs.size());
     for (Pair<HRegionInfo, ServerName> pair: pairs) {
       result.add(pair.getFirst());
     }
     return result;
   }
 
   /**
    * Gets the meta region location, if available.  Does not block.
    * @param zkw zookeeper connection to use
    * @return server name or null if we failed to get the data.
    */
   public ServerName getMetaRegionLocation(final ZooKeeperWatcher zkw) {
     try {
       RegionState state = getMetaRegionState(zkw);
       return state.isOpened() ? state.getServerName() : null;
     } catch (KeeperException ke) {
       return null;
     }
   }
 
   /**
    * Gets the meta region location, if available.  Does not block.
    * @param zkw
    * @param replicaId
    * @return server name
    */
   public ServerName getMetaRegionLocation(final ZooKeeperWatcher zkw, int replicaId) {
     try {
       RegionState state = getMetaRegionState(zkw, replicaId);
       return state.isOpened() ? state.getServerName() : null;
     } catch (KeeperException ke) {
       return null;
     }
   }
 
   /**
    * Gets the meta region location, if available, and waits for up to the
    * specified timeout if not immediately available.
    * Given the zookeeper notification could be delayed, we will try to
    * get the latest data.
    * @param zkw
    * @param timeout maximum time to wait, in millis
    * @return server name for server hosting meta region formatted as per
    * {@link ServerName}, or null if none available
    * @throws InterruptedException if interrupted while waiting
    * @throws NotAllMetaRegionsOnlineException
    */
   public ServerName waitMetaRegionLocation(ZooKeeperWatcher zkw, long timeout)
   throws InterruptedException, NotAllMetaRegionsOnlineException {
     return waitMetaRegionLocation(zkw, HRegionInfo.DEFAULT_REPLICA_ID, timeout);
   }
 
   /**
    * Gets the meta region location, if available, and waits for up to the
    * specified timeout if not immediately available.
    * Given the zookeeper notification could be delayed, we will try to
    * get the latest data.
    * @param zkw
    * @param replicaId
    * @param timeout maximum time to wait, in millis
    * @return server name for server hosting meta region formatted as per
    * {@link ServerName}, or null if none available
    * @throws InterruptedException
    * @throws NotAllMetaRegionsOnlineException
    */
   public ServerName waitMetaRegionLocation(ZooKeeperWatcher zkw, int replicaId, long timeout)
   throws InterruptedException, NotAllMetaRegionsOnlineException {
     try {
       if (ZKUtil.checkExists(zkw, zkw.baseZNode) == -1) {
         String errorMsg = "Check the value configured in 'zookeeper.znode.parent'. "
             + "There could be a mismatch with the one configured in the master.";
         LOG.error(errorMsg);
         throw new IllegalArgumentException(errorMsg);
       }
     } catch (KeeperException e) {
       throw new IllegalStateException("KeeperException while trying to check baseZNode:", e);
     }
     ServerName sn = blockUntilAvailable(zkw, replicaId, timeout);
 
     if (sn == null) {
       throw new NotAllMetaRegionsOnlineException("Timed out; " + timeout + "ms");
     }
 
     return sn;
   }
 
   /**
    * Waits indefinitely for availability of <code>hbase:meta</code>.  Used during
    * cluster startup.  Does not verify meta, just that something has been
    * set up in zk.
    * @see #waitMetaRegionLocation(org.apache.hadoop.hbase.zookeeper.ZooKeeperWatcher, long)
    * @throws InterruptedException if interrupted while waiting
    */
   public void waitMetaRegionLocation(ZooKeeperWatcher zkw) throws InterruptedException {
     Stopwatch stopwatch = new Stopwatch().start();
     while (!stopped) {
       try {
         if (waitMetaRegionLocation(zkw, 100) != null) break;
         long sleepTime = stopwatch.elapsedMillis();
         // +1 in case sleepTime=0
         if ((sleepTime + 1) % 10000 == 0) {
           LOG.warn("Have been waiting for meta to be assigned for " + sleepTime + "ms");
         }
       } catch (NotAllMetaRegionsOnlineException e) {
         if (LOG.isTraceEnabled()) {
           LOG.trace("hbase:meta still not available, sleeping and retrying." +
             " Reason: " + e.getMessage());
         }
       }
     }
   }
 
   /**
    * Verify <code>hbase:meta</code> is deployed and accessible.
    * @param hConnection
    * @param zkw
    * @param timeout How long to wait on zk for meta address (passed through to
    * the internal call to {@link #getMetaServerConnection}.
    * @return True if the <code>hbase:meta</code> location is healthy.
    * @throws java.io.IOException
    * @throws InterruptedException
    */
   public boolean verifyMetaRegionLocation(HConnection hConnection,
       ZooKeeperWatcher zkw, final long timeout)
   throws InterruptedException, IOException {
     return verifyMetaRegionLocation(hConnection, zkw, timeout, HRegionInfo.DEFAULT_REPLICA_ID);
   }
 
   /**
    * Verify <code>hbase:meta</code> is deployed and accessible.
    * @param hConnection
    * @param zkw
    * @param timeout How long to wait on zk for meta address (passed through to
    * @param replicaId
    * @return True if the <code>hbase:meta</code> location is healthy.
    * @throws InterruptedException
    * @throws IOException
    */
   public boolean verifyMetaRegionLocation(HConnection hConnection,
       ZooKeeperWatcher zkw, final long timeout, int replicaId)
   throws InterruptedException, IOException {
     AdminProtos.AdminService.BlockingInterface service = null;
     try {
       service = getMetaServerConnection(hConnection, zkw, timeout, replicaId);
     } catch (NotAllMetaRegionsOnlineException e) {
       // Pass
     } catch (ServerNotRunningYetException e) {
       // Pass -- remote server is not up so can't be carrying root
     } catch (UnknownHostException e) {
       // Pass -- server name doesn't resolve so it can't be assigned anything.
     } catch (RegionServerStoppedException e) {
       // Pass -- server name sends us to a server that is dying or already dead.
     }
     return (service != null) && verifyRegionLocation(service,
             getMetaRegionLocation(zkw, replicaId), RegionReplicaUtil.getRegionInfoForReplica(
                 HRegionInfo.FIRST_META_REGIONINFO, replicaId).getRegionName());
   }
 
   /**
    * Verify we can connect to <code>hostingServer</code> and that its carrying
    * <code>regionName</code>.
    * @param hostingServer Interface to the server hosting <code>regionName</code>
    * @param address The servername that goes with the <code>metaServer</code>
    * Interface.  Used logging.
    * @param regionName The regionname we are interested in.
    * @return True if we were able to verify the region located at other side of
    * the Interface.
    * @throws IOException
    */
   // TODO: We should be able to get the ServerName from the AdminProtocol
   // rather than have to pass it in.  Its made awkward by the fact that the
   // HRI is likely a proxy against remote server so the getServerName needs
   // to be fixed to go to a local method or to a cache before we can do this.
   private boolean verifyRegionLocation(AdminService.BlockingInterface hostingServer,
       final ServerName address, final byte [] regionName)
   throws IOException {
     if (hostingServer == null) {
       LOG.info("Passed hostingServer is null");
       return false;
     }
     Throwable t;
     try {
       // Try and get regioninfo from the hosting server.
       return ProtobufUtil.getRegionInfo(hostingServer, regionName) != null;
     } catch (ConnectException e) {
       t = e;
     } catch (RetriesExhaustedException e) {
       t = e;
     } catch (RemoteException e) {
       IOException ioe = e.unwrapRemoteException();
       t = ioe;
     } catch (IOException e) {
       Throwable cause = e.getCause();
       if (cause != null && cause instanceof EOFException) {
         t = cause;
       } else if (cause != null && cause.getMessage() != null
           && cause.getMessage().contains("Connection reset")) {
         t = cause;
       } else {
         t = e;
       }
     }
     LOG.info("Failed verification of " + Bytes.toStringBinary(regionName) +
       " at address=" + address + ", exception=" + t.getMessage());
     return false;
   }
 
   /**
    * Gets a connection to the server hosting meta, as reported by ZooKeeper,
    * waiting up to the specified timeout for availability.
    * <p>WARNING: Does not retry.  Use an {@link org.apache.hadoop.hbase.client.HTable} instead.
    * @param hConnection
    * @param zkw
    * @param timeout How long to wait on meta location
    * @param replicaId
    * @return connection to server hosting meta
    * @throws InterruptedException
    * @throws NotAllMetaRegionsOnlineException if timed out waiting
    * @throws IOException
    */
   private AdminService.BlockingInterface getMetaServerConnection(HConnection hConnection,
       ZooKeeperWatcher zkw, long timeout, int replicaId)
   throws InterruptedException, NotAllMetaRegionsOnlineException, IOException {
     return getCachedConnection(hConnection, waitMetaRegionLocation(zkw, replicaId, timeout));
   }
 
   /**
    * @param sn ServerName to get a connection against.
    * @return The AdminProtocol we got when we connected to <code>sn</code>
    * May have come from cache, may not be good, may have been setup by this
    * invocation, or may be null.
    * @throws IOException
    */
   @SuppressWarnings("deprecation")
   private static AdminService.BlockingInterface getCachedConnection(HConnection hConnection,
     ServerName sn)
   throws IOException {
     if (sn == null) {
       return null;
     }
     AdminService.BlockingInterface service = null;
     try {
       service = hConnection.getAdmin(sn);
     } catch (RetriesExhaustedException e) {
       if (e.getCause() != null && e.getCause() instanceof ConnectException) {
         // Catch this; presume it means the cached connection has gone bad.
       } else {
         throw e;
       }
     } catch (SocketTimeoutException e) {
       LOG.debug("Timed out connecting to " + sn);
     } catch (NoRouteToHostException e) {
       LOG.debug("Connecting to " + sn, e);
     } catch (SocketException e) {
       LOG.debug("Exception connecting to " + sn);
     } catch (UnknownHostException e) {
       LOG.debug("Unknown host exception connecting to  " + sn);
     } catch (FailedServerException e) {
       if (LOG.isDebugEnabled()) {
         LOG.debug("Server " + sn + " is in failed server list.");
       }
     } catch (IOException ioe) {
       Throwable cause = ioe.getCause();
       if (ioe instanceof ConnectException) {
         // Catch. Connect refused.
       } else if (cause != null && cause instanceof EOFException) {
         // Catch. Other end disconnected us.
       } else if (cause != null && cause.getMessage() != null &&
         cause.getMessage().toLowerCase().contains("connection reset")) {
         // Catch. Connection reset.
       } else {
         throw ioe;
       }
 
     }
     return service;
   }
 
   /**
    * Sets the location of <code>hbase:meta</code> in ZooKeeper to the
    * specified server address.
    * @param zookeeper zookeeper reference
    * @param serverName The server hosting <code>hbase:meta</code>
    * @param state The region transition state
    * @throws KeeperException unexpected zookeeper exception
    */
   public static void setMetaLocation(ZooKeeperWatcher zookeeper,
       ServerName serverName, RegionState.State state) throws KeeperException {
     setMetaLocation(zookeeper, serverName, HRegionInfo.DEFAULT_REPLICA_ID, state);
   }
 
   /**
    * Sets the location of <code>hbase:meta</code> in ZooKeeper to the
    * specified server address.
    * @param zookeeper
    * @param serverName
    * @param replicaId
    * @param state
    * @throws KeeperException
    */
   public static void setMetaLocation(ZooKeeperWatcher zookeeper,
       ServerName serverName, int replicaId, RegionState.State state) throws KeeperException {
     LOG.info("Setting hbase:meta region location in ZooKeeper as " + serverName);
     // Make the MetaRegionServer pb and then get its bytes and save this as
     // the znode content.
     MetaRegionServer pbrsr = MetaRegionServer.newBuilder()
       .setServer(ProtobufUtil.toServerName(serverName))
       .setRpcVersion(HConstants.RPC_CURRENT_VERSION)
       .setState(state.convert()).build();
     byte[] data = ProtobufUtil.prependPBMagic(pbrsr.toByteArray());
     try {
       ZKUtil.setData(zookeeper, zookeeper.getZNodeForReplica(replicaId), data);
     } catch(KeeperException.NoNodeException nne) {
       if (replicaId == HRegionInfo.DEFAULT_REPLICA_ID) {
         LOG.debug("META region location doesn't exist, create it");
       } else {
         LOG.debug("META region location doesn't exist for replicaId " + replicaId +
             ", create it");
       }
       ZKUtil.createAndWatch(zookeeper, zookeeper.getZNodeForReplica(replicaId), data);
     }
   }
 
   /**
    * Load the meta region state from the meta server ZNode.
    */
   public static RegionState getMetaRegionState(ZooKeeperWatcher zkw) throws KeeperException {
     return getMetaRegionState(zkw, HRegionInfo.DEFAULT_REPLICA_ID);
   }
 
   /**
    * Load the meta region state from the meta server ZNode.
    * @param zkw
    * @param replicaId
    * @return regionstate
    * @throws KeeperException
    */
   public static RegionState getMetaRegionState(ZooKeeperWatcher zkw, int replicaId)
       throws KeeperException {
     RegionState.State state = RegionState.State.OPEN;
     ServerName serverName = null;
     try {
       byte[] data = ZKUtil.getData(zkw, zkw.getZNodeForReplica(replicaId));
       if (data != null && data.length > 0 && ProtobufUtil.isPBMagicPrefix(data)) {
         try {
           int prefixLen = ProtobufUtil.lengthOfPBMagic();
           ZooKeeperProtos.MetaRegionServer rl =
             ZooKeeperProtos.MetaRegionServer.PARSER.parseFrom
               (data, prefixLen, data.length - prefixLen);
           if (rl.hasState()) {
             state = RegionState.State.convert(rl.getState());
           }
           HBaseProtos.ServerName sn = rl.getServer();
           serverName = ServerName.valueOf(
             sn.getHostName(), sn.getPort(), sn.getStartCode());
         } catch (InvalidProtocolBufferException e) {
           throw new DeserializationException("Unable to parse meta region location");
         }
       } else {
         // old style of meta region location?
         serverName = ServerName.parseFrom(data);
       }
     } catch (DeserializationException e) {
       throw ZKUtil.convert(e);
     } catch (InterruptedException e) {
       Thread.currentThread().interrupt();
     }
     if (serverName == null) {
       state = RegionState.State.OFFLINE;
     }
     return new RegionState(
         RegionReplicaUtil.getRegionInfoForReplica(HRegionInfo.FIRST_META_REGIONINFO, replicaId),
       state, serverName);
   }
 
   /**
    * Deletes the location of <code>hbase:meta</code> in ZooKeeper.
    * @param zookeeper zookeeper reference
    * @throws KeeperException unexpected zookeeper exception
    */
   public void deleteMetaLocation(ZooKeeperWatcher zookeeper)
   throws KeeperException {
     deleteMetaLocation(zookeeper, HRegionInfo.DEFAULT_REPLICA_ID);
   }
 
   public void deleteMetaLocation(ZooKeeperWatcher zookeeper, int replicaId)
   throws KeeperException {
     if (replicaId == HRegionInfo.DEFAULT_REPLICA_ID) {
       LOG.info("Deleting hbase:meta region location in ZooKeeper");
     } else {
       LOG.info("Deleting hbase:meta for " + replicaId + " region location in ZooKeeper");
     }
     try {
       // Just delete the node.  Don't need any watches.
       ZKUtil.deleteNode(zookeeper, zookeeper.getZNodeForReplica(replicaId));
     } catch(KeeperException.NoNodeException nne) {
       // Has already been deleted
     }
   }
   /**
    * Wait until the primary meta region is available. Get the secondary
    * locations as well but don't block for those.
    * @param zkw
    * @param timeout
    * @param conf
    * @return ServerName or null if we timed out.
    * @throws InterruptedException
    */
   public List<ServerName> blockUntilAvailable(final ZooKeeperWatcher zkw,
       final long timeout, Configuration conf)
           throws InterruptedException {
     int numReplicasConfigured = 1;
     try {
       List<String> metaReplicaNodes = zkw.getMetaReplicaNodes();
       numReplicasConfigured = metaReplicaNodes.size();
     } catch (KeeperException e) {
       LOG.warn("Got ZK exception " + e);
     }
     List<ServerName> servers = new ArrayList<ServerName>(numReplicasConfigured);
     ServerName server = blockUntilAvailable(zkw, timeout);
     if (server == null) return null;
     servers.add(server);
 
     for (int replicaId = 1; replicaId < numReplicasConfigured; replicaId++) {
       // return all replica locations for the meta
       servers.add(getMetaRegionLocation(zkw, replicaId));
     }
     return servers;
   }
 
   /**
    * Wait until the meta region is available and is not in transition.
    * @param zkw zookeeper connection to use
    * @param timeout maximum time to wait, in millis
    * @return ServerName or null if we timed out.
    * @throws InterruptedException
    */
   public ServerName blockUntilAvailable(final ZooKeeperWatcher zkw,
       final long timeout)
   throws InterruptedException {
     return blockUntilAvailable(zkw, HRegionInfo.DEFAULT_REPLICA_ID, timeout);
   }
 
   /**
    * Wait until the meta region is available and is not in transition.
    * @param zkw
    * @param replicaId
    * @param timeout
    * @return ServerName or null if we timed out.
    * @throws InterruptedException
    */
   public ServerName blockUntilAvailable(final ZooKeeperWatcher zkw, int replicaId,
       final long timeout)
   throws InterruptedException {
     if (timeout < 0) throw new IllegalArgumentException();
     if (zkw == null) throw new IllegalArgumentException();
     Stopwatch sw = new Stopwatch().start();
     ServerName sn = null;
     try {
       while (true) {
         sn = getMetaRegionLocation(zkw, replicaId);
         if (sn != null || sw.elapsedMillis()
             > timeout - HConstants.SOCKET_RETRY_WAIT_MS) {
           break;
         }
         Thread.sleep(HConstants.SOCKET_RETRY_WAIT_MS);
       }
     } finally {
       sw.stop();
     }
     return sn;
   }
 
   /**
    * Stop working.
    * Interrupts any ongoing waits.
    */
   public void stop() {
     if (!stopped) {
       LOG.debug("Stopping MetaTableLocator");
       stopped = true;
     }
   }
 }