/*
    * Copyright The Apache Software Foundation
    *
    * 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.master;
  
  import java.io.IOException;
  import java.io.InterruptedIOException;
  import java.util.List;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.hbase.TableName;
  import org.apache.hadoop.hbase.InterProcessLock;
  import org.apache.hadoop.hbase.InterProcessLock.MetadataHandler;
  import org.apache.hadoop.hbase.InterProcessReadWriteLock;
  import org.apache.hadoop.hbase.ServerName;
  import org.apache.hadoop.hbase.exceptions.LockTimeoutException;
  import org.apache.hadoop.hbase.protobuf.ProtobufUtil;
  import org.apache.hadoop.hbase.protobuf.generated.ZooKeeperProtos;
  import org.apache.hadoop.hbase.util.Bytes;
  import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
  import org.apache.hadoop.hbase.zookeeper.ZKUtil;
  import org.apache.hadoop.hbase.zookeeper.ZooKeeperWatcher;
  import org.apache.hadoop.hbase.zookeeper.lock.ZKInterProcessReadWriteLock;
  import org.apache.zookeeper.KeeperException;
  
  /**
   * A manager for distributed table level locks.
   */
  @InterfaceAudience.Private
  public abstract class TableLockManager {
  
    private static final Log LOG = LogFactory.getLog(TableLockManager.class);
  
    /** Configuration key for enabling table-level locks for schema changes */
    public static final String TABLE_LOCK_ENABLE =
      "hbase.table.lock.enable";
  
    /** by default we should enable table-level locks for schema changes */
    private static final boolean DEFAULT_TABLE_LOCK_ENABLE = true;
  
    /** Configuration key for time out for trying to acquire table locks */
    protected static final String TABLE_WRITE_LOCK_TIMEOUT_MS =
      "hbase.table.write.lock.timeout.ms";
  
    /** Configuration key for time out for trying to acquire table locks */
    protected static final String TABLE_READ_LOCK_TIMEOUT_MS =
      "hbase.table.read.lock.timeout.ms";
  
    protected static final long DEFAULT_TABLE_WRITE_LOCK_TIMEOUT_MS =
      600 * 1000; //10 min default
  
    protected static final long DEFAULT_TABLE_READ_LOCK_TIMEOUT_MS =
      600 * 1000; //10 min default
  
    public static final String TABLE_LOCK_EXPIRE_TIMEOUT = "hbase.table.lock.expire.ms";
  
    public static final long DEFAULT_TABLE_LOCK_EXPIRE_TIMEOUT_MS =
        600 * 1000; //10 min default
  
    /**
     * A distributed lock for a table.
     */
    @InterfaceAudience.Private
    public interface TableLock {
      /**
       * Acquire the lock, with the configured lock timeout.
       * @throws LockTimeoutException If unable to acquire a lock within a specified
       * time period (if any)
       * @throws IOException If unrecoverable error occurs
       */
      void acquire() throws IOException;
  
      /**
       * Release the lock already held.
       * @throws IOException If there is an unrecoverable error releasing the lock
       */
      void release() throws IOException;
    }
  
    /**
    * Returns a TableLock for locking the table for exclusive access
    * @param tableName Table to lock
    * @param purpose Human readable reason for locking the table
    * @return A new TableLock object for acquiring a write lock
    */
   public abstract TableLock writeLock(TableName tableName, String purpose);
 
   /**
    * Returns a TableLock for locking the table for shared access among read-lock holders
    * @param tableName Table to lock
    * @param purpose Human readable reason for locking the table
    * @return A new TableLock object for acquiring a read lock
    */
   public abstract TableLock readLock(TableName tableName, String purpose);
 
   /**
    * Visits all table locks(read and write), and lock attempts with the given callback
    * MetadataHandler.
    * @param handler the metadata handler to call
    * @throws IOException If there is an unrecoverable error
    */
   public abstract void visitAllLocks(MetadataHandler handler) throws IOException;
 
   /**
    * Force releases all table locks(read and write) that have been held longer than
    * "hbase.table.lock.expire.ms". Assumption is that the clock skew between zookeeper
    * and this servers is negligible.
    * The behavior of the lock holders still thinking that they have the lock is undefined.
    * @throws IOException If there is an unrecoverable error
    */
   public abstract void reapAllExpiredLocks() throws IOException;
 
   /**
    * Force releases table write locks and lock attempts even if this thread does
    * not own the lock. The behavior of the lock holders still thinking that they
    * have the lock is undefined. This should be used carefully and only when
    * we can ensure that all write-lock holders have died. For example if only
    * the master can hold write locks, then we can reap it's locks when the backup
    * master starts.
    * @throws IOException If there is an unrecoverable error
    */
   public abstract void reapWriteLocks() throws IOException;
 
   /**
    * Called after a table has been deleted, and after the table lock is  released.
    * TableLockManager should do cleanup for the table state.
    * @param tableName name of the table
    * @throws IOException If there is an unrecoverable error releasing the lock
    */
   public abstract void tableDeleted(TableName tableName)
       throws IOException;
 
   /**
    * Creates and returns a TableLockManager according to the configuration
    */
   public static TableLockManager createTableLockManager(Configuration conf,
       ZooKeeperWatcher zkWatcher, ServerName serverName) {
     // Initialize table level lock manager for schema changes, if enabled.
     if (conf.getBoolean(TABLE_LOCK_ENABLE,
         DEFAULT_TABLE_LOCK_ENABLE)) {
       long writeLockTimeoutMs = conf.getLong(TABLE_WRITE_LOCK_TIMEOUT_MS,
           DEFAULT_TABLE_WRITE_LOCK_TIMEOUT_MS);
       long readLockTimeoutMs = conf.getLong(TABLE_READ_LOCK_TIMEOUT_MS,
           DEFAULT_TABLE_READ_LOCK_TIMEOUT_MS);
       long lockExpireTimeoutMs = conf.getLong(TABLE_LOCK_EXPIRE_TIMEOUT,
           DEFAULT_TABLE_LOCK_EXPIRE_TIMEOUT_MS);
 
       return new ZKTableLockManager(zkWatcher, serverName, writeLockTimeoutMs, readLockTimeoutMs, lockExpireTimeoutMs);
     }
 
     return new NullTableLockManager();
   }
 
   /**
    * A null implementation
    */
   @InterfaceAudience.Private
   public static class NullTableLockManager extends TableLockManager {
     static class NullTableLock implements TableLock {
       @Override
       public void acquire() throws IOException {
       }
       @Override
       public void release() throws IOException {
       }
     }
     @Override
     public TableLock writeLock(TableName tableName, String purpose) {
       return new NullTableLock();
     }
     @Override
     public TableLock readLock(TableName tableName, String purpose) {
       return new NullTableLock();
     }
     @Override
     public void reapAllExpiredLocks() throws IOException {
     }
     @Override
     public void reapWriteLocks() throws IOException {
     }
     @Override
     public void tableDeleted(TableName tableName) throws IOException {
     }
     @Override
     public void visitAllLocks(MetadataHandler handler) throws IOException {
     }
   }
 
   /** Public for hbck */
   public static ZooKeeperProtos.TableLock fromBytes(byte[] bytes) {
     int pblen = ProtobufUtil.lengthOfPBMagic();
     if (bytes == null || bytes.length < pblen) {
       return null;
     }
     try {
       ZooKeeperProtos.TableLock.Builder builder = ZooKeeperProtos.TableLock.newBuilder();
       ProtobufUtil.mergeFrom(builder, bytes, pblen, bytes.length - pblen);
       return builder.build();
     } catch (IOException ex) {
       LOG.warn("Exception in deserialization", ex);
     }
     return null;
   }
 
   /**
    * ZooKeeper based TableLockManager
    */
   @InterfaceAudience.Private
   private static class ZKTableLockManager extends TableLockManager {
 
     private static final MetadataHandler METADATA_HANDLER = new MetadataHandler() {
       @Override
       public void handleMetadata(byte[] ownerMetadata) {
         if (!LOG.isDebugEnabled()) {
           return;
         }
         ZooKeeperProtos.TableLock data = fromBytes(ownerMetadata);
         if (data == null) {
           return;
         }
         LOG.debug("Table is locked by " +
             String.format("[tableName=%s:%s, lockOwner=%s, threadId=%s, " +
                 "purpose=%s, isShared=%s, createTime=%s]",
                 data.getTableName().getNamespace().toStringUtf8(),
                 data.getTableName().getQualifier().toStringUtf8(),
                 ProtobufUtil.toServerName(data.getLockOwner()), data.getThreadId(),
                 data.getPurpose(), data.getIsShared(), data.getCreateTime()));
       }
     };
 
     private static class TableLockImpl implements TableLock {
       long lockTimeoutMs;
       TableName tableName;
       InterProcessLock lock;
       boolean isShared;
       ZooKeeperWatcher zkWatcher;
       ServerName serverName;
       String purpose;
 
       public TableLockImpl(TableName tableName, ZooKeeperWatcher zkWatcher,
           ServerName serverName, long lockTimeoutMs, boolean isShared, String purpose) {
         this.tableName = tableName;
         this.zkWatcher = zkWatcher;
         this.serverName = serverName;
         this.lockTimeoutMs = lockTimeoutMs;
         this.isShared = isShared;
         this.purpose = purpose;
       }
 
       @Override
       public void acquire() throws IOException {
         if (LOG.isTraceEnabled()) {
           LOG.trace("Attempt to acquire table " + (isShared ? "read" : "write") +
             " lock on: " + tableName + " for:" + purpose);
         }
 
         lock = createTableLock();
         try {
           if (lockTimeoutMs == -1) {
             // Wait indefinitely
             lock.acquire();
           } else {
             if (!lock.tryAcquire(lockTimeoutMs)) {
               throw new LockTimeoutException("Timed out acquiring " +
                 (isShared ? "read" : "write") + "lock for table:" + tableName +
                 "for:" + purpose + " after " + lockTimeoutMs + " ms.");
             }
           }
         } catch (InterruptedException e) {
           LOG.warn("Interrupted acquiring a lock for " + tableName, e);
           Thread.currentThread().interrupt();
           throw new InterruptedIOException("Interrupted acquiring a lock");
         }
         if (LOG.isTraceEnabled()) LOG.trace("Acquired table " + (isShared ? "read" : "write")
             + " lock on " + tableName + " for " + purpose);
       }
 
       @Override
       public void release() throws IOException {
         if (LOG.isTraceEnabled()) {
           LOG.trace("Attempt to release table " + (isShared ? "read" : "write")
               + " lock on " + tableName);
         }
         if (lock == null) {
           throw new IllegalStateException("Table " + tableName +
             " is not locked!");
         }
 
         try {
           lock.release();
         } catch (InterruptedException e) {
           LOG.warn("Interrupted while releasing a lock for " + tableName);
           throw new InterruptedIOException();
         }
         if (LOG.isTraceEnabled()) {
           LOG.trace("Released table lock on " + tableName);
         }
       }
 
       private InterProcessLock createTableLock() {
         String tableLockZNode = ZKUtil.joinZNode(zkWatcher.tableLockZNode,
             tableName.getNameAsString());
 
         ZooKeeperProtos.TableLock data = ZooKeeperProtos.TableLock.newBuilder()
           .setTableName(ProtobufUtil.toProtoTableName(tableName))
           .setLockOwner(ProtobufUtil.toServerName(serverName))
           .setThreadId(Thread.currentThread().getId())
           .setPurpose(purpose)
           .setIsShared(isShared)
           .setCreateTime(EnvironmentEdgeManager.currentTime()).build();
         byte[] lockMetadata = toBytes(data);
 
         InterProcessReadWriteLock lock = new ZKInterProcessReadWriteLock(zkWatcher, tableLockZNode,
           METADATA_HANDLER);
         return isShared ? lock.readLock(lockMetadata) : lock.writeLock(lockMetadata);
       }
     }
 
     private static byte[] toBytes(ZooKeeperProtos.TableLock data) {
       return ProtobufUtil.prependPBMagic(data.toByteArray());
     }
 
     private final ServerName serverName;
     private final ZooKeeperWatcher zkWatcher;
     private final long writeLockTimeoutMs;
     private final long readLockTimeoutMs;
     private final long lockExpireTimeoutMs;
 
     /**
      * Initialize a new manager for table-level locks.
      * @param zkWatcher
      * @param serverName Address of the server responsible for acquiring and
      * releasing the table-level locks
      * @param writeLockTimeoutMs Timeout (in milliseconds) for acquiring a write lock for a
      * given table, or -1 for no timeout
      * @param readLockTimeoutMs Timeout (in milliseconds) for acquiring a read lock for a
      * given table, or -1 for no timeout
      */
     public ZKTableLockManager(ZooKeeperWatcher zkWatcher,
       ServerName serverName, long writeLockTimeoutMs, long readLockTimeoutMs, long lockExpireTimeoutMs) {
       this.zkWatcher = zkWatcher;
       this.serverName = serverName;
       this.writeLockTimeoutMs = writeLockTimeoutMs;
       this.readLockTimeoutMs = readLockTimeoutMs;
       this.lockExpireTimeoutMs = lockExpireTimeoutMs;
     }
 
     @Override
     public TableLock writeLock(TableName tableName, String purpose) {
       return new TableLockImpl(tableName, zkWatcher,
           serverName, writeLockTimeoutMs, false, purpose);
     }
 
     public TableLock readLock(TableName tableName, String purpose) {
       return new TableLockImpl(tableName, zkWatcher,
           serverName, readLockTimeoutMs, true, purpose);
     }
 
     public void visitAllLocks(MetadataHandler handler) throws IOException {
       for (String tableName : getTableNames()) {
         String tableLockZNode = ZKUtil.joinZNode(zkWatcher.tableLockZNode, tableName);
         ZKInterProcessReadWriteLock lock = new ZKInterProcessReadWriteLock(
             zkWatcher, tableLockZNode, null);
         lock.readLock(null).visitLocks(handler);
         lock.writeLock(null).visitLocks(handler);
       }
     }
 
     private List<String> getTableNames() throws IOException {
 
       List<String> tableNames;
       try {
         tableNames = ZKUtil.listChildrenNoWatch(zkWatcher, zkWatcher.tableLockZNode);
       } catch (KeeperException e) {
         LOG.error("Unexpected ZooKeeper error when listing children", e);
         throw new IOException("Unexpected ZooKeeper exception", e);
       }
       return tableNames;
     }
 
     @Override
     public void reapWriteLocks() throws IOException {
       //get the table names
       try {
         for (String tableName : getTableNames()) {
           String tableLockZNode = ZKUtil.joinZNode(zkWatcher.tableLockZNode, tableName);
           ZKInterProcessReadWriteLock lock = new ZKInterProcessReadWriteLock(
               zkWatcher, tableLockZNode, null);
           lock.writeLock(null).reapAllLocks();
         }
       } catch (IOException ex) {
         throw ex;
       } catch (Exception ex) {
         LOG.warn("Caught exception while reaping table write locks", ex);
       }
     }
 
     @Override
     public void reapAllExpiredLocks() throws IOException {
       //get the table names
       try {
         for (String tableName : getTableNames()) {
           String tableLockZNode = ZKUtil.joinZNode(zkWatcher.tableLockZNode, tableName);
           ZKInterProcessReadWriteLock lock = new ZKInterProcessReadWriteLock(
               zkWatcher, tableLockZNode, null);
           lock.readLock(null).reapExpiredLocks(lockExpireTimeoutMs);
           lock.writeLock(null).reapExpiredLocks(lockExpireTimeoutMs);
         }
       } catch (IOException ex) {
         throw ex;
       } catch (Exception ex) {
         throw new IOException(ex);
       }
     }
 
     @Override
     public void tableDeleted(TableName tableName) throws IOException {
       //table write lock from DeleteHandler is already released, just delete the parent znode
       String tableNameStr = tableName.getNameAsString();
       String tableLockZNode = ZKUtil.joinZNode(zkWatcher.tableLockZNode, tableNameStr);
       try {
         ZKUtil.deleteNode(zkWatcher, tableLockZNode);
       } catch (KeeperException ex) {
         if (ex.code() == KeeperException.Code.NOTEMPTY) {
           //we might get this in rare occasions where a CREATE table or some other table operation
           //is waiting to acquire the lock. In this case, parent znode won't be deleted.
           LOG.warn("Could not delete the znode for table locks because NOTEMPTY: "
               + tableLockZNode);
           return;
         }
         throw new IOException(ex);
       }
     }
   }
 }