/**
    * 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.procedure;
  
  import java.io.IOException;
  import java.util.ArrayDeque;
  import java.util.Deque;
  import java.util.concurrent.locks.Condition;
  import java.util.concurrent.locks.ReentrantLock;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.hbase.TableName;
  import org.apache.hadoop.hbase.TableExistsException;
  import org.apache.hadoop.hbase.TableNotFoundException;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.classification.InterfaceStability;
  import org.apache.hadoop.hbase.procedure2.Procedure;
  import org.apache.hadoop.hbase.procedure2.ProcedureFairRunQueues;
  import org.apache.hadoop.hbase.procedure2.ProcedureRunnableSet;
  import org.apache.hadoop.hbase.master.TableLockManager;
  import org.apache.hadoop.hbase.master.TableLockManager.TableLock;
  import org.apache.hadoop.hbase.master.procedure.TableProcedureInterface.TableOperationType;
  
  /**
   * ProcedureRunnableSet for the Master Procedures.
   * This RunnableSet tries to provide to the ProcedureExecutor procedures
   * that can be executed without having to wait on a lock.
   * Most of the master operations can be executed concurrently, if the they
   * are operating on different tables (e.g. two create table can be performed
   * at the same, time assuming table A and table B).
   *
   * Each procedure should implement an interface providing information for this queue.
   * for example table related procedures should implement TableProcedureInterface.
   * each procedure will be pushed in its own queue, and based on the operation type
   * we may take smarter decision. e.g. we can abort all the operations preceding
   * a delete table, or similar.
   */
  @InterfaceAudience.Private
  @InterfaceStability.Evolving
  public class MasterProcedureQueue implements ProcedureRunnableSet {
    private static final Log LOG = LogFactory.getLog(MasterProcedureQueue.class);
  
    private final ProcedureFairRunQueues<TableName, RunQueue> fairq;
    private final ReentrantLock lock = new ReentrantLock();
    private final Condition waitCond = lock.newCondition();
    private final TableLockManager lockManager;
  
    private final int metaTablePriority;
    private final int userTablePriority;
    private final int sysTablePriority;
  
    private int queueSize;
  
    public MasterProcedureQueue(final Configuration conf, final TableLockManager lockManager) {
      this.fairq = new ProcedureFairRunQueues<TableName, RunQueue>(1);
      this.lockManager = lockManager;
  
      // TODO: should this be part of the HTD?
      metaTablePriority = conf.getInt("hbase.master.procedure.queue.meta.table.priority", 3);
      sysTablePriority = conf.getInt("hbase.master.procedure.queue.system.table.priority", 2);
      userTablePriority = conf.getInt("hbase.master.procedure.queue.user.table.priority", 1);
    }
  
    @Override
    public void addFront(final Procedure proc) {
      lock.lock();
      try {
        getRunQueueOrCreate(proc).addFront(proc);
        queueSize++;
        waitCond.signal();
      } finally {
        lock.unlock();
      }
    }
  
    @Override
    public void addBack(final Procedure proc) {
      lock.lock();
      try {
        getRunQueueOrCreate(proc).addBack(proc);
        queueSize++;
       waitCond.signal();
     } finally {
       lock.unlock();
     }
   }
 
   @Override
   public void yield(final Procedure proc) {
     addFront(proc);
   }
 
   @Override
   @edu.umd.cs.findbugs.annotations.SuppressWarnings("WA_AWAIT_NOT_IN_LOOP")
   public Long poll() {
     lock.lock();
     try {
       if (queueSize == 0) {
         waitCond.await();
         if (queueSize == 0) {
           return null;
         }
       }
 
       RunQueue queue = fairq.poll();
       if (queue != null && queue.isAvailable()) {
         queueSize--;
         return queue.poll();
       }
     } catch (InterruptedException e) {
       Thread.currentThread().interrupt();
       return null;
     } finally {
       lock.unlock();
     }
     return null;
   }
 
   @Override
   public void signalAll() {
     lock.lock();
     try {
       waitCond.signalAll();
     } finally {
       lock.unlock();
     }
   }
 
   @Override
   public void clear() {
     lock.lock();
     try {
       fairq.clear();
       queueSize = 0;
     } finally {
       lock.unlock();
     }
   }
 
   @Override
   public int size() {
     lock.lock();
     try {
       return queueSize;
     } finally {
       lock.unlock();
     }
   }
 
   @Override
   public String toString() {
     lock.lock();
     try {
       return "MasterProcedureQueue size=" + queueSize + ": " + fairq;
     } finally {
       lock.unlock();
     }
   }
 
   @Override
   public void completionCleanup(Procedure proc) {
     if (proc instanceof TableProcedureInterface) {
       TableProcedureInterface iProcTable = (TableProcedureInterface)proc;
       boolean tableDeleted;
       if (proc.hasException()) {
         IOException procEx =  proc.getException().unwrapRemoteException();
         if (iProcTable.getTableOperationType() == TableOperationType.CREATE) {
           // create failed because the table already exist
           tableDeleted = !(procEx instanceof TableExistsException);
         } else {
           // the operation failed because the table does not exist
           tableDeleted = (procEx instanceof TableNotFoundException);
         }
       } else {
         // the table was deleted
         tableDeleted = (iProcTable.getTableOperationType() == TableOperationType.DELETE);
       }
       if (tableDeleted) {
         markTableAsDeleted(iProcTable.getTableName());
       }
     }
   }
 
   private RunQueue getRunQueueOrCreate(final Procedure proc) {
     if (proc instanceof TableProcedureInterface) {
       final TableName table = ((TableProcedureInterface)proc).getTableName();
       return getRunQueueOrCreate(table);
     }
     // TODO: at the moment we only have Table procedures
     // if you are implementing a non-table procedure, you have two option create
     // a group for all the non-table procedures or try to find a key for your
     // non-table procedure and implement something similar to the TableRunQueue.
     throw new UnsupportedOperationException("RQs for non-table procedures are not implemented yet");
   }
 
   private TableRunQueue getRunQueueOrCreate(final TableName table) {
     final TableRunQueue queue = getRunQueue(table);
     if (queue != null) return queue;
     return (TableRunQueue)fairq.add(table, createTableRunQueue(table));
   }
 
   private TableRunQueue createTableRunQueue(final TableName table) {
     int priority = userTablePriority;
     if (table.equals(TableName.META_TABLE_NAME)) {
       priority = metaTablePriority;
     } else if (table.isSystemTable()) {
       priority = sysTablePriority;
     }
     return new TableRunQueue(priority);
   }
 
   private TableRunQueue getRunQueue(final TableName table) {
     return (TableRunQueue)fairq.get(table);
   }
 
   /**
    * Try to acquire the read lock on the specified table.
    * other read operations in the table-queue may be executed concurrently,
    * otherwise they have to wait until all the read-locks are released.
    * @param table Table to lock
    * @param purpose Human readable reason for locking the table
    * @return true if we were able to acquire the lock on the table, otherwise false.
    */
   public boolean tryAcquireTableRead(final TableName table, final String purpose) {
     return getRunQueueOrCreate(table).tryRead(lockManager, table, purpose);
   }
 
   /**
    * Release the read lock taken with tryAcquireTableRead()
    * @param table the name of the table that has the read lock
    */
   public void releaseTableRead(final TableName table) {
     getRunQueue(table).releaseRead(lockManager, table);
   }
 
   /**
    * Try to acquire the write lock on the specified table.
    * other operations in the table-queue will be executed after the lock is released.
    * @param table Table to lock
    * @param purpose Human readable reason for locking the table
    * @return true if we were able to acquire the lock on the table, otherwise false.
    */
   public boolean tryAcquireTableWrite(final TableName table, final String purpose) {
     return getRunQueueOrCreate(table).tryWrite(lockManager, table, purpose);
   }
 
   /**
    * Release the write lock taken with tryAcquireTableWrite()
    * @param table the name of the table that has the write lock
    */
   public void releaseTableWrite(final TableName table) {
     getRunQueue(table).releaseWrite(lockManager, table);
   }
 
   /**
    * Tries to remove the queue and the table-lock of the specified table.
    * If there are new operations pending (e.g. a new create),
    * the remove will not be performed.
    * @param table the name of the table that should be marked as deleted
    * @return true if deletion succeeded, false otherwise meaning that there are
    *    other new operations pending for that table (e.g. a new create).
    */
   protected boolean markTableAsDeleted(final TableName table) {
     TableRunQueue queue = getRunQueue(table);
     if (queue != null) {
       lock.lock();
       try {
         if (queue.isEmpty() && queue.acquireDeleteLock()) {
           fairq.remove(table);
 
           // Remove the table lock
           try {
             lockManager.tableDeleted(table);
           } catch (IOException e) {
             LOG.warn("Received exception from TableLockManager.tableDeleted:", e); //not critical
           }
         } else {
           // TODO: If there are no create, we can drop all the other ops
           return false;
         }
       } finally {
         lock.unlock();
       }
     }
     return true;
   }
 
   private interface RunQueue extends ProcedureFairRunQueues.FairObject {
     void addFront(Procedure proc);
     void addBack(Procedure proc);
     Long poll();
     boolean acquireDeleteLock();
   }
 
   /**
    * Run Queue for a Table. It contains a read-write lock that is used by the
    * MasterProcedureQueue to decide if we should fetch an item from this queue
    * or skip to another one which will be able to run without waiting for locks.
    */
   private static class TableRunQueue implements RunQueue {
     private final Deque<Long> runnables = new ArrayDeque<Long>();
     private final int priority;
 
     private TableLock tableLock = null;
     private boolean wlock = false;
     private int rlock = 0;
 
     public TableRunQueue(int priority) {
       this.priority = priority;
     }
 
     @Override
     public void addFront(final Procedure proc) {
       runnables.addFirst(proc.getProcId());
     }
 
     // TODO: Improve run-queue push with TableProcedureInterface.getType()
     //       we can take smart decisions based on the type of the operation (e.g. create/delete)
     @Override
     public void addBack(final Procedure proc) {
       runnables.addLast(proc.getProcId());
     }
 
     @Override
     public Long poll() {
       return runnables.poll();
     }
 
     @Override
     public boolean isAvailable() {
       synchronized (this) {
         return !wlock && !runnables.isEmpty();
       }
     }
 
     public boolean isEmpty() {
       return runnables.isEmpty();
     }
 
     @Override
     public synchronized boolean acquireDeleteLock() {
       if (isLocked()) {
         return false;
       }
       wlock = true;
       return true;
     }
 
     public boolean isLocked() {
       synchronized (this) {
         return wlock || rlock > 0;
       }
     }
 
     public boolean tryRead(final TableLockManager lockManager,
         final TableName tableName, final String purpose) {
       synchronized (this) {
         if (wlock) {
           return false;
         }
 
         // Take zk-read-lock
         tableLock = lockManager.readLock(tableName, purpose);
         try {
           tableLock.acquire();
         } catch (IOException e) {
           LOG.error("failed acquire read lock on " + tableName, e);
           tableLock = null;
           return false;
         }
 
         rlock++;
       }
       return true;
     }
 
     public void releaseRead(final TableLockManager lockManager,
         final TableName tableName) {
       synchronized (this) {
         releaseTableLock(lockManager, rlock == 1);
         rlock--;
       }
     }
 
     public boolean tryWrite(final TableLockManager lockManager,
         final TableName tableName, final String purpose) {
       synchronized (this) {
         if (wlock || rlock > 0) {
           return false;
         }
 
         // Take zk-write-lock
         tableLock = lockManager.writeLock(tableName, purpose);
         try {
           tableLock.acquire();
         } catch (IOException e) {
           LOG.error("failed acquire write lock on " + tableName, e);
           tableLock = null;
           return false;
         }
         wlock = true;
       }
       return true;
     }
 
     public void releaseWrite(final TableLockManager lockManager,
         final TableName tableName) {
       synchronized (this) {
         releaseTableLock(lockManager, true);
         wlock = false;
       }
     }
 
     private void releaseTableLock(final TableLockManager lockManager, boolean reset) {
       for (int i = 0; i < 3; ++i) {
         try {
           tableLock.release();
           if (reset) {
             tableLock = null;
           }
           break;
         } catch (IOException e) {
           LOG.warn("Could not release the table write-lock", e);
         }
       }
     }
 
     @Override
     public int getPriority() {
       return priority;
     }
 
     @Override
     public String toString() {
       return runnables.toString();
     }
   }
 }