MigrationMemoryManager.hpp

/*
 * @project        The CERN Tape Archive (CTA)
 * @copyright      Copyright(C) 2021 CERN
 * @license        This program is free software: you can redistribute it and/or modify
 *                 it under the terms of the GNU General Public License as published by
 *                 the Free Software Foundation, either version 3 of the License, or
 *                 (at your option) any later version.
 *
 *                 This program is distributed in the hope that it will be useful,
 *                 but WITHOUT ANY WARRANTY; without even the implied warranty of
 *                 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *                 GNU General Public License for more details.
 *
 *                 You should have received a copy of the GNU General Public License
 *                 along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#pragma once

#include "common/threading/BlockingQueue.hpp"
#include "common/threading/Thread.hpp"
#include "common/log/LogContext.hpp"

namespace castor {
namespace exception {
// Forward declaration  
class Exception;
}
namespace tape {
namespace tapeserver {
namespace daemon {
// Forward declaration
class TapeWriteTask;
class MemBlock;
class DataPipeline;
/**
 * The memory manager is responsible for allocating memory blocks and distributing
 * the free ones around to any class in need. The distribution is actively run in
 * a thread.
 */
class MigrationMemoryManager: private cta::threading::Thread {
public:
  
  /**
   * Constructor
   * @param numberOfBlocks: number of blocks to allocate
   * @param blockSize: size of each block
   */
  MigrationMemoryManager(const size_t numberOfBlocks, const size_t blockSize, 
          cta::log::LogContext lc) 
          ;
  
  /**
   * 
   * @return the nominal capacity of one block 
   */
  size_t blockCapacity();
  
  /**
   * Are all sheep back to the farm?
   * @return 
   */
  bool areBlocksAllBack() throw();
  
  /**
   * Start serving clients (in the dedicated thread)
   */
  void startThreads() ;
  
  /**
   * Waiting for clients to finish (in the dedicated thread)
   */
  void waitThreads() ;
  
  /**
   * Adds a new client in need for free memory blocks
   * @param c: the new client
   */
  void addClient(DataPipeline* c) ;
  
  /**
   * Takes back a block which has been released by one of the clients
   * @param mb: the pointer to the block
   */
  void releaseBlock(MemBlock *mb) ;
  
  /**
   * Function used to specify that there are no more clients for this memory manager.
   * See the definition of endOfClients below.
   */
  void finish() ;

  /**
   * Destructor
   */
  ~MigrationMemoryManager() throw();
private:
  
  
  const size_t m_blockCapacity;
  
  /**
   * Total number of allocated memory blocks
   */
  size_t m_totalNumberOfBlocks;
  
  /**
   * Total amount of memory allocated
   */
  size_t m_totalMemoryAllocated;
  
  /**
   * Count of blocks provided
   */
  size_t m_blocksProvided;
  
  /**
   * Count of blocks returned
   */
  size_t m_blocksReturned;
  
  /**
   * Mutex protecting the counters
   */
  cta::threading::Mutex m_countersMutex;
  
  /**
   * Container for the free blocks
   */
  cta::threading::BlockingQueue<MemBlock *> m_freeBlocks;
  
  /**
   * The client queue: we will feed them as soon as blocks
   * become free. This is done in a dedicated thread.
   */
  cta::threading::BlockingQueue<DataPipeline *> m_clientQueue;

  /**
   * Logging purpose. Given the fact the class is threaded, the LogContext
   * has to be copied.
   */
  cta::log::LogContext m_lc;
    
  /**
   * Thread routine: pops a client and provides him blocks until he is happy!
   */
  void run() ;
  
};

}
}
}
}