~drizzle-trunk/drizzle/development

/*

 * Copyright (C) 2010 Joseph Daly <skinny.moey@gmail.com>

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions are met:

 *

 *   * Redistributions of source code must retain the above copyright notice,

 *     this list of conditions and the following disclaimer.

 *   * Redistributions in binary form must reproduce the above copyright notice,

 *     this list of conditions and the following disclaimer in the documentation

 *     and/or other materials provided with the distribution.

 *   * Neither the name of Joseph Daly nor the names of its contributors

 *     may be used to endorse or promote products derived from this software

 *     without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"

 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE

 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR

 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN

 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF

 * THE POSSIBILITY OF SUCH DAMAGE.

 *

 */

/**

 * @details

 *

 * The scoreboard is a pre-allocated vector of vectors of ScoreBoardSlots. It

 * can be thought of as a vector of buckets where each bucket contains

 * pre-allocated ScoreBoardSlots. To determine which bucket gets used for

 * recording statistics the modulus operator is used on the session_id. This 

 * will result in a bucket to search for a unused ScoreBoardSlot. 

 * 

 * Locking  

 *   

 * Each bucket has a its own lock this allows a search of bucket 1 and bucket 2

 * to happen concurrently.  

 *

 */

#include <config.h>

#include <drizzled/plugin.h>

#include <drizzled/statistics_variables.h>

#include "scoreboard.h"

#include <math.h>

using namespace drizzled;

using namespace std;

Scoreboard::Scoreboard(uint32_t in_number_sessions, uint32_t in_number_buckets)

  :

    number_sessions(in_number_sessions),

    number_buckets(in_number_buckets)

{

  /* calculate the number of elements in each bucket */

  number_per_bucket= static_cast<uint32_t> ( ceil( static_cast<double>(number_sessions) / static_cast<double>(number_buckets) ) );

  vector_of_scoreboard_vectors.reserve(number_buckets);

  /* populate the vector of scoreboard vectors */

  for (uint32_t j= 0; j < number_buckets; ++j)

  {

    vector<ScoreboardSlot* > *scoreboard_vector= new vector<ScoreboardSlot*>;

    scoreboard_vector->reserve(number_per_bucket);

    /* preallocate the individual vectors */

    for (uint32_t h= 0; h < number_per_bucket; ++h)

      scoreboard_vector->push_back(new ScoreboardSlot);

    /* insert the vector into the vector of scoreboard vectors */

    vector_of_scoreboard_vectors.push_back(scoreboard_vector); 

  }

  vector_of_scoreboard_locks.reserve(number_buckets);

  /* populate the scoreboard locks vector each ScoreboardSlot vector gets a lock */

  for (uint32_t k= 0; k < number_buckets; ++k)

    vector_of_scoreboard_locks.push_back(new boost::shared_mutex);

  /* calculate the approximate memory allocation of the scoreboard */

  size_t statusVarsSize= sizeof(StatusVars) + sizeof(system_status_var);

  size_t userCommandsSize= sizeof(UserCommands) + sizeof(uint64_t) * SQLCOM_END;

  scoreboard_size_bytes= (statusVarsSize + userCommandsSize) * number_per_bucket * number_buckets;

}

Scoreboard::~Scoreboard()

{

  BOOST_FOREACH(std::vector<ScoreboardSlot*>* it0, vector_of_scoreboard_vectors)

  {

    BOOST_FOREACH(ScoreboardSlot* it, *it0)

      delete it; 

    delete it0;

  }

  BOOST_FOREACH(boost::shared_mutex* it, vector_of_scoreboard_locks)

    delete it;

}

uint32_t Scoreboard::getBucketNumber(Session *session) const

{

  return session->getSessionId() % number_buckets;

}

ScoreboardSlot* Scoreboard::findScoreboardSlotToLog(Session *session) 

{

  /* our bucket */

  uint32_t bucket_number= getBucketNumber(session);

  /* our vector corresponding to bucket_number */

  vector<ScoreboardSlot* > *scoreboard_vector= vector_of_scoreboard_vectors.at(bucket_number);

  /* Check if this session has already claimed a slot */

  int32_t session_scoreboard_slot= session->getScoreboardIndex();

  if (session_scoreboard_slot != -1)

    return scoreboard_vector->at(session_scoreboard_slot);

  boost::shared_mutex* LOCK_scoreboard_vector= vector_of_scoreboard_locks.at(bucket_number);

  LOCK_scoreboard_vector->lock();

  int32_t slot_index= 0;

  for (vector<ScoreboardSlot*>::iterator it= scoreboard_vector->begin(); it != scoreboard_vector->end(); ++it, ++slot_index)

  {

    ScoreboardSlot& slot= **it;

    if (slot.isInUse())

      continue;

    slot.setInUse(true);

    slot.setSessionId(session->getSessionId());

    slot.setUser(session->user()->username());

    slot.setIp(session->user()->address());

    session->setScoreboardIndex(slot_index);

    LOCK_scoreboard_vector->unlock();

    return &slot; 

  }

  LOCK_scoreboard_vector->unlock(); 

  /* its possible we did not claim a slot if the scoreboard size is somehow smaller then the 

     active connections */ 

  return NULL; 

}

ScoreboardSlot* Scoreboard::findOurScoreboardSlot(Session *session)

{

  /* Check if this session has already claimed a slot */

  int32_t session_scoreboard_slot= session->getScoreboardIndex();

  if (session_scoreboard_slot == -1) 

    return NULL;

  return vector_of_scoreboard_vectors.at(getBucketNumber(session))->at(session_scoreboard_slot);

}