mariadb-columnstore-engine/versioning/BRM/rwlockmonitor.cpp

/* Copyright (C) 2014 InfiniDB, Inc.

   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; version 2 of
   the License.

   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, write to the Free Software
   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
   MA 02110-1301, USA. */

/*
 * rwlockmonitor.cpp
 *
 *  Created on: Aug 15, 2011
 *      Author: pleblanc
 */
#include <unistd.h>
#include <iostream>
#define RWLOCKMONITOR_DLLEXPORT
#include "rwlockmonitor.h"
#undef RWLOCKMONITOR_DLLEXPORT
#include "logger.h"
#include "errorids.h"

using namespace std;
using namespace rwlock;
using namespace logging;

namespace BRM
{
RWLockMonitor::RWLockMonitor(const std::atomic<bool>* d, const std::atomic<bool>* ls, const uint32_t k) : die(d), lockStatus(ls), key(k)
{
  ts.tv_sec = 210;  // 3:30 timer
  ts.tv_nsec = 0;
  secsBetweenAttempts = 30;
  lock.reset(new RWLock(key));
}

RWLockMonitor::~RWLockMonitor()
{
}

void RWLockMonitor::operator()()
{
  /*
   * Grab a timed write lock.
   *   on failure
   *     if there's an active reader, do read_unlock()
   *     log everything else.
   *     *** write lock fixing is being postponed for now.
   */

  LockState state;
  bool gotTheLock;
  bool reportedProblem = false;
  Logger logger(30);

  while (!(*die))
  {
    gotTheLock = lock->timed_write_lock(ts, &state);

    if (*die)
      break;

    if (!gotTheLock)
    {
      if (state.mutexLocked)
      {
        if (!reportedProblem)
        {
          // Message msg(ERR_BRM_MUTEX);
          Message msg(M0092);
          logger.logMessage(LOG_TYPE_CRITICAL, msg, LoggingID());
          reportedProblem = true;
        }
      }

      else if (state.reading > 0)
      {
        if (!reportedProblem)
        {
          // Message msg(ERR_RECOVERABLE_LOCK_STATE);
          Message msg(M0094);
          Message::Args args;

          args.add(state.reading);
          args.add(state.readerswaiting);
          args.add(state.writing);
          args.add(state.writerswaiting);
          msg.format(args);
          logger.logMessage(LOG_TYPE_WARNING, msg, LoggingID());
          reportedProblem = true;
        }

        for (int i = 0; i < state.reading; i++)
          lock->read_unlock();
      }

      // the write lock is held but not by this process, not good.
      // there's a slight race here between these two vars but it's miniscule,
      // and the worst thing that happens is a false positive error msg.
      else if (state.writing > 0 && !(*lockStatus))
      {
        if (!reportedProblem)
        {
          // Message msg(ERR_UNRECOVERABLE_LOCK_STATE);
          Message msg(M0093);
          Message::Args args;

          args.add(state.reading);
          args.add(state.readerswaiting);
          args.add(state.writing);
          args.add(state.writerswaiting);
          msg.format(args);
          logger.logMessage(LOG_TYPE_CRITICAL, msg, LoggingID());
          reportedProblem = true;
        }

        /* put write lock recovery code here */
      }
      else
      {
        // the workernode is legitmately taking a long time
        // cout << "holds the lock. " << " r=" << state.reading << " rwt=" << state.readerswaiting <<
        //		" w=" << state.writing << " wwt=" << state.writerswaiting << endl;
      }
    }
    else
    {
      /* got the write lock.  If there was a problem before it's been fixed. */
      lock->write_unlock();

      if (reportedProblem)
      {
        // Message msg(ERR_SUCCESSFUL_RECOVERY);
        Message msg(M0095);
        logger.logMessage(LOG_TYPE_WARNING, msg, LoggingID());
        reportedProblem = false;
      }

      sleep(secsBetweenAttempts);
    }
  }
}

} /* namespace BRM */