cache.cxx

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/* ====================================================================
 * The Vovida Software License, Version 1.0 
 * 
 * Copyright (c) 2000 Vovida Networks, Inc.  All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 
 * 2. 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.
 * 
 * 3. The names "VOCAL", "Vovida Open Communication Application Library",
 *    and "Vovida Open Communication Application Library (VOCAL)" must
 *    not be used to endorse or promote products derived from this
 *    software without prior written permission. For written
 *    permission, please contact [e-mail].
 *
 * 4. Products derived from this software may not be called "VOCAL", nor
 *    may "VOCAL" appear in their name, without prior written
 *    permission of Vovida Networks, Inc.
 * 
 * THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, TITLE AND
 * NON-INFRINGEMENT ARE DISCLAIMED.  IN NO EVENT SHALL VOVIDA
 * NETWORKS, INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT DAMAGES
 * IN EXCESS OF $1,000, NOR FOR ANY 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.
 * 
 * ====================================================================
 * 
 * This software consists of voluntary contributions made by Vovida
 * Networks, Inc. and many individuals on behalf of Vovida Networks,
 * Inc.  For more information on Vovida Networks, Inc., please see
 * <http://www.vovida.org/>.
 *
 */
 
 
/**
 * Cache.cxx -- 11/03/03
 * 
 * This provides a cache system to the clients, the cache deals with 
 * the issues of finding the database etc, etc.
 */

#include "Cache.hxx"

#include "RecordTypes.h"
#include "Record.hxx"
#include "UpdateRegInfoRec.hxx"
#include "DBResultset.hxx"

#include "ConnectionManager.hxx"
#include "CacheManager.hxx"

#include "support.hxx"

#include "cpLog.h"

#include <sys/types.h>
#include <unistd.h>
#include <string>

Cache* Cache::myInstance = NULL;
int Cache::usageCount = 0;

/**
 * Returns the existing instance of the Cache object 
 * Or creates one if none exist
 * A basic implementation of the singleton design 
 * pattern.
 * @return Cache* A pointer to the single instance of the Cache
 */

Cache* Cache::getInstance() {

  // Standard singleton pattern, check if an instance exists
  if (myInstance == NULL) { 
    // No existing instance
    myInstance = new Cache();
    usageCount = 0;
  }

  cpLog(LOG_DEBUG, "Retrieving instance, user count is %d.", (usageCount+1));

  usageCount++;
  return myInstance;
}

void Cache::freeInstance() { 

  cpLog(LOG_DEBUG, "Freeing cache instance");

  usageCount--;
}

void Cache::destroy() { 

  if (myInstance) { 
    cpLog(LOG_DEBUG, "Stopping manager threads");

    // Stop the cache manager (the destructor automatically stops the thread)
    if (myInstance->myCacheManager) {
      (myInstance->myCacheManager)->shutdown();
      (myInstance->myCacheManager)->join();
      delete myInstance->myCacheManager;
    }

    // Stop the listeners from running
    myInstance->stopAllListeners();
  
    // Nothing should be accessing the cache so delete the objects themselves.

    (myInstance->myCache)->empty();
    // delete myDBManager; -- can't destory this !
    if (myInstance->myDBThread){
       delete myInstance->myDBThread;
    }
    
    cpLog(LOG_DEBUG, "Destroying Cache Object\n");

    if (myInstance->myCache){
       delete myInstance->myCache;
    }
    cpLog(LOG_DEBUG, "Deleting main cache instance");

    usageCount = 0;
    delete myInstance;
    myInstance = NULL;
  }
}

Record* Cache::getRecord(RecordType rtype, KeyType key, bool useCache) {

  cpLog(LOG_DEBUG, "Fetching record of %s with key %s", Record::stringRecordType(rtype).c_str(), key.c_str());

  Record *rec = NULL;

  if (useCache) { 
    rec = myCache->get(rtype, key);
  }
  
  // 'rec' will be NULL if the object is not present
  if (rec == NULL) { 

    cpLog(LOG_DEBUG, "Record not found in cache");
    
    // Otherwise create a blank record
    rec = Record::createNewRecord(rtype);
  
    // Get a database connection
    DBConnection* dbconn = myDBManager->searchDBConPool(dbinfo);

    if (!dbconn) { 
      cpLog(LOG_ERR, "Can't get database connection");
      return NULL;
    }

    // And look up the database
    if (!rec->populateRecord(key, dbconn)) { 
      delete rec;
      rec = NULL;
      cpLog(LOG_DEBUG, "Record is NULL!\n");
      myDBManager->returnDBCon(dbconn);
      return rec;
    };      

    // Insert this into the cache if it exists (and we're using the cache)
    if (rec && useCache) { 
        myCache->insert(rtype, key, rec); 
    }

    myDBManager->returnDBCon(dbconn);

  } else { 

    cpLog(LOG_DEBUG, "Object found in cache (will reinsert with correct access time)");
  }

  // Sanity check that we created the right type of message
  if ((rec != NULL) && (rec->getRecordType() != rtype)) { 
    // Only happens if Record subclass is incorrectly coded

    // Delete the rogue object and return NULL, we should probably really
    // ASSERT here as this is an error in the system
    cpLog(LOG_ERR, "getRecord() returned incorrect record type");

    // Erase this from the cache as well, this will force a database lookup next time
    myCache->remove(rtype, key);

    delete rec;
    rec = NULL; 
  }

  /* 
   * The cache system is taking care of coping objects so we can just
   * return this pointer.
   */
   
  return rec;
}

bool Cache::insertRecord(Record* rec) { 
  cpLog(LOG_DEBUG, "Inserting record of type %s with key %s", 
	(Record::stringRecordType(rec->getRecordType())).c_str(), 
	rec->getKey().c_str());
  // Get a database connection, that let the record insert itself
  DBConnection* dbconn = myDBManager->searchDBConPool(dbinfo);
    
  if (!dbconn) {
    cpLog(LOG_ERR, "Can't get database connection");
    return false;
  }

  bool result = rec->insertRecord(dbconn);

  if (!result) cpLog(LOG_ERR, "Database insert failed");

  myDBManager->returnDBCon(dbconn);

  // The update callback will automatically amend the cache if required, 
  // if we did it here the update would be done twice

  return result;
}


bool Cache::changeRecord(Record* rec) { 
  cpLog(LOG_DEBUG, "Changing record of type %s with key %s", 
	(Record::stringRecordType(rec->getRecordType())).c_str(), 
	rec->getKey().c_str());
  // Get a database connection, that let the record insert itself
  DBConnection* dbconn = myDBManager->searchDBConPool(dbinfo);
  
  if (!dbconn) { 
    cpLog(LOG_ERR, "Can't get database connection");
    return false;
  }

  bool result = rec->amendRecord(dbconn);

  if (!result) cpLog(LOG_ERR, "Database change failed");

  myDBManager->returnDBCon(dbconn);

  // The update callback will automatically amend the cache if required, 
  // if we did it here the update would be done twice

  return result;   
}

bool Cache::deleteRecord(Record* rec) { 
  cpLog(LOG_DEBUG, "Deleting record of type %s with key %s", 
	(Record::stringRecordType(rec->getRecordType())).c_str(), 
	rec->getKey().c_str());
  // Get a database connection, that let the record insert itself
  DBConnection* dbconn = myDBManager->searchDBConPool(dbinfo);
  
  if (!dbconn) { 
    cpLog(LOG_ERR, "Can't get database connection");
    return false;
  }

  bool result = rec->deleteRecord(dbconn);

  if (!result) cpLog(LOG_ERR, "Database delete failed");

  myDBManager->returnDBCon(dbconn);

  // The update callback will automatically amend the cache if required, 
  // if we did it here the update would be done twice

  return result;
}

bool Cache::registerForUpdates(string hostname, RecordType recType, callBackFuncPtr callBackFunc) { 

  // Can't register to listen for update reg records as that would risk 
  // creating loops, and only the clients should change them anyway
  if (recType == UPDATE_REG_INFO_RECORD) return false;
  
  cpLog(LOG_DEBUG, 
	"Registering for update messages for records of type %s on %s",