Zabbix

/*

** Copyright (C) 2001-2025 Zabbix SIA

**

** This program is free software: you can redistribute it and/or modify it under the terms of

** the GNU Affero General Public License as published by the Free Software Foundation, version 3.

**

** 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 Affero General Public License for more details.

**

** You should have received a copy of the GNU Affero General Public License along with this program.

** If not, see <https://www.gnu.org/licenses/>.

**/

​

#include "zbxcachevalue.h"

​

#include "zbxmutexs.h"

#include "zbxtime.h"

#include "zbxvariant.h"

​

/*

 * The cache (zbx_vc_cache_t) is organized as a hashset of item records (zbx_vc_item_t).

 *

 * Each record holds item data (itemid, value_type), statistics (hits, last access time,...)

 * and the historical data (timestamp,value pairs in ascending order).

 *

 * The historical data are stored from largest request (+timeshift) range to the

 * current time. The data is automatically fetched from DB whenever a request

 * exceeds cached value range.

 *

 * In addition to active range value cache tracks item range for last 24 hours. Once

 * per day the active range is updated with daily range and the daily range is reset.

 *

 * If an item is already being cached the new values are automatically added to the cache

 * after being written into database.

 *

 * When cache runs out of memory to store new items it enters in low memory mode.

 * In low memory mode cache continues to function as before with few restrictions:

 *   1) items that weren't accessed during the last day are removed from cache.

 *   2) items with worst hits/values ratio might be removed from cache to free the space.

 *   3) no new items are added to the cache.

 *

 * The low memory mode can't be turned off - it will persist until server is rebooted.

 * In low memory mode a warning message is written into log every 5 minutes.

 */

​

ZBX_PTR_VECTOR_IMPL(vc_item_stats_ptr, zbx_vc_item_stats_t *)

​

void    zbx_vc_item_stats_free(zbx_vc_item_stats_t * vc_item_stats)

{

    zbx_free(vc_item_stats);

}

​

/* the period of low memory warning messages */

#define ZBX_VC_LOW_MEMORY_WARNING_PERIOD    (5 * SEC_PER_MIN)

​

/* time period after which value cache will switch back to normal mode */

#define ZBX_VC_LOW_MEMORY_RESET_PERIOD      SEC_PER_DAY

​

#define ZBX_VC_LOW_MEMORY_ITEM_PRINT_LIMIT  25

​

static zbx_shmem_info_t *vc_mem = NULL;

​