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/*
Using hash table for counting events
Copyright (C) Amitay Isaacs 2017
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/>.
*/
#ifndef __CTDB_HASH_COUNT_H__
#define __CTDB_HASH_COUNT_H__
/**
* @file hash_count.h
*
* @brief Count key-based events for specified interval
*
* This can be used to measure the rate of events based on any interval.
* For example, number of occurrences per second.
*/
/**
* @brief Handler callback function called when counter is incremented
*
* This function is called every time a counter is incremented for a key.
* The counter argument is the number of times the increment function is
* called during a count interval.
*
* This function should not modify key and data arguments.
*/
typedef void (*hash_count_update_handler_fn)(TDB_DATA key, uint64_t counter,
void *private_data);
/**
* @brief Abstract structure representing hash based counting
*/
struct hash_count_context;
/**
* @brief Initialize hash counting
*
* This return a new hash count context which is a talloc context. Freeing
* this context will free all the memory associated with hash count.
*
* @param[in] mem_ctx Talloc memory context
* @param[in] count_interval The time interval for counting events
* @param[in] handler Function called when counter is incremented
* @param[in] private_data Private data to handler function
* @param[out] result The new hash_count structure
* @return 0 on success, errno on failure
*/
int hash_count_init(TALLOC_CTX *mem_ctx, struct timeval count_interval,
hash_count_update_handler_fn handler, void *private_data,
struct hash_count_context **result);
/**
* @brief Increment a counter for a key
*
* First time this is called for a key, corresponding counter is set to 1
* and the start time is noted. For all subsequent calls made during the
* count_interval (used in initializing the context) will increment
* corresponding counter for the key. After the count_interval has elapsed,
* the counter will be reset to 1.
*
* @param[in] hcount The hash count context
* @param[in] key The key for which counter is updated
* @return 0 on success, errno on failure
*
* This will result in a callback function being called.
*/
int hash_count_increment(struct hash_count_context *hcount, TDB_DATA key);
/**
* @brief Remove keys for which count interval has elapsed
*
* This function is used to clean the database of keys for which there are
* no recent events.
*
* @param[in] hcount The hash count context
* @param[out] delete_count The number of keys deleted
*/
void hash_count_expire(struct hash_count_context *hcount, int *delete_count);
#endif /* __CTDB_HASH_COUNT_H__ */
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