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|
/*
+----------------------------------------------------------------------+
| PHP Version 5 |
+----------------------------------------------------------------------+
| Copyright (c) 1997-2007 The PHP Group |
+----------------------------------------------------------------------+
| This source file is subject to version 3.0 of the PHP license, |
| that is bundled with this package in the file LICENSE, and is |
| available through the world-wide-web at the following url: |
| http://www.php.net/license/3_0.txt. |
| If you did not receive a copy of the PHP license and are unable to |
| obtain it through the world-wide-web, please send a note to |
| license@php.net so we can mail you a copy immediately. |
+----------------------------------------------------------------------+
| Authors: Antony Dovgal <tony2001@phpclub.net> |
| Mikael Johansson <mikael AT synd DOT info> |
+----------------------------------------------------------------------+
*/
/* $Id$ */
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <stdlib.h>
#include "php.h"
#include "php_memcache.h"
ZEND_EXTERN_MODULE_GLOBALS(memcache)
typedef struct mmc_consistent_point {
mmc_t *server;
unsigned int point;
} mmc_consistent_point_t;
typedef struct mmc_consistent_state {
int num_servers;
mmc_consistent_point_t *points;
int num_points;
mmc_t *buckets[MMC_CONSISTENT_BUCKETS];
int buckets_populated;
mmc_hash_function_t *hash;
} mmc_consistent_state_t;
void *mmc_consistent_create_state(mmc_hash_function_t *hash) /* {{{ */
{
mmc_consistent_state_t *state = emalloc(sizeof(mmc_consistent_state_t));
ZEND_SECURE_ZERO(state, sizeof(mmc_consistent_state_t));
state->hash = hash;
return state;
}
/* }}} */
void mmc_consistent_free_state(void *s) /* {{{ */
{
mmc_consistent_state_t *state = s;
if (state != NULL) {
if (state->points != NULL) {
efree(state->points);
}
efree(state);
}
}
/* }}} */
static int mmc_consistent_compare(const void *a, const void *b) /* {{{ */
{
if (((mmc_consistent_point_t *)a)->point < ((mmc_consistent_point_t *)b)->point) {
return -1;
}
if (((mmc_consistent_point_t *)a)->point > ((mmc_consistent_point_t *)b)->point) {
return 1;
}
return 0;
}
/* }}} */
static mmc_t *mmc_consistent_find(mmc_consistent_state_t *state, unsigned int point) /* {{{ */
{
int lo = 0, hi = state->num_points - 1, mid;
while (1) {
/* point is outside interval or lo >= hi, wrap-around */
if (point <= state->points[lo].point || point > state->points[hi].point) {
return state->points[lo].server;
}
/* test middle point */
mid = lo + (hi - lo) / 2;
/* perfect match */
if (point <= state->points[mid].point && point > (mid ? state->points[mid-1].point : 0)) {
return state->points[mid].server;
}
/* too low, go up */
if (state->points[mid].point < point) {
lo = mid + 1;
}
else {
hi = mid - 1;
}
}
}
/* }}} */
static void mmc_consistent_populate_buckets(mmc_consistent_state_t *state) /* {{{ */
{
unsigned int i, step = 0xffffffff / MMC_CONSISTENT_BUCKETS;
qsort((void *)state->points, state->num_points, sizeof(mmc_consistent_point_t), mmc_consistent_compare);
for (i=0; i<MMC_CONSISTENT_BUCKETS; i++) {
state->buckets[i] = mmc_consistent_find(state, step * i);
}
state->buckets_populated = 1;
}
/* }}} */
mmc_t *mmc_consistent_find_server(void *s, const char *key, unsigned int key_len) /* {{{ */
{
mmc_consistent_state_t *state = s;
if (state->num_servers > 1) {
unsigned int hash;
if (!state->buckets_populated) {
mmc_consistent_populate_buckets(state);
}
hash = mmc_hash(state->hash, key, key_len);
return state->buckets[hash % MMC_CONSISTENT_BUCKETS];
}
return state->points[0].server;
}
/* }}} */
void mmc_consistent_add_server(void *s, mmc_t *mmc, unsigned int weight) /* {{{ */
{
mmc_consistent_state_t *state = s;
int i, key_len, points = weight * MMC_CONSISTENT_POINTS;
unsigned int seed = state->hash->init(), hash;
/* buffer for "host:port-i\0" */
char *key = emalloc(strlen(mmc->host) + MAX_LENGTH_OF_LONG * 2 + 3);
key_len = sprintf(key, "%s:%d-", mmc->host, mmc->tcp.port);
seed = state->hash->combine(seed, key, key_len);
/* add weight * MMC_CONSISTENT_POINTS number of points for this server */
state->points = erealloc(state->points, sizeof(*state->points) * (state->num_points + points));
for (i=0; i<points; i++) {
key_len = sprintf(key, "%d", i);
hash = state->hash->finish(state->hash->combine(seed, key, key_len));
state->points[state->num_points + i].server = mmc;
state->points[state->num_points + i].point = hash;
}
state->num_points += points;
state->num_servers++;
state->buckets_populated = 0;
efree(key);
}
/* }}} */
mmc_hash_strategy_t mmc_consistent_hash = {
mmc_consistent_create_state,
mmc_consistent_free_state,
mmc_consistent_find_server,
mmc_consistent_add_server
};
/*
* Local variables:
* tab-width: 4
* c-basic-offset: 4
* End:
* vim600: noet sw=4 ts=4 fdm=marker
* vim<600: noet sw=4 ts=4
*/
|
