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/* -*- Mode: C; tab-width: 4; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/*
* Detailed statistics management. For simple stats like total number of
* "get" requests, we use inline code in memcached.c and friends, but when
* stats detail mode is activated, the code here records more information.
*
* Author:
* Steven Grimm <sgrimm@facebook.com>
*/
#include "memcached.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
/*
* Stats are tracked on the basis of key prefixes. This is a simple
* fixed-size hash of prefixes; we run the prefixes through the same
* CRC function used by the cache hashtable.
*/
static PREFIX_STATS *prefix_stats[PREFIX_HASH_SIZE];
static char prefix_delimiter;
static int num_prefixes = 0;
static int total_prefix_size = 0;
void stats_prefix_init(char delimiter) {
prefix_delimiter = delimiter;
memset(prefix_stats, 0, sizeof(prefix_stats));
}
/*
* Cleans up all our previously collected stats. NOTE: the stats lock is
* assumed to be held when this is called.
*/
void stats_prefix_clear(void) {
int i;
for (i = 0; i < PREFIX_HASH_SIZE; i++) {
PREFIX_STATS *cur, *next;
for (cur = prefix_stats[i]; cur != NULL; cur = next) {
next = cur->next;
free(cur->prefix);
free(cur);
}
prefix_stats[i] = NULL;
}
num_prefixes = 0;
total_prefix_size = 0;
}
/*
* Returns the stats structure for a prefix, creating it if it's not already
* in the list.
*/
/*@null@*/
PREFIX_STATS *stats_prefix_find(const char *key, const size_t nkey) {
PREFIX_STATS *pfs;
uint32_t hashval;
size_t length;
bool bailout = true;
assert(key != NULL);
for (length = 0; length < nkey && key[length] != '\0'; length++) {
if (key[length] == prefix_delimiter) {
bailout = false;
break;
}
}
if (bailout) {
return NULL;
}
hashval = hash(key, length) % PREFIX_HASH_SIZE;
for (pfs = prefix_stats[hashval]; NULL != pfs; pfs = pfs->next) {
if (strncmp(pfs->prefix, key, length) == 0)
return pfs;
}
pfs = calloc(sizeof(PREFIX_STATS), 1);
if (NULL == pfs) {
perror("Can't allocate space for stats structure: calloc");
return NULL;
}
pfs->prefix = malloc(length + 1);
if (NULL == pfs->prefix) {
perror("Can't allocate space for copy of prefix: malloc");
free(pfs);
return NULL;
}
strncpy(pfs->prefix, key, length);
pfs->prefix[length] = '\0'; /* because strncpy() sucks */
pfs->prefix_len = length;
pfs->next = prefix_stats[hashval];
prefix_stats[hashval] = pfs;
num_prefixes++;
total_prefix_size += length;
return pfs;
}
/*
* Records a "get" of a key.
*/
void stats_prefix_record_get(const char *key, const size_t nkey, const bool is_hit) {
PREFIX_STATS *pfs;
STATS_LOCK();
pfs = stats_prefix_find(key, nkey);
if (NULL != pfs) {
pfs->num_gets++;
if (is_hit) {
pfs->num_hits++;
}
}
STATS_UNLOCK();
}
/*
* Records a "delete" of a key.
*/
void stats_prefix_record_delete(const char *key, const size_t nkey) {
PREFIX_STATS *pfs;
STATS_LOCK();
pfs = stats_prefix_find(key, nkey);
if (NULL != pfs) {
pfs->num_deletes++;
}
STATS_UNLOCK();
}
/*
* Records a "set" of a key.
*/
void stats_prefix_record_set(const char *key, const size_t nkey) {
PREFIX_STATS *pfs;
STATS_LOCK();
pfs = stats_prefix_find(key, nkey);
if (NULL != pfs) {
pfs->num_sets++;
}
STATS_UNLOCK();
}
/*
* Returns stats in textual form suitable for writing to a client.
*/
/*@null@*/
char *stats_prefix_dump(int *length) {
const char *format = "PREFIX %s get %llu hit %llu set %llu del %llu\r\n";
PREFIX_STATS *pfs;
char *buf;
int i, pos;
size_t size = 0, written = 0, total_written = 0;
/*
* Figure out how big the buffer needs to be. This is the sum of the
* lengths of the prefixes themselves, plus the size of one copy of
* the per-prefix output with 20-digit values for all the counts,
* plus space for the "END" at the end.
*/
STATS_LOCK();
size = strlen(format) + total_prefix_size +
num_prefixes * (strlen(format) - 2 /* %s */
+ 4 * (20 - 4)) /* %llu replaced by 20-digit num */
+ sizeof("END\r\n");
buf = malloc(size);
if (NULL == buf) {
perror("Can't allocate stats response: malloc");
STATS_UNLOCK();
return NULL;
}
pos = 0;
for (i = 0; i < PREFIX_HASH_SIZE; i++) {
for (pfs = prefix_stats[i]; NULL != pfs; pfs = pfs->next) {
written = snprintf(buf + pos, size-pos, format,
pfs->prefix, pfs->num_gets, pfs->num_hits,
pfs->num_sets, pfs->num_deletes);
pos += written;
total_written += written;
assert(total_written < size);
}
}
STATS_UNLOCK();
memcpy(buf + pos, "END\r\n", 6);
*length = pos + 5;
return buf;
}
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