/*
redis里的回调函数
*/
#include<stdio.h>
#include<stdlib.h>
  
  
static void zmalloc_default_oom(size_t size) 
{
    printf("zmalloc_default_oom\n");
    fprintf(stderr, "zmalloc: Out of memory trying to allocate %d bytes\n",size);
    fflush(stderr);
}
  
static void (*zmalloc_oom_handler)(size_t) = zmalloc_default_oom;
  
  
void zmalloc_set_oom_handler(void (*oom_handler)(size_t)) 
{
    printf("zmalloc_set_oom_handler\n");
    zmalloc_oom_handler = oom_handler;
}
  
void redisOutOfMemoryHandler(size_t allocation_size) 
{
    printf("redisOutOfMemoryHandler------:%d\n",allocation_size);
}
  
int main(void)
{
    //zmalloc_set_oom_handler(redisOutOfMemoryHandler);
    zmalloc_oom_handler(10);
    getchar();
    return 0;
}

int main(void)
{
    zmalloc_set_oom_handler(redisOutOfMemoryHandler);
    zmalloc_oom_handler(10);
    getchar();
    return 0;
}

int main(int argc, char **argv) 
{
    struct timeval tv;
                 
    /* We need to initialize our libraries, and the server configuration. */
#ifdef INIT_SETPROCTITLE_REPLACEMENT
    //初始化参数
    spt_init(argc, argv);
#endif
    setlocale(LC_COLLATE,"");
    /*
    zmalloc_enable_thread_safeness()
    开启了内存分配管理的线程安全变量，当内存分配时，
    redis会统计一个总内存分配量，这是一个共享资源，
    所以需要原子性操作，在redis的内存分配代码里，
    当需要原子操作时，就需要打开线程安全变量。
    */
    zmalloc_enable_thread_safeness();
    /*
    zmalloc_set_oom_handler()
    是一个内存分配错误处理，
    当无法得到需要的内存量时，
    会调用redisOutOfMemoryHandler函数。
    */
    zmalloc_set_oom_handler(redisOutOfMemoryHandler);
    srand(time(NULL)^getpid());
    gettimeofday(&tv,NULL);
    dictSetHashFunctionSeed(tv.tv_sec^tv.tv_usec^getpid());
    server.sentinel_mode = checkForSentinelMode(argc,argv);
    initServerConfig();
    ..........
}

zmalloc_set_oom_handler注册回调函数

redisOutOfMemoryHandler主要是个log日志打印，即在内存分配失败的时候触发回调函数，打印log。

void *zmalloc(size_t size) {
    void *ptr = malloc(size+PREFIX_SIZE);
 
    if (!ptr) zmalloc_oom_handler(size);
#ifdef HAVE_MALLOC_SIZE
    update_zmalloc_stat_alloc(zmalloc_size(ptr));
    return ptr;
#else
    *((size_t*)ptr) = size;
    update_zmalloc_stat_alloc(size+PREFIX_SIZE);
    return (char*)ptr+PREFIX_SIZE;
#endif
}

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
 
/* Log levels */
#define REDIS_DEBUG 0
#define REDIS_VERBOSE 1
#define REDIS_NOTICE 2
#define REDIS_WARNING 3
 
 
#define REDIS_MAX_LOGMSG_LEN    1024 /* 默认信息长度 */
 
void redisLogRaw(int level, const char *msg);
void redisLog(int level, const char *fmt, ...);
 
/*
verbosity表示开启log的级别
需要写log的时候，log级别小于等于verbosity写log
否则不会写log
 
*/
struct redisServer {
    int verbosity;                  /* 日志级别*/
    char *logfile;                  /* Path of log file */
};
 
struct redisServer server; /* server global state */
 
 
void redisLog(int level, const char *fmt, ...) 
{
    //如果level级别大于verbosity则不打印
    if (level> server.verbosity) 
    {
        return;
    }
    va_list ap;
    char msg[REDIS_MAX_LOGMSG_LEN];
 
 
    va_start(ap, fmt);
    vsnprintf(msg, sizeof(msg), fmt, ap);
    va_end(ap);
 
    redisLogRaw(level,msg);
}
 
void redisLogRaw(int level, const char *msg) 
{
#if 1
     
    FILE *fp;
    char buf[64];
//  int rawmode = (level & REDIS_LOG_RAW);
    //int log_to_stdout = server.logfile[0] == ‘\0‘;
 
    //level &= 0xff; /* clear flags */
    //if (level < server.verbosity) return;
    if(server.logfile != NULL)
    {
        fp=fopen(server.logfile,"a");
    }
    else
    {
        fp=stdout;
    }
 
     
    int off;
//  struct timeval tv;
 
    //gettimeofday(&tv,NULL);
    //off = strftime(buf,sizeof(buf),"%d %b %H:%M:%S.",localtime(&tv.tv_sec));
    //snprintf(buf+off,sizeof(buf)-off,"%03d",(int)tv.tv_usec/1000);
    //fprintf(fp,"[%d] %s %c %s\n",(int)getpid(),buf,c[level],msg);
    fprintf(fp," %s\n",msg);
    fflush(fp);
 
    if(server.logfile != NULL)
    {
        fclose(fp);
    }
     
 
#endif
}
int main(void)
{
    server.verbosity=2;
    server.logfile=NULL;
    redisLog(1,"11111111\n");
    redisLog(2,"22222\n");
    redisLog(3,"333\n");
    getchar();
     
    return 0;
}