Nginx源码分析 --时间 日期 日志

Cache的工作原理是基于程序访问的局部性（通俗说就是把经常用到的数据放在一个高速的cache里面）。

Cache存储器：电脑中为高速缓冲存储器，是位于CPU和主存储器DRAM（Dynamic Random Access Memory）之间，规模较小，但速度很高的存储器，通常由SRAM（Static Random Access Memory静态存储器）组成。 

Cache的功能是提高CPU数据输入输出的速率。

Cache容量小但速度快，内存速度较低但容量大，通过优化调度算法，系统的性能会大大改善，仿佛其存储系统容量与内存相当而访问速度近似Cache。

2.基于 ngx_cached_time，Nginx还定义了另外一个全局变量ngx_current_msec,表示自epoch 以来的毫秒数,即sec * 1000 + msec:(运行时间)
 

#define ngx_tm_sec            tm_sec
#define ngx_tm_min            tm_min
#define ngx_tm_hour           tm_hour
#define ngx_tm_mday           tm_mday
#define ngx_tm_mon            tm_mon
#define ngx_tm_year           tm_year
#define ngx_tm_wday           tm_wday
#define ngx_tm_isdst          tm_isdst
 
#define ngx_tm_sec_t          int
#define ngx_tm_min_t          int
#define ngx_tm_hour_t         int
#define ngx_tm_mday_t         int
#define ngx_tm_mon_t          int
#define ngx_tm_year_t         int
#define ngx_tm_wday_t         int

2.2操作函数

void
ngx_localtime(time_t s, ngx_tm_t *tm)
{
#if (NGX_HAVE_LOCALTIME_R)
    (void) localtime_r(&s, tm);
 
#else
    ngx_tm_t  *t;
 
    t = localtime(&s);
    *tm = *t;
 
#endif
 
    tm->ngx_tm_mon++;
    tm->ngx_tm_year += 1900;
}
 
ngx_libc_gmtime(time_t s, struct tm *tm)
{
#if (NGX_HAVE_LOCALTIME_R)
    (void) gmtime_r(&s, tm);
 
#else
    struct tm  *t;
 
    t = gmtime(&s);
    *tm = *t;
 
#endif
}

u_char *
ngx_http_time(u_char *buf, time_t t)
{
    ngx_tm_t  tm;
 
    ngx_gmtime(t, &tm);
 
    return ngx_sprintf(buf, "%s, %02d %s %4d %02d:%02d:%02d GMT",
                       week[tm.ngx_tm_wday],
                       tm.ngx_tm_mday,
                       months[tm.ngx_tm_mon - 1],
                       tm.ngx_tm_year,
                       tm.ngx_tm_hour,
                       tm.ngx_tm_min,
                       tm.ngx_tm_sec);
}
 

u_char *ngx_http_cookie_time(u_char *buf, time_t t);

ngx_http_cookie_time(u_char *buf, time_t t)
{
    ngx_tm_t  tm;
 
    ngx_gmtime(t, &tm);
 
    /*
     * Netscape 3.x does not understand 4-digit years at all and
     * 2-digit years more than "37"
     */
 
    return ngx_sprintf(buf,
                       (tm.ngx_tm_year > 2037) ?
                                         "%s, %02d-%s-%d %02d:%02d:%02d GMT":
                                         "%s, %02d-%s-%02d %02d:%02d:%02d GMT",
                       week[tm.ngx_tm_wday],
                       tm.ngx_tm_mday,
                       months[tm.ngx_tm_mon - 1],
                       (tm.ngx_tm_year > 2037) ? tm.ngx_tm_year:
                                                 tm.ngx_tm_year % 100,
                       tm.ngx_tm_hour,
                       tm.ngx_tm_min,
                       tm.ngx_tm_sec);
}
 

时间格式

extern volatile ngx_str_t    ngx_cached_err_log_time;
extern volatile ngx_str_t    ngx_cached_http_time;
extern volatile ngx_str_t    ngx_cached_http_log_time;
extern volatile ngx_str_t    ngx_cached_http_log_iso8601;
extern volatile ngx_str_t    ngx_cached_syslog_time;
 

从上到下：

错误日志的日期字符串

HTTP 格式的日期字符串

3.源码分析--日志

3.1数据结构

struct ngx_log_s {
    ngx_uint_t           log_level;
    ngx_open_file_t     *file;
 
    ngx_atomic_uint_t    connection;
 
    time_t               disk_full_time;
 
    ngx_log_handler_pt   handler;
    void                *data;
 
    ngx_log_writer_pt    writer;
    void                *wdata;
 
    /*
     * we declare "action" as "char *" because the actions are usually
     * the static strings and in the "u_char *" case we have to override
     * their types all the time
     */
 
    char                *action;
 
    ngx_log_t           *next;
};

针对服务器http/TCP而言

我们只需要了解

1. ngx_uint_t           log_level;     日志级别

2.  ngx_log_t           *next;        日志对象链表指针

3.2操作函数

void ngx_log_error_core(ngx_uint_t level, ngx_log_t *log, ngx_err_t err,
    const char *fmt, ...);