nginx 设置进程title

刚好看到nginx设置进程title的源码，因此做一些总结。

linux进程实际是以argv[0]处的值来作为进程的title的，因此若需要修改进程的title只需要修改argv[0]处的值即可。

简单的方法就是直接将想要设置的title复制给argv[0]即可，如下示：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

extern char** environ;

int main(int argc, char* argv[])
{
    char s_title[] = "ymc title for simple way!";
    size_t i_size = strlen(s_title);

    memcpy(argv[0], s_title, i_size);
    argv[0][i_size] = '\0';

    while(1){
        system("ps -ef|awk '$8 ~ /ymc/ {print $0}'");
        sleep(10);
    }

    return 0;
}

运行结果为：

[root@localhost prc_title]# ./prc_title_simple 
root     19062 14675  0 20:17 pts/0    00:00:00 ymc title for simple way!
root     19062 14675  0 20:17 pts/0    00:00:00 ymc title for simple way!

但是这种方式是以破坏性的方式，进程的进程title的修改。由于程序的参数存储空间的后面紧跟的就是环境变量的存储位置，在不考虑参数的破坏性的情况下

过长的title也会损坏环境变量environ的值。因此在nginx中，是将环境变量进行移位存储处理的。下面是nginx处理进程设置title的思路。

/*
 * To change the process title in Linux and Solaris we have to set argv[1]
 * to NULL and to copy the title to the same place where the argv[0] points to.
 * However, argv[0] may be too small to hold a new title.  Fortunately, Linux
 * and Solaris store argv[] and environ[] one after another.  So we should
 * ensure that is the continuous memory and then we allocate the new memory
 * for environ[] and copy it.  After this we could use the memory starting
 * from argv[0] for our process title.
 *
 * The Solaris's standard /bin/ps does not show the changed process title.
 * You have to use "/usr/ucb/ps -w" instead.  Besides, the UCB ps dos not
 * show a new title if its length less than the origin command line length.
 * To avoid it we append to a new title the origin command line in the
 * parenthesis.
 */

然后由于nginx中考虑多进程的情况，因此他会在初始化时就完成environ的迁移。下面是初始化函数

//指向环境变量，默认的
extern char **environ;
//指向之前的用于存放参数及环境变量的空间的最后位置。
static char *ngx_os_argv_last;

ngx_int_t
ngx_init_setproctitle(ngx_log_t *log)
{
    u_char      *p;
    size_t       size;
    ngx_uint_t   i;

    size = 0;
    //计算环境变量所用的总的空间的大小，然后以申请足够的空间用于存放环境变量
    for (i = 0; environ[i]; i++) {
        size += ngx_strlen(environ[i]) + 1;
    }
    //为环境就是分配空间
    p = ngx_alloc(size, log);
    if (p == NULL) {
        return NGX_ERROR;
    }
    //下面开始计算前面用于存放环境变量的最后位置
    ngx_os_argv_last = ngx_os_argv[0];
    //首先计算参数的最后位置
    for (i = 0; ngx_os_argv[i]; i++) {
        if (ngx_os_argv_last == ngx_os_argv[i]) {
            ngx_os_argv_last = ngx_os_argv[i] + ngx_strlen(ngx_os_argv[i]) + 1;
        }
    }
    //再计算环境变量占用的最后位置，并完成环境变量的拷贝
    for (i = 0; environ[i]; i++) {
        if (ngx_os_argv_last == environ[i]) {

            size = ngx_strlen(environ[i]) + 1;
            ngx_os_argv_last = environ[i] + size;

            ngx_cpystrn(p, (u_char *) environ[i], size);
            environ[i] = (char *) p;
            p += size;
        }
    }

    ngx_os_argv_last--;

    return NGX_OK;
}

然后是具体的设置title的函数

void
ngx_setproctitle(char *title)
{
    u_char     *p;

#if (NGX_SOLARIS)

    ngx_int_t   i;
    size_t      size;

#endif

    ngx_os_argv[1] = NULL;
    //设置title，
    p = ngx_cpystrn((u_char *) ngx_os_argv[0], (u_char *) "nginx: ",
                    ngx_os_argv_last - ngx_os_argv[0]);

    p = ngx_cpystrn(p, (u_char *) title, ngx_os_argv_last - (char *) p);

#if (NGX_SOLARIS)

    size = 0;

    for (i = 0; i < ngx_argc; i++) {
        size += ngx_strlen(ngx_argv[i]) + 1;
    }

    if (size > (size_t) ((char *) p - ngx_os_argv[0])) {

        /*
         * ngx_setproctitle() is too rare operation so we use
         * the non-optimized copies
         */

        p = ngx_cpystrn(p, (u_char *) " (", ngx_os_argv_last - (char *) p);

        for (i = 0; i < ngx_argc; i++) {
            p = ngx_cpystrn(p, (u_char *) ngx_argv[i],
                            ngx_os_argv_last - (char *) p);
            p = ngx_cpystrn(p, (u_char *) " ", ngx_os_argv_last - (char *) p);
        }

        if (*(p - 1) == ' ') {
            *(p - 1) = ')';
        }
    }

#endif

    if (ngx_os_argv_last - (char *) p) {
        ngx_memset(p, NGX_SETPROCTITLE_PAD, ngx_os_argv_last - (char *) p);
    }

    ngx_log_debug1(NGX_LOG_DEBUG_CORE, ngx_cycle->log, 0,
                   "setproctitle: \"%s\"", ngx_os_argv[0]);
}

最后就是根据nginx的思想的一个简单修改title的示例：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

extern char** environ;

void my_initproctitle(char* argv[], char** last);
void my_setproctitle(char* argv[], char** last, char* title);

int main(int argc, char* argv[])
{
    char s_title[] = "ymc title ymc title";
    char* p_last = NULL;

   my_initproctitle(argv, &p_last);
   my_setproctitle(argv, &p_last, s_title);

    while(1)
    {
        system("ps -ef|awk '$8 ~ /ymc/ {print $0}'");
        sleep(10);
    }

    return 0;
}

void my_initproctitle(char* argv[], char** last)
{
    int i = 0;
    char* p_tmp = NULL;
    size_t i_size = 0;

    for(i = 0; environ[i]; i++){
        i_size += strlen(environ[i]) + 1;
    }

    p_tmp = malloc(i_size);
    if(p_tmp == NULL){
        return ;
    }

    *last = argv[0];
    for(i = 0; argv[i]; i++){
        *last += strlen(argv[i]) + 1;
    }

    for(i = 0; environ[i]; i++){
        i_size = strlen(environ[i]) + 1;
        *last += i_size;

        strncpy(p_tmp, environ[i], i_size);
        environ[i] = p_tmp;
        p_tmp += i_size;
    }

    (*last)--;

    return ;

}

void my_setproctitle(char* argv[], char** last, char* title)
{
    char* p_tmp = NULL;
    /* argv[1] = NULL; */

    p_tmp = argv[0];
    /* memset(p_tmp, 0, *last - p_tmp); */
    strncpy(p_tmp, title, *last - p_tmp);

    return ;
}

运行结果：

[root@localhost prc_title]# ./prc_title
root     19507 14675  0 20:33 pts/0    00:00:00 ymc title ymc title

这里还有个问题就是没考虑新的存储environ的空间的释放。

转载请注明出处：http://www.cnblogs.com/doop-ymc/p/3432184.html