unix 的信号signal常用于进程管理.
比如管理员或者操作系统通过向master进程实现重启和关闭服务．
master进程通过向worker进程发信号管理worker进程．
通常会在进程自定义信号处理函数,处理相关的逻辑.
自定义信号处理函数,从使用者的角度看,很简单,有点像快捷键的定制.
FPM 信号处理有以下几个特点:
- master进程,不是直接处理信号,而是通过socketpair创建一个管道,把信号转换一个字符,写到管道里,master进程事件处理无限循环,读取到这个字符时,调用对应的函数.
socketpair,通常管道不同进程通信,而这里确是在同一个进程内部通信,左手交右手,感觉多此一举.
这样做的好处是: 避免信号处理函数与事件处理逻辑同时运行的情况.
注意worker 进程没有用到这个socketpair管道. - worker 进程的信号处理常见的方式,直接绑定处理函数.
处理过程: sig_soft_quit -> fpm_php_soft_quit -> fcgi_set_in_shutdown
fcgi_set_in_shutdown 函数很简单 就是设置in_shutdown这个全局的worker进程开关
worker进程无限循环时,每次都会检查这个开关, in_shutdown=1 时,跳出循环,优雅退出.
源码注释说明:
//fpm_signals.c
#include "fpm_config.h"
...
//整数数组,存放socketpair创建的管道两端文件句柄
static int sp[2];
...
//worker进程信号处理函数
static void sig_soft_quit(int signo) /* {{{ */
{
int saved_errno = errno;
/* closing fastcgi listening socket will force fcgi_accept() exit immediately */
close(0);
if (0 > socket(AF_UNIX, SOCK_STREAM, 0)) {
zlog(ZLOG_WARNING, "failed to create a new socket");
}
fpm_php_soft_quit();
errno = saved_errno;
}
//master进程信号处理函数
static void sig_handler(int signo) /* {{{ */
{
//C99 的数组初始化语法
//信号整数和字符的对应关系.
static const char sig_chars[NSIG + 1] = {
[SIGTERM] = 'T',
[SIGINT] = 'I',
[SIGUSR1] = '1',
[SIGUSR2] = '2',
[SIGQUIT] = 'Q',
[SIGCHLD] = 'C'
};
char s;
int saved_errno;
if (fpm_globals.parent_pid != getpid()) {
return;
}
saved_errno = errno;
s = sig_chars[signo];
//信号对应的字符写到管道
write(sp[1], &s, sizeof(s));
errno = saved_errno;
}
int fpm_signals_init_main() /* {{{ */
{
struct sigaction act;
//创建socketpair管道,管道两端的文件句柄fd 放在数组sp里
if (0 > socketpair(AF_UNIX, SOCK_STREAM, 0, sp)) {
zlog(ZLOG_SYSERROR, "failed to init signals: socketpair()");
return -1;
}
if (0 > fd_set_blocked(sp[0], 0) || 0 > fd_set_blocked(sp[1], 0)) {
zlog(ZLOG_SYSERROR, "failed to init signals: fd_set_blocked()");
return -1;
}
if (0 > fcntl(sp[0], F_SETFD, FD_CLOEXEC) || 0 > fcntl(sp[1], F_SETFD, FD_CLOEXEC)) {
zlog(ZLOG_SYSERROR, "falied to init signals: fcntl(F_SETFD, FD_CLOEXEC)");
return -1;
}
memset(&act, 0, sizeof(act));
act.sa_handler = sig_handler; //所有信号使用同一个处理函数
sigfillset(&act.sa_mask);
if (0 > sigaction(SIGTERM, &act, 0) ||
0 > sigaction(SIGINT, &act, 0) ||
0 > sigaction(SIGUSR1, &act, 0) ||
0 > sigaction(SIGUSR2, &act, 0) ||
0 > sigaction(SIGCHLD, &act, 0) ||
0 > sigaction(SIGQUIT, &act, 0)) {
zlog(ZLOG_SYSERROR, "failed to init signals: sigaction()");
return -1;
}
return 0;
}
int fpm_signals_init_child()
{
struct sigaction act, act_dfl;
memset(&act, 0, sizeof(act));
memset(&act_dfl, 0, sizeof(act_dfl));
act.sa_handler = &sig_soft_quit;
act.sa_flags |= SA_RESTART;
act_dfl.sa_handler = SIG_DFL; //系统默认动作
//worker 进程不使用socketpair创建的管道
close(sp[0]);
close(sp[1]);
if (0 > sigaction(SIGTERM, &act_dfl, 0) ||
0 > sigaction(SIGINT, &act_dfl, 0) ||
0 > sigaction(SIGUSR1, &act_dfl, 0) ||
0 > sigaction(SIGUSR2, &act_dfl, 0) ||
0 > sigaction(SIGCHLD, &act_dfl, 0) ||
0 > sigaction(SIGQUIT, &act, 0)) {
zlog(ZLOG_SYSERROR, "failed to init child signals: sigaction()");
return -1;
}
return 0;
}
int fpm_signals_get_fd()
{
return sp[0];
}
master 进程的信号被写到了管道,管道另一端的处理:
//fpm_events.c
static void fpm_got_signal(struct fpm_event_s *ev, short which, void *arg)
{
char c;
int res, ret;
int fd = ev->fd;
do {
do {
res = read(fd, &c, 1);
} while (res == -1 && errno == EINTR);
if (res <= 0) {
if (res < 0 && errno != EAGAIN && errno != EWOULDBLOCK) {
zlog(ZLOG_SYSERROR, "unable to read from the signal pipe");
}
return;
}
//依据读取到的字符做处理
switch (c) {
...
case 'Q' : /* SIGQUIT */
zlog(ZLOG_DEBUG, "received SIGQUIT");
zlog(ZLOG_NOTICE, "Finishing ...");
fpm_pctl(FPM_PCTL_STATE_FINISHING, FPM_PCTL_ACTION_SET);
break;
case '1' : /* SIGUSR1 */
zlog(ZLOG_DEBUG, "received SIGUSR1");
if (0 == fpm_stdio_open_error_log(1)) {
zlog(ZLOG_NOTICE, "error log file re-opened");
} else {
zlog(ZLOG_ERROR, "unable to re-opened error log file");
}
ret = fpm_log_open(1);
if (ret == 0) {
zlog(ZLOG_NOTICE, "access log file re-opened");
} else if (ret == -1) {
zlog(ZLOG_ERROR, "unable to re-opened access log file");
}
/* else no access log are set */
break;
case '2' : /* SIGUSR2 */
zlog(ZLOG_DEBUG, "received SIGUSR2");
zlog(ZLOG_NOTICE, "Reloading in progress ...");
fpm_pctl(FPM_PCTL_STATE_RELOADING, FPM_PCTL_ACTION_SET);
break;
}
if (fpm_globals.is_child) {
break;
}
} while (1);
return;
}