unix 的信號signal常用于進程管理.

比如管理員或者操作系統通過向master進程實現重啟和關閉服務．

master進程通過向worker進程發信號管理worker進程．

通常會在進程自定義信號處理函數,處理相關的邏輯.

自定義信號處理函數,從使用者的角度看,很簡單,有點像快捷鍵的定制.

FPM 信號處理有以下幾個特點:

master進程,不是直接處理信號,而是通過socketpair創建一個管道,把信號轉換一個字符,寫到管道里,master進程事件處理無限循環,讀取到這個字符時,調用對應的函數.

socketpair,通常管道不同進程通信,而這里確是在同一個進程內部通信,左手交右手,感覺多此一舉.

這樣做的好處是: 避免信號處理函數與事件處理邏輯同時運行的情況.

注意worker 進程沒有用到這個socketpair管道.

worker 進程的信號處理常見的方式,直接綁定處理函數.

處理過程: sig_soft_quit -> fpm_php_soft_quit -> fcgi_set_in_shutdown

fcgi_set_in_shutdown 函數很簡單 就是設置in_shutdown這個全局的worker進程開關

worker進程無限循環時,每次都會檢查這個開關, in_shutdown=1 時,跳出循環,優雅退出.

源碼注釋說明:

//fpm_signals.c

#include "fpm_config.h"

...

//整數數組,存放socketpair創建的管道兩端文件句柄

static int sp[2];

...

//worker進程信號處理函數

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進程信號處理函數

static void sig_handler(int signo) /* {{{ */

{

//C99 的數組初始化語法

//信號整數和字符的對應關系.

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];

//信號對應的字符寫到管道

write(sp[1], &s, sizeof(s));

errno = saved_errno;

}

int fpm_signals_init_main() /* {{{ */

{

struct sigaction act;

//創建socketpair管道,管道兩端的文件句柄fd 放在數組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; //所有信號使用同一個處理函數

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; //系統默認動作

//worker 進程不使用socketpair創建的管道

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 進程的信號被寫到了管道,管道另一端的處理:

//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;

}

//依據讀取到的字符做處理

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;

}

總結

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