Nginx--信号
信号的初始化
nginx启动的时候会调用ngxinitsignals函数遍历signals中的信号并进行信号处理函数注册
signals结构体
ngxsignalt结构体
typedef struct {
int signo;
char *signame;
char *name;
void (*handler)(int signo);
} ngx_signal_t;
signals初始化
主要包含nginx需要处理的信号量和对应的信号处理函数（ngxsignalhandler或者SIG_IGN)
ngx_signal_t signals[] = {
{ ngx_signal_value(NGX_RECONFIGURE_SIGNAL),
"SIG" ngx_value(NGX_RECONFIGURE_SIGNAL),
"reload",
ngx_signal_handler },
{ ngx_signal_value(NGX_REOPEN_SIGNAL),
"SIG" ngx_value(NGX_REOPEN_SIGNAL),
"reopen",
ngx_signal_handler },
{ ngx_signal_value(NGX_NOACCEPT_SIGNAL),
"SIG" ngx_value(NGX_NOACCEPT_SIGNAL),
"",
ngx_signal_handler },
{ ngx_signal_value(NGX_TERMINATE_SIGNAL),
"SIG" ngx_value(NGX_TERMINATE_SIGNAL),
"stop",
ngx_signal_handler },
{ ngx_signal_value(NGX_SHUTDOWN_SIGNAL),
"SIG" ngx_value(NGX_SHUTDOWN_SIGNAL),
"quit",
ngx_signal_handler },
{ ngx_signal_value(NGX_CHANGEBIN_SIGNAL),
"SIG" ngx_value(NGX_CHANGEBIN_SIGNAL),
"",
ngx_signal_handler },
{ SIGALRM, "SIGALRM", "", ngx_signal_handler },
{ SIGINT, "SIGINT", "", ngx_signal_handler },
{ SIGIO, "SIGIO", "", ngx_signal_handler },
{ SIGCHLD, "SIGCHLD", "", ngx_signal_handler },
{ SIGSYS, "SIGSYS, SIG_IGN", "", SIG_IGN },
{ SIGPIPE, "SIGPIPE, SIG_IGN", "", SIG_IGN },
{ 0, NULL, "", NULL }
};
ngxinitsignals
信号初始化，遍历signals,注册信号处理函数
ngx_int_t
ngx_init_signals(ngx_log_t *log)
{
ngx_signal_t *sig;
struct sigaction sa;
/* 遍历signals,注册信号处理函数 */
for (sig = signals; sig->signo != 0; sig++) {
ngx_memzero(&sa, sizeof(struct sigaction));
sa.sa_handler = sig->handler;
sigemptyset(&sa.sa_mask);
if (sigaction(sig->signo, &sa, NULL) == -1) {
/* ...... */
}
}
return NGX_OK;
}
ngxsignalhandler
信号处理函数,主要分为两个部分：
1.MASTER/SINGLE进程的信号处理，接收到某信号后设置对应的全局标志位
比如收到QUIT信号后，设置ngx_terminate的值为1
2.WORKER/HELPER进程的信号处理，接收到某信号后设置对应的全局标志位
void
ngx_signal_handler(int signo)
{
char *action;
ngx_int_t ignore;
ngx_err_t err;
ngx_signal_t *sig;
ignore = 0;
err = ngx_errno;
for (sig = signals; sig->signo != 0; sig++) {
if (sig->signo == signo) {
break;
}
}
ngx_time_sigsafe_update();
action = "";
switch (ngx_process) {
master进程的信号处理
case NGX_PROCESS_MASTER:
case NGX_PROCESS_SINGLE:
switch (signo) {
case ngx_signal_value(NGX_SHUTDOWN_SIGNAL):
/* 如果接受到quit信号，则准备退出进程。*/
ngx_quit = 1;
action = ", shutting down";
break;
case ngx_signal_value(NGX_TERMINATE_SIGNAL):
case SIGINT:
/* 如果接受到quit信号，则准备kill worker进程。*/
ngx_terminate = 1;
action = ", exiting";
break;
/* winch信号，停止接受accept */
case ngx_signal_value(NGX_NOACCEPT_SIGNAL):
if (ngx_daemonized) {
ngx_noaccept = 1;
action = ", stop accepting connections";
}
break;
/* sighup信号用来reconfig */
case ngx_signal_value(NGX_RECONFIGURE_SIGNAL):
ngx_reconfigure = 1;
action = ", reconfiguring";
break;
/* 用户信号 ，重新打开log */
case ngx_signal_value(NGX_REOPEN_SIGNAL):
ngx_reopen = 1;
action = ", reopening logs";
break;
/* 热代码替换 */
case ngx_signal_value(NGX_CHANGEBIN_SIGNAL):
if (getppid() > 1 || ngx_new_binary > 0) {
/*
* Ignore the signal in the new binary if its parent is
* not the init process, i.e. the old binary's process
* is still running. Or ignore the signal in the old binary's
* process if the new binary's process is already running.
* 若进程的父进程（old 代码进程是父进程）不是init进程（getppid==1)，忽略此信号。
* 新的代码进程已在运行中（ngx_new_binary > 0)，old代码进程忽略信号，
*/
action = ", ignoring";
ignore = 1;
break;
}
/* 正常情况下，需要热代码替换。设置标志位 */
ngx_change_binary = 1;
action = ", changing binary";
break;
case SIGALRM:
ngx_sigalrm = 1;
break;
case SIGIO:
ngx_sigio = 1;
break;
/* 子进程退出 */
case SIGCHLD:
ngx_reap = 1;
break;
}
break;
worker进程的信号处理
/* worker的信号处理 */
case NGX_PROCESS_WORKER:
case NGX_PROCESS_HELPER:
switch (signo) {
case ngx_signal_value(NGX_NOACCEPT_SIGNAL):
if (!ngx_daemonized) {
break;
}
ngx_debug_quit = 1;
case ngx_signal_value(NGX_SHUTDOWN_SIGNAL):
ngx_quit = 1;
action = ", shutting down";
break;
case ngx_signal_value(NGX_TERMINATE_SIGNAL):
case SIGINT:
ngx_terminate = 1;
action = ", exiting";
break;
case ngx_signal_value(NGX_REOPEN_SIGNAL):
ngx_reopen = 1;
action = ", reopening logs";
break;
case ngx_signal_value(NGX_RECONFIGURE_SIGNAL):
case ngx_signal_value(NGX_CHANGEBIN_SIGNAL):
case SIGIO:
action = ", ignoring";
break;
}
break;
}
ngx_log_error(NGX_LOG_NOTICE, ngx_cycle->log, 0,
"signal %d (%s) received%s", signo, sig->signame, action);
if (ignore) {
ngx_log_error(NGX_LOG_CRIT, ngx_cycle->log, 0,
"the changing binary signal is ignored: "
"you should shutdown or terminate "
"before either old or new binary's process");
}
/*
* 最终如果信号是sigchld，我们收割僵尸进程(用waitpid)
*/
if (signo == SIGCHLD) {
ngx_process_get_status();
}
ngx_set_errno(err);
}