NGX 信号处理流程
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int ngx_cdecl
main(int argc, char *const *argv)
{
....
#if !(NGX_WIN32)
if (ngx_init_signals(cycle->log) != NGX_OK) { // 服务器启动时进行初始化信号处理
return 1;
}
if (!ngx_inherited && ccf->daemon) {
if (ngx_daemon(cycle->log) != NGX_OK) {
return 1;
}
ngx_daemonized = 1;
}
if (ngx_inherited) {
ngx_daemonized = 1;
}
#endif ......
// 单进程服务器
if (ngx_process == NGX_PROCESS_SINGLE) {
ngx_single_process_cycle(cycle);
} else {
ngx_master_process_cycle(cycle);
}
return 0;
}
下来再看看ngx_init_signals函数实现之前先看看结构typedef struct {
int signo; // 信号值
char *signame; // 信号名字
char *name; // 服务器响应信号操作的名字
void (*handler)(int signo);// 信号处理函数
} ngx_signal_t;
再看看全局变量ngx_signal_t signals[] 所有的信号及其处理函数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 }
};
ngx_init_signals函数是将上面初始化的信号注册到系统中去ngx_int_t ngx_init_signals(ngx_log_t *log) { ngx_signal_t *sig; struct sigaction sa; // 将所有信号注册到系统中 for (sig = signals; sig->signo != 0; sig++) { ngx_memzero(&sa, sizeof(struct sigaction));// 信号处理函数 sa.sa_handler = sig->handler;//sa_mask 用来设置在处理该信号时暂时将sa_mask 指定的信号搁置 sigemptyset(&sa.sa_mask); if (sigaction(sig->signo, &sa, NULL) == -1) { ngx_log_error(NGX_LOG_EMERG, log, ngx_errno, "sigaction(%s) failed", sig->signame); return NGX_ERROR; } } return NGX_OK; }下面看看重头函数ngx_signal_handler实现这里解释一个信号处理，其他类似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; // 检查信号值是否是注册信号 for (sig = signals; sig->signo != 0; sig++) { if (sig->signo == signo) {// 确认找到 break; } } ngx_time_sigsafe_update(); action = ""; // 进程类型 switch (ngx_process) { // 主进程或单进程 case NGX_PROCESS_MASTER: case NGX_PROCESS_SINGLE: switch (signo) { case ngx_signal_value(NGX_SHUTDOWN_SIGNAL): ngx_quit = 1; action = ", shutting down"; break; case ngx_signal_value(NGX_TERMINATE_SIGNAL): case SIGINT:// 系统受到 SIGINT，系统调用此信号处理函数，设置全局变量ngx_terminate值置1 下面的分支类似 ngx_terminate = 1;break;action = ", exiting";
case ngx_signal_value(NGX_NOACCEPT_SIGNAL):
if (ngx_daemonized) {
ngx_noaccept = 1;
action = ", stop accepting connections";
}
break;
case ngx_signal_value(NGX_RECONFIGURE_SIGNAL):
ngx_reconfigure = 1;
action = ", reconfiguring";
break;
case ngx_signal_value(NGX_REOPEN_SIGNAL):
ngx_reopen = 1;
action = ", reopening logs";
break;
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.
*/
action = ", ignoring";
ignore = 1;
break;
}
ngx_change_binary = 1;
action = ", changing binary";
break;
case SIGALRM:
ngx_sigalrm = 1;
break;
case SIGIO:
ngx_sigio = 1;
break;
case SIGCHLD:
ngx_reap = 1;
break;
}
break;
// 工作进程...
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");
}
if (signo == SIGCHLD) {
ngx_process_get_status();
}
ngx_set_errno(err);
}
这里处理完毕了吗，还没有以服务器模式为NGX_PROCESS_MASTER为例，ngx_master_process_cycle函数中创建完工作进程和管理进程后，主进程进入循环，并停滞在// 等待信号唤醒 sigsuspend(&set);// 注意set是一个空信号集进程收到信号并处理信号函数后，此函数返回，程序进入下面执行ngx_terminate在信号处理函数中被置1if (ngx_terminate) { if (delay == 0) { delay = 50; } if (sigio) { sigio--; continue; } sigio = ccf->worker_processes + 2 /* cache processes */; if (delay > 1000) { ngx_signal_worker_processes(cycle, SIGKILL); } else {// 向工作线程发送NGX_TERMINATE_SIGNAL信号 ngx_signal_worker_processes(cycle, ngx_signal_value(NGX_TERMINATE_SIGNAL)); } continue; }这就是信号处理流程，那么有一个问题，信号如何被发送的？
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