6、进程通信

工作原理

Kill -WINCH

备注：向父进程发送kill –WINCH信号的时候，ngx_master_process_cycle父进程通知子进程退出。

ngx_signal_worker_processes(ngx_cycle_t *cycle, int signo)

static void

ngx_signal_worker_processes(ngx_cycle_t *cycle, int signo)

{

ngx_int_t i;

ngx_err_t err;

ngx_channel_t ch;

#if (NGX_BROKEN_SCM_RIGHTS)

ch.command = 0;

#else

switch (signo) {

case ngx_signal_value(NGX_SHUTDOWN_SIGNAL): //kill -QUIT

ch.command = NGX_CMD_QUIT;

break;

case ngx_signal_value(NGX_TERMINATE_SIGNAL): //CTRL+C

ch.command = NGX_CMD_TERMINATE;

break;

case ngx_signal_value(NGX_REOPEN_SIGNAL): //kill -USR1

ch.command = NGX_CMD_REOPEN;

break;

default:

ch.command = 0;

}

#endif

ch.fd = -1;

for (i = 0; i < ngx_last_process; i++) {

ngx_log_debug7(NGX_LOG_DEBUG_EVENT, cycle->log, 0,

"child: %d %P e:%d t:%d d:%d r:%d j:%d",

i,

ngx_processes[i].pid,

ngx_processes[i].exiting,

ngx_processes[i].exited,

ngx_processes[i].detached,

ngx_processes[i].respawn,

ngx_processes[i].just_spawn);

if (ngx_processes[i].detached || ngx_processes[i].pid == -1) {

continue;

}

if (ngx_processes[i].just_spawn) {

ngx_processes[i].just_spawn = 0;

continue;

}

//子进程退出的时候，会将ngx_processes[i].exiting置为1

if (ngx_processes[i].exiting

&& signo == ngx_signal_value(NGX_SHUTDOWN_SIGNAL))

{

continue;

}

if (ch.command) { // NGX_CMD_QUIT

// ngx_write_channel成功的话，就continue

//否则 kill 信号到子进程

if (ngx_write_channel(ngx_processes[i].channel[0],

&ch;, sizeof(ngx_channel_t), cycle->log)

== NGX_OK)

{

if (signo != ngx_signal_value(NGX_REOPEN_SIGNAL)) {

ngx_processes[i].exiting = 1;

}

continue;

}

}

ngx_log_debug2(NGX_LOG_DEBUG_CORE, cycle->log, 0,

"kill (%P, %d)" , ngx_processes[i].pid, signo);

if (kill(ngx_processes[i].pid, signo) == -1) {

err = ngx_errno;

ngx_log_error(NGX_LOG_ALERT, cycle->log, err,

"kill(%P, %d) failed", ngx_processes[i].pid, signo);

if (err == NGX_ESRCH) {

ngx_processes[i].exited = 1;

ngx_processes[i].exiting = 0;

ngx_reap = 1;

}

continue;

}

if (signo != ngx_signal_value(NGX_REOPEN_SIGNAL)) {

ngx_processes[i].exiting = 1;

}

}

}

ngx_write_channel(ngx_socket_t s, ngx_channel_t *ch, size_t size,ngx_log_t *log)

ngx_int_t

ngx_write_channel(ngx_socket_t s, ngx_channel_t *ch, size_t size,

ngx_log_t *log)

{

ssize_t n;

ngx_err_t err;

struct iovec iov[1];

struct msghdr msg;

#if (NGX_HAVE_MSGHDR_MSG_CONTROL)

union {

struct cmsghdr cm;

char space[CMSG_SPACE(sizeof(int))];

} cmsg;

if (ch->fd == -1) {

msg.msg_control = NULL;

msg.msg_controllen = 0;

} else { //here

msg.msg_control = (caddr_t) &cmsg;

msg.msg_controllen = sizeof(cmsg);

cmsg.cm.cmsg_len = CMSG_LEN(sizeof(int));

cmsg.cm.cmsg_level = SOL_SOCKET;

cmsg.cm.cmsg_type = SCM_RIGHTS;

/*

* We have to use ngx_memcpy() instead of simple

* *(int *) CMSG_DATA(&cmsg.cm;) = ch->fd;

* because some gcc 4.4 with -O2/3/s optimization issues the warning:

* dereferencing type-punned pointer will break strict-aliasing rules

*

* Fortunately, gcc with -O1 compiles this ngx_memcpy()

* in the same simple assignment as in the code above

*/

ngx_memcpy(CMSG_DATA(&cmsg.cm;), &ch-;>fd, sizeof(int));

}

msg.msg_flags = 0;

#else

if (ch->fd == -1) {

msg.msg_accrights = NULL;

msg.msg_accrightslen = 0;

} else {

msg.msg_accrights = (caddr_t) &ch-;>fd;

msg.msg_accrightslen = sizeof(int);

}

#endif

iov[0].iov_base = (char *) ch;

iov[0].iov_len = size;

msg.msg_name = NULL;

msg.msg_namelen = 0;

msg.msg_iov = iov;

msg.msg_iovlen = 1;

n = sendmsg(s , &msg;, 0);

if (n == -1) { //32 ?

err = ngx_errno;

if (err == NGX_EAGAIN) {

return NGX_AGAIN;

}

ngx_log_error(NGX_LOG_ALERT, log, err, "sendmsg() failed");

return NGX_ERROR;

}

return NGX_OK;

}

ngx_channel_handler(ngx_event_t *ev)

static void

ngx_channel_handler(ngx_event_t *ev)

{

ngx_int_t n;

ngx_channel_t ch;

ngx_connection_t *c;

if (ev->timedout) {

ev->timedout = 0;

return;

}

c = ev->data;

ngx_log_debug0(NGX_LOG_DEBUG_CORE, ev->log, 0, "channel handler");

for ( ;; ) {

n = ngx_read_channel(c->fd, &ch;, sizeof(ngx_channel_t), ev->log);

ngx_log_debug1(NGX_LOG_DEBUG_CORE, ev->log, 0, "channel: %i", n);

if (n == NGX_ERROR) {

if (ngx_event_flags & NGX_USE_EPOLL_EVENT) {

ngx_del_conn(c, 0);

}

ngx_close_connection(c);

return;

}

if (ngx_event_flags & NGX_USE_EVENTPORT_EVENT) {

if (ngx_add_event(ev, NGX_READ_EVENT, 0) == NGX_ERROR) {

return;

}

}

if (n == NGX_AGAIN) {

return;

}

ngx_log_debug1(NGX_LOG_DEBUG_CORE, ev->log, 0,

"channel command: %d", ch.command);

switch (ch.command) {

case NGX_CMD_QUIT:

ngx_quit = 1;

break;

case NGX_CMD_TERMINATE:

ngx_terminate = 1;

break;

case NGX_CMD_REOPEN:

ngx_reopen = 1;

break;

case NGX_CMD_OPEN_CHANNEL:

ngx_log_debug3(NGX_LOG_DEBUG_CORE, ev->log, 0,

"get channel s:%i pid:%P fd:%d",

ch.slot, ch.pid, ch.fd);

ngx_processes[ch.slot].pid = ch.pid;

ngx_processes[ch.slot].channel[0] = ch.fd;

break;

case NGX_CMD_CLOSE_CHANNEL:

ngx_log_debug4(NGX_LOG_DEBUG_CORE, ev->log, 0,

"close channel s:%i pid:%P our:%P fd:%d",

ch.slot, ch.pid, ngx_processes[ch.slot].pid,

ngx_processes[ch.slot].channel[0]);

if (close(ngx_processes[ch.slot].channel[0]) == -1) {

ngx_log_error(NGX_LOG_ALERT, ev->log, ngx_errno,

"close() channel failed");

}

ngx_processes[ch.slot].channel[0] = -1;

break;

}

}

}

ngx_worker_process_cycle(ngx_cycle_t *cycle, void *data)

7、示例参考

信号处理

#include

#include

#include

void ngx_signal_handler(int signo)

{

printf("ngx_signal_handler!\n");

}

int main()

{

struct sigaction sa;

memset(&sa;, 0, sizeof(struct sigaction));

sa.sa_handler = ngx_signal_handler;

sigemptyset(&sa.sa;_mask);

if (sigaction(SIGINT, &sa;, NULL) == -1) {

printf("sigaction() failed\n");

return -1;

}

sigset_t set;

//注释or不注释，结果是一样的

//这部分的代码主要是为了验证信号集是否add成功

/*

sigemptyset(&set;);

sigaddset(&set;, SIGINT);

if (sigprocmask(SIG_BLOCK, &set;, NULL) == -1) {

printf("sigprocmask() failed\n");

return -1;

}

sigemptyset(&set;);

*/

int i;

for (i=0; i<100; i++){

sleep(1);

sigsuspend(&set;); //如果没有收到信号，会一直挂起在这里

printf("i = %d\n", i);

}

}