view src/event/ngx_event.c @ 8122:106328a70f4e

Added warning about redefinition of listen socket protocol options. The "listen" directive in the http module can be used multiple times in different server blocks. Originally, it was supposed to be specified once with various socket options, and without any parameters in virtual server blocks. For example: server { listen 80 backlog=1024; server_name foo; ... } server { listen 80; server_name bar; ... } server { listen 80; server_name bazz; ... } The address part of the syntax ("address[:port]" / "port" / "unix:path") uniquely identifies the listening socket, and therefore is enough for name-based virtual servers (to let nginx know that the virtual server accepts requests on the listening socket in question). To ensure that listening options do not conflict between virtual servers, they were allowed only once. For example, the following configuration will be rejected ("duplicate listen options for 0.0.0.0:80 in ..."): server { listen 80 backlog=1024; server_name foo; ... } server { listen 80 backlog=512; server_name bar; ... } At some point it was, however, noticed, that it is sometimes convenient to repeat some options for clarity. In nginx 0.8.51 the "ssl" parameter was allowed to be specified multiple times, e.g.: server { listen 443 ssl backlog=1024; server_name foo; ... } server { listen 443 ssl; server_name bar; ... } server { listen 443 ssl; server_name bazz; ... } This approach makes configuration more readable, since SSL sockets are immediately visible in the configuration. If this is not needed, just the address can still be used. Later, additional protocol-specific options similar to "ssl" were introduced, notably "http2" and "proxy_protocol". With these options, one can write: server { listen 443 ssl backlog=1024; server_name foo; ... } server { listen 443 http2; server_name bar; ... } server { listen 443 proxy_protocol; server_name bazz; ... } The resulting socket will use ssl, http2, and proxy_protocol, but this is not really obvious from the configuration. To emphasize such misleading configurations are discouraged, nginx now warns as long as the "listen" directive is used with options different from the options previously used if this is potentially confusing. In particular, the following configurations are allowed: server { listen 8401 ssl backlog=1024; server_name foo; } server { listen 8401 ssl; server_name bar; } server { listen 8401 ssl; server_name bazz; } server { listen 8402 ssl http2 backlog=1024; server_name foo; } server { listen 8402 ssl; server_name bar; } server { listen 8402 ssl; server_name bazz; } server { listen 8403 ssl; server_name bar; } server { listen 8403 ssl; server_name bazz; } server { listen 8403 ssl http2; server_name foo; } server { listen 8404 ssl http2 backlog=1024; server_name foo; } server { listen 8404 http2; server_name bar; } server { listen 8404 http2; server_name bazz; } server { listen 8405 ssl http2 backlog=1024; server_name foo; } server { listen 8405 ssl http2; server_name bar; } server { listen 8405 ssl http2; server_name bazz; } server { listen 8406 ssl; server_name foo; } server { listen 8406; server_name bar; } server { listen 8406; server_name bazz; } And the following configurations will generate warnings: server { listen 8501 ssl http2 backlog=1024; server_name foo; } server { listen 8501 http2; server_name bar; } server { listen 8501 ssl; server_name bazz; } server { listen 8502 backlog=1024; server_name foo; } server { listen 8502 ssl; server_name bar; } server { listen 8503 ssl; server_name foo; } server { listen 8503 http2; server_name bar; } server { listen 8504 ssl; server_name foo; } server { listen 8504 http2; server_name bar; } server { listen 8504 proxy_protocol; server_name bazz; } server { listen 8505 ssl http2 proxy_protocol; server_name foo; } server { listen 8505 ssl http2; server_name bar; } server { listen 8505 ssl; server_name bazz; } server { listen 8506 ssl http2; server_name foo; } server { listen 8506 ssl; server_name bar; } server { listen 8506; server_name bazz; } server { listen 8507 ssl; server_name bar; } server { listen 8507; server_name bazz; } server { listen 8507 ssl http2; server_name foo; } server { listen 8508 ssl; server_name bar; } server { listen 8508; server_name bazz; } server { listen 8508 ssl backlog=1024; server_name foo; } server { listen 8509; server_name bazz; } server { listen 8509 ssl; server_name bar; } server { listen 8509 ssl backlog=1024; server_name foo; } The basic idea is that at most two sets of protocol options are allowed: the main one (with socket options, if any), and a shorter one, with options being a subset of the main options, repeated for clarity. As long as the shorter set of protocol options is used, all listen directives except the main one should use it.
author Maxim Dounin <mdounin@mdounin.ru>
date Sat, 28 Jan 2023 01:29:45 +0300
parents 8852f39311de
children 91ad1abfb285
line wrap: on
line source


/*
 * Copyright (C) Igor Sysoev
 * Copyright (C) Nginx, Inc.
 */


#include <ngx_config.h>
#include <ngx_core.h>
#include <ngx_event.h>


#define DEFAULT_CONNECTIONS  512


extern ngx_module_t ngx_kqueue_module;
extern ngx_module_t ngx_eventport_module;
extern ngx_module_t ngx_devpoll_module;
extern ngx_module_t ngx_epoll_module;
extern ngx_module_t ngx_select_module;


static char *ngx_event_init_conf(ngx_cycle_t *cycle, void *conf);
static ngx_int_t ngx_event_module_init(ngx_cycle_t *cycle);
static ngx_int_t ngx_event_process_init(ngx_cycle_t *cycle);
static char *ngx_events_block(ngx_conf_t *cf, ngx_command_t *cmd, void *conf);

static char *ngx_event_connections(ngx_conf_t *cf, ngx_command_t *cmd,
    void *conf);
static char *ngx_event_use(ngx_conf_t *cf, ngx_command_t *cmd, void *conf);
static char *ngx_event_debug_connection(ngx_conf_t *cf, ngx_command_t *cmd,
    void *conf);

static void *ngx_event_core_create_conf(ngx_cycle_t *cycle);
static char *ngx_event_core_init_conf(ngx_cycle_t *cycle, void *conf);


static ngx_uint_t     ngx_timer_resolution;
sig_atomic_t          ngx_event_timer_alarm;

static ngx_uint_t     ngx_event_max_module;

ngx_uint_t            ngx_event_flags;
ngx_event_actions_t   ngx_event_actions;


static ngx_atomic_t   connection_counter = 1;
ngx_atomic_t         *ngx_connection_counter = &connection_counter;


ngx_atomic_t         *ngx_accept_mutex_ptr;
ngx_shmtx_t           ngx_accept_mutex;
ngx_uint_t            ngx_use_accept_mutex;
ngx_uint_t            ngx_accept_events;
ngx_uint_t            ngx_accept_mutex_held;
ngx_msec_t            ngx_accept_mutex_delay;
ngx_int_t             ngx_accept_disabled;
ngx_uint_t            ngx_use_exclusive_accept;


#if (NGX_STAT_STUB)

static ngx_atomic_t   ngx_stat_accepted0;
ngx_atomic_t         *ngx_stat_accepted = &ngx_stat_accepted0;
static ngx_atomic_t   ngx_stat_handled0;
ngx_atomic_t         *ngx_stat_handled = &ngx_stat_handled0;
static ngx_atomic_t   ngx_stat_requests0;
ngx_atomic_t         *ngx_stat_requests = &ngx_stat_requests0;
static ngx_atomic_t   ngx_stat_active0;
ngx_atomic_t         *ngx_stat_active = &ngx_stat_active0;
static ngx_atomic_t   ngx_stat_reading0;
ngx_atomic_t         *ngx_stat_reading = &ngx_stat_reading0;
static ngx_atomic_t   ngx_stat_writing0;
ngx_atomic_t         *ngx_stat_writing = &ngx_stat_writing0;
static ngx_atomic_t   ngx_stat_waiting0;
ngx_atomic_t         *ngx_stat_waiting = &ngx_stat_waiting0;

#endif



static ngx_command_t  ngx_events_commands[] = {

    { ngx_string("events"),
      NGX_MAIN_CONF|NGX_CONF_BLOCK|NGX_CONF_NOARGS,
      ngx_events_block,
      0,
      0,
      NULL },

      ngx_null_command
};


static ngx_core_module_t  ngx_events_module_ctx = {
    ngx_string("events"),
    NULL,
    ngx_event_init_conf
};


ngx_module_t  ngx_events_module = {
    NGX_MODULE_V1,
    &ngx_events_module_ctx,                /* module context */
    ngx_events_commands,                   /* module directives */
    NGX_CORE_MODULE,                       /* module type */
    NULL,                                  /* init master */
    NULL,                                  /* init module */
    NULL,                                  /* init process */
    NULL,                                  /* init thread */
    NULL,                                  /* exit thread */
    NULL,                                  /* exit process */
    NULL,                                  /* exit master */
    NGX_MODULE_V1_PADDING
};


static ngx_str_t  event_core_name = ngx_string("event_core");


static ngx_command_t  ngx_event_core_commands[] = {

    { ngx_string("worker_connections"),
      NGX_EVENT_CONF|NGX_CONF_TAKE1,
      ngx_event_connections,
      0,
      0,
      NULL },

    { ngx_string("use"),
      NGX_EVENT_CONF|NGX_CONF_TAKE1,
      ngx_event_use,
      0,
      0,
      NULL },

    { ngx_string("multi_accept"),
      NGX_EVENT_CONF|NGX_CONF_FLAG,
      ngx_conf_set_flag_slot,
      0,
      offsetof(ngx_event_conf_t, multi_accept),
      NULL },

    { ngx_string("accept_mutex"),
      NGX_EVENT_CONF|NGX_CONF_FLAG,
      ngx_conf_set_flag_slot,
      0,
      offsetof(ngx_event_conf_t, accept_mutex),
      NULL },

    { ngx_string("accept_mutex_delay"),
      NGX_EVENT_CONF|NGX_CONF_TAKE1,
      ngx_conf_set_msec_slot,
      0,
      offsetof(ngx_event_conf_t, accept_mutex_delay),
      NULL },

    { ngx_string("debug_connection"),
      NGX_EVENT_CONF|NGX_CONF_TAKE1,
      ngx_event_debug_connection,
      0,
      0,
      NULL },

      ngx_null_command
};


static ngx_event_module_t  ngx_event_core_module_ctx = {
    &event_core_name,
    ngx_event_core_create_conf,            /* create configuration */
    ngx_event_core_init_conf,              /* init configuration */

    { NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL }
};


ngx_module_t  ngx_event_core_module = {
    NGX_MODULE_V1,
    &ngx_event_core_module_ctx,            /* module context */
    ngx_event_core_commands,               /* module directives */
    NGX_EVENT_MODULE,                      /* module type */
    NULL,                                  /* init master */
    ngx_event_module_init,                 /* init module */
    ngx_event_process_init,                /* init process */
    NULL,                                  /* init thread */
    NULL,                                  /* exit thread */
    NULL,                                  /* exit process */
    NULL,                                  /* exit master */
    NGX_MODULE_V1_PADDING
};


void
ngx_process_events_and_timers(ngx_cycle_t *cycle)
{
    ngx_uint_t  flags;
    ngx_msec_t  timer, delta;

    if (ngx_timer_resolution) {
        timer = NGX_TIMER_INFINITE;
        flags = 0;

    } else {
        timer = ngx_event_find_timer();
        flags = NGX_UPDATE_TIME;

#if (NGX_WIN32)

        /* handle signals from master in case of network inactivity */

        if (timer == NGX_TIMER_INFINITE || timer > 500) {
            timer = 500;
        }

#endif
    }

    if (ngx_use_accept_mutex) {
        if (ngx_accept_disabled > 0) {
            ngx_accept_disabled--;

        } else {
            if (ngx_trylock_accept_mutex(cycle) == NGX_ERROR) {
                return;
            }

            if (ngx_accept_mutex_held) {
                flags |= NGX_POST_EVENTS;

            } else {
                if (timer == NGX_TIMER_INFINITE
                    || timer > ngx_accept_mutex_delay)
                {
                    timer = ngx_accept_mutex_delay;
                }
            }
        }
    }

    if (!ngx_queue_empty(&ngx_posted_next_events)) {
        ngx_event_move_posted_next(cycle);
        timer = 0;
    }

    delta = ngx_current_msec;

    (void) ngx_process_events(cycle, timer, flags);

    delta = ngx_current_msec - delta;

    ngx_log_debug1(NGX_LOG_DEBUG_EVENT, cycle->log, 0,
                   "timer delta: %M", delta);

    ngx_event_process_posted(cycle, &ngx_posted_accept_events);

    if (ngx_accept_mutex_held) {
        ngx_shmtx_unlock(&ngx_accept_mutex);
    }

    ngx_event_expire_timers();

    ngx_event_process_posted(cycle, &ngx_posted_events);
}


ngx_int_t
ngx_handle_read_event(ngx_event_t *rev, ngx_uint_t flags)
{
    if (ngx_event_flags & NGX_USE_CLEAR_EVENT) {

        /* kqueue, epoll */

        if (!rev->active && !rev->ready) {
            if (ngx_add_event(rev, NGX_READ_EVENT, NGX_CLEAR_EVENT)
                == NGX_ERROR)
            {
                return NGX_ERROR;
            }
        }

        return NGX_OK;

    } else if (ngx_event_flags & NGX_USE_LEVEL_EVENT) {

        /* select, poll, /dev/poll */

        if (!rev->active && !rev->ready) {
            if (ngx_add_event(rev, NGX_READ_EVENT, NGX_LEVEL_EVENT)
                == NGX_ERROR)
            {
                return NGX_ERROR;
            }

            return NGX_OK;
        }

        if (rev->active && (rev->ready || (flags & NGX_CLOSE_EVENT))) {
            if (ngx_del_event(rev, NGX_READ_EVENT, NGX_LEVEL_EVENT | flags)
                == NGX_ERROR)
            {
                return NGX_ERROR;
            }

            return NGX_OK;
        }

    } else if (ngx_event_flags & NGX_USE_EVENTPORT_EVENT) {

        /* event ports */

        if (!rev->active && !rev->ready) {
            if (ngx_add_event(rev, NGX_READ_EVENT, 0) == NGX_ERROR) {
                return NGX_ERROR;
            }

            return NGX_OK;
        }

        if (rev->oneshot && rev->ready) {
            if (ngx_del_event(rev, NGX_READ_EVENT, 0) == NGX_ERROR) {
                return NGX_ERROR;
            }

            return NGX_OK;
        }
    }

    /* iocp */

    return NGX_OK;
}


ngx_int_t
ngx_handle_write_event(ngx_event_t *wev, size_t lowat)
{
    ngx_connection_t  *c;

    if (lowat) {
        c = wev->data;

        if (ngx_send_lowat(c, lowat) == NGX_ERROR) {
            return NGX_ERROR;
        }
    }

    if (ngx_event_flags & NGX_USE_CLEAR_EVENT) {

        /* kqueue, epoll */

        if (!wev->active && !wev->ready) {
            if (ngx_add_event(wev, NGX_WRITE_EVENT,
                              NGX_CLEAR_EVENT | (lowat ? NGX_LOWAT_EVENT : 0))
                == NGX_ERROR)
            {
                return NGX_ERROR;
            }
        }

        return NGX_OK;

    } else if (ngx_event_flags & NGX_USE_LEVEL_EVENT) {

        /* select, poll, /dev/poll */

        if (!wev->active && !wev->ready) {
            if (ngx_add_event(wev, NGX_WRITE_EVENT, NGX_LEVEL_EVENT)
                == NGX_ERROR)
            {
                return NGX_ERROR;
            }

            return NGX_OK;
        }

        if (wev->active && wev->ready) {
            if (ngx_del_event(wev, NGX_WRITE_EVENT, NGX_LEVEL_EVENT)
                == NGX_ERROR)
            {
                return NGX_ERROR;
            }

            return NGX_OK;
        }

    } else if (ngx_event_flags & NGX_USE_EVENTPORT_EVENT) {

        /* event ports */

        if (!wev->active && !wev->ready) {
            if (ngx_add_event(wev, NGX_WRITE_EVENT, 0) == NGX_ERROR) {
                return NGX_ERROR;
            }

            return NGX_OK;
        }

        if (wev->oneshot && wev->ready) {
            if (ngx_del_event(wev, NGX_WRITE_EVENT, 0) == NGX_ERROR) {
                return NGX_ERROR;
            }

            return NGX_OK;
        }
    }

    /* iocp */

    return NGX_OK;
}


static char *
ngx_event_init_conf(ngx_cycle_t *cycle, void *conf)
{
#if (NGX_HAVE_REUSEPORT)
    ngx_uint_t        i;
    ngx_core_conf_t  *ccf;
    ngx_listening_t  *ls;
#endif

    if (ngx_get_conf(cycle->conf_ctx, ngx_events_module) == NULL) {
        ngx_log_error(NGX_LOG_EMERG, cycle->log, 0,
                      "no \"events\" section in configuration");
        return NGX_CONF_ERROR;
    }

    if (cycle->connection_n < cycle->listening.nelts + 1) {

        /*
         * there should be at least one connection for each listening
         * socket, plus an additional connection for channel
         */

        ngx_log_error(NGX_LOG_EMERG, cycle->log, 0,
                      "%ui worker_connections are not enough "
                      "for %ui listening sockets",
                      cycle->connection_n, cycle->listening.nelts);

        return NGX_CONF_ERROR;
    }

#if (NGX_HAVE_REUSEPORT)

    ccf = (ngx_core_conf_t *) ngx_get_conf(cycle->conf_ctx, ngx_core_module);

    if (!ngx_test_config && ccf->master) {

        ls = cycle->listening.elts;
        for (i = 0; i < cycle->listening.nelts; i++) {

            if (!ls[i].reuseport || ls[i].worker != 0) {
                continue;
            }

            if (ngx_clone_listening(cycle, &ls[i]) != NGX_OK) {
                return NGX_CONF_ERROR;
            }

            /* cloning may change cycle->listening.elts */

            ls = cycle->listening.elts;
        }
    }

#endif

    return NGX_CONF_OK;
}


static ngx_int_t
ngx_event_module_init(ngx_cycle_t *cycle)
{
    void              ***cf;
    u_char              *shared;
    size_t               size, cl;
    ngx_shm_t            shm;
    ngx_time_t          *tp;
    ngx_core_conf_t     *ccf;
    ngx_event_conf_t    *ecf;

    cf = ngx_get_conf(cycle->conf_ctx, ngx_events_module);
    ecf = (*cf)[ngx_event_core_module.ctx_index];

    if (!ngx_test_config && ngx_process <= NGX_PROCESS_MASTER) {
        ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0,
                      "using the \"%s\" event method", ecf->name);
    }

    ccf = (ngx_core_conf_t *) ngx_get_conf(cycle->conf_ctx, ngx_core_module);

    ngx_timer_resolution = ccf->timer_resolution;

#if !(NGX_WIN32)
    {
    ngx_int_t      limit;
    struct rlimit  rlmt;

    if (getrlimit(RLIMIT_NOFILE, &rlmt) == -1) {
        ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
                      "getrlimit(RLIMIT_NOFILE) failed, ignored");

    } else {
        if (ecf->connections > (ngx_uint_t) rlmt.rlim_cur
            && (ccf->rlimit_nofile == NGX_CONF_UNSET
                || ecf->connections > (ngx_uint_t) ccf->rlimit_nofile))
        {
            limit = (ccf->rlimit_nofile == NGX_CONF_UNSET) ?
                         (ngx_int_t) rlmt.rlim_cur : ccf->rlimit_nofile;

            ngx_log_error(NGX_LOG_WARN, cycle->log, 0,
                          "%ui worker_connections exceed "
                          "open file resource limit: %i",
                          ecf->connections, limit);
        }
    }
    }
#endif /* !(NGX_WIN32) */


    if (ccf->master == 0) {
        return NGX_OK;
    }

    if (ngx_accept_mutex_ptr) {
        return NGX_OK;
    }


    /* cl should be equal to or greater than cache line size */

    cl = 128;

    size = cl            /* ngx_accept_mutex */
           + cl          /* ngx_connection_counter */
           + cl;         /* ngx_temp_number */

#if (NGX_STAT_STUB)

    size += cl           /* ngx_stat_accepted */
           + cl          /* ngx_stat_handled */
           + cl          /* ngx_stat_requests */
           + cl          /* ngx_stat_active */
           + cl          /* ngx_stat_reading */
           + cl          /* ngx_stat_writing */
           + cl;         /* ngx_stat_waiting */

#endif

    shm.size = size;
    ngx_str_set(&shm.name, "nginx_shared_zone");
    shm.log = cycle->log;

    if (ngx_shm_alloc(&shm) != NGX_OK) {
        return NGX_ERROR;
    }

    shared = shm.addr;

    ngx_accept_mutex_ptr = (ngx_atomic_t *) shared;
    ngx_accept_mutex.spin = (ngx_uint_t) -1;

    if (ngx_shmtx_create(&ngx_accept_mutex, (ngx_shmtx_sh_t *) shared,
                         cycle->lock_file.data)
        != NGX_OK)
    {
        return NGX_ERROR;
    }

    ngx_connection_counter = (ngx_atomic_t *) (shared + 1 * cl);

    (void) ngx_atomic_cmp_set(ngx_connection_counter, 0, 1);

    ngx_log_debug2(NGX_LOG_DEBUG_EVENT, cycle->log, 0,
                   "counter: %p, %uA",
                   ngx_connection_counter, *ngx_connection_counter);

    ngx_temp_number = (ngx_atomic_t *) (shared + 2 * cl);

    tp = ngx_timeofday();

    ngx_random_number = (tp->msec << 16) + ngx_pid;

#if (NGX_STAT_STUB)

    ngx_stat_accepted = (ngx_atomic_t *) (shared + 3 * cl);
    ngx_stat_handled = (ngx_atomic_t *) (shared + 4 * cl);
    ngx_stat_requests = (ngx_atomic_t *) (shared + 5 * cl);
    ngx_stat_active = (ngx_atomic_t *) (shared + 6 * cl);
    ngx_stat_reading = (ngx_atomic_t *) (shared + 7 * cl);
    ngx_stat_writing = (ngx_atomic_t *) (shared + 8 * cl);
    ngx_stat_waiting = (ngx_atomic_t *) (shared + 9 * cl);

#endif

    return NGX_OK;
}


#if !(NGX_WIN32)

static void
ngx_timer_signal_handler(int signo)
{
    ngx_event_timer_alarm = 1;

#if 1
    ngx_log_debug0(NGX_LOG_DEBUG_EVENT, ngx_cycle->log, 0, "timer signal");
#endif
}

#endif


static ngx_int_t
ngx_event_process_init(ngx_cycle_t *cycle)
{
    ngx_uint_t           m, i;
    ngx_event_t         *rev, *wev;
    ngx_listening_t     *ls;
    ngx_connection_t    *c, *next, *old;
    ngx_core_conf_t     *ccf;
    ngx_event_conf_t    *ecf;
    ngx_event_module_t  *module;

    ccf = (ngx_core_conf_t *) ngx_get_conf(cycle->conf_ctx, ngx_core_module);
    ecf = ngx_event_get_conf(cycle->conf_ctx, ngx_event_core_module);

    if (ccf->master && ccf->worker_processes > 1 && ecf->accept_mutex) {
        ngx_use_accept_mutex = 1;
        ngx_accept_mutex_held = 0;
        ngx_accept_mutex_delay = ecf->accept_mutex_delay;

    } else {
        ngx_use_accept_mutex = 0;
    }

#if (NGX_WIN32)

    /*
     * disable accept mutex on win32 as it may cause deadlock if
     * grabbed by a process which can't accept connections
     */

    ngx_use_accept_mutex = 0;

#endif

    ngx_use_exclusive_accept = 0;

    ngx_queue_init(&ngx_posted_accept_events);
    ngx_queue_init(&ngx_posted_next_events);
    ngx_queue_init(&ngx_posted_events);

    if (ngx_event_timer_init(cycle->log) == NGX_ERROR) {
        return NGX_ERROR;
    }

    for (m = 0; cycle->modules[m]; m++) {
        if (cycle->modules[m]->type != NGX_EVENT_MODULE) {
            continue;
        }

        if (cycle->modules[m]->ctx_index != ecf->use) {
            continue;
        }

        module = cycle->modules[m]->ctx;

        if (module->actions.init(cycle, ngx_timer_resolution) != NGX_OK) {
            /* fatal */
            exit(2);
        }

        break;
    }

#if !(NGX_WIN32)

    if (ngx_timer_resolution && !(ngx_event_flags & NGX_USE_TIMER_EVENT)) {
        struct sigaction  sa;
        struct itimerval  itv;

        ngx_memzero(&sa, sizeof(struct sigaction));
        sa.sa_handler = ngx_timer_signal_handler;
        sigemptyset(&sa.sa_mask);

        if (sigaction(SIGALRM, &sa, NULL) == -1) {
            ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
                          "sigaction(SIGALRM) failed");
            return NGX_ERROR;
        }

        itv.it_interval.tv_sec = ngx_timer_resolution / 1000;
        itv.it_interval.tv_usec = (ngx_timer_resolution % 1000) * 1000;
        itv.it_value.tv_sec = ngx_timer_resolution / 1000;
        itv.it_value.tv_usec = (ngx_timer_resolution % 1000 ) * 1000;

        if (setitimer(ITIMER_REAL, &itv, NULL) == -1) {
            ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
                          "setitimer() failed");
        }
    }

    if (ngx_event_flags & NGX_USE_FD_EVENT) {
        struct rlimit  rlmt;

        if (getrlimit(RLIMIT_NOFILE, &rlmt) == -1) {
            ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,
                          "getrlimit(RLIMIT_NOFILE) failed");
            return NGX_ERROR;
        }

        cycle->files_n = (ngx_uint_t) rlmt.rlim_cur;

        cycle->files = ngx_calloc(sizeof(ngx_connection_t *) * cycle->files_n,
                                  cycle->log);
        if (cycle->files == NULL) {
            return NGX_ERROR;
        }
    }

#else

    if (ngx_timer_resolution && !(ngx_event_flags & NGX_USE_TIMER_EVENT)) {
        ngx_log_error(NGX_LOG_WARN, cycle->log, 0,
                      "the \"timer_resolution\" directive is not supported "
                      "with the configured event method, ignored");
        ngx_timer_resolution = 0;
    }

#endif

    cycle->connections =
        ngx_alloc(sizeof(ngx_connection_t) * cycle->connection_n, cycle->log);
    if (cycle->connections == NULL) {
        return NGX_ERROR;
    }

    c = cycle->connections;

    cycle->read_events = ngx_alloc(sizeof(ngx_event_t) * cycle->connection_n,
                                   cycle->log);
    if (cycle->read_events == NULL) {
        return NGX_ERROR;
    }

    rev = cycle->read_events;
    for (i = 0; i < cycle->connection_n; i++) {
        rev[i].closed = 1;
        rev[i].instance = 1;
    }

    cycle->write_events = ngx_alloc(sizeof(ngx_event_t) * cycle->connection_n,
                                    cycle->log);
    if (cycle->write_events == NULL) {
        return NGX_ERROR;
    }

    wev = cycle->write_events;
    for (i = 0; i < cycle->connection_n; i++) {
        wev[i].closed = 1;
    }

    i = cycle->connection_n;
    next = NULL;

    do {
        i--;

        c[i].data = next;
        c[i].read = &cycle->read_events[i];
        c[i].write = &cycle->write_events[i];
        c[i].fd = (ngx_socket_t) -1;

        next = &c[i];
    } while (i);

    cycle->free_connections = next;
    cycle->free_connection_n = cycle->connection_n;

    /* for each listening socket */

    ls = cycle->listening.elts;
    for (i = 0; i < cycle->listening.nelts; i++) {

#if (NGX_HAVE_REUSEPORT)
        if (ls[i].reuseport && ls[i].worker != ngx_worker) {
            continue;
        }
#endif

        c = ngx_get_connection(ls[i].fd, cycle->log);

        if (c == NULL) {
            return NGX_ERROR;
        }

        c->type = ls[i].type;
        c->log = &ls[i].log;

        c->listening = &ls[i];
        ls[i].connection = c;

        rev = c->read;

        rev->log = c->log;
        rev->accept = 1;

#if (NGX_HAVE_DEFERRED_ACCEPT)
        rev->deferred_accept = ls[i].deferred_accept;
#endif

        if (!(ngx_event_flags & NGX_USE_IOCP_EVENT)
            && cycle->old_cycle)
        {
            if (ls[i].previous) {

                /*
                 * delete the old accept events that were bound to
                 * the old cycle read events array
                 */

                old = ls[i].previous->connection;

                if (ngx_del_event(old->read, NGX_READ_EVENT, NGX_CLOSE_EVENT)
                    == NGX_ERROR)
                {
                    return NGX_ERROR;
                }

                old->fd = (ngx_socket_t) -1;
            }
        }

#if (NGX_WIN32)

        if (ngx_event_flags & NGX_USE_IOCP_EVENT) {
            ngx_iocp_conf_t  *iocpcf;

            rev->handler = ngx_event_acceptex;

            if (ngx_use_accept_mutex) {
                continue;
            }

            if (ngx_add_event(rev, 0, NGX_IOCP_ACCEPT) == NGX_ERROR) {
                return NGX_ERROR;
            }

            ls[i].log.handler = ngx_acceptex_log_error;

            iocpcf = ngx_event_get_conf(cycle->conf_ctx, ngx_iocp_module);
            if (ngx_event_post_acceptex(&ls[i], iocpcf->post_acceptex)
                == NGX_ERROR)
            {
                return NGX_ERROR;
            }

        } else {
            rev->handler = ngx_event_accept;

            if (ngx_use_accept_mutex) {
                continue;
            }

            if (ngx_add_event(rev, NGX_READ_EVENT, 0) == NGX_ERROR) {
                return NGX_ERROR;
            }
        }

#else

        rev->handler = (c->type == SOCK_STREAM) ? ngx_event_accept
                                                : ngx_event_recvmsg;

#if (NGX_HAVE_REUSEPORT)

        if (ls[i].reuseport) {
            if (ngx_add_event(rev, NGX_READ_EVENT, 0) == NGX_ERROR) {
                return NGX_ERROR;
            }

            continue;
        }

#endif

        if (ngx_use_accept_mutex) {
            continue;
        }

#if (NGX_HAVE_EPOLLEXCLUSIVE)

        if ((ngx_event_flags & NGX_USE_EPOLL_EVENT)
            && ccf->worker_processes > 1)
        {
            ngx_use_exclusive_accept = 1;

            if (ngx_add_event(rev, NGX_READ_EVENT, NGX_EXCLUSIVE_EVENT)
                == NGX_ERROR)
            {
                return NGX_ERROR;
            }

            continue;
        }

#endif

        if (ngx_add_event(rev, NGX_READ_EVENT, 0) == NGX_ERROR) {
            return NGX_ERROR;
        }

#endif

    }

    return NGX_OK;
}


ngx_int_t
ngx_send_lowat(ngx_connection_t *c, size_t lowat)
{
    int  sndlowat;

#if (NGX_HAVE_LOWAT_EVENT)

    if (ngx_event_flags & NGX_USE_KQUEUE_EVENT) {
        c->write->available = lowat;
        return NGX_OK;
    }

#endif

    if (lowat == 0 || c->sndlowat) {
        return NGX_OK;
    }

    sndlowat = (int) lowat;

    if (setsockopt(c->fd, SOL_SOCKET, SO_SNDLOWAT,
                   (const void *) &sndlowat, sizeof(int))
        == -1)
    {
        ngx_connection_error(c, ngx_socket_errno,
                             "setsockopt(SO_SNDLOWAT) failed");
        return NGX_ERROR;
    }

    c->sndlowat = 1;

    return NGX_OK;
}


static char *
ngx_events_block(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
{
    char                 *rv;
    void               ***ctx;
    ngx_uint_t            i;
    ngx_conf_t            pcf;
    ngx_event_module_t   *m;

    if (*(void **) conf) {
        return "is duplicate";
    }

    /* count the number of the event modules and set up their indices */

    ngx_event_max_module = ngx_count_modules(cf->cycle, NGX_EVENT_MODULE);

    ctx = ngx_pcalloc(cf->pool, sizeof(void *));
    if (ctx == NULL) {
        return NGX_CONF_ERROR;
    }

    *ctx = ngx_pcalloc(cf->pool, ngx_event_max_module * sizeof(void *));
    if (*ctx == NULL) {
        return NGX_CONF_ERROR;
    }

    *(void **) conf = ctx;

    for (i = 0; cf->cycle->modules[i]; i++) {
        if (cf->cycle->modules[i]->type != NGX_EVENT_MODULE) {
            continue;
        }

        m = cf->cycle->modules[i]->ctx;

        if (m->create_conf) {
            (*ctx)[cf->cycle->modules[i]->ctx_index] =
                                                     m->create_conf(cf->cycle);
            if ((*ctx)[cf->cycle->modules[i]->ctx_index] == NULL) {
                return NGX_CONF_ERROR;
            }
        }
    }

    pcf = *cf;
    cf->ctx = ctx;
    cf->module_type = NGX_EVENT_MODULE;
    cf->cmd_type = NGX_EVENT_CONF;

    rv = ngx_conf_parse(cf, NULL);

    *cf = pcf;

    if (rv != NGX_CONF_OK) {
        return rv;
    }

    for (i = 0; cf->cycle->modules[i]; i++) {
        if (cf->cycle->modules[i]->type != NGX_EVENT_MODULE) {
            continue;
        }

        m = cf->cycle->modules[i]->ctx;

        if (m->init_conf) {
            rv = m->init_conf(cf->cycle,
                              (*ctx)[cf->cycle->modules[i]->ctx_index]);
            if (rv != NGX_CONF_OK) {
                return rv;
            }
        }
    }

    return NGX_CONF_OK;
}


static char *
ngx_event_connections(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
{
    ngx_event_conf_t  *ecf = conf;

    ngx_str_t  *value;

    if (ecf->connections != NGX_CONF_UNSET_UINT) {
        return "is duplicate";
    }

    value = cf->args->elts;
    ecf->connections = ngx_atoi(value[1].data, value[1].len);
    if (ecf->connections == (ngx_uint_t) NGX_ERROR) {
        ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
                           "invalid number \"%V\"", &value[1]);

        return NGX_CONF_ERROR;
    }

    cf->cycle->connection_n = ecf->connections;

    return NGX_CONF_OK;
}


static char *
ngx_event_use(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
{
    ngx_event_conf_t  *ecf = conf;

    ngx_int_t             m;
    ngx_str_t            *value;
    ngx_event_conf_t     *old_ecf;
    ngx_event_module_t   *module;

    if (ecf->use != NGX_CONF_UNSET_UINT) {
        return "is duplicate";
    }

    value = cf->args->elts;

    if (cf->cycle->old_cycle->conf_ctx) {
        old_ecf = ngx_event_get_conf(cf->cycle->old_cycle->conf_ctx,
                                     ngx_event_core_module);
    } else {
        old_ecf = NULL;
    }


    for (m = 0; cf->cycle->modules[m]; m++) {
        if (cf->cycle->modules[m]->type != NGX_EVENT_MODULE) {
            continue;
        }

        module = cf->cycle->modules[m]->ctx;
        if (module->name->len == value[1].len) {
            if (ngx_strcmp(module->name->data, value[1].data) == 0) {
                ecf->use = cf->cycle->modules[m]->ctx_index;
                ecf->name = module->name->data;

                if (ngx_process == NGX_PROCESS_SINGLE
                    && old_ecf
                    && old_ecf->use != ecf->use)
                {
                    ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
                               "when the server runs without a master process "
                               "the \"%V\" event type must be the same as "
                               "in previous configuration - \"%s\" "
                               "and it cannot be changed on the fly, "
                               "to change it you need to stop server "
                               "and start it again",
                               &value[1], old_ecf->name);

                    return NGX_CONF_ERROR;
                }

                return NGX_CONF_OK;
            }
        }
    }

    ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
                       "invalid event type \"%V\"", &value[1]);

    return NGX_CONF_ERROR;
}


static char *
ngx_event_debug_connection(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
{
#if (NGX_DEBUG)
    ngx_event_conf_t  *ecf = conf;

    ngx_int_t             rc;
    ngx_str_t            *value;
    ngx_url_t             u;
    ngx_cidr_t            c, *cidr;
    ngx_uint_t            i;
    struct sockaddr_in   *sin;
#if (NGX_HAVE_INET6)
    struct sockaddr_in6  *sin6;
#endif

    value = cf->args->elts;

#if (NGX_HAVE_UNIX_DOMAIN)

    if (ngx_strcmp(value[1].data, "unix:") == 0) {
        cidr = ngx_array_push(&ecf->debug_connection);
        if (cidr == NULL) {
            return NGX_CONF_ERROR;
        }

        cidr->family = AF_UNIX;
        return NGX_CONF_OK;
    }

#endif

    rc = ngx_ptocidr(&value[1], &c);

    if (rc != NGX_ERROR) {
        if (rc == NGX_DONE) {
            ngx_conf_log_error(NGX_LOG_WARN, cf, 0,
                               "low address bits of %V are meaningless",
                               &value[1]);
        }

        cidr = ngx_array_push(&ecf->debug_connection);
        if (cidr == NULL) {
            return NGX_CONF_ERROR;
        }

        *cidr = c;

        return NGX_CONF_OK;
    }

    ngx_memzero(&u, sizeof(ngx_url_t));
    u.host = value[1];

    if (ngx_inet_resolve_host(cf->pool, &u) != NGX_OK) {
        if (u.err) {
            ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
                               "%s in debug_connection \"%V\"",
                               u.err, &u.host);
        }

        return NGX_CONF_ERROR;
    }

    cidr = ngx_array_push_n(&ecf->debug_connection, u.naddrs);
    if (cidr == NULL) {
        return NGX_CONF_ERROR;
    }

    ngx_memzero(cidr, u.naddrs * sizeof(ngx_cidr_t));

    for (i = 0; i < u.naddrs; i++) {
        cidr[i].family = u.addrs[i].sockaddr->sa_family;

        switch (cidr[i].family) {

#if (NGX_HAVE_INET6)
        case AF_INET6:
            sin6 = (struct sockaddr_in6 *) u.addrs[i].sockaddr;
            cidr[i].u.in6.addr = sin6->sin6_addr;
            ngx_memset(cidr[i].u.in6.mask.s6_addr, 0xff, 16);
            break;
#endif

        default: /* AF_INET */
            sin = (struct sockaddr_in *) u.addrs[i].sockaddr;
            cidr[i].u.in.addr = sin->sin_addr.s_addr;
            cidr[i].u.in.mask = 0xffffffff;
            break;
        }
    }

#else

    ngx_conf_log_error(NGX_LOG_WARN, cf, 0,
                       "\"debug_connection\" is ignored, you need to rebuild "
                       "nginx using --with-debug option to enable it");

#endif

    return NGX_CONF_OK;
}


static void *
ngx_event_core_create_conf(ngx_cycle_t *cycle)
{
    ngx_event_conf_t  *ecf;

    ecf = ngx_palloc(cycle->pool, sizeof(ngx_event_conf_t));
    if (ecf == NULL) {
        return NULL;
    }

    ecf->connections = NGX_CONF_UNSET_UINT;
    ecf->use = NGX_CONF_UNSET_UINT;
    ecf->multi_accept = NGX_CONF_UNSET;
    ecf->accept_mutex = NGX_CONF_UNSET;
    ecf->accept_mutex_delay = NGX_CONF_UNSET_MSEC;
    ecf->name = (void *) NGX_CONF_UNSET;

#if (NGX_DEBUG)

    if (ngx_array_init(&ecf->debug_connection, cycle->pool, 4,
                       sizeof(ngx_cidr_t)) == NGX_ERROR)
    {
        return NULL;
    }

#endif

    return ecf;
}


static char *
ngx_event_core_init_conf(ngx_cycle_t *cycle, void *conf)
{
    ngx_event_conf_t  *ecf = conf;

#if (NGX_HAVE_EPOLL) && !(NGX_TEST_BUILD_EPOLL)
    int                  fd;
#endif
    ngx_int_t            i;
    ngx_module_t        *module;
    ngx_event_module_t  *event_module;

    module = NULL;

#if (NGX_HAVE_EPOLL) && !(NGX_TEST_BUILD_EPOLL)

    fd = epoll_create(100);

    if (fd != -1) {
        (void) close(fd);
        module = &ngx_epoll_module;

    } else if (ngx_errno != NGX_ENOSYS) {
        module = &ngx_epoll_module;
    }

#endif

#if (NGX_HAVE_DEVPOLL) && !(NGX_TEST_BUILD_DEVPOLL)

    module = &ngx_devpoll_module;

#endif

#if (NGX_HAVE_KQUEUE)

    module = &ngx_kqueue_module;

#endif

#if (NGX_HAVE_SELECT)

    if (module == NULL) {
        module = &ngx_select_module;
    }

#endif

    if (module == NULL) {
        for (i = 0; cycle->modules[i]; i++) {

            if (cycle->modules[i]->type != NGX_EVENT_MODULE) {
                continue;
            }

            event_module = cycle->modules[i]->ctx;

            if (ngx_strcmp(event_module->name->data, event_core_name.data) == 0)
            {
                continue;
            }

            module = cycle->modules[i];
            break;
        }
    }

    if (module == NULL) {
        ngx_log_error(NGX_LOG_EMERG, cycle->log, 0, "no events module found");
        return NGX_CONF_ERROR;
    }

    ngx_conf_init_uint_value(ecf->connections, DEFAULT_CONNECTIONS);
    cycle->connection_n = ecf->connections;

    ngx_conf_init_uint_value(ecf->use, module->ctx_index);

    event_module = module->ctx;
    ngx_conf_init_ptr_value(ecf->name, event_module->name->data);

    ngx_conf_init_value(ecf->multi_accept, 0);
    ngx_conf_init_value(ecf->accept_mutex, 0);
    ngx_conf_init_msec_value(ecf->accept_mutex_delay, 500);

    return NGX_CONF_OK;
}