xref: /unit/src/nxt_router.c (revision 1473)

/*
 * Copyright (C) Igor Sysoev
 * Copyright (C) Valentin V. Bartenev
 * Copyright (C) NGINX, Inc.
 */

#include <nxt_router.h>
#include <nxt_conf.h>
#if (NXT_TLS)
#include <nxt_cert.h>
#endif
#include <nxt_http.h>
#include <nxt_port_memory_int.h>
#include <nxt_unit_request.h>
#include <nxt_unit_response.h>
#include <nxt_router_request.h>

typedef struct {
    nxt_str_t         type;
    uint32_t          processes;
    uint32_t          max_processes;
    uint32_t          spare_processes;
    nxt_msec_t        timeout;
    nxt_msec_t        res_timeout;
    nxt_msec_t        idle_timeout;
    uint32_t          requests;
    nxt_conf_value_t  *limits_value;
    nxt_conf_value_t  *processes_value;
    nxt_conf_value_t  *targets_value;
} nxt_router_app_conf_t;


typedef struct {
    nxt_str_t         pass;
    nxt_str_t         application;
} nxt_router_listener_conf_t;


#if (NXT_TLS)

typedef struct {
    nxt_str_t          name;
    nxt_socket_conf_t  *conf;

    nxt_queue_link_t   link;  /* for nxt_socket_conf_t.tls */
} nxt_router_tlssock_t;

#endif


typedef struct {
    nxt_socket_conf_t       *socket_conf;
    nxt_router_temp_conf_t  *temp_conf;
} nxt_socket_rpc_t;


typedef struct {
    nxt_app_t               *app;
    nxt_router_temp_conf_t  *temp_conf;
} nxt_app_rpc_t;


struct nxt_port_select_state_s {
    nxt_app_t               *app;
    nxt_request_app_link_t  *req_app_link;

    nxt_port_t              *failed_port;
    int                     failed_port_use_delta;

    uint8_t                 start_process;    /* 1 bit */
    nxt_request_app_link_t  *shared_ra;
    nxt_port_t              *port;
};

typedef struct nxt_port_select_state_s nxt_port_select_state_t;

static void nxt_router_greet_controller(nxt_task_t *task,
    nxt_port_t *controller_port);

static void nxt_router_port_select(nxt_task_t *task,
    nxt_port_select_state_t *state);

static nxt_int_t nxt_router_port_post_select(nxt_task_t *task,
    nxt_port_select_state_t *state);

static nxt_int_t nxt_router_start_app_process(nxt_task_t *task, nxt_app_t *app);
static void nxt_request_app_link_update_peer(nxt_task_t *task,
    nxt_request_app_link_t *req_app_link);


nxt_inline void
nxt_request_app_link_inc_use(nxt_request_app_link_t *req_app_link)
{
    nxt_atomic_fetch_add(&req_app_link->use_count, 1);
}

nxt_inline void
nxt_request_app_link_chk_use(nxt_request_app_link_t *req_app_link, int i)
{
#if (NXT_DEBUG)
    int  c;

    c = nxt_atomic_fetch_add(&req_app_link->use_count, i);

    nxt_assert((c + i) > 0);
#else
    (void) nxt_atomic_fetch_add(&req_app_link->use_count, i);
#endif
}

static void nxt_request_app_link_use(nxt_task_t *task,
    nxt_request_app_link_t *req_app_link, int i);

static nxt_router_temp_conf_t *nxt_router_temp_conf(nxt_task_t *task);
static void nxt_router_conf_apply(nxt_task_t *task, void *obj, void *data);
static void nxt_router_conf_ready(nxt_task_t *task,
    nxt_router_temp_conf_t *tmcf);
static void nxt_router_conf_error(nxt_task_t *task,
    nxt_router_temp_conf_t *tmcf);
static void nxt_router_conf_send(nxt_task_t *task,
    nxt_router_temp_conf_t *tmcf, nxt_port_msg_type_t type);

static nxt_int_t nxt_router_conf_create(nxt_task_t *task,
    nxt_router_temp_conf_t *tmcf, u_char *start, u_char *end);
static nxt_int_t nxt_router_conf_process_static(nxt_task_t *task,
    nxt_router_conf_t *rtcf, nxt_conf_value_t *conf);
static nxt_app_t *nxt_router_app_find(nxt_queue_t *queue, nxt_str_t *name);
static void nxt_router_listen_socket_rpc_create(nxt_task_t *task,
    nxt_router_temp_conf_t *tmcf, nxt_socket_conf_t *skcf);
static void nxt_router_listen_socket_ready(nxt_task_t *task,
    nxt_port_recv_msg_t *msg, void *data);
static void nxt_router_listen_socket_error(nxt_task_t *task,
    nxt_port_recv_msg_t *msg, void *data);
#if (NXT_TLS)
static void nxt_router_tls_rpc_create(nxt_task_t *task,
    nxt_router_temp_conf_t *tmcf, nxt_router_tlssock_t *tls);
static void nxt_router_tls_rpc_handler(nxt_task_t *task,
    nxt_port_recv_msg_t *msg, void *data);
#endif
static void nxt_router_app_rpc_create(nxt_task_t *task,
    nxt_router_temp_conf_t *tmcf, nxt_app_t *app);
static void nxt_router_app_prefork_ready(nxt_task_t *task,
    nxt_port_recv_msg_t *msg, void *data);
static void nxt_router_app_prefork_error(nxt_task_t *task,
    nxt_port_recv_msg_t *msg, void *data);
static nxt_socket_conf_t *nxt_router_socket_conf(nxt_task_t *task,
    nxt_router_temp_conf_t *tmcf, nxt_str_t *name);
static nxt_int_t nxt_router_listen_socket_find(nxt_router_temp_conf_t *tmcf,
    nxt_socket_conf_t *nskcf, nxt_sockaddr_t *sa);

static nxt_int_t nxt_router_engines_create(nxt_task_t *task,
    nxt_router_t *router, nxt_router_temp_conf_t *tmcf,
    const nxt_event_interface_t *interface);
static nxt_int_t nxt_router_engine_conf_create(nxt_router_temp_conf_t *tmcf,
    nxt_router_engine_conf_t *recf);
static nxt_int_t nxt_router_engine_conf_update(nxt_router_temp_conf_t *tmcf,
    nxt_router_engine_conf_t *recf);
static nxt_int_t nxt_router_engine_conf_delete(nxt_router_temp_conf_t *tmcf,
    nxt_router_engine_conf_t *recf);
static nxt_int_t nxt_router_engine_joints_create(nxt_router_temp_conf_t *tmcf,
    nxt_router_engine_conf_t *recf, nxt_queue_t *sockets,
    nxt_work_handler_t handler);
static nxt_int_t nxt_router_engine_quit(nxt_router_temp_conf_t *tmcf,
    nxt_router_engine_conf_t *recf);
static nxt_int_t nxt_router_engine_joints_delete(nxt_router_temp_conf_t *tmcf,
    nxt_router_engine_conf_t *recf, nxt_queue_t *sockets);

static nxt_int_t nxt_router_threads_create(nxt_task_t *task, nxt_runtime_t *rt,
    nxt_router_temp_conf_t *tmcf);
static nxt_int_t nxt_router_thread_create(nxt_task_t *task, nxt_runtime_t *rt,
    nxt_event_engine_t *engine);
static void nxt_router_apps_sort(nxt_task_t *task, nxt_router_t *router,
    nxt_router_temp_conf_t *tmcf);

static void nxt_router_engines_post(nxt_router_t *router,
    nxt_router_temp_conf_t *tmcf);
static void nxt_router_engine_post(nxt_event_engine_t *engine,
    nxt_work_t *jobs);

static void nxt_router_thread_start(void *data);
static void nxt_router_listen_socket_create(nxt_task_t *task, void *obj,
    void *data);
static void nxt_router_listen_socket_update(nxt_task_t *task, void *obj,
    void *data);
static void nxt_router_listen_socket_delete(nxt_task_t *task, void *obj,
    void *data);
static void nxt_router_worker_thread_quit(nxt_task_t *task, void *obj,
    void *data);
static void nxt_router_listen_socket_close(nxt_task_t *task, void *obj,
    void *data);
static void nxt_router_thread_exit_handler(nxt_task_t *task, void *obj,
    void *data);
static void nxt_router_listen_socket_release(nxt_task_t *task,
    nxt_socket_conf_t *skcf);

static void nxt_router_access_log_writer(nxt_task_t *task,
    nxt_http_request_t *r, nxt_router_access_log_t *access_log);
static u_char *nxt_router_access_log_date(u_char *buf, nxt_realtime_t *now,
    struct tm *tm, size_t size, const char *format);
static void nxt_router_access_log_open(nxt_task_t *task,
    nxt_router_temp_conf_t *tmcf);
static void nxt_router_access_log_ready(nxt_task_t *task,
    nxt_port_recv_msg_t *msg, void *data);
static void nxt_router_access_log_error(nxt_task_t *task,
    nxt_port_recv_msg_t *msg, void *data);
static void nxt_router_access_log_release(nxt_task_t *task,
    nxt_thread_spinlock_t *lock, nxt_router_access_log_t *access_log);
static void nxt_router_access_log_reopen_completion(nxt_task_t *task, void *obj,
    void *data);
static void nxt_router_access_log_reopen_ready(nxt_task_t *task,
    nxt_port_recv_msg_t *msg, void *data);
static void nxt_router_access_log_reopen_error(nxt_task_t *task,
    nxt_port_recv_msg_t *msg, void *data);

static void nxt_router_app_port_ready(nxt_task_t *task,
    nxt_port_recv_msg_t *msg, void *data);
static void nxt_router_app_port_error(nxt_task_t *task,
    nxt_port_recv_msg_t *msg, void *data);

static void nxt_router_app_unlink(nxt_task_t *task, nxt_app_t *app);

static void nxt_router_app_port_release(nxt_task_t *task, nxt_port_t *port,
    nxt_apr_action_t action);
static nxt_int_t nxt_router_app_port(nxt_task_t *task, nxt_app_t *app,
    nxt_request_app_link_t *req_app_link);

static void nxt_router_app_prepare_request(nxt_task_t *task,
    nxt_request_app_link_t *req_app_link);
static nxt_buf_t *nxt_router_prepare_msg(nxt_task_t *task,
    nxt_http_request_t *r, nxt_port_t *port, const nxt_str_t *prefix);

static void nxt_router_app_timeout(nxt_task_t *task, void *obj, void *data);
static void nxt_router_adjust_idle_timer(nxt_task_t *task, void *obj,
    void *data);
static void nxt_router_app_idle_timeout(nxt_task_t *task, void *obj,
    void *data);
static void nxt_router_app_joint_release_handler(nxt_task_t *task, void *obj,
    void *data);
static void nxt_router_free_app(nxt_task_t *task, void *obj, void *data);

static const nxt_http_request_state_t  nxt_http_request_send_state;
static void nxt_http_request_send_body(nxt_task_t *task, void *obj, void *data);

static void nxt_router_app_joint_use(nxt_task_t *task,
    nxt_app_joint_t *app_joint, int i);

static nxt_int_t nxt_router_http_request_done(nxt_task_t *task,
    nxt_http_request_t *r);
static void nxt_router_http_request_release(nxt_task_t *task, void *obj,
    void *data);
static void nxt_router_oosm_handler(nxt_task_t *task, nxt_port_recv_msg_t *msg);

extern const nxt_http_request_state_t  nxt_http_websocket;

static nxt_router_t  *nxt_router;

static const nxt_str_t http_prefix = nxt_string("HTTP_");
static const nxt_str_t empty_prefix = nxt_string("");

static const nxt_str_t  *nxt_app_msg_prefix[] = {
    &empty_prefix,
    &http_prefix,
    &http_prefix,
    &http_prefix,
    &http_prefix,
    &empty_prefix,
};


nxt_port_handlers_t  nxt_router_process_port_handlers = {
    .quit         = nxt_worker_process_quit_handler,
    .new_port     = nxt_router_new_port_handler,
    .change_file  = nxt_port_change_log_file_handler,
    .mmap         = nxt_port_mmap_handler,
    .data         = nxt_router_conf_data_handler,
    .remove_pid   = nxt_router_remove_pid_handler,
    .access_log   = nxt_router_access_log_reopen_handler,
    .rpc_ready    = nxt_port_rpc_handler,
    .rpc_error    = nxt_port_rpc_handler,
    .oosm         = nxt_router_oosm_handler,
};


nxt_int_t
nxt_router_start(nxt_task_t *task, void *data)
{
    nxt_int_t      ret;
    nxt_port_t     *controller_port;
    nxt_router_t   *router;
    nxt_runtime_t  *rt;

    rt = task->thread->runtime;

#if (NXT_TLS)
    rt->tls = nxt_service_get(rt->services, "SSL/TLS", "OpenSSL");
    if (nxt_slow_path(rt->tls == NULL)) {
        return NXT_ERROR;
    }

    ret = rt->tls->library_init(task);
    if (nxt_slow_path(ret != NXT_OK)) {
        return ret;
    }
#endif

    ret = nxt_http_init(task);
    if (nxt_slow_path(ret != NXT_OK)) {
        return ret;
    }

    router = nxt_zalloc(sizeof(nxt_router_t));
    if (nxt_slow_path(router == NULL)) {
        return NXT_ERROR;
    }

    nxt_queue_init(&router->engines);
    nxt_queue_init(&router->sockets);
    nxt_queue_init(&router->apps);

    nxt_router = router;

    controller_port = rt->port_by_type[NXT_PROCESS_CONTROLLER];
    if (controller_port != NULL) {
        nxt_router_greet_controller(task, controller_port);
    }

    return NXT_OK;
}


static void
nxt_router_greet_controller(nxt_task_t *task, nxt_port_t *controller_port)
{
    nxt_port_socket_write(task, controller_port, NXT_PORT_MSG_PROCESS_READY,
                          -1, 0, 0, NULL);
}


static void
nxt_router_start_app_process_handler(nxt_task_t *task, nxt_port_t *port,
    void *data)
{
    size_t         size;
    uint32_t       stream;
    nxt_mp_t       *mp;
    nxt_int_t      ret;
    nxt_app_t      *app;
    nxt_buf_t      *b;
    nxt_port_t     *main_port;
    nxt_runtime_t  *rt;

    app = data;

    rt = task->thread->runtime;
    main_port = rt->port_by_type[NXT_PROCESS_MAIN];

    nxt_debug(task, "app '%V' %p start process", &app->name, app);

    size = app->name.length + 1 + app->conf.length;

    b = nxt_buf_mem_ts_alloc(task, task->thread->engine->mem_pool, size);

    if (nxt_slow_path(b == NULL)) {
        goto failed;
    }

    nxt_buf_cpystr(b, &app->name);
    *b->mem.free++ = '\0';
    nxt_buf_cpystr(b, &app->conf);

    nxt_router_app_joint_use(task, app->joint, 1);

    stream = nxt_port_rpc_register_handler(task, port,
                                           nxt_router_app_port_ready,
                                           nxt_router_app_port_error,
                                           -1, app->joint);

    if (nxt_slow_path(stream == 0)) {
        nxt_router_app_joint_use(task, app->joint, -1);

        goto failed;
    }

    ret = nxt_port_socket_write(task, main_port, NXT_PORT_MSG_START_WORKER, -1,
                                stream, port->id, b);

    if (nxt_slow_path(ret != NXT_OK)) {
        nxt_port_rpc_cancel(task, port, stream);

        nxt_router_app_joint_use(task, app->joint, -1);

        goto failed;
    }

    nxt_router_app_use(task, app, -1);

    return;

failed:

    if (b != NULL) {
        mp = b->data;
        nxt_mp_free(mp, b);
        nxt_mp_release(mp);
    }

    nxt_thread_mutex_lock(&app->mutex);

    app->pending_processes--;

    nxt_thread_mutex_unlock(&app->mutex);

    nxt_router_app_use(task, app, -1);
}


static void
nxt_router_app_joint_use(nxt_task_t *task, nxt_app_joint_t *app_joint, int i)
{
    app_joint->use_count += i;

    if (app_joint->use_count == 0) {
        nxt_assert(app_joint->app == NULL);

        nxt_free(app_joint);
    }
}


static nxt_int_t
nxt_router_start_app_process(nxt_task_t *task, nxt_app_t *app)
{
    nxt_int_t      res;
    nxt_port_t     *router_port;
    nxt_runtime_t  *rt;

    rt = task->thread->runtime;
    router_port = rt->port_by_type[NXT_PROCESS_ROUTER];

    nxt_router_app_use(task, app, 1);

    res = nxt_port_post(task, router_port, nxt_router_start_app_process_handler,
                        app);

    if (res == NXT_OK) {
        return res;
    }

    nxt_thread_mutex_lock(&app->mutex);

    app->pending_processes--;

    nxt_thread_mutex_unlock(&app->mutex);

    nxt_router_app_use(task, app, -1);

    return NXT_ERROR;
}


nxt_inline void
nxt_request_app_link_init(nxt_task_t *task,
    nxt_request_app_link_t *req_app_link, nxt_request_rpc_data_t *req_rpc_data)
{
    nxt_buf_t           *body;
    nxt_event_engine_t  *engine;

    engine = task->thread->engine;

    nxt_memzero(req_app_link, sizeof(nxt_request_app_link_t));

    req_app_link->stream = req_rpc_data->stream;
    req_app_link->use_count = 1;
    req_app_link->req_rpc_data = req_rpc_data;
    req_rpc_data->req_app_link = req_app_link;
    req_app_link->reply_port = engine->port;
    req_app_link->request = req_rpc_data->request;
    req_app_link->apr_action = NXT_APR_GOT_RESPONSE;

    req_app_link->work.handler = NULL;
    req_app_link->work.task = &engine->task;
    req_app_link->work.obj = req_app_link;
    req_app_link->work.data = engine;

    body = req_rpc_data->request->body;

    if (body != NULL && nxt_buf_is_file(body)) {
        req_app_link->body_fd = body->file->fd;

        body->file->fd = -1;

    } else {
        req_app_link->body_fd = -1;
    }
}


nxt_inline nxt_request_app_link_t *
nxt_request_app_link_alloc(nxt_task_t *task,
    nxt_request_app_link_t *ra_src, nxt_request_rpc_data_t *req_rpc_data)
{
    nxt_mp_t                *mp;
    nxt_request_app_link_t  *req_app_link;

    if (ra_src != NULL && ra_src->mem_pool != NULL) {
        return ra_src;
    }

    mp = req_rpc_data->request->mem_pool;

    req_app_link = nxt_mp_alloc(mp, sizeof(nxt_request_app_link_t));

    if (nxt_slow_path(req_app_link == NULL)) {

        req_rpc_data->req_app_link = NULL;

        if (ra_src != NULL) {
            ra_src->req_rpc_data = NULL;
        }

        return NULL;
    }

    nxt_mp_retain(mp);

    nxt_request_app_link_init(task, req_app_link, req_rpc_data);

    if (ra_src != NULL) {
        req_app_link->body_fd = ra_src->body_fd;
    }

    req_app_link->mem_pool = mp;

    return req_app_link;
}


nxt_inline nxt_bool_t
nxt_router_msg_cancel(nxt_task_t *task, nxt_msg_info_t *msg_info,
    uint32_t stream)
{
    nxt_buf_t   *b, *next;
    nxt_bool_t  cancelled;

    if (msg_info->buf == NULL) {
        return 0;
    }

    cancelled = nxt_port_mmap_tracking_cancel(task, &msg_info->tracking,
                                              stream);

    if (cancelled) {
        nxt_debug(task, "stream #%uD: cancelled by router", stream);
    }

    for (b = msg_info->buf; b != NULL; b = next) {
        next = b->next;
        b->next = NULL;

        b->completion_handler = msg_info->completion_handler;

        if (b->is_port_mmap_sent) {
            b->is_port_mmap_sent = cancelled == 0;
            b->completion_handler(task, b, b->parent);
        }
    }

    msg_info->buf = NULL;

    return cancelled;
}


static void
nxt_request_app_link_update_peer_handler(nxt_task_t *task, void *obj,
    void *data)
{
    nxt_request_app_link_t  *req_app_link;

    req_app_link = obj;

    nxt_request_app_link_update_peer(task, req_app_link);

    nxt_request_app_link_use(task, req_app_link, -1);
}


static void
nxt_request_app_link_update_peer(nxt_task_t *task,
    nxt_request_app_link_t *req_app_link)
{
    nxt_event_engine_t      *engine;
    nxt_request_rpc_data_t  *req_rpc_data;

    engine = req_app_link->work.data;

    if (task->thread->engine != engine) {
        nxt_request_app_link_inc_use(req_app_link);

        req_app_link->work.handler = nxt_request_app_link_update_peer_handler;
        req_app_link->work.task = &engine->task;
        req_app_link->work.next = NULL;

        nxt_debug(task, "req_app_link stream #%uD post update peer to %p",
                  req_app_link->stream, engine);

        nxt_event_engine_post(engine, &req_app_link->work);

        return;
    }

    nxt_debug(task, "req_app_link stream #%uD update peer",
              req_app_link->stream);

    req_rpc_data = req_app_link->req_rpc_data;

    if (req_rpc_data != NULL && req_app_link->app_port != NULL) {
        nxt_port_rpc_ex_set_peer(task, engine->port, req_rpc_data,
                                 req_app_link->app_port->pid);
    }
}


static void
nxt_request_app_link_release(nxt_task_t *task,
    nxt_request_app_link_t *req_app_link)
{
    nxt_mp_t                *mp;
    nxt_http_request_t      *r;
    nxt_request_rpc_data_t  *req_rpc_data;

    nxt_assert(task->thread->engine == req_app_link->work.data);
    nxt_assert(req_app_link->use_count == 0);

    nxt_debug(task, "req_app_link stream #%uD release", req_app_link->stream);

    req_rpc_data = req_app_link->req_rpc_data;

    if (req_rpc_data != NULL) {
        if (nxt_slow_path(req_app_link->err_code != 0)) {
            nxt_http_request_error(task, req_rpc_data->request,
                                   req_app_link->err_code);

        } else {
            req_rpc_data->app_port = req_app_link->app_port;
            req_rpc_data->apr_action = req_app_link->apr_action;
            req_rpc_data->msg_info = req_app_link->msg_info;

            if (req_rpc_data->app->timeout != 0) {
                r = req_rpc_data->request;

                r->timer.handler = nxt_router_app_timeout;
                r->timer_data = req_rpc_data;
                nxt_timer_add(task->thread->engine, &r->timer,
                              req_rpc_data->app->timeout);
            }

            req_app_link->app_port = NULL;
            req_app_link->msg_info.buf = NULL;
        }

        req_rpc_data->req_app_link = NULL;
        req_app_link->req_rpc_data = NULL;
    }

    if (req_app_link->app_port != NULL) {
        nxt_router_app_port_release(task, req_app_link->app_port,
                                    req_app_link->apr_action);

        req_app_link->app_port = NULL;
    }

    if (req_app_link->body_fd != -1) {
        nxt_fd_close(req_app_link->body_fd);

        req_app_link->body_fd = -1;
    }

    nxt_router_msg_cancel(task, &req_app_link->msg_info, req_app_link->stream);

    mp = req_app_link->mem_pool;

    if (mp != NULL) {
        nxt_mp_free(mp, req_app_link);
        nxt_mp_release(mp);
    }
}


static void
nxt_request_app_link_release_handler(nxt_task_t *task, void *obj, void *data)
{
    nxt_request_app_link_t  *req_app_link;

    req_app_link = obj;

    nxt_assert(req_app_link->work.data == data);

    nxt_atomic_fetch_add(&req_app_link->use_count, -1);

    nxt_request_app_link_release(task, req_app_link);
}


static void
nxt_request_app_link_use(nxt_task_t *task, nxt_request_app_link_t *req_app_link,
    int i)
{
    int                 c;
    nxt_event_engine_t  *engine;

    c = nxt_atomic_fetch_add(&req_app_link->use_count, i);

    if (i < 0 && c == -i) {
        engine = req_app_link->work.data;

        if (task->thread->engine == engine) {
            nxt_request_app_link_release(task, req_app_link);

            return;
        }

        nxt_request_app_link_inc_use(req_app_link);

        req_app_link->work.handler = nxt_request_app_link_release_handler;
        req_app_link->work.task = &engine->task;
        req_app_link->work.next = NULL;

        nxt_debug(task, "req_app_link stream #%uD post release to %p",
                  req_app_link->stream, engine);

        nxt_event_engine_post(engine, &req_app_link->work);
    }
}


nxt_inline void
nxt_request_app_link_error(nxt_task_t *task, nxt_app_t *app,
    nxt_request_app_link_t *req_app_link, const char *str)
{
    req_app_link->app_port = NULL;
    req_app_link->err_code = 500;
    req_app_link->err_str = str;

    nxt_alert(task, "app \"%V\" internal error: %s on #%uD",
              &app->name, str, req_app_link->stream);
}


nxt_inline void
nxt_request_app_link_pending(nxt_task_t *task, nxt_app_t *app,
    nxt_request_app_link_t *req_app_link)
{
    nxt_queue_insert_tail(&req_app_link->app_port->pending_requests,
                          &req_app_link->link_port_pending);
    nxt_queue_insert_tail(&app->pending, &req_app_link->link_app_pending);

    nxt_request_app_link_inc_use(req_app_link);

    req_app_link->res_time = nxt_thread_monotonic_time(task->thread)
                             + app->res_timeout;

    nxt_debug(task, "req_app_link stream #%uD enqueue to pending_requests",
              req_app_link->stream);
}


nxt_inline nxt_bool_t
nxt_queue_chk_remove(nxt_queue_link_t *lnk)
{
    if (lnk->next != NULL) {
        nxt_queue_remove(lnk);

        lnk->next = NULL;

        return 1;
    }

    return 0;
}