xref: /unit/src/nxt_controller.c (revision 1451)

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

#include <nxt_main.h>
#include <nxt_runtime.h>
#include <nxt_main_process.h>
#include <nxt_conf.h>
#include <nxt_cert.h>


typedef struct {
    nxt_conf_value_t  *root;
    nxt_mp_t          *pool;
} nxt_controller_conf_t;


typedef struct {
    nxt_http_request_parse_t  parser;
    size_t                    length;
    nxt_controller_conf_t     conf;
    nxt_conn_t                *conn;
    nxt_queue_link_t          link;
} nxt_controller_request_t;


typedef struct {
    nxt_uint_t        status;
    nxt_conf_value_t  *conf;

    u_char            *title;
    nxt_str_t         detail;
    ssize_t           offset;
    nxt_uint_t        line;
    nxt_uint_t        column;
} nxt_controller_response_t;


static void nxt_controller_process_new_port_handler(nxt_task_t *task,
    nxt_port_recv_msg_t *msg);
static void nxt_controller_send_current_conf(nxt_task_t *task);
static void nxt_controller_router_ready_handler(nxt_task_t *task,
    nxt_port_recv_msg_t *msg);
static nxt_int_t nxt_controller_conf_default(void);
static void nxt_controller_conf_init_handler(nxt_task_t *task,
    nxt_port_recv_msg_t *msg, void *data);
static nxt_int_t nxt_controller_conf_send(nxt_task_t *task,
    nxt_conf_value_t *conf, nxt_port_rpc_handler_t handler, void *data);

static void nxt_controller_conn_init(nxt_task_t *task, void *obj, void *data);
static void nxt_controller_conn_read(nxt_task_t *task, void *obj, void *data);
static nxt_msec_t nxt_controller_conn_timeout_value(nxt_conn_t *c,
    uintptr_t data);
static void nxt_controller_conn_read_error(nxt_task_t *task, void *obj,
    void *data);
static void nxt_controller_conn_read_timeout(nxt_task_t *task, void *obj,
    void *data);
static void nxt_controller_conn_body_read(nxt_task_t *task, void *obj,
    void *data);
static void nxt_controller_conn_write(nxt_task_t *task, void *obj, void *data);
static void nxt_controller_conn_write_error(nxt_task_t *task, void *obj,
    void *data);
static void nxt_controller_conn_write_timeout(nxt_task_t *task, void *obj,
    void *data);
static void nxt_controller_conn_close(nxt_task_t *task, void *obj, void *data);
static void nxt_controller_conn_free(nxt_task_t *task, void *obj, void *data);

static nxt_int_t nxt_controller_request_content_length(void *ctx,
    nxt_http_field_t *field, uintptr_t data);

static void nxt_controller_process_request(nxt_task_t *task,
    nxt_controller_request_t *req);
static void nxt_controller_process_config(nxt_task_t *task,
    nxt_controller_request_t *req, nxt_str_t *path);
#if (NXT_TLS)
static void nxt_controller_process_cert(nxt_task_t *task,
    nxt_controller_request_t *req, nxt_str_t *path);
static void nxt_controller_process_cert_save(nxt_task_t *task,
    nxt_port_recv_msg_t *msg, void *data);
static nxt_bool_t nxt_controller_cert_in_use(nxt_str_t *name);
#endif
static void nxt_controller_conf_handler(nxt_task_t *task,
    nxt_port_recv_msg_t *msg, void *data);
static void nxt_controller_conf_store(nxt_task_t *task,
    nxt_conf_value_t *conf);
static void nxt_controller_response(nxt_task_t *task,
    nxt_controller_request_t *req, nxt_controller_response_t *resp);
static u_char *nxt_controller_date(u_char *buf, nxt_realtime_t *now,
    struct tm *tm, size_t size, const char *format);


static nxt_http_field_proc_t  nxt_controller_request_fields[] = {
    { nxt_string("Content-Length"),
      &nxt_controller_request_content_length, 0 },
};

static nxt_lvlhsh_t            nxt_controller_fields_hash;

static nxt_uint_t              nxt_controller_listening;
static nxt_uint_t              nxt_controller_router_ready;
static nxt_controller_conf_t   nxt_controller_conf;
static nxt_queue_t             nxt_controller_waiting_requests;


static const nxt_event_conn_state_t  nxt_controller_conn_read_state;
static const nxt_event_conn_state_t  nxt_controller_conn_body_read_state;
static const nxt_event_conn_state_t  nxt_controller_conn_write_state;
static const nxt_event_conn_state_t  nxt_controller_conn_close_state;


nxt_port_handlers_t  nxt_controller_process_port_handlers = {
    .quit           = nxt_worker_process_quit_handler,
    .new_port       = nxt_controller_process_new_port_handler,
    .change_file    = nxt_port_change_log_file_handler,
    .mmap           = nxt_port_mmap_handler,
    .process_ready  = nxt_controller_router_ready_handler,
    .data           = nxt_port_data_handler,
    .remove_pid     = nxt_port_remove_pid_handler,
    .rpc_ready      = nxt_port_rpc_handler,
    .rpc_error      = nxt_port_rpc_handler,
};


nxt_int_t
nxt_controller_start(nxt_task_t *task, void *data)
{
    nxt_mp_t               *mp;
    nxt_int_t              ret;
    nxt_str_t              *json;
    nxt_runtime_t          *rt;
    nxt_conf_value_t       *conf;
    nxt_conf_validation_t  vldt;
    nxt_controller_init_t  *init;

    rt = task->thread->runtime;

    ret = nxt_http_fields_hash(&nxt_controller_fields_hash, rt->mem_pool,
                               nxt_controller_request_fields,
                               nxt_nitems(nxt_controller_request_fields));

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

    nxt_queue_init(&nxt_controller_waiting_requests);

    init = data;

#if (NXT_TLS)

    if (init->certs != NULL) {
        nxt_cert_info_init(task, init->certs);
        nxt_cert_store_release(init->certs);
    }

#endif

    json = &init->conf;

    if (json->start == NULL) {
        return NXT_OK;
    }

    mp = nxt_mp_create(1024, 128, 256, 32);
    if (nxt_slow_path(mp == NULL)) {
        return NXT_ERROR;
    }

    conf = nxt_conf_json_parse_str(mp, json);
    nxt_free(json->start);

    if (nxt_slow_path(conf == NULL)) {
        nxt_alert(task, "failed to restore previous configuration: "
                  "file is corrupted or not enough memory");

        nxt_mp_destroy(mp);
        return NXT_OK;
    }

    nxt_memzero(&vldt, sizeof(nxt_conf_validation_t));

    vldt.pool = nxt_mp_create(1024, 128, 256, 32);
    if (nxt_slow_path(vldt.pool == NULL)) {
        nxt_mp_destroy(mp);
        return NXT_ERROR;
    }

    vldt.conf = conf;

    ret = nxt_conf_validate(&vldt);

    if (nxt_slow_path(ret != NXT_OK)) {

        if (ret == NXT_DECLINED) {
            nxt_alert(task, "the previous configuration is invalid: %V",
                      &vldt.error);

            nxt_mp_destroy(vldt.pool);
            nxt_mp_destroy(mp);

            return NXT_OK;
        }

        /* ret == NXT_ERROR */

        return NXT_ERROR;
    }

    nxt_mp_destroy(vldt.pool);

    nxt_controller_conf.root = conf;
    nxt_controller_conf.pool = mp;

    return NXT_OK;
}


static void
nxt_controller_process_new_port_handler(nxt_task_t *task,
    nxt_port_recv_msg_t *msg)
{
    nxt_port_new_port_handler(task, msg);

    if (msg->u.new_port->type != NXT_PROCESS_ROUTER
        || !nxt_controller_router_ready)
    {
        return;
    }

    nxt_controller_send_current_conf(task);
}


static void
nxt_controller_send_current_conf(nxt_task_t *task)
{
    nxt_int_t         rc;
    nxt_runtime_t     *rt;
    nxt_conf_value_t  *conf;

    conf = nxt_controller_conf.root;

    if (conf != NULL) {
        rc = nxt_controller_conf_send(task, conf,
                                      nxt_controller_conf_init_handler, NULL);

        if (nxt_fast_path(rc == NXT_OK)) {
            return;
        }

        nxt_mp_destroy(nxt_controller_conf.pool);

        if (nxt_slow_path(nxt_controller_conf_default() != NXT_OK)) {
            nxt_abort();
        }
    }

    if (nxt_slow_path(nxt_controller_conf_default() != NXT_OK)) {
        nxt_abort();
    }

    rt = task->thread->runtime;

    if (nxt_slow_path(nxt_listen_event(task, rt->controller_socket) == NULL)) {
        nxt_abort();
    }

    nxt_controller_listening = 1;
}


static void
nxt_controller_router_ready_handler(nxt_task_t *task,
    nxt_port_recv_msg_t *msg)
{
    nxt_port_t     *router_port;
    nxt_runtime_t  *rt;

    rt = task->thread->runtime;

    router_port = rt->port_by_type[NXT_PROCESS_ROUTER];

    nxt_controller_router_ready = 1;

    if (router_port != NULL) {
        nxt_controller_send_current_conf(task);
    }
}


static nxt_int_t
nxt_controller_conf_default(void)
{
    nxt_mp_t          *mp;
    nxt_conf_value_t  *conf;

    static const nxt_str_t json
        = nxt_string("{ \"listeners\": {}, \"applications\": {} }");

    mp = nxt_mp_create(1024, 128, 256, 32);

    if (nxt_slow_path(mp == NULL)) {
        return NXT_ERROR;
    }

    conf = nxt_conf_json_parse_str(mp, &json);

    if (nxt_slow_path(conf == NULL)) {
        return NXT_ERROR;
    }

    nxt_controller_conf.root = conf;
    nxt_controller_conf.pool = mp;

    return NXT_OK;
}


static void
nxt_controller_conf_init_handler(nxt_task_t *task, nxt_port_recv_msg_t *msg,
    void *data)
{
    nxt_runtime_t  *rt;

    if (msg->port_msg.type != NXT_PORT_MSG_RPC_READY) {
        nxt_alert(task, "failed to apply previous configuration");

        nxt_mp_destroy(nxt_controller_conf.pool);

        if (nxt_slow_path(nxt_controller_conf_default() != NXT_OK)) {
            nxt_abort();
        }
    }

    if (nxt_controller_listening == 0) {
        rt = task->thread->runtime;

        if (nxt_slow_path(nxt_listen_event(task, rt->controller_socket)
                          == NULL))
        {
            nxt_abort();
        }

        nxt_controller_listening = 1;
    }
}


static nxt_int_t
nxt_controller_conf_send(nxt_task_t *task, nxt_conf_value_t *conf,
    nxt_port_rpc_handler_t handler, void *data)
{
    size_t         size;
    uint32_t       stream;
    nxt_int_t      rc;
    nxt_buf_t      *b;
    nxt_port_t     *router_port, *controller_port;
    nxt_runtime_t  *rt;

    rt = task->thread->runtime;

    router_port = rt->port_by_type[NXT_PROCESS_ROUTER];

    if (nxt_slow_path(router_port == NULL || !nxt_controller_router_ready)) {
        return NXT_DECLINED;
    }

    controller_port = rt->port_by_type[NXT_PROCESS_CONTROLLER];

    size = nxt_conf_json_length(conf, NULL);

    b = nxt_port_mmap_get_buf(task, router_port, size);
    if (nxt_slow_path(b == NULL)) {
        return NXT_ERROR;
    }

    b->mem.free = nxt_conf_json_print(b->mem.free, conf, NULL);

    stream = nxt_port_rpc_register_handler(task, controller_port,
                                           handler, handler,
                                           router_port->pid, data);

    if (nxt_slow_path(stream == 0)) {
        return NXT_ERROR;
    }

    rc = nxt_port_socket_write(task, router_port, NXT_PORT_MSG_DATA_LAST, -1,
                               stream, controller_port->id, b);

    if (nxt_slow_path(rc != NXT_OK)) {
        nxt_port_rpc_cancel(task, controller_port, stream);
        return NXT_ERROR;
    }

    return NXT_OK;
}


nxt_int_t
nxt_runtime_controller_socket(nxt_task_t *task, nxt_runtime_t *rt)
{
    nxt_listen_socket_t  *ls;

    ls = nxt_mp_alloc(rt->mem_pool, sizeof(nxt_listen_socket_t));
    if (ls == NULL) {
        return NXT_ERROR;
    }

    ls->sockaddr = rt->controller_listen;

    nxt_listen_socket_remote_size(ls);

    ls->socket = -1;
    ls->backlog = NXT_LISTEN_BACKLOG;
    ls->read_after_accept = 1;
    ls->flags = NXT_NONBLOCK;

#if 0
    /* STUB */
    wq = nxt_mp_zget(cf->mem_pool, sizeof(nxt_work_queue_t));
    if (wq == NULL) {
        return NXT_ERROR;
    }
    nxt_work_queue_name(wq, "listen");
    /**/

    ls->work_queue = wq;
#endif
    ls->handler = nxt_controller_conn_init;

    if (nxt_listen_socket_create(task, rt->mem_pool, ls) != NXT_OK) {
        return NXT_ERROR;
    }

    rt->controller_socket = ls;

    return NXT_OK;
}


static void
nxt_controller_conn_init(nxt_task_t *task, void *obj, void *data)
{
    nxt_buf_t                 *b;
    nxt_conn_t                *c;
    nxt_event_engine_t        *engine;
    nxt_controller_request_t  *r;

    c = obj;

    nxt_debug(task, "controller conn init fd:%d", c->socket.fd);

    r = nxt_mp_zget(c->mem_pool, sizeof(nxt_controller_request_t));
    if (nxt_slow_path(r == NULL)) {
        nxt_controller_conn_free(task, c, NULL);
        return;
    }

    r->conn = c;

    if (nxt_slow_path(nxt_http_parse_request_init(&r->parser, c->mem_pool)
                      != NXT_OK))
    {
        nxt_controller_conn_free(task, c, NULL);
        return;
    }

    r->parser.encoded_slashes = 1;

    b = nxt_buf_mem_alloc(c->mem_pool, 1024, 0);
    if (nxt_slow_path(b == NULL)) {
        nxt_controller_conn_free(task, c, NULL);
        return;
    }

    c->read = b;
    c->socket.data = r;
    c->socket.read_ready = 1;
    c->read_state = &nxt_controller_conn_read_state;

    engine = task->thread->engine;
    c->read_work_queue = &engine->read_work_queue;
    c->write_work_queue = &engine->write_work_queue;

    nxt_conn_read(engine, c);
}


static const nxt_event_conn_state_t  nxt_controller_conn_read_state
    nxt_aligned(64) =
{
    .ready_handler = nxt_controller_conn_read,
    .close_handler = nxt_controller_conn_close,
    .error_handler = nxt_controller_conn_read_error,

    .timer_handler = nxt_controller_conn_read_timeout,
    .timer_value = nxt_controller_conn_timeout_value,
    .timer_data = 60 * 1000,
};


static void
nxt_controller_conn_read(nxt_task_t *task, void *obj, void *data)
{
    size_t                    preread;
    nxt_buf_t                 *b;
    nxt_int_t                 rc;
    nxt_conn_t                *c;
    nxt_controller_request_t  *r;

    c = obj;
    r = data;

    nxt_debug(task, "controller conn read");

    nxt_queue_remove(&c->link);
    nxt_queue_self(&c->link);

    b = c->read;

    rc = nxt_http_parse_request(&r->parser, &b->mem);

    if (nxt_slow_path(rc != NXT_DONE)) {

        if (rc == NXT_AGAIN) {
            if (nxt_buf_mem_free_size(&b->mem) == 0) {
                nxt_log(task, NXT_LOG_ERR, "too long request headers");
                nxt_controller_conn_close(task, c, r);
                return;
            }

            nxt_conn_read(task->thread->engine, c);
            return;
        }

        /* rc == NXT_ERROR */

        nxt_log(task, NXT_LOG_ERR, "parsing error");

        nxt_controller_conn_close(task, c, r);
        return;
    }

    rc = nxt_http_fields_process(r->parser.fields, &nxt_controller_fields_hash,
                                 r);

    if (nxt_slow_path(rc != NXT_OK)) {
        nxt_controller_conn_close(task, c, r);
        return;
    }

    preread = nxt_buf_mem_used_size(&b->mem);

    nxt_debug(task, "controller request header parsing complete, "
                    "body length: %uz, preread: %uz",
                    r->length, preread);

    if (preread >= r->length) {
        nxt_controller_process_request(task, r);
        return;
    }

    if (r->length - preread > (size_t) nxt_buf_mem_free_size(&b->mem)) {
        b = nxt_buf_mem_alloc(c->mem_pool, r->length, 0);
        if (nxt_slow_path(b == NULL)) {
            nxt_controller_conn_free(task, c, NULL);
            return;
        }

        b->mem.free = nxt_cpymem(b->mem.free, c->read->mem.pos, preread);

        c->read = b;
    }

    c->read_state = &nxt_controller_conn_body_read_state;

    nxt_conn_read(task->thread->engine, c);
}


static nxt_msec_t
nxt_controller_conn_timeout_value(nxt_conn_t *c, uintptr_t data)
{
    return (nxt_msec_t) data;
}


static void
nxt_controller_conn_read_error(nxt_task_t *task, void *obj, void *data)
{
    nxt_conn_t  *c;

    c = obj;

    nxt_debug(task, "controller conn read error");

    nxt_controller_conn_close(task, c, data);
}


static void
nxt_controller_conn_read_timeout(nxt_task_t *task, void *obj, void *data)
{
    nxt_timer_t  *timer;
    nxt_conn_t   *c;

    timer = obj;

    c = nxt_read_timer_conn(timer);
    c->socket.timedout = 1;
    c->socket.closed = 1;

    nxt_debug(task, "controller conn read timeout");

    nxt_controller_conn_close(task, c, data);
}


static const nxt_event_conn_state_t  nxt_controller_conn_body_read_state
    nxt_aligned(64) =
{
    .ready_handler = nxt_controller_conn_body_read,
    .close_handler = nxt_controller_conn_close,
    .error_handler = nxt_controller_conn_read_error,

    .timer_handler = nxt_controller_conn_read_timeout,
    .timer_value = nxt_controller_conn_timeout_value,
    .timer_data = 60 * 1000,
    .timer_autoreset = 1,
};


static void
nxt_controller_conn_body_read(nxt_task_t *task, void *obj, void *data)
{
    size_t                    read;
    nxt_buf_t                 *b;
    nxt_conn_t                *c;
    nxt_controller_request_t  *r;

    c = obj;
    r = data;
    b = c->read;

    read = nxt_buf_mem_used_size(&b->mem);

    nxt_debug(task, "controller conn body read: %uz of %uz",
              read, r->length);

    if (read >= r->length) {
        nxt_controller_process_request(task, r);
        return;
    }

    nxt_conn_read(task->thread->engine, c);
}


static const nxt_event_conn_state_t  nxt_controller_conn_write_state
    nxt_aligned(64) =
{
    .ready_handler = nxt_controller_conn_write,
    .error_handler = nxt_controller_conn_write_error,

    .timer_handler = nxt_controller_conn_write_timeout,
    .timer_value = nxt_controller_conn_timeout_value,
    .timer_data = 60 * 1000,
    .timer_autoreset = 1,
};


static void
nxt_controller_conn_write(nxt_task_t *task, void *obj, void *data)
{
    nxt_buf_t   *b;
    nxt_conn_t  *c;

    c = obj;

    nxt_debug(task, "controller conn write");

    b = c->write;

    if (b->mem.pos != b->mem.free) {
        nxt_conn_write(task->thread->engine, c);
        return;
    }

    nxt_debug(task, "controller conn write complete");

    nxt_controller_conn_close(task, c, data);
}


static void
nxt_controller_conn_write_error(nxt_task_t *task, void *obj, void *data)
{
    nxt_conn_t  *c;

    c = obj;

    nxt_debug(task, "controller conn write error");

    nxt_controller_conn_close(task, c, data);
}


static void
nxt_controller_conn_write_timeout(nxt_task_t *task, void *obj, void *data)
{
    nxt_conn_t   *c;
    nxt_timer_t  *timer;

    timer = obj;

    c = nxt_write_timer_conn(timer);
    c->socket.timedout = 1;
    c->socket.closed = 1;

    nxt_debug(task, "controller conn write timeout");

    nxt_controller_conn_close(task, c, data);
}


static const nxt_event_conn_state_t  nxt_controller_conn_close_state
    nxt_aligned(64) =
{
    .ready_handler = nxt_controller_conn_free,
};


static void
nxt_controller_conn_close(nxt_task_t *task, void *obj, void *data)
{
    nxt_conn_t  *c;

    c = obj;

    nxt_debug(task, "controller conn close");

    nxt_queue_remove(&c->link);

    c->write_state = &nxt_controller_conn_close_state;

    nxt_conn_close(task->thread->engine, c);
}


static void
nxt_controller_conn_free(nxt_task_t *task, void *obj, void *data)
{
    nxt_conn_t  *c;

    c = obj;

    nxt_debug(task, "controller conn free");

    nxt_sockaddr_cache_free(task->thread->engine, c);

    nxt_conn_free(task, c);
}


static nxt_int_t
nxt_controller_request_content_length(void *ctx, nxt_http_field_t *field,
    uintptr_t data)
{
    off_t                     length;
    nxt_controller_request_t  *r;

    r = ctx;

    length = nxt_off_t_parse(field->value, field->value_length);

    if (nxt_fast_path(length >= 0)) {

        if (nxt_slow_path(length > NXT_SIZE_T_MAX)) {
            nxt_log_error(NXT_LOG_ERR, &r->conn->log,
                          "Content-Length is too big");
            return NXT_ERROR;
        }

        r->length = length;
        return NXT_OK;
    }

    nxt_log_error(NXT_LOG_ERR, &r->conn->log, "Content-Length is invalid");

    return NXT_ERROR;
}


static void
nxt_controller_process_request(nxt_task_t *task, nxt_controller_request_t *req)
{
    uint32_t                   i, count;
    nxt_str_t                  path;
    nxt_conn_t                 *c;
    nxt_conf_value_t           *value;
    nxt_controller_response_t  resp;
#if (NXT_TLS)
    nxt_conf_value_t           *certs;

    static nxt_str_t certificates = nxt_string("certificates");
#endif
    static nxt_str_t config = nxt_string("config");

    c = req->conn;
    path = req->parser.path;

    if (path.length > 1 && path.start[path.length - 1] == '/') {
        path.length--;
    }

    if (nxt_str_start(&path, "/config", 7)
        && (path.length == 7 || path.start[7] == '/'))
    {
        if (path.length == 7) {
            path.length = 1;

        } else {
            path.length -= 7;
            path.start += 7;
        }

        nxt_controller_process_config(task, req, &path);
        return;
    }

#if (NXT_TLS)

    if (nxt_str_start(&path, "/certificates", 13)
        && (path.length == 13 || path.start[13] == '/'))
    {
        if (path.length == 13) {
            path.length = 1;

        } else {
            path.length -= 13;
            path.start += 13;
        }

        nxt_controller_process_cert(task, req, &path);
        return;
    }

#endif

    nxt_memzero(&resp, sizeof(nxt_controller_response_t));

    if (path.length == 1 && path.start[0] == '/') {

        if (!nxt_str_eq(&req->parser.method, "GET", 3)) {
            goto invalid_method;
        }

        count = 1;
#if (NXT_TLS)
        count++;
#endif

        value = nxt_conf_create_object(c->mem_pool, count);
        if (nxt_slow_path(value == NULL)) {
            goto alloc_fail;
        }

        i = 0;

#if (NXT_TLS)
        certs = nxt_cert_info_get_all(c->mem_pool);
        if (nxt_slow_path(certs == NULL)) {
            goto alloc_fail;
        }

        nxt_conf_set_member(value, &certificates, certs, i++);
#endif

        nxt_conf_set_member(value, &config, nxt_controller_conf.root, i);

        resp.status = 200;
        resp.conf = value;

        nxt_controller_response(task, req, &resp);
        return;
    }

    resp.status = 404;
    resp.title = (u_char *) "Value doesn't exist.";
    resp.offset = -1;

    nxt_controller_response(task, req, &resp);
    return;

invalid_method:

    resp.status = 405;
    resp.title = (u_char *) "Invalid method.";
    resp.offset = -1;

    nxt_controller_response(task, req, &resp);
    return;

alloc_fail:

    resp.status = 500;
    resp.title = (u_char *) "Memory allocation failed.";
    resp.offset = -1;

    nxt_controller_response(task, req, &resp);
    return;
}


static void
nxt_controller_process_config(nxt_task_t *task, nxt_controller_request_t *req,
    nxt_str_t *path)
{
    nxt_mp_t                   *mp;
    nxt_int_t                  rc;
    nxt_conn_t                 *c;
    nxt_bool_t                 post;
    nxt_buf_mem_t              *mbuf;
    nxt_conf_op_t              *ops;
    nxt_conf_value_t           *value;
    nxt_conf_validation_t      vldt;
    nxt_conf_json_error_t      error;
    nxt_controller_response_t  resp;

    static const nxt_str_t empty_obj = nxt_string("{}");

    nxt_memzero(&resp, sizeof(nxt_controller_response_t));

    c = req->conn;

    if (nxt_str_eq(&req->parser.method, "GET", 3)) {

        value = nxt_conf_get_path(nxt_controller_conf.root, path);

        if (value == NULL) {
            goto not_found;
        }

        resp.status = 200;
        resp.conf = value;

        nxt_controller_response(task, req, &resp);
        return;
    }

    if (nxt_str_eq(&req->parser.method, "POST", 4)) {
        if (path->length == 1) {
            goto not_allowed;
        }

        post = 1;

    } else {
        post = 0;
    }

    if (post || nxt_str_eq(&req->parser.method, "PUT", 3)) {

        if (!nxt_queue_is_empty(&nxt_controller_waiting_requests)) {
            nxt_queue_insert_tail(&nxt_controller_waiting_requests, &req->link);
            return;
        }

        mp = nxt_mp_create(1024, 128, 256, 32);

        if (nxt_slow_path(mp == NULL)) {
            goto alloc_fail;
        }

        mbuf = &c->read->mem;

        nxt_memzero(&error, sizeof(nxt_conf_json_error_t));

        /* Skip UTF-8 BOM. */
        if (nxt_buf_mem_used_size(mbuf) >= 3
            && nxt_memcmp(mbuf->pos, "\xEF\xBB\xBF", 3) == 0)
        {
            mbuf->pos += 3;
        }

        value = nxt_conf_json_parse(mp, mbuf->pos, mbuf->free, &error);

        if (value == NULL) {
            nxt_mp_destroy(mp);

            if (error.pos == NULL) {
                goto alloc_fail;
            }

            resp.status = 400;
            resp.title = (u_char *) "Invalid JSON.";
            resp.detail.length = nxt_strlen(error.detail);
            resp.detail.start = error.detail;
            resp.offset = error.pos - mbuf->pos;

            nxt_conf_json_position(mbuf->pos, error.pos,
                                   &resp.line, &resp.column);

            nxt_controller_response(task, req, &resp);
            return;
        }

        if (path->length != 1) {
            rc = nxt_conf_op_compile(c->mem_pool, &ops,
                                     nxt_controller_conf.root,
                                     path, value, post);

            if (rc != NXT_CONF_OP_OK) {
                nxt_mp_destroy(mp);

                switch (rc) {
                case NXT_CONF_OP_NOT_FOUND:
                    goto not_found;

                case NXT_CONF_OP_NOT_ALLOWED:
                    goto not_allowed;
                }

                /* rc == NXT_CONF_OP_ERROR */
                goto alloc_fail;
            }

            value = nxt_conf_clone(mp, ops, nxt_controller_conf.root);

            if (nxt_slow_path(value == NULL)) {
                nxt_mp_destroy(mp);
                goto alloc_fail;
            }
        }

        nxt_memzero(&vldt, sizeof(nxt_conf_validation_t));

        vldt.conf = value;
        vldt.pool = c->mem_pool;

        rc = nxt_conf_validate(&vldt);

        if (nxt_slow_path(rc != NXT_OK)) {
            nxt_mp_destroy(mp);

            if (rc == NXT_DECLINED) {