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view src/http/modules/ngx_http_random_index_module.c @ 7281:bd6563e81cea

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Limit req: improved handling of negative times. Negative times can appear since workers only update time on an event loop iteration start. If a worker was blocked for a long time during an event loop iteration, it is possible that another worker already updated the time stored in the node. As such, time since last update of the node (ms) will be negative. Previous code used ngx_abs(ms) in the calculations. That is, negative times were effectively treated as positive ones. As a result, it was not possible to maintain high request rates, where the same node can be updated multiple times from during an event loop iteration. In particular, this affected setups with many SSL handshakes, see http://mailman.nginx.org/pipermail/nginx/2018-May/056291.html. Fix is to only update the last update time stored in the node if the new time is larger than previously stored one. If a future time is stored in the node, we preserve this time as is. To prevent breaking things on platforms without monotonic time available if system time is updated backwards, a safety limit of 60 seconds is used. If the time stored in the node is more than 60 seconds in the future, we assume that the time was changed backwards and update lr->last to the current time.
author Maxim Dounin <mdounin@mdounin.ru>
date Wed, 30 May 2018 15:40:34 +0300
parents 47daf95d0138
children 061ec464813f
line wrap: on
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/*
 * Copyright (C) Igor Sysoev
 * Copyright (C) Nginx, Inc.
 */


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


typedef struct {
    ngx_flag_t  enable;
} ngx_http_random_index_loc_conf_t;


#define NGX_HTTP_RANDOM_INDEX_PREALLOCATE  50


static ngx_int_t ngx_http_random_index_error(ngx_http_request_t *r,
    ngx_dir_t *dir, ngx_str_t *name);
static ngx_int_t ngx_http_random_index_init(ngx_conf_t *cf);
static void *ngx_http_random_index_create_loc_conf(ngx_conf_t *cf);
static char *ngx_http_random_index_merge_loc_conf(ngx_conf_t *cf,
    void *parent, void *child);


static ngx_command_t  ngx_http_random_index_commands[] = {

    { ngx_string("random_index"),
      NGX_HTTP_LOC_CONF|NGX_CONF_FLAG,
      ngx_conf_set_flag_slot,
      NGX_HTTP_LOC_CONF_OFFSET,
      offsetof(ngx_http_random_index_loc_conf_t, enable),
      NULL },

      ngx_null_command
};


static ngx_http_module_t  ngx_http_random_index_module_ctx = {
    NULL,                                  /* preconfiguration */
    ngx_http_random_index_init,            /* postconfiguration */

    NULL,                                  /* create main configuration */
    NULL,                                  /* init main configuration */

    NULL,                                  /* create server configuration */
    NULL,                                  /* merge server configuration */

    ngx_http_random_index_create_loc_conf, /* create location configuration */
    ngx_http_random_index_merge_loc_conf   /* merge location configuration */
};


ngx_module_t  ngx_http_random_index_module = {
    NGX_MODULE_V1,
    &ngx_http_random_index_module_ctx,     /* module context */
    ngx_http_random_index_commands,        /* module directives */
    NGX_HTTP_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_int_t
ngx_http_random_index_handler(ngx_http_request_t *r)
{
    u_char                            *last, *filename;
    size_t                             len, allocated, root;
    ngx_err_t                          err;
    ngx_int_t                          rc;
    ngx_str_t                          path, uri, *name;
    ngx_dir_t                          dir;
    ngx_uint_t                         n, level;
    ngx_array_t                        names;
    ngx_http_random_index_loc_conf_t  *rlcf;

    if (r->uri.data[r->uri.len - 1] != '/') {
        return NGX_DECLINED;
    }

    if (!(r->method & (NGX_HTTP_GET|NGX_HTTP_HEAD|NGX_HTTP_POST))) {
        return NGX_DECLINED;
    }

    rlcf = ngx_http_get_module_loc_conf(r, ngx_http_random_index_module);

    if (!rlcf->enable) {
        return NGX_DECLINED;
    }

#if (NGX_HAVE_D_TYPE)
    len = NGX_DIR_MASK_LEN;
#else
    len = NGX_HTTP_RANDOM_INDEX_PREALLOCATE;
#endif

    last = ngx_http_map_uri_to_path(r, &path, &root, len);
    if (last == NULL) {
        return NGX_HTTP_INTERNAL_SERVER_ERROR;
    }

    allocated = path.len;

    path.len = last - path.data - 1;
    path.data[path.len] = '\0';

    ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                   "http random index: \"%s\"", path.data);

    if (ngx_open_dir(&path, &dir) == NGX_ERROR) {
        err = ngx_errno;

        if (err == NGX_ENOENT
            || err == NGX_ENOTDIR
            || err == NGX_ENAMETOOLONG)
        {
            level = NGX_LOG_ERR;
            rc = NGX_HTTP_NOT_FOUND;

        } else if (err == NGX_EACCES) {
            level = NGX_LOG_ERR;
            rc = NGX_HTTP_FORBIDDEN;

        } else {
            level = NGX_LOG_CRIT;
            rc = NGX_HTTP_INTERNAL_SERVER_ERROR;
        }

        ngx_log_error(level, r->connection->log, err,
                      ngx_open_dir_n " \"%s\" failed", path.data);

        return rc;
    }

    if (ngx_array_init(&names, r->pool, 32, sizeof(ngx_str_t)) != NGX_OK) {
        return ngx_http_random_index_error(r, &dir, &path);
    }

    filename = path.data;
    filename[path.len] = '/';

    for ( ;; ) {
        ngx_set_errno(0);

        if (ngx_read_dir(&dir) == NGX_ERROR) {
            err = ngx_errno;

            if (err != NGX_ENOMOREFILES) {
                ngx_log_error(NGX_LOG_CRIT, r->connection->log, err,
                              ngx_read_dir_n " \"%V\" failed", &path);
                return ngx_http_random_index_error(r, &dir, &path);
            }

            break;
        }

        ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                       "http random index file: \"%s\"", ngx_de_name(&dir));

        if (ngx_de_name(&dir)[0] == '.') {
            continue;
        }

        len = ngx_de_namelen(&dir);

        if (dir.type == 0 || ngx_de_is_link(&dir)) {

            /* 1 byte for '/' and 1 byte for terminating '\0' */

            if (path.len + 1 + len + 1 > allocated) {
                allocated = path.len + 1 + len + 1
                                     + NGX_HTTP_RANDOM_INDEX_PREALLOCATE;

                filename = ngx_pnalloc(r->pool, allocated);
                if (filename == NULL) {
                    return ngx_http_random_index_error(r, &dir, &path);
                }

                last = ngx_cpystrn(filename, path.data, path.len + 1);
                *last++ = '/';
            }

            ngx_cpystrn(last, ngx_de_name(&dir), len + 1);

            if (ngx_de_info(filename, &dir) == NGX_FILE_ERROR) {
                err = ngx_errno;

                if (err != NGX_ENOENT) {
                    ngx_log_error(NGX_LOG_CRIT, r->connection->log, err,
                                  ngx_de_info_n " \"%s\" failed", filename);
                    return ngx_http_random_index_error(r, &dir, &path);
                }

                if (ngx_de_link_info(filename, &dir) == NGX_FILE_ERROR) {
                    ngx_log_error(NGX_LOG_CRIT, r->connection->log, ngx_errno,
                                  ngx_de_link_info_n " \"%s\" failed",
                                  filename);
                    return ngx_http_random_index_error(r, &dir, &path);
                }
            }
        }

        if (!ngx_de_is_file(&dir)) {
            continue;
        }

        name = ngx_array_push(&names);
        if (name == NULL) {
            return ngx_http_random_index_error(r, &dir, &path);
        }

        name->len = len;

        name->data = ngx_pnalloc(r->pool, len);
        if (name->data == NULL) {
            return ngx_http_random_index_error(r, &dir, &path);
        }

        ngx_memcpy(name->data, ngx_de_name(&dir), len);
    }

    if (ngx_close_dir(&dir) == NGX_ERROR) {
        ngx_log_error(NGX_LOG_ALERT, r->connection->log, ngx_errno,
                      ngx_close_dir_n " \"%V\" failed", &path);
    }

    n = names.nelts;

    if (n == 0) {
        return NGX_DECLINED;
    }

    name = names.elts;

    n = (ngx_uint_t) (((uint64_t) ngx_random() * n) / 0x80000000);

    uri.len = r->uri.len + name[n].len;

    uri.data = ngx_pnalloc(r->pool, uri.len);
    if (uri.data == NULL) {
        return NGX_HTTP_INTERNAL_SERVER_ERROR;
    }

    last = ngx_copy(uri.data, r->uri.data, r->uri.len);
    ngx_memcpy(last, name[n].data, name[n].len);

    return ngx_http_internal_redirect(r, &uri, &r->args);
}


static ngx_int_t
ngx_http_random_index_error(ngx_http_request_t *r, ngx_dir_t *dir,
    ngx_str_t *name)
{
    if (ngx_close_dir(dir) == NGX_ERROR) {
        ngx_log_error(NGX_LOG_ALERT, r->connection->log, ngx_errno,
                      ngx_close_dir_n " \"%V\" failed", name);
    }

    return NGX_HTTP_INTERNAL_SERVER_ERROR;
}


static void *
ngx_http_random_index_create_loc_conf(ngx_conf_t *cf)
{
    ngx_http_random_index_loc_conf_t  *conf;

    conf = ngx_palloc(cf->pool, sizeof(ngx_http_random_index_loc_conf_t));
    if (conf == NULL) {
        return NULL;
    }

    conf->enable = NGX_CONF_UNSET;

    return conf;
}


static char *
ngx_http_random_index_merge_loc_conf(ngx_conf_t *cf, void *parent, void *child)
{
    ngx_http_random_index_loc_conf_t *prev = parent;
    ngx_http_random_index_loc_conf_t *conf = child;

    ngx_conf_merge_value(conf->enable, prev->enable, 0);

    return NGX_CONF_OK;
}


static ngx_int_t
ngx_http_random_index_init(ngx_conf_t *cf)
{
    ngx_http_handler_pt        *h;
    ngx_http_core_main_conf_t  *cmcf;

    cmcf = ngx_http_conf_get_module_main_conf(cf, ngx_http_core_module);

    h = ngx_array_push(&cmcf->phases[NGX_HTTP_CONTENT_PHASE].handlers);
    if (h == NULL) {
        return NGX_ERROR;
    }

    *h = ngx_http_random_index_handler;

    return NGX_OK;
}