Initial commit

src/http/modules/ngx_http_limit_req_module.c

@@ -0,0 +1,960 @@
+
+/*
+ * Copyright (C) Igor Sysoev
+ * Copyright (C) Nginx, Inc.
+ */
+
+
+#include <ngx_config.h>
+#include <ngx_core.h>
+#include <ngx_http.h>
+
+
+typedef struct {
+    u_char                       color;
+    u_char                       dummy;
+    u_short                      len;
+    ngx_queue_t                  queue;
+    ngx_msec_t                   last;
+    /* integer value, 1 corresponds to 0.001 r/s */
+    ngx_uint_t                   excess;
+    ngx_uint_t                   count;
+    u_char                       data[1];
+} ngx_http_limit_req_node_t;
+
+
+typedef struct {
+    ngx_rbtree_t                  rbtree;
+    ngx_rbtree_node_t             sentinel;
+    ngx_queue_t                   queue;
+} ngx_http_limit_req_shctx_t;
+
+
+typedef struct {
+    ngx_http_limit_req_shctx_t  *sh;
+    ngx_slab_pool_t             *shpool;
+    /* integer value, 1 corresponds to 0.001 r/s */
+    ngx_uint_t                   rate;
+    ngx_http_complex_value_t     key;
+    ngx_http_limit_req_node_t   *node;
+} ngx_http_limit_req_ctx_t;
+
+
+typedef struct {
+    ngx_shm_zone_t              *shm_zone;
+    /* integer value, 1 corresponds to 0.001 r/s */
+    ngx_uint_t                   burst;
+    ngx_uint_t                   nodelay; /* unsigned  nodelay:1 */
+} ngx_http_limit_req_limit_t;
+
+
+typedef struct {
+    ngx_array_t                  limits;
+    ngx_uint_t                   limit_log_level;
+    ngx_uint_t                   delay_log_level;
+    ngx_uint_t                   status_code;
+} ngx_http_limit_req_conf_t;
+
+
+static void ngx_http_limit_req_delay(ngx_http_request_t *r);
+static ngx_int_t ngx_http_limit_req_lookup(ngx_http_limit_req_limit_t *limit,
+    ngx_uint_t hash, ngx_str_t *key, ngx_uint_t *ep, ngx_uint_t account);
+static ngx_msec_t ngx_http_limit_req_account(ngx_http_limit_req_limit_t *limits,
+    ngx_uint_t n, ngx_uint_t *ep, ngx_http_limit_req_limit_t **limit);
+static void ngx_http_limit_req_expire(ngx_http_limit_req_ctx_t *ctx,
+    ngx_uint_t n);
+
+static void *ngx_http_limit_req_create_conf(ngx_conf_t *cf);
+static char *ngx_http_limit_req_merge_conf(ngx_conf_t *cf, void *parent,
+    void *child);
+static char *ngx_http_limit_req_zone(ngx_conf_t *cf, ngx_command_t *cmd,
+    void *conf);
+static char *ngx_http_limit_req(ngx_conf_t *cf, ngx_command_t *cmd,
+    void *conf);
+static ngx_int_t ngx_http_limit_req_init(ngx_conf_t *cf);
+
+
+static ngx_conf_enum_t  ngx_http_limit_req_log_levels[] = {
+    { ngx_string("info"), NGX_LOG_INFO },
+    { ngx_string("notice"), NGX_LOG_NOTICE },
+    { ngx_string("warn"), NGX_LOG_WARN },
+    { ngx_string("error"), NGX_LOG_ERR },
+    { ngx_null_string, 0 }
+};
+
+
+static ngx_conf_num_bounds_t  ngx_http_limit_req_status_bounds = {
+    ngx_conf_check_num_bounds, 400, 599
+};
+
+
+static ngx_command_t  ngx_http_limit_req_commands[] = {
+
+    { ngx_string("limit_req_zone"),
+      NGX_HTTP_MAIN_CONF|NGX_CONF_TAKE3,
+      ngx_http_limit_req_zone,
+      0,
+      0,
+      NULL },
+
+    { ngx_string("limit_req"),
+      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_TAKE123,
+      ngx_http_limit_req,
+      NGX_HTTP_LOC_CONF_OFFSET,
+      0,
+      NULL },
+
+    { ngx_string("limit_req_log_level"),
+      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_TAKE1,
+      ngx_conf_set_enum_slot,
+      NGX_HTTP_LOC_CONF_OFFSET,
+      offsetof(ngx_http_limit_req_conf_t, limit_log_level),
+      &ngx_http_limit_req_log_levels },
+
+    { ngx_string("limit_req_status"),
+      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_TAKE1,
+      ngx_conf_set_num_slot,
+      NGX_HTTP_LOC_CONF_OFFSET,
+      offsetof(ngx_http_limit_req_conf_t, status_code),
+      &ngx_http_limit_req_status_bounds },
+
+      ngx_null_command
+};
+
+
+static ngx_http_module_t  ngx_http_limit_req_module_ctx = {
+    NULL,                                  /* preconfiguration */
+    ngx_http_limit_req_init,               /* postconfiguration */
+
+    NULL,                                  /* create main configuration */
+    NULL,                                  /* init main configuration */
+
+    NULL,                                  /* create server configuration */
+    NULL,                                  /* merge server configuration */
+
+    ngx_http_limit_req_create_conf,        /* create location configuration */
+    ngx_http_limit_req_merge_conf          /* merge location configuration */
+};
+
+
+ngx_module_t  ngx_http_limit_req_module = {
+    NGX_MODULE_V1,
+    &ngx_http_limit_req_module_ctx,        /* module context */
+    ngx_http_limit_req_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_limit_req_handler(ngx_http_request_t *r)
+{
+    uint32_t                     hash;
+    ngx_str_t                    key;
+    ngx_int_t                    rc;
+    ngx_uint_t                   n, excess;
+    ngx_msec_t                   delay;
+    ngx_http_limit_req_ctx_t    *ctx;
+    ngx_http_limit_req_conf_t   *lrcf;
+    ngx_http_limit_req_limit_t  *limit, *limits;
+
+    if (r->main->limit_req_set) {
+        return NGX_DECLINED;
+    }
+
+    lrcf = ngx_http_get_module_loc_conf(r, ngx_http_limit_req_module);
+    limits = lrcf->limits.elts;
+
+    excess = 0;
+
+    rc = NGX_DECLINED;
+
+#if (NGX_SUPPRESS_WARN)
+    limit = NULL;
+#endif
+
+    for (n = 0; n < lrcf->limits.nelts; n++) {
+
+        limit = &limits[n];
+
+        ctx = limit->shm_zone->data;
+
+        if (ngx_http_complex_value(r, &ctx->key, &key) != NGX_OK) {
+            return NGX_HTTP_INTERNAL_SERVER_ERROR;
+        }
+
+        if (key.len == 0) {
+            continue;
+        }
+
+        if (key.len > 65535) {
+            ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
+                          "the value of the \"%V\" key "
+                          "is more than 65535 bytes: \"%V\"",
+                          &ctx->key.value, &key);
+            continue;
+        }
+
+        hash = ngx_crc32_short(key.data, key.len);
+
+        ngx_shmtx_lock(&ctx->shpool->mutex);
+
+        rc = ngx_http_limit_req_lookup(limit, hash, &key, &excess,
+                                       (n == lrcf->limits.nelts - 1));
+
+        ngx_shmtx_unlock(&ctx->shpool->mutex);
+
+        ngx_log_debug4(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
+                       "limit_req[%ui]: %i %ui.%03ui",
+                       n, rc, excess / 1000, excess % 1000);
+
+        if (rc != NGX_AGAIN) {
+            break;
+        }
+    }
+
+    if (rc == NGX_DECLINED) {
+        return NGX_DECLINED;
+    }
+
+    r->main->limit_req_set = 1;
+
+    if (rc == NGX_BUSY || rc == NGX_ERROR) {
+
+        if (rc == NGX_BUSY) {
+            ngx_log_error(lrcf->limit_log_level, r->connection->log, 0,
+                          "limiting requests, excess: %ui.%03ui by zone \"%V\"",
+                          excess / 1000, excess % 1000,
+                          &limit->shm_zone->shm.name);
+        }
+
+        while (n--) {
+            ctx = limits[n].shm_zone->data;
+
+            if (ctx->node == NULL) {
+                continue;
+            }
+
+            ngx_shmtx_lock(&ctx->shpool->mutex);
+
+            ctx->node->count--;
+
+            ngx_shmtx_unlock(&ctx->shpool->mutex);
+
+            ctx->node = NULL;
+        }
+
+        return lrcf->status_code;
+    }
+
+    /* rc == NGX_AGAIN || rc == NGX_OK */
+
+    if (rc == NGX_AGAIN) {
+        excess = 0;
+    }
+
+    delay = ngx_http_limit_req_account(limits, n, &excess, &limit);
+
+    if (!delay) {
+        return NGX_DECLINED;
+    }
+
+    ngx_log_error(lrcf->delay_log_level, r->connection->log, 0,
+                  "delaying request, excess: %ui.%03ui, by zone \"%V\"",
+                  excess / 1000, excess % 1000, &limit->shm_zone->shm.name);
+
+    if (ngx_handle_read_event(r->connection->read, 0) != NGX_OK) {
+        return NGX_HTTP_INTERNAL_SERVER_ERROR;
+    }
+
+    r->read_event_handler = ngx_http_test_reading;
+    r->write_event_handler = ngx_http_limit_req_delay;
+
+    r->connection->write->delayed = 1;
+    ngx_add_timer(r->connection->write, delay);
+
+    return NGX_AGAIN;
+}
+
+
+static void
+ngx_http_limit_req_delay(ngx_http_request_t *r)
+{
+    ngx_event_t  *wev;
+
+    ngx_log_debug0(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
+                   "limit_req delay");
+
+    wev = r->connection->write;
+
+    if (wev->delayed) {
+
+        if (ngx_handle_write_event(wev, 0) != NGX_OK) {
+            ngx_http_finalize_request(r, NGX_HTTP_INTERNAL_SERVER_ERROR);
+        }
+
+        return;
+    }
+
+    if (ngx_handle_read_event(r->connection->read, 0) != NGX_OK) {
+        ngx_http_finalize_request(r, NGX_HTTP_INTERNAL_SERVER_ERROR);
+        return;
+    }
+
+    r->read_event_handler = ngx_http_block_reading;
+    r->write_event_handler = ngx_http_core_run_phases;
+
+    ngx_http_core_run_phases(r);
+}
+
+
+static void
+ngx_http_limit_req_rbtree_insert_value(ngx_rbtree_node_t *temp,
+    ngx_rbtree_node_t *node, ngx_rbtree_node_t *sentinel)
+{
+    ngx_rbtree_node_t          **p;
+    ngx_http_limit_req_node_t   *lrn, *lrnt;
+
+    for ( ;; ) {
+
+        if (node->key < temp->key) {
+
+            p = &temp->left;
+
+        } else if (node->key > temp->key) {
+
+            p = &temp->right;
+
+        } else { /* node->key == temp->key */
+
+            lrn = (ngx_http_limit_req_node_t *) &node->color;
+            lrnt = (ngx_http_limit_req_node_t *) &temp->color;
+
+            p = (ngx_memn2cmp(lrn->data, lrnt->data, lrn->len, lrnt->len) < 0)
+                ? &temp->left : &temp->right;
+        }
+
+        if (*p == sentinel) {
+            break;
+        }
+
+        temp = *p;
+    }
+
+    *p = node;
+    node->parent = temp;
+    node->left = sentinel;
+    node->right = sentinel;
+    ngx_rbt_red(node);
+}
+
+
+static ngx_int_t
+ngx_http_limit_req_lookup(ngx_http_limit_req_limit_t *limit, ngx_uint_t hash,
+    ngx_str_t *key, ngx_uint_t *ep, ngx_uint_t account)
+{
+    size_t                      size;
+    ngx_int_t                   rc, excess;
+    ngx_msec_t                  now;
+    ngx_msec_int_t              ms;
+    ngx_rbtree_node_t          *node, *sentinel;
+    ngx_http_limit_req_ctx_t   *ctx;
+    ngx_http_limit_req_node_t  *lr;
+
+    now = ngx_current_msec;
+
+    ctx = limit->shm_zone->data;
+
+    node = ctx->sh->rbtree.root;
+    sentinel = ctx->sh->rbtree.sentinel;
+
+    while (node != sentinel) {
+
+        if (hash < node->key) {
+            node = node->left;
+            continue;
+        }
+
+        if (hash > node->key) {
+            node = node->right;
+            continue;
+        }
+
+        /* hash == node->key */
+
+        lr = (ngx_http_limit_req_node_t *) &node->color;
+
+        rc = ngx_memn2cmp(key->data, lr->data, key->len, (size_t) lr->len);
+
+        if (rc == 0) {
+            ngx_queue_remove(&lr->queue);
+            ngx_queue_insert_head(&ctx->sh->queue, &lr->queue);
+
+            ms = (ngx_msec_int_t) (now - lr->last);
+
+            excess = lr->excess - ctx->rate * ngx_abs(ms) / 1000 + 1000;
+
+            if (excess < 0) {
+                excess = 0;
+            }
+
+            *ep = excess;
+
+            if ((ngx_uint_t) excess > limit->burst) {
+                return NGX_BUSY;
+            }
+
+            if (account) {
+                lr->excess = excess;
+                lr->last = now;
+                return NGX_OK;
+            }
+
+            lr->count++;
+
+            ctx->node = lr;
+
+            return NGX_AGAIN;
+        }
+
+        node = (rc < 0) ? node->left : node->right;
+    }
+
+    *ep = 0;
+
+    size = offsetof(ngx_rbtree_node_t, color)
+           + offsetof(ngx_http_limit_req_node_t, data)
+           + key->len;
+
+    ngx_http_limit_req_expire(ctx, 1);
+
+    node = ngx_slab_alloc_locked(ctx->shpool, size);
+
+    if (node == NULL) {
+        ngx_http_limit_req_expire(ctx, 0);
+
+        node = ngx_slab_alloc_locked(ctx->shpool, size);
+        if (node == NULL) {
+            ngx_log_error(NGX_LOG_ALERT, ngx_cycle->log, 0,
+                          "could not allocate node%s", ctx->shpool->log_ctx);
+            return NGX_ERROR;
+        }
+    }
+
+    node->key = hash;
+
+    lr = (ngx_http_limit_req_node_t *) &node->color;
+
+    lr->len = (u_short) key->len;
+    lr->excess = 0;
+
+    ngx_memcpy(lr->data, key->data, key->len);
+
+    ngx_rbtree_insert(&ctx->sh->rbtree, node);
+
+    ngx_queue_insert_head(&ctx->sh->queue, &lr->queue);
+
+    if (account) {
+        lr->last = now;
+        lr->count = 0;
+        return NGX_OK;
+    }
+
+    lr->last = 0;
+    lr->count = 1;
+
+    ctx->node = lr;
+
+    return NGX_AGAIN;
+}
+
+
+static ngx_msec_t
+ngx_http_limit_req_account(ngx_http_limit_req_limit_t *limits, ngx_uint_t n,
+    ngx_uint_t *ep, ngx_http_limit_req_limit_t **limit)
+{
+    ngx_int_t                   excess;
+    ngx_msec_t                  now, delay, max_delay;
+    ngx_msec_int_t              ms;
+    ngx_http_limit_req_ctx_t   *ctx;
+    ngx_http_limit_req_node_t  *lr;
+
+    excess = *ep;
+
+    if (excess == 0 || (*limit)->nodelay) {
+        max_delay = 0;
+
+    } else {
+        ctx = (*limit)->shm_zone->data;
+        max_delay = excess * 1000 / ctx->rate;
+    }
+
+    while (n--) {
+        ctx = limits[n].shm_zone->data;
+        lr = ctx->node;
+
+        if (lr == NULL) {
+            continue;
+        }
+
+        ngx_shmtx_lock(&ctx->shpool->mutex);
+
+        now = ngx_current_msec;
+        ms = (ngx_msec_int_t) (now - lr->last);
+
+        excess = lr->excess - ctx->rate * ngx_abs(ms) / 1000 + 1000;
+
+        if (excess < 0) {
+            excess = 0;
+        }
+
+        lr->last = now;
+        lr->excess = excess;
+        lr->count--;
+
+        ngx_shmtx_unlock(&ctx->shpool->mutex);
+
+        ctx->node = NULL;
+
+        if (limits[n].nodelay) {
+            continue;
+        }
+
+        delay = excess * 1000 / ctx->rate;
+
+        if (delay > max_delay) {
+            max_delay = delay;
+            *ep = excess;
+            *limit = &limits[n];
+        }
+    }
+
+    return max_delay;
+}
+
+
+static void
+ngx_http_limit_req_expire(ngx_http_limit_req_ctx_t *ctx, ngx_uint_t n)
+{
+    ngx_int_t                   excess;
+    ngx_msec_t                  now;
+    ngx_queue_t                *q;
+    ngx_msec_int_t              ms;
+    ngx_rbtree_node_t          *node;
+    ngx_http_limit_req_node_t  *lr;
+
+    now = ngx_current_msec;
+
+    /*
+     * n == 1 deletes one or two zero rate entries
+     * n == 0 deletes oldest entry by force
+     *        and one or two zero rate entries
+     */
+
+    while (n < 3) {
+
+        if (ngx_queue_empty(&ctx->sh->queue)) {
+            return;
+        }
+
+        q = ngx_queue_last(&ctx->sh->queue);
+
+        lr = ngx_queue_data(q, ngx_http_limit_req_node_t, queue);
+
+        if (lr->count) {
+
+            /*
+             * There is not much sense in looking further,
+             * because we bump nodes on the lookup stage.
+             */
+
+            return;
+        }
+
+        if (n++ != 0) {
+
+            ms = (ngx_msec_int_t) (now - lr->last);
+            ms = ngx_abs(ms);
+
+            if (ms < 60000) {
+                return;
+            }
+
+            excess = lr->excess - ctx->rate * ms / 1000;
+
+            if (excess > 0) {
+                return;
+            }
+        }
+
+        ngx_queue_remove(q);
+
+        node = (ngx_rbtree_node_t *)
+                   ((u_char *) lr - offsetof(ngx_rbtree_node_t, color));
+
+        ngx_rbtree_delete(&ctx->sh->rbtree, node);
+
+        ngx_slab_free_locked(ctx->shpool, node);
+    }
+}
+
+
+static ngx_int_t
+ngx_http_limit_req_init_zone(ngx_shm_zone_t *shm_zone, void *data)
+{
+    ngx_http_limit_req_ctx_t  *octx = data;
+
+    size_t                     len;
+    ngx_http_limit_req_ctx_t  *ctx;
+
+    ctx = shm_zone->data;
+
+    if (octx) {
+        if (ctx->key.value.len != octx->key.value.len
+            || ngx_strncmp(ctx->key.value.data, octx->key.value.data,
+                           ctx->key.value.len)
+               != 0)
+        {
+            ngx_log_error(NGX_LOG_EMERG, shm_zone->shm.log, 0,
+                          "limit_req \"%V\" uses the \"%V\" key "
+                          "while previously it used the \"%V\" key",
+                          &shm_zone->shm.name, &ctx->key.value,
+                          &octx->key.value);
+            return NGX_ERROR;
+        }
+
+        ctx->sh = octx->sh;
+        ctx->shpool = octx->shpool;
+
+        return NGX_OK;
+    }
+
+    ctx->shpool = (ngx_slab_pool_t *) shm_zone->shm.addr;
+
+    if (shm_zone->shm.exists) {
+        ctx->sh = ctx->shpool->data;
+
+        return NGX_OK;
+    }
+
+    ctx->sh = ngx_slab_alloc(ctx->shpool, sizeof(ngx_http_limit_req_shctx_t));
+    if (ctx->sh == NULL) {
+        return NGX_ERROR;
+    }
+
+    ctx->shpool->data = ctx->sh;
+
+    ngx_rbtree_init(&ctx->sh->rbtree, &ctx->sh->sentinel,
+                    ngx_http_limit_req_rbtree_insert_value);
+
+    ngx_queue_init(&ctx->sh->queue);
+
+    len = sizeof(" in limit_req zone \"\"") + shm_zone->shm.name.len;
+
+    ctx->shpool->log_ctx = ngx_slab_alloc(ctx->shpool, len);
+    if (ctx->shpool->log_ctx == NULL) {
+        return NGX_ERROR;
+    }
+
+    ngx_sprintf(ctx->shpool->log_ctx, " in limit_req zone \"%V\"%Z",
+                &shm_zone->shm.name);
+
+    ctx->shpool->log_nomem = 0;
+
+    return NGX_OK;
+}
+
+
+static void *
+ngx_http_limit_req_create_conf(ngx_conf_t *cf)
+{
+    ngx_http_limit_req_conf_t  *conf;
+
+    conf = ngx_pcalloc(cf->pool, sizeof(ngx_http_limit_req_conf_t));
+    if (conf == NULL) {
+        return NULL;
+    }
+
+    /*
+     * set by ngx_pcalloc():
+     *
+     *     conf->limits.elts = NULL;
+     */
+
+    conf->limit_log_level = NGX_CONF_UNSET_UINT;
+    conf->status_code = NGX_CONF_UNSET_UINT;
+
+    return conf;
+}
+
+
+static char *
+ngx_http_limit_req_merge_conf(ngx_conf_t *cf, void *parent, void *child)
+{
+    ngx_http_limit_req_conf_t *prev = parent;
+    ngx_http_limit_req_conf_t *conf = child;
+
+    if (conf->limits.elts == NULL) {
+        conf->limits = prev->limits;
+    }
+
+    ngx_conf_merge_uint_value(conf->limit_log_level, prev->limit_log_level,
+                              NGX_LOG_ERR);
+
+    conf->delay_log_level = (conf->limit_log_level == NGX_LOG_INFO) ?
+                                NGX_LOG_INFO : conf->limit_log_level + 1;
+
+    ngx_conf_merge_uint_value(conf->status_code, prev->status_code,
+                              NGX_HTTP_SERVICE_UNAVAILABLE);
+
+    return NGX_CONF_OK;
+}
+
+
+static char *
+ngx_http_limit_req_zone(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
+{
+    u_char                            *p;
+    size_t                             len;
+    ssize_t                            size;
+    ngx_str_t                         *value, name, s;
+    ngx_int_t                          rate, scale;
+    ngx_uint_t                         i;
+    ngx_shm_zone_t                    *shm_zone;
+    ngx_http_limit_req_ctx_t          *ctx;
+    ngx_http_compile_complex_value_t   ccv;
+
+    value = cf->args->elts;
+
+    ctx = ngx_pcalloc(cf->pool, sizeof(ngx_http_limit_req_ctx_t));
+    if (ctx == NULL) {
+        return NGX_CONF_ERROR;
+    }
+
+    ngx_memzero(&ccv, sizeof(ngx_http_compile_complex_value_t));
+
+    ccv.cf = cf;
+    ccv.value = &value[1];
+    ccv.complex_value = &ctx->key;
+
+    if (ngx_http_compile_complex_value(&ccv) != NGX_OK) {
+        return NGX_CONF_ERROR;
+    }
+
+    size = 0;
+    rate = 1;
+    scale = 1;
+    name.len = 0;
+
+    for (i = 2; i < cf->args->nelts; i++) {
+
+        if (ngx_strncmp(value[i].data, "zone=", 5) == 0) {
+
+            name.data = value[i].data + 5;
+
+            p = (u_char *) ngx_strchr(name.data, ':');
+
+            if (p == NULL) {
+                ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
+                                   "invalid zone size \"%V\"", &value[i]);
+                return NGX_CONF_ERROR;
+            }
+
+            name.len = p - name.data;
+
+            s.data = p + 1;
+            s.len = value[i].data + value[i].len - s.data;
+
+            size = ngx_parse_size(&s);
+
+            if (size == NGX_ERROR) {
+                ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
+                                   "invalid zone size \"%V\"", &value[i]);
+                return NGX_CONF_ERROR;
+            }
+
+            if (size < (ssize_t) (8 * ngx_pagesize)) {
+                ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
+                                   "zone \"%V\" is too small", &value[i]);
+                return NGX_CONF_ERROR;
+            }
+
+            continue;
+        }
+
+        if (ngx_strncmp(value[i].data, "rate=", 5) == 0) {
+
+            len = value[i].len;
+            p = value[i].data + len - 3;
+
+            if (ngx_strncmp(p, "r/s", 3) == 0) {
+                scale = 1;
+                len -= 3;
+
+            } else if (ngx_strncmp(p, "r/m", 3) == 0) {
+                scale = 60;
+                len -= 3;
+            }
+
+            rate = ngx_atoi(value[i].data + 5, len - 5);
+            if (rate <= 0) {
+                ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
+                                   "invalid rate \"%V\"", &value[i]);
+                return NGX_CONF_ERROR;
+            }
+
+            continue;
+        }
+
+        ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
+                           "invalid parameter \"%V\"", &value[i]);
+        return NGX_CONF_ERROR;
+    }
+
+    if (name.len == 0) {
+        ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
+                           "\"%V\" must have \"zone\" parameter",
+                           &cmd->name);
+        return NGX_CONF_ERROR;
+    }
+
+    ctx->rate = rate * 1000 / scale;
+
+    shm_zone = ngx_shared_memory_add(cf, &name, size,
+                                     &ngx_http_limit_req_module);
+    if (shm_zone == NULL) {
+        return NGX_CONF_ERROR;
+    }
+
+    if (shm_zone->data) {
+        ctx = shm_zone->data;
+
+        ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
+                           "%V \"%V\" is already bound to key \"%V\"",
+                           &cmd->name, &name, &ctx->key.value);
+        return NGX_CONF_ERROR;
+    }
+
+    shm_zone->init = ngx_http_limit_req_init_zone;
+    shm_zone->data = ctx;
+
+    return NGX_CONF_OK;
+}
+
+
+static char *
+ngx_http_limit_req(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
+{
+    ngx_http_limit_req_conf_t  *lrcf = conf;
+
+    ngx_int_t                    burst;
+    ngx_str_t                   *value, s;
+    ngx_uint_t                   i, nodelay;
+    ngx_shm_zone_t              *shm_zone;
+    ngx_http_limit_req_limit_t  *limit, *limits;
+
+    value = cf->args->elts;
+
+    shm_zone = NULL;
+    burst = 0;
+    nodelay = 0;
+
+    for (i = 1; i < cf->args->nelts; i++) {
+
+        if (ngx_strncmp(value[i].data, "zone=", 5) == 0) {
+
+            s.len = value[i].len - 5;
+            s.data = value[i].data + 5;
+
+            shm_zone = ngx_shared_memory_add(cf, &s, 0,
+                                             &ngx_http_limit_req_module);
+            if (shm_zone == NULL) {
+                return NGX_CONF_ERROR;
+            }
+
+            continue;
+        }
+
+        if (ngx_strncmp(value[i].data, "burst=", 6) == 0) {
+
+            burst = ngx_atoi(value[i].data + 6, value[i].len - 6);
+            if (burst <= 0) {
+                ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
+                                   "invalid burst rate \"%V\"", &value[i]);
+                return NGX_CONF_ERROR;
+            }
+
+            continue;
+        }
+
+        if (ngx_strcmp(value[i].data, "nodelay") == 0) {
+            nodelay = 1;
+            continue;
+        }
+
+        ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
+                           "invalid parameter \"%V\"", &value[i]);
+        return NGX_CONF_ERROR;
+    }
+
+    if (shm_zone == NULL) {
+        ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
+                           "\"%V\" must have \"zone\" parameter",
+                           &cmd->name);
+        return NGX_CONF_ERROR;
+    }
+
+    limits = lrcf->limits.elts;
+
+    if (limits == NULL) {
+        if (ngx_array_init(&lrcf->limits, cf->pool, 1,
+                           sizeof(ngx_http_limit_req_limit_t))
+            != NGX_OK)
+        {
+            return NGX_CONF_ERROR;
+        }
+    }
+
+    for (i = 0; i < lrcf->limits.nelts; i++) {
+        if (shm_zone == limits[i].shm_zone) {
+            return "is duplicate";
+        }
+    }
+
+    limit = ngx_array_push(&lrcf->limits);
+    if (limit == NULL) {
+        return NGX_CONF_ERROR;
+    }
+
+    limit->shm_zone = shm_zone;
+    limit->burst = burst * 1000;
+    limit->nodelay = nodelay;
+
+    return NGX_CONF_OK;
+}
+
+
+static ngx_int_t
+ngx_http_limit_req_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_PREACCESS_PHASE].handlers);
+    if (h == NULL) {
+        return NGX_ERROR;
+    }
+
+    *h = ngx_http_limit_req_handler;
+
+    return NGX_OK;
+}