src/http/modules/ngx_http_upstream_hash_module.c - nginx - Git at Google


 /*
  * Copyright (C) Roman Arutyunyan
  * Copyright (C) Nginx, Inc.
  */


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


 typedef struct {
     uint32_t                            hash;
     ngx_str_t                          *server;
 } ngx_http_upstream_chash_point_t;


 typedef struct {
     ngx_uint_t                          number;
     ngx_http_upstream_chash_point_t     point[1];
 } ngx_http_upstream_chash_points_t;


 typedef struct {
     ngx_http_complex_value_t            key;
     ngx_http_upstream_chash_points_t   *points;
 } ngx_http_upstream_hash_srv_conf_t;


 typedef struct {
     /* the round robin data must be first */
     ngx_http_upstream_rr_peer_data_t    rrp;
     ngx_http_upstream_hash_srv_conf_t  *conf;
     ngx_str_t                           key;
     ngx_uint_t                          tries;
     ngx_uint_t                          rehash;
     uint32_t                            hash;
     ngx_event_get_peer_pt               get_rr_peer;
 } ngx_http_upstream_hash_peer_data_t;


 static ngx_int_t ngx_http_upstream_init_hash(ngx_conf_t *cf,
     ngx_http_upstream_srv_conf_t *us);
 static ngx_int_t ngx_http_upstream_init_hash_peer(ngx_http_request_t *r,
     ngx_http_upstream_srv_conf_t *us);
 static ngx_int_t ngx_http_upstream_get_hash_peer(ngx_peer_connection_t *pc,
     void *data);

 static ngx_int_t ngx_http_upstream_init_chash(ngx_conf_t *cf,
     ngx_http_upstream_srv_conf_t *us);
 static int ngx_libc_cdecl
     ngx_http_upstream_chash_cmp_points(const void *one, const void *two);
 static ngx_uint_t ngx_http_upstream_find_chash_point(
     ngx_http_upstream_chash_points_t *points, uint32_t hash);
 static ngx_int_t ngx_http_upstream_init_chash_peer(ngx_http_request_t *r,
     ngx_http_upstream_srv_conf_t *us);
 static ngx_int_t ngx_http_upstream_get_chash_peer(ngx_peer_connection_t *pc,
     void *data);

 static void *ngx_http_upstream_hash_create_conf(ngx_conf_t *cf);
 static char *ngx_http_upstream_hash(ngx_conf_t *cf, ngx_command_t *cmd,
     void *conf);


 static ngx_command_t  ngx_http_upstream_hash_commands[] = {

     { ngx_string("hash"),
       NGX_HTTP_UPS_CONF|NGX_CONF_TAKE12,
       ngx_http_upstream_hash,
       NGX_HTTP_SRV_CONF_OFFSET,
       0,
       NULL },

       ngx_null_command
 };


 static ngx_http_module_t  ngx_http_upstream_hash_module_ctx = {
     NULL,                                  /* preconfiguration */
     NULL,                                  /* postconfiguration */

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

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

     NULL,                                  /* create location configuration */
     NULL                                   /* merge location configuration */
 };


 ngx_module_t  ngx_http_upstream_hash_module = {
     NGX_MODULE_V1,
     &ngx_http_upstream_hash_module_ctx,    /* module context */
     ngx_http_upstream_hash_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_upstream_init_hash(ngx_conf_t *cf, ngx_http_upstream_srv_conf_t *us)
 {
     if (ngx_http_upstream_init_round_robin(cf, us) != NGX_OK) {
         return NGX_ERROR;
     }

     us->peer.init = ngx_http_upstream_init_hash_peer;

     return NGX_OK;
 }


 static ngx_int_t
 ngx_http_upstream_init_hash_peer(ngx_http_request_t *r,
     ngx_http_upstream_srv_conf_t *us)
 {
     ngx_http_upstream_hash_srv_conf_t   *hcf;
     ngx_http_upstream_hash_peer_data_t  *hp;

     hp = ngx_palloc(r->pool, sizeof(ngx_http_upstream_hash_peer_data_t));
     if (hp == NULL) {
         return NGX_ERROR;
     }

     r->upstream->peer.data = &hp->rrp;

     if (ngx_http_upstream_init_round_robin_peer(r, us) != NGX_OK) {
         return NGX_ERROR;
     }

     r->upstream->peer.get = ngx_http_upstream_get_hash_peer;

     hcf = ngx_http_conf_upstream_srv_conf(us, ngx_http_upstream_hash_module);

     if (ngx_http_complex_value(r, &hcf->key, &hp->key) != NGX_OK) {
         return NGX_ERROR;
     }

     ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                    "upstream hash key:\"%V\"", &hp->key);

     hp->conf = hcf;
     hp->tries = 0;
     hp->rehash = 0;
     hp->hash = 0;
     hp->get_rr_peer = ngx_http_upstream_get_round_robin_peer;

     return NGX_OK;
 }


 static ngx_int_t
 ngx_http_upstream_get_hash_peer(ngx_peer_connection_t *pc, void *data)
 {
     ngx_http_upstream_hash_peer_data_t  *hp = data;

     time_t                        now;
     u_char                        buf[NGX_INT_T_LEN];
     size_t                        size;
     uint32_t                      hash;
     ngx_int_t                     w;
     uintptr_t                     m;
     ngx_uint_t                    n, p;
     ngx_http_upstream_rr_peer_t  *peer;

     ngx_log_debug1(NGX_LOG_DEBUG_HTTP, pc->log, 0,
                    "get hash peer, try: %ui", pc->tries);

     ngx_http_upstream_rr_peers_rlock(hp->rrp.peers);

     if (hp->tries > 20 || hp->rrp.peers->single) {
         ngx_http_upstream_rr_peers_unlock(hp->rrp.peers);
         return hp->get_rr_peer(pc, &hp->rrp);
     }

     now = ngx_time();

     pc->cached = 0;
     pc->connection = NULL;

     for ( ;; ) {

         /*
          * Hash expression is compatible with Cache::Memcached:
          * ((crc32([REHASH] KEY) >> 16) & 0x7fff) + PREV_HASH
          * with REHASH omitted at the first iteration.
          */

         ngx_crc32_init(hash);

         if (hp->rehash > 0) {
             size = ngx_sprintf(buf, "%ui", hp->rehash) - buf;
             ngx_crc32_update(&hash, buf, size);
         }

         ngx_crc32_update(&hash, hp->key.data, hp->key.len);
         ngx_crc32_final(hash);

         hash = (hash >> 16) & 0x7fff;

         hp->hash += hash;
         hp->rehash++;

         w = hp->hash % hp->rrp.peers->total_weight;
         peer = hp->rrp.peers->peer;
         p = 0;

         while (w >= peer->weight) {
             w -= peer->weight;
             peer = peer->next;
             p++;
         }

         n = p / (8 * sizeof(uintptr_t));
         m = (uintptr_t) 1 << p % (8 * sizeof(uintptr_t));

         if (hp->rrp.tried[n] & m) {
             goto next;
         }

         ngx_http_upstream_rr_peer_lock(hp->rrp.peers, peer);

         ngx_log_debug2(NGX_LOG_DEBUG_HTTP, pc->log, 0,
                        "get hash peer, value:%uD, peer:%ui", hp->hash, p);

         if (peer->down) {
             ngx_http_upstream_rr_peer_unlock(hp->rrp.peers, peer);
             goto next;
         }

         if (peer->max_fails
             && peer->fails >= peer->max_fails
             && now - peer->checked <= peer->fail_timeout)
         {
             ngx_http_upstream_rr_peer_unlock(hp->rrp.peers, peer);
             goto next;
         }

         if (peer->max_conns && peer->conns >= peer->max_conns) {
             ngx_http_upstream_rr_peer_unlock(hp->rrp.peers, peer);
             goto next;
         }

         break;

     next:

         if (++hp->tries > 20) {
             ngx_http_upstream_rr_peers_unlock(hp->rrp.peers);
             return hp->get_rr_peer(pc, &hp->rrp);
         }
     }

     hp->rrp.current = peer;

     pc->sockaddr = peer->sockaddr;
     pc->socklen = peer->socklen;
     pc->name = &peer->name;

     peer->conns++;

     if (now - peer->checked > peer->fail_timeout) {
         peer->checked = now;
     }

     ngx_http_upstream_rr_peer_unlock(hp->rrp.peers, peer);
     ngx_http_upstream_rr_peers_unlock(hp->rrp.peers);

     hp->rrp.tried[n] |= m;

     return NGX_OK;
 }


 static ngx_int_t
 ngx_http_upstream_init_chash(ngx_conf_t *cf, ngx_http_upstream_srv_conf_t *us)
 {
     u_char                             *host, *port, c;
     size_t                              host_len, port_len, size;
     uint32_t                            hash, base_hash;
     ngx_str_t                          *server;
     ngx_uint_t                          npoints, i, j;
     ngx_http_upstream_rr_peer_t        *peer;
     ngx_http_upstream_rr_peers_t       *peers;
     ngx_http_upstream_chash_points_t   *points;
     ngx_http_upstream_hash_srv_conf_t  *hcf;
     union {
         uint32_t                        value;
         u_char                          byte[4];
     } prev_hash;

     if (ngx_http_upstream_init_round_robin(cf, us) != NGX_OK) {
         return NGX_ERROR;
     }

     us->peer.init = ngx_http_upstream_init_chash_peer;

     peers = us->peer.data;
     npoints = peers->total_weight * 160;

     size = sizeof(ngx_http_upstream_chash_points_t)
            + sizeof(ngx_http_upstream_chash_point_t) * (npoints - 1);

     points = ngx_palloc(cf->pool, size);
     if (points == NULL) {
         return NGX_ERROR;
     }

     points->number = 0;

     for (peer = peers->peer; peer; peer = peer->next) {
         server = &peer->server;

         /*
          * Hash expression is compatible with Cache::Memcached::Fast:
          * crc32(HOST \0 PORT PREV_HASH).
          */

         if (server->len >= 5
             && ngx_strncasecmp(server->data, (u_char *) "unix:", 5) == 0)
         {
             host = server->data + 5;
             host_len = server->len - 5;
             port = NULL;
             port_len = 0;
             goto done;
         }

         for (j = 0; j < server->len; j++) {
             c = server->data[server->len - j - 1];

             if (c == ':') {
                 host = server->data;
                 host_len = server->len - j - 1;
                 port = server->data + server->len - j;
                 port_len = j;
                 goto done;
             }

             if (c < '0' || c > '9') {
                 break;
             }
         }

         host = server->data;
         host_len = server->len;
         port = NULL;
         port_len = 0;

     done:

         ngx_crc32_init(base_hash);
         ngx_crc32_update(&base_hash, host, host_len);
         ngx_crc32_update(&base_hash, (u_char *) "", 1);
         ngx_crc32_update(&base_hash, port, port_len);

         prev_hash.value = 0;
         npoints = peer->weight * 160;

         for (j = 0; j < npoints; j++) {
             hash = base_hash;

             ngx_crc32_update(&hash, prev_hash.byte, 4);
             ngx_crc32_final(hash);

             points->point[points->number].hash = hash;
             points->point[points->number].server = server;
             points->number++;

 #if (NGX_HAVE_LITTLE_ENDIAN)
             prev_hash.value = hash;
 #else
             prev_hash.byte[0] = (u_char) (hash & 0xff);
             prev_hash.byte[1] = (u_char) ((hash >> 8) & 0xff);
             prev_hash.byte[2] = (u_char) ((hash >> 16) & 0xff);
             prev_hash.byte[3] = (u_char) ((hash >> 24) & 0xff);
 #endif
         }
     }

     ngx_qsort(points->point,
               points->number,
               sizeof(ngx_http_upstream_chash_point_t),
               ngx_http_upstream_chash_cmp_points);

     for (i = 0, j = 1; j < points->number; j++) {
         if (points->point[i].hash != points->point[j].hash) {
             points->point[++i] = points->point[j];
         }
     }

     points->number = i + 1;

     hcf = ngx_http_conf_upstream_srv_conf(us, ngx_http_upstream_hash_module);
     hcf->points = points;

     return NGX_OK;
 }


 static int ngx_libc_cdecl
 ngx_http_upstream_chash_cmp_points(const void *one, const void *two)
 {
     ngx_http_upstream_chash_point_t *first =
                                        (ngx_http_upstream_chash_point_t *) one;
     ngx_http_upstream_chash_point_t *second =
                                        (ngx_http_upstream_chash_point_t *) two;

     if (first->hash < second->hash) {
         return -1;

     } else if (first->hash > second->hash) {
         return 1;

     } else {
         return 0;
     }
 }


 static ngx_uint_t
 ngx_http_upstream_find_chash_point(ngx_http_upstream_chash_points_t *points,
     uint32_t hash)
 {
     ngx_uint_t                        i, j, k;
     ngx_http_upstream_chash_point_t  *point;

     /* find first point >= hash */

     point = &points->point[0];

     i = 0;
     j = points->number;

     while (i < j) {
         k = (i + j) / 2;

         if (hash > point[k].hash) {
             i = k + 1;

         } else if (hash < point[k].hash) {
             j = k;

         } else {
             return k;
         }
     }

     return i;
 }


 static ngx_int_t
 ngx_http_upstream_init_chash_peer(ngx_http_request_t *r,
     ngx_http_upstream_srv_conf_t *us)
 {
     uint32_t                             hash;
     ngx_http_upstream_hash_srv_conf_t   *hcf;
     ngx_http_upstream_hash_peer_data_t  *hp;

     if (ngx_http_upstream_init_hash_peer(r, us) != NGX_OK) {
         return NGX_ERROR;
     }

     r->upstream->peer.get = ngx_http_upstream_get_chash_peer;

     hp = r->upstream->peer.data;
     hcf = ngx_http_conf_upstream_srv_conf(us, ngx_http_upstream_hash_module);

     hash = ngx_crc32_long(hp->key.data, hp->key.len);

     ngx_http_upstream_rr_peers_rlock(hp->rrp.peers);

     hp->hash = ngx_http_upstream_find_chash_point(hcf->points, hash);

     ngx_http_upstream_rr_peers_unlock(hp->rrp.peers);

     return NGX_OK;
 }


 static ngx_int_t
 ngx_http_upstream_get_chash_peer(ngx_peer_connection_t *pc, void *data)
 {
     ngx_http_upstream_hash_peer_data_t  *hp = data;

     time_t                              now;
     intptr_t                            m;
     ngx_str_t                          *server;
     ngx_int_t                           total;
     ngx_uint_t                          i, n, best_i;
     ngx_http_upstream_rr_peer_t        *peer, *best;
     ngx_http_upstream_chash_point_t    *point;
     ngx_http_upstream_chash_points_t   *points;
     ngx_http_upstream_hash_srv_conf_t  *hcf;

     ngx_log_debug1(NGX_LOG_DEBUG_HTTP, pc->log, 0,
                    "get consistent hash peer, try: %ui", pc->tries);

     ngx_http_upstream_rr_peers_wlock(hp->rrp.peers);

     if (hp->tries > 20 || hp->rrp.peers->single) {
         ngx_http_upstream_rr_peers_unlock(hp->rrp.peers);
         return hp->get_rr_peer(pc, &hp->rrp);
     }

     pc->cached = 0;
     pc->connection = NULL;

     now = ngx_time();
     hcf = hp->conf;

     points = hcf->points;
     point = &points->point[0];

     for ( ;; ) {
         server = point[hp->hash % points->number].server;

         ngx_log_debug2(NGX_LOG_DEBUG_HTTP, pc->log, 0,
                        "consistent hash peer:%uD, server:\"%V\"",
                        hp->hash, server);

         best = NULL;
         best_i = 0;
         total = 0;

         for (peer = hp->rrp.peers->peer, i = 0;
              peer;
              peer = peer->next, i++)
         {
             n = i / (8 * sizeof(uintptr_t));
             m = (uintptr_t) 1 << i % (8 * sizeof(uintptr_t));

             if (hp->rrp.tried[n] & m) {
                 continue;
             }

             if (peer->down) {
                 continue;
             }

             if (peer->max_fails
                 && peer->fails >= peer->max_fails
                 && now - peer->checked <= peer->fail_timeout)
             {
                 continue;
             }

             if (peer->max_conns && peer->conns >= peer->max_conns) {
                 continue;
             }

             if (peer->server.len != server->len
                 || ngx_strncmp(peer->server.data, server->data, server->len)
                    != 0)
             {
                 continue;
             }

             peer->current_weight += peer->effective_weight;
             total += peer->effective_weight;

             if (peer->effective_weight < peer->weight) {
                 peer->effective_weight++;
             }

             if (best == NULL || peer->current_weight > best->current_weight) {
                 best = peer;
                 best_i = i;
             }
         }

         if (best) {
             best->current_weight -= total;
             goto found;
         }

         hp->hash++;
         hp->tries++;

         if (hp->tries > 20) {
             ngx_http_upstream_rr_peers_unlock(hp->rrp.peers);
             return hp->get_rr_peer(pc, &hp->rrp);
         }
     }

 found:

     hp->rrp.current = best;

     pc->sockaddr = best->sockaddr;
     pc->socklen = best->socklen;
     pc->name = &best->name;

     best->conns++;

     if (now - best->checked > best->fail_timeout) {
         best->checked = now;
     }

     ngx_http_upstream_rr_peers_unlock(hp->rrp.peers);

     n = best_i / (8 * sizeof(uintptr_t));
     m = (uintptr_t) 1 << best_i % (8 * sizeof(uintptr_t));

     hp->rrp.tried[n] |= m;

     return NGX_OK;
 }


 static void *
 ngx_http_upstream_hash_create_conf(ngx_conf_t *cf)
 {
     ngx_http_upstream_hash_srv_conf_t  *conf;

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

     conf->points = NULL;

     return conf;
 }


 static char *
 ngx_http_upstream_hash(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
 {
     ngx_http_upstream_hash_srv_conf_t  *hcf = conf;

     ngx_str_t                         *value;
     ngx_http_upstream_srv_conf_t      *uscf;
     ngx_http_compile_complex_value_t   ccv;

     value = cf->args->elts;

     ngx_memzero(&ccv, sizeof(ngx_http_compile_complex_value_t));

     ccv.cf = cf;
     ccv.value = &value[1];
     ccv.complex_value = &hcf->key;

     if (ngx_http_compile_complex_value(&ccv) != NGX_OK) {
         return NGX_CONF_ERROR;
     }

     uscf = ngx_http_conf_get_module_srv_conf(cf, ngx_http_upstream_module);

     if (uscf->peer.init_upstream) {
         ngx_conf_log_error(NGX_LOG_WARN, cf, 0,
                            "load balancing method redefined");
     }

     uscf->flags = NGX_HTTP_UPSTREAM_CREATE
                   |NGX_HTTP_UPSTREAM_WEIGHT
                   |NGX_HTTP_UPSTREAM_MAX_CONNS
                   |NGX_HTTP_UPSTREAM_MAX_FAILS
                   |NGX_HTTP_UPSTREAM_FAIL_TIMEOUT
                   |NGX_HTTP_UPSTREAM_DOWN;

     if (cf->args->nelts == 2) {
         uscf->peer.init_upstream = ngx_http_upstream_init_hash;

     } else if (ngx_strcmp(value[2].data, "consistent") == 0) {
         uscf->peer.init_upstream = ngx_http_upstream_init_chash;

     } else {
         ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
                            "invalid parameter \"%V\"", &value[2]);
         return NGX_CONF_ERROR;
     }

     return NGX_CONF_OK;
 }

	/*
	* Copyright (C) Roman Arutyunyan
	* Copyright (C) Nginx, Inc.
	*/


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


	typedef struct {
	uint32_t hash;
	ngx_str_t *server;
	} ngx_http_upstream_chash_point_t;


	typedef struct {
	ngx_uint_t number;
	ngx_http_upstream_chash_point_t point[1];
	} ngx_http_upstream_chash_points_t;


	typedef struct {
	ngx_http_complex_value_t key;
	ngx_http_upstream_chash_points_t *points;
	} ngx_http_upstream_hash_srv_conf_t;


	typedef struct {
	/* the round robin data must be first */
	ngx_http_upstream_rr_peer_data_t rrp;
	ngx_http_upstream_hash_srv_conf_t *conf;
	ngx_str_t key;
	ngx_uint_t tries;
	ngx_uint_t rehash;
	uint32_t hash;
	ngx_event_get_peer_pt get_rr_peer;
	} ngx_http_upstream_hash_peer_data_t;


	static ngx_int_t ngx_http_upstream_init_hash(ngx_conf_t *cf,
	ngx_http_upstream_srv_conf_t *us);
	static ngx_int_t ngx_http_upstream_init_hash_peer(ngx_http_request_t *r,
	ngx_http_upstream_srv_conf_t *us);
	static ngx_int_t ngx_http_upstream_get_hash_peer(ngx_peer_connection_t *pc,
	void *data);

	static ngx_int_t ngx_http_upstream_init_chash(ngx_conf_t *cf,
	ngx_http_upstream_srv_conf_t *us);
	static int ngx_libc_cdecl
	ngx_http_upstream_chash_cmp_points(const void one, const void two);
	static ngx_uint_t ngx_http_upstream_find_chash_point(
	ngx_http_upstream_chash_points_t *points, uint32_t hash);
	static ngx_int_t ngx_http_upstream_init_chash_peer(ngx_http_request_t *r,
	ngx_http_upstream_srv_conf_t *us);
	static ngx_int_t ngx_http_upstream_get_chash_peer(ngx_peer_connection_t *pc,
	void *data);

	static void ngx_http_upstream_hash_create_conf(ngx_conf_t cf);
	static char ngx_http_upstream_hash(ngx_conf_t cf, ngx_command_t *cmd,
	void *conf);


	static ngx_command_t ngx_http_upstream_hash_commands[] = {

	{ ngx_string("hash"),
	NGX_HTTP_UPS_CONF\|NGX_CONF_TAKE12,
	ngx_http_upstream_hash,
	NGX_HTTP_SRV_CONF_OFFSET,
	0,
	NULL },

	ngx_null_command
	};


	static ngx_http_module_t ngx_http_upstream_hash_module_ctx = {
	NULL, /* preconfiguration */
	NULL, /* postconfiguration */

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

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

	NULL, /* create location configuration */
	NULL /* merge location configuration */
	};


	ngx_module_t ngx_http_upstream_hash_module = {
	NGX_MODULE_V1,
	&ngx_http_upstream_hash_module_ctx, /* module context */
	ngx_http_upstream_hash_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_upstream_init_hash(ngx_conf_t cf, ngx_http_upstream_srv_conf_t us)
	{
	if (ngx_http_upstream_init_round_robin(cf, us) != NGX_OK) {
	return NGX_ERROR;
	}

	us->peer.init = ngx_http_upstream_init_hash_peer;

	return NGX_OK;
	}


	static ngx_int_t
	ngx_http_upstream_init_hash_peer(ngx_http_request_t *r,
	ngx_http_upstream_srv_conf_t *us)
	{
	ngx_http_upstream_hash_srv_conf_t *hcf;
	ngx_http_upstream_hash_peer_data_t *hp;

	hp = ngx_palloc(r->pool, sizeof(ngx_http_upstream_hash_peer_data_t));
	if (hp == NULL) {
	return NGX_ERROR;
	}

	r->upstream->peer.data = &hp->rrp;

	if (ngx_http_upstream_init_round_robin_peer(r, us) != NGX_OK) {
	return NGX_ERROR;
	}

	r->upstream->peer.get = ngx_http_upstream_get_hash_peer;

	hcf = ngx_http_conf_upstream_srv_conf(us, ngx_http_upstream_hash_module);

	if (ngx_http_complex_value(r, &hcf->key, &hp->key) != NGX_OK) {
	return NGX_ERROR;
	}

	ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
	"upstream hash key:\"%V\"", &hp->key);

	hp->conf = hcf;
	hp->tries = 0;
	hp->rehash = 0;
	hp->hash = 0;
	hp->get_rr_peer = ngx_http_upstream_get_round_robin_peer;

	return NGX_OK;
	}


	static ngx_int_t
	ngx_http_upstream_get_hash_peer(ngx_peer_connection_t pc, void data)
	{
	ngx_http_upstream_hash_peer_data_t *hp = data;

	time_t now;
	u_char buf[NGX_INT_T_LEN];
	size_t size;
	uint32_t hash;
	ngx_int_t w;
	uintptr_t m;
	ngx_uint_t n, p;
	ngx_http_upstream_rr_peer_t *peer;

	ngx_log_debug1(NGX_LOG_DEBUG_HTTP, pc->log, 0,
	"get hash peer, try: %ui", pc->tries);

	ngx_http_upstream_rr_peers_rlock(hp->rrp.peers);

	if (hp->tries > 20 \|\| hp->rrp.peers->single) {
	ngx_http_upstream_rr_peers_unlock(hp->rrp.peers);
	return hp->get_rr_peer(pc, &hp->rrp);
	}

	now = ngx_time();

	pc->cached = 0;
	pc->connection = NULL;

	for ( ;; ) {

	/*
	* Hash expression is compatible with Cache::Memcached:
	* ((crc32([REHASH] KEY) >> 16) & 0x7fff) + PREV_HASH
	* with REHASH omitted at the first iteration.
	*/

	ngx_crc32_init(hash);

	if (hp->rehash > 0) {
	size = ngx_sprintf(buf, "%ui", hp->rehash) - buf;
	ngx_crc32_update(&hash, buf, size);
	}

	ngx_crc32_update(&hash, hp->key.data, hp->key.len);
	ngx_crc32_final(hash);

	hash = (hash >> 16) & 0x7fff;

	hp->hash += hash;
	hp->rehash++;

	w = hp->hash % hp->rrp.peers->total_weight;
	peer = hp->rrp.peers->peer;
	p = 0;

	while (w >= peer->weight) {
	w -= peer->weight;
	peer = peer->next;
	p++;
	}

	n = p / (8 * sizeof(uintptr_t));
	m = (uintptr_t) 1 << p % (8 * sizeof(uintptr_t));

	if (hp->rrp.tried[n] & m) {
	goto next;
	}

	ngx_http_upstream_rr_peer_lock(hp->rrp.peers, peer);

	ngx_log_debug2(NGX_LOG_DEBUG_HTTP, pc->log, 0,
	"get hash peer, value:%uD, peer:%ui", hp->hash, p);

	if (peer->down) {
	ngx_http_upstream_rr_peer_unlock(hp->rrp.peers, peer);
	goto next;
	}

	if (peer->max_fails
	&& peer->fails >= peer->max_fails
	&& now - peer->checked <= peer->fail_timeout)
	{
	ngx_http_upstream_rr_peer_unlock(hp->rrp.peers, peer);
	goto next;
	}

	if (peer->max_conns && peer->conns >= peer->max_conns) {
	ngx_http_upstream_rr_peer_unlock(hp->rrp.peers, peer);
	goto next;
	}

	break;

	next:

	if (++hp->tries > 20) {
	ngx_http_upstream_rr_peers_unlock(hp->rrp.peers);
	return hp->get_rr_peer(pc, &hp->rrp);
	}
	}

	hp->rrp.current = peer;

	pc->sockaddr = peer->sockaddr;
	pc->socklen = peer->socklen;
	pc->name = &peer->name;

	peer->conns++;

	if (now - peer->checked > peer->fail_timeout) {
	peer->checked = now;
	}

	ngx_http_upstream_rr_peer_unlock(hp->rrp.peers, peer);
	ngx_http_upstream_rr_peers_unlock(hp->rrp.peers);

	hp->rrp.tried[n] \|= m;

	return NGX_OK;
	}


	static ngx_int_t
	ngx_http_upstream_init_chash(ngx_conf_t cf, ngx_http_upstream_srv_conf_t us)
	{
	u_char host, port, c;
	size_t host_len, port_len, size;
	uint32_t hash, base_hash;
	ngx_str_t *server;
	ngx_uint_t npoints, i, j;
	ngx_http_upstream_rr_peer_t *peer;
	ngx_http_upstream_rr_peers_t *peers;
	ngx_http_upstream_chash_points_t *points;
	ngx_http_upstream_hash_srv_conf_t *hcf;
	union {
	uint32_t value;
	u_char byte[4];
	} prev_hash;

	if (ngx_http_upstream_init_round_robin(cf, us) != NGX_OK) {
	return NGX_ERROR;
	}

	us->peer.init = ngx_http_upstream_init_chash_peer;

	peers = us->peer.data;
	npoints = peers->total_weight * 160;

	size = sizeof(ngx_http_upstream_chash_points_t)
	+ sizeof(ngx_http_upstream_chash_point_t) * (npoints - 1);

	points = ngx_palloc(cf->pool, size);
	if (points == NULL) {
	return NGX_ERROR;
	}

	points->number = 0;

	for (peer = peers->peer; peer; peer = peer->next) {
	server = &peer->server;

	/*
	* Hash expression is compatible with Cache::Memcached::Fast:
	* crc32(HOST \0 PORT PREV_HASH).
	*/

	if (server->len >= 5
	&& ngx_strncasecmp(server->data, (u_char *) "unix:", 5) == 0)
	{
	host = server->data + 5;
	host_len = server->len - 5;
	port = NULL;
	port_len = 0;
	goto done;
	}

	for (j = 0; j < server->len; j++) {
	c = server->data[server->len - j - 1];

	if (c == ':') {
	host = server->data;
	host_len = server->len - j - 1;
	port = server->data + server->len - j;
	port_len = j;
	goto done;
	}

	if (c < '0' \|\| c > '9') {
	break;
	}
	}

	host = server->data;
	host_len = server->len;
	port = NULL;
	port_len = 0;

	done:

	ngx_crc32_init(base_hash);
	ngx_crc32_update(&base_hash, host, host_len);
	ngx_crc32_update(&base_hash, (u_char *) "", 1);
	ngx_crc32_update(&base_hash, port, port_len);

	prev_hash.value = 0;
	npoints = peer->weight * 160;

	for (j = 0; j < npoints; j++) {
	hash = base_hash;

	ngx_crc32_update(&hash, prev_hash.byte, 4);
	ngx_crc32_final(hash);

	points->point[points->number].hash = hash;
	points->point[points->number].server = server;
	points->number++;

	#if (NGX_HAVE_LITTLE_ENDIAN)
	prev_hash.value = hash;
	#else
	prev_hash.byte[0] = (u_char) (hash & 0xff);
	prev_hash.byte[1] = (u_char) ((hash >> 8) & 0xff);
	prev_hash.byte[2] = (u_char) ((hash >> 16) & 0xff);
	prev_hash.byte[3] = (u_char) ((hash >> 24) & 0xff);
	#endif
	}
	}

	ngx_qsort(points->point,
	points->number,
	sizeof(ngx_http_upstream_chash_point_t),
	ngx_http_upstream_chash_cmp_points);

	for (i = 0, j = 1; j < points->number; j++) {
	if (points->point[i].hash != points->point[j].hash) {
	points->point[++i] = points->point[j];
	}
	}

	points->number = i + 1;

	hcf = ngx_http_conf_upstream_srv_conf(us, ngx_http_upstream_hash_module);
	hcf->points = points;

	return NGX_OK;
	}


	static int ngx_libc_cdecl
	ngx_http_upstream_chash_cmp_points(const void one, const void two)
	{
	ngx_http_upstream_chash_point_t *first =
	(ngx_http_upstream_chash_point_t *) one;
	ngx_http_upstream_chash_point_t *second =
	(ngx_http_upstream_chash_point_t *) two;

	if (first->hash < second->hash) {
	return -1;

	} else if (first->hash > second->hash) {
	return 1;

	} else {
	return 0;
	}
	}


	static ngx_uint_t
	ngx_http_upstream_find_chash_point(ngx_http_upstream_chash_points_t *points,
	uint32_t hash)
	{
	ngx_uint_t i, j, k;
	ngx_http_upstream_chash_point_t *point;

	/* find first point >= hash */

	point = &points->point[0];

	i = 0;
	j = points->number;

	while (i < j) {
	k = (i + j) / 2;

	if (hash > point[k].hash) {
	i = k + 1;

	} else if (hash < point[k].hash) {
	j = k;

	} else {
	return k;
	}
	}

	return i;
	}


	static ngx_int_t
	ngx_http_upstream_init_chash_peer(ngx_http_request_t *r,
	ngx_http_upstream_srv_conf_t *us)
	{
	uint32_t hash;
	ngx_http_upstream_hash_srv_conf_t *hcf;
	ngx_http_upstream_hash_peer_data_t *hp;

	if (ngx_http_upstream_init_hash_peer(r, us) != NGX_OK) {
	return NGX_ERROR;
	}

	r->upstream->peer.get = ngx_http_upstream_get_chash_peer;

	hp = r->upstream->peer.data;
	hcf = ngx_http_conf_upstream_srv_conf(us, ngx_http_upstream_hash_module);

	hash = ngx_crc32_long(hp->key.data, hp->key.len);

	ngx_http_upstream_rr_peers_rlock(hp->rrp.peers);

	hp->hash = ngx_http_upstream_find_chash_point(hcf->points, hash);

	ngx_http_upstream_rr_peers_unlock(hp->rrp.peers);

	return NGX_OK;
	}


	static ngx_int_t
	ngx_http_upstream_get_chash_peer(ngx_peer_connection_t pc, void data)
	{
	ngx_http_upstream_hash_peer_data_t *hp = data;

	time_t now;
	intptr_t m;
	ngx_str_t *server;
	ngx_int_t total;
	ngx_uint_t i, n, best_i;
	ngx_http_upstream_rr_peer_t peer, best;
	ngx_http_upstream_chash_point_t *point;
	ngx_http_upstream_chash_points_t *points;
	ngx_http_upstream_hash_srv_conf_t *hcf;

	ngx_log_debug1(NGX_LOG_DEBUG_HTTP, pc->log, 0,
	"get consistent hash peer, try: %ui", pc->tries);

	ngx_http_upstream_rr_peers_wlock(hp->rrp.peers);

	if (hp->tries > 20 \|\| hp->rrp.peers->single) {
	ngx_http_upstream_rr_peers_unlock(hp->rrp.peers);
	return hp->get_rr_peer(pc, &hp->rrp);
	}

	pc->cached = 0;
	pc->connection = NULL;

	now = ngx_time();
	hcf = hp->conf;

	points = hcf->points;
	point = &points->point[0];

	for ( ;; ) {
	server = point[hp->hash % points->number].server;

	ngx_log_debug2(NGX_LOG_DEBUG_HTTP, pc->log, 0,
	"consistent hash peer:%uD, server:\"%V\"",
	hp->hash, server);

	best = NULL;
	best_i = 0;
	total = 0;

	for (peer = hp->rrp.peers->peer, i = 0;
	peer;
	peer = peer->next, i++)
	{
	n = i / (8 * sizeof(uintptr_t));
	m = (uintptr_t) 1 << i % (8 * sizeof(uintptr_t));

	if (hp->rrp.tried[n] & m) {
	continue;
	}

	if (peer->down) {
	continue;
	}

	if (peer->max_fails
	&& peer->fails >= peer->max_fails
	&& now - peer->checked <= peer->fail_timeout)
	{
	continue;
	}

	if (peer->max_conns && peer->conns >= peer->max_conns) {
	continue;
	}

	if (peer->server.len != server->len
	\|\| ngx_strncmp(peer->server.data, server->data, server->len)
	!= 0)
	{
	continue;
	}

	peer->current_weight += peer->effective_weight;
	total += peer->effective_weight;

	if (peer->effective_weight < peer->weight) {
	peer->effective_weight++;
	}

	if (best == NULL \|\| peer->current_weight > best->current_weight) {
	best = peer;
	best_i = i;
	}
	}

	if (best) {
	best->current_weight -= total;
	goto found;
	}

	hp->hash++;
	hp->tries++;

	if (hp->tries > 20) {
	ngx_http_upstream_rr_peers_unlock(hp->rrp.peers);
	return hp->get_rr_peer(pc, &hp->rrp);
	}
	}

	found:

	hp->rrp.current = best;

	pc->sockaddr = best->sockaddr;
	pc->socklen = best->socklen;
	pc->name = &best->name;

	best->conns++;

	if (now - best->checked > best->fail_timeout) {
	best->checked = now;
	}

	ngx_http_upstream_rr_peers_unlock(hp->rrp.peers);

	n = best_i / (8 * sizeof(uintptr_t));
	m = (uintptr_t) 1 << best_i % (8 * sizeof(uintptr_t));

	hp->rrp.tried[n] \|= m;

	return NGX_OK;
	}


	static void *
	ngx_http_upstream_hash_create_conf(ngx_conf_t *cf)
	{
	ngx_http_upstream_hash_srv_conf_t *conf;

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

	conf->points = NULL;

	return conf;
	}


	static char *
	ngx_http_upstream_hash(ngx_conf_t cf, ngx_command_t cmd, void *conf)
	{
	ngx_http_upstream_hash_srv_conf_t *hcf = conf;

	ngx_str_t *value;
	ngx_http_upstream_srv_conf_t *uscf;
	ngx_http_compile_complex_value_t ccv;

	value = cf->args->elts;

	ngx_memzero(&ccv, sizeof(ngx_http_compile_complex_value_t));

	ccv.cf = cf;
	ccv.value = &value[1];
	ccv.complex_value = &hcf->key;

	if (ngx_http_compile_complex_value(&ccv) != NGX_OK) {
	return NGX_CONF_ERROR;
	}

	uscf = ngx_http_conf_get_module_srv_conf(cf, ngx_http_upstream_module);

	if (uscf->peer.init_upstream) {
	ngx_conf_log_error(NGX_LOG_WARN, cf, 0,
	"load balancing method redefined");
	}

	uscf->flags = NGX_HTTP_UPSTREAM_CREATE
	\|NGX_HTTP_UPSTREAM_WEIGHT
	\|NGX_HTTP_UPSTREAM_MAX_CONNS
	\|NGX_HTTP_UPSTREAM_MAX_FAILS
	\|NGX_HTTP_UPSTREAM_FAIL_TIMEOUT
	\|NGX_HTTP_UPSTREAM_DOWN;

	if (cf->args->nelts == 2) {
	uscf->peer.init_upstream = ngx_http_upstream_init_hash;

	} else if (ngx_strcmp(value[2].data, "consistent") == 0) {
	uscf->peer.init_upstream = ngx_http_upstream_init_chash;

	} else {
	ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
	"invalid parameter \"%V\"", &value[2]);
	return NGX_CONF_ERROR;
	}

	return NGX_CONF_OK;
	}