git.m6w6.name Git - awesomized/libmemcached/blob - libhashkit/ketama.cc

   1 /*  vim:expandtab:shiftwidth=2:tabstop=2:smarttab:
   2  *
   3  *  HashKit library
   4  *
   5  *  Copyright (C) 2011-2012 Data Differential, http://datadifferential.com/
   6  *  Copyright (C) 2006-2009 Brian Aker All rights reserved.
   7  *
   8  *  Redistribution and use in source and binary forms, with or without
   9  *  modification, are permitted provided that the following conditions are
  10  *  met:
  11  *
  12  *      * Redistributions of source code must retain the above copyright
  13  *  notice, this list of conditions and the following disclaimer.
  14  *
  15  *      * Redistributions in binary form must reproduce the above
  16  *  copyright notice, this list of conditions and the following disclaimer
  17  *  in the documentation and/or other materials provided with the
  18  *  distribution.
  19  *
  20  *      * The names of its contributors may not be used to endorse or
  21  *  promote products derived from this software without specific prior
  22  *  written permission.
  23  *
  24  *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  25  *  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  26  *  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  27  *  A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  28  *  OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  29  *  SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  30  *  LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  31  *  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  32  *  THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  33  *  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  34  *  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  35  *
  36  */
  37
  38
  39 #include <libhashkit/common.h>
  40 #include <math.h>
  41
  42 #if 0
  43 static uint32_t ketama_server_hash(const char *key, unsigned int key_length, int alignment)
  44 {
  45   unsigned char results[16];
  46
  47   md5_signature((unsigned char*)key, key_length, results);
  48   return ((uint32_t) (results[3 + alignment * 4] & 0xFF) << 24)
  49     | ((uint32_t) (results[2 + alignment * 4] & 0xFF) << 16)
  50     | ((uint32_t) (results[1 + alignment * 4] & 0xFF) << 8)
  51     | (results[0 + alignment * 4] & 0xFF);
  52 }
  53
  54 static int continuum_points_cmp(const void *t1, const void *t2)
  55 {
  56   hashkit_continuum_point_st *ct1= (hashkit_continuum_point_st *)t1;
  57   hashkit_continuum_point_st *ct2= (hashkit_continuum_point_st *)t2;
  58
  59   if (ct1->value == ct2->value)
  60     return 0;
  61   else if (ct1->value > ct2->value)
  62     return 1;
  63   else
  64     return -1;
  65 }
  66
  67 int update_continuum(hashkit_st *hashkit)
  68 {
  69   uint32_t count;
  70   uint32_t continuum_index= 0;
  71   uint32_t value;
  72   uint32_t points_index;
  73   uint32_t points_count= 0;
  74   uint32_t points_per_server;
  75   uint32_t points_per_hash;
  76   uint64_t total_weight= 0;
  77   uint32_t live_servers;
  78   uint8_t *context;
  79
  80   if (hashkit->active_fn != NULL || hashkit->weight_fn != NULL)
  81   {
  82     live_servers= 0;
  83
  84     for (count= 0, context= hashkit->list; count < hashkit->list_size;
  85          count++, context+= hashkit->context_size)
  86     {
  87       if (hashkit->active_fn != NULL)
  88       {
  89         if (hashkit->active_fn(context))
  90           live_servers++;
  91         else
  92           continue;
  93       }
  94
  95       if (hashkit->weight_fn != NULL)
  96         total_weight+= hashkit->weight_fn(context);
  97     }
  98   }
  99
 100   if (hashkit->active_fn == NULL)
 101     live_servers= (uint32_t)hashkit->list_size;
 102
 103   if (live_servers == 0)
 104     return 0;
 105
 106   if (hashkit->weight_fn == NULL)
 107   {
 108     points_per_server= HASHKIT_POINTS_PER_NODE;
 109     points_per_hash= 1;
 110   }
 111   else
 112   {
 113     points_per_server= HASHKIT_POINTS_PER_NODE_WEIGHTED;
 114     points_per_hash= 4;
 115   }
 116
 117   if (live_servers > hashkit->continuum_count)
 118   {
 119     hashkit_continuum_point_st *new_continuum;
 120
 121     new_continuum= realloc(hashkit->continuum,
 122                            sizeof(hashkit_continuum_point_st) *
 123                            (live_servers + HASHKIT_CONTINUUM_ADDITION) *
 124                            points_per_server);
 125
 126     if (new_continuum == NULL)
 127       return ENOMEM;
 128
 129     hashkit->continuum= new_continuum;
 130     hashkit->continuum_count= live_servers + HASHKIT_CONTINUUM_ADDITION;
 131   }
 132
 133   for (count= 0, context= hashkit->list; count < hashkit->list_size;
 134        count++, context+= hashkit->context_size)
 135   {
 136     if (hashkit->active_fn != NULL && hashkit->active_fn(context) == false)
 137       continue;
 138
 139     if (hashkit->weight_fn != NULL)
 140     {
 141         float pct = (float)hashkit->weight_fn(context) / (float)total_weight;
 142         points_per_server= (uint32_t) ((floorf((float) (pct * HASHKIT_POINTS_PER_NODE_WEIGHTED / 4 * (float)live_servers + 0.0000000001))) * 4);
 143     }
 144
 145     for (points_index= 0;
 146          points_index < points_per_server / points_per_hash;
 147          points_index++)
 148     {
 149       char sort_host[HASHKIT_CONTINUUM_KEY_SIZE]= "";
 150       size_t sort_host_length;
 151
 152       if (hashkit->continuum_key_fn == NULL)
 153       {
 154         sort_host_length= (size_t) snprintf(sort_host, HASHKIT_CONTINUUM_KEY_SIZE, "%u",
 155                                             points_index);
 156       }
 157       else
 158       {
 159         sort_host_length= hashkit->continuum_key_fn(sort_host, HASHKIT_CONTINUUM_KEY_SIZE,
 160                                                  points_index, context);
 161       }
 162
 163       if (hashkit->weight_fn == NULL)
 164       {
 165         if (hashkit->continuum_hash_fn == NULL)
 166           value= hashkit_default(sort_host, sort_host_length);
 167         else
 168           value= hashkit->continuum_hash_fn(sort_host, sort_host_length);
 169
 170         hashkit->continuum[continuum_index].index= count;
 171         hashkit->continuum[continuum_index++].value= value;
 172       }
 173       else
 174       {
 175         unsigned int i;
 176         for (i = 0; i < points_per_hash; i++)
 177         {
 178            value= ketama_server_hash(sort_host, (uint32_t) sort_host_length, (int) i);
 179            hashkit->continuum[continuum_index].index= count;
 180            hashkit->continuum[continuum_index++].value= value;
 181         }
 182       }
 183     }
 184
 185     points_count+= points_per_server;
 186   }
 187
 188   hashkit->continuum_points_count= points_count;
 189   qsort(hashkit->continuum, hashkit->continuum_points_count, sizeof(hashkit_continuum_point_st),
 190         continuum_points_cmp);
 191
 192   return 0;
 193 }
 194 #endif