git.m6w6.name Git - m6w6/libmemcached/blob - src/libmemcached/hash.cc

   1 /*
   2     +--------------------------------------------------------------------+
   3     | libmemcached - C/C++ Client Library for memcached                  |
   4     +--------------------------------------------------------------------+
   5     | Redistribution and use in source and binary forms, with or without |
   6     | modification, are permitted under the terms of the BSD license.    |
   7     | You should have received a copy of the license in a bundled file   |
   8     | named LICENSE; in case you did not receive a copy you can review   |
   9     | the terms online at: https://opensource.org/licenses/BSD-3-Clause  |
  10     +--------------------------------------------------------------------+
  11     | Copyright (c) 2006-2014 Brian Aker   https://datadifferential.com/ |
  12     | Copyright (c) 2020 Michael Wallner   <mike@php.net>                |
  13     +--------------------------------------------------------------------+
  14 */
  15
  16 #include "libmemcached/common.h"
  17
  18 #include <sys/time.h>
  19
  20 #include "libmemcached/virtual_bucket.h"
  21
  22 uint32_t memcached_generate_hash_value(const char *key, size_t key_length,
  23                                        memcached_hash_t hash_algorithm) {
  24   return libhashkit_digest(key, key_length, (hashkit_hash_algorithm_t) hash_algorithm);
  25 }
  26
  27 static inline uint32_t generate_hash(const Memcached *ptr, const char *key, size_t key_length) {
  28   return hashkit_digest(&ptr->hashkit, key, key_length);
  29 }
  30
  31 static uint32_t dispatch_host(const Memcached *ptr, uint32_t hash) {
  32   switch (ptr->distribution) {
  33   case MEMCACHED_DISTRIBUTION_CONSISTENT:
  34   case MEMCACHED_DISTRIBUTION_CONSISTENT_WEIGHTED:
  35   case MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA:
  36   case MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA_SPY: {
  37     uint32_t num = ptr->ketama.continuum_points_counter;
  38     WATCHPOINT_ASSERT(ptr->ketama.continuum);
  39
  40     memcached_continuum_item_st *begin, *end, *left, *right, *middle;
  41     begin = left = ptr->ketama.continuum;
  42     end = right = ptr->ketama.continuum + num;
  43
  44     while (left < right) {
  45       middle = left + (right - left) / 2;
  46       if (middle->value < hash)
  47         left = middle + 1;
  48       else
  49         right = middle;
  50     }
  51     if (right == end)
  52       right = begin;
  53     return right->index;
  54   }
  55   case MEMCACHED_DISTRIBUTION_MODULA:
  56     return hash % memcached_server_count(ptr);
  57   case MEMCACHED_DISTRIBUTION_RANDOM:
  58     return (uint32_t) random() % memcached_server_count(ptr);
  59   case MEMCACHED_DISTRIBUTION_VIRTUAL_BUCKET: {
  60     return memcached_virtual_bucket_get(ptr, hash);
  61   }
  62   default:
  63   case MEMCACHED_DISTRIBUTION_CONSISTENT_MAX:
  64     WATCHPOINT_ASSERT(0); /* We have added a distribution without extending the logic */
  65     return hash % memcached_server_count(ptr);
  66   }
  67   /* NOTREACHED */
  68 }
  69
  70 /*
  71   One version is public and will not modify the distribution hash, the other will.
  72 */
  73 static inline uint32_t _generate_hash_wrapper(const Memcached *ptr, const char *key,
  74                                               size_t key_length) {
  75   WATCHPOINT_ASSERT(memcached_server_count(ptr));
  76
  77   if (memcached_server_count(ptr) == 1)
  78     return 0;
  79
  80   if (ptr->flags.hash_with_namespace) {
  81     size_t temp_length = memcached_array_size(ptr->_namespace) + key_length;
  82     char temp[MEMCACHED_MAX_KEY];
  83
  84     if (temp_length > MEMCACHED_MAX_KEY - 1)
  85       return 0;
  86
  87     strncpy(temp, memcached_array_string(ptr->_namespace), memcached_array_size(ptr->_namespace));
  88     strncpy(temp + memcached_array_size(ptr->_namespace), key, key_length);
  89
  90     return generate_hash(ptr, temp, temp_length);
  91   } else {
  92     return generate_hash(ptr, key, key_length);
  93   }
  94 }
  95
  96 static inline void _regen_for_auto_eject(Memcached *ptr) {
  97   if (_is_auto_eject_host(ptr) && ptr->ketama.next_distribution_rebuild) {
  98     struct timeval now;
  99
 100     if (gettimeofday(&now, NULL) == 0 and now.tv_sec > ptr->ketama.next_distribution_rebuild) {
 101       run_distribution(ptr);
 102     }
 103   }
 104 }
 105
 106 void memcached_autoeject(memcached_st *ptr) {
 107   _regen_for_auto_eject(ptr);
 108 }
 109
 110 uint32_t memcached_generate_hash_with_redistribution(memcached_st *ptr, const char *key,
 111                                                      size_t key_length) {
 112   uint32_t hash = _generate_hash_wrapper(ptr, key, key_length);
 113
 114   _regen_for_auto_eject(ptr);
 115
 116   return dispatch_host(ptr, hash);
 117 }
 118
 119 uint32_t memcached_generate_hash(const memcached_st *shell, const char *key, size_t key_length) {
 120   const Memcached *ptr = memcached2Memcached(shell);
 121   if (ptr) {
 122     return dispatch_host(ptr, _generate_hash_wrapper(ptr, key, key_length));
 123   }
 124
 125   return UINT32_MAX;
 126 }
 127
 128 const hashkit_st *memcached_get_hashkit(const memcached_st *shell) {
 129   const Memcached *ptr = memcached2Memcached(shell);
 130   if (ptr) {
 131     return &ptr->hashkit;
 132   }
 133
 134   return NULL;
 135 }
 136
 137 memcached_return_t memcached_set_hashkit(memcached_st *shell, hashkit_st *hashk) {
 138   Memcached *self = memcached2Memcached(shell);
 139   if (self) {
 140     hashkit_free(&self->hashkit);
 141     hashkit_clone(&self->hashkit, hashk);
 142
 143     return MEMCACHED_SUCCESS;
 144   }
 145
 146   return MEMCACHED_INVALID_ARGUMENTS;
 147 }
 148
 149 const char *libmemcached_string_hash(memcached_hash_t type) {
 150   return libhashkit_string_hash((hashkit_hash_algorithm_t) type);
 151 }