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 #include "libmemcached/virtual_bucket.h"
  18 #include "p9y/gettimeofday.hpp"
  19 #include "p9y/random.hpp"
  20
  21 uint32_t memcached_generate_hash_value(const char *key, size_t key_length,
  22                                        memcached_hash_t hash_algorithm) {
  23   return libhashkit_digest(key, key_length, (hashkit_hash_algorithm_t) hash_algorithm);
  24 }
  25
  26 static inline uint32_t generate_hash(const Memcached *ptr, const char *key, size_t key_length) {
  27   return hashkit_digest(&ptr->hashkit, key, key_length);
  28 }
  29
  30 static uint32_t dispatch_host(const Memcached *ptr, uint32_t hash) {
  31   switch (ptr->distribution) {
  32   case MEMCACHED_DISTRIBUTION_CONSISTENT:
  33   case MEMCACHED_DISTRIBUTION_CONSISTENT_WEIGHTED:
  34   case MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA:
  35   case MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA_SPY: {
  36     uint32_t num = ptr->ketama.continuum_points_counter;
  37     WATCHPOINT_ASSERT(ptr->ketama.continuum);
  38
  39     memcached_continuum_item_st *begin, *end, *left, *right, *middle;
  40     begin = left = ptr->ketama.continuum;
  41     end = right = ptr->ketama.continuum + num;
  42
  43     while (left < right) {
  44       middle = left + (right - left) / 2;
  45       if (middle->value < hash)
  46         left = middle + 1;
  47       else
  48         right = middle;
  49     }
  50     if (right == end)
  51       right = begin;
  52     return right->index;
  53   }
  54   case MEMCACHED_DISTRIBUTION_MODULA:
  55     return hash % memcached_server_count(ptr);
  56   case MEMCACHED_DISTRIBUTION_RANDOM:
  57     return (uint32_t) random() % memcached_server_count(ptr);
  58   case MEMCACHED_DISTRIBUTION_VIRTUAL_BUCKET: {
  59     return memcached_virtual_bucket_get(ptr, hash);
  60   }
  61   default:
  62   case MEMCACHED_DISTRIBUTION_CONSISTENT_MAX:
  63     WATCHPOINT_ASSERT(0); /* We have added a distribution without extending the logic */
  64     return hash % memcached_server_count(ptr);
  65   }
  66   /* NOTREACHED */
  67 }
  68
  69 /*
  70   One version is public and will not modify the distribution hash, the other will.
  71 */
  72 static inline uint32_t _generate_hash_wrapper(const Memcached *ptr, const char *key,
  73                                               size_t key_length) {
  74   WATCHPOINT_ASSERT(memcached_server_count(ptr));
  75
  76   if (memcached_server_count(ptr) == 1)
  77     return 0;
  78
  79   if (ptr->flags.hash_with_namespace) {
  80     size_t temp_length = memcached_array_size(ptr->_namespace) + key_length;
  81     char temp[MEMCACHED_MAX_KEY];
  82
  83     if (temp_length > MEMCACHED_MAX_KEY - 1)
  84       return 0;
  85
  86     strncpy(temp, memcached_array_string(ptr->_namespace), memcached_array_size(ptr->_namespace));
  87     strncpy(temp + memcached_array_size(ptr->_namespace), key, key_length);
  88
  89     return generate_hash(ptr, temp, temp_length);
  90   } else {
  91     return generate_hash(ptr, key, key_length);
  92   }
  93 }
  94
  95 static inline void _regen_for_auto_eject(Memcached *ptr) {
  96   if (_is_auto_eject_host(ptr) && ptr->ketama.next_distribution_rebuild) {
  97     struct timeval now;
  98
  99     if (gettimeofday(&now, NULL) == 0 and now.tv_sec > ptr->ketama.next_distribution_rebuild) {
 100       run_distribution(ptr);
 101     }
 102   }
 103 }
 104
 105 void memcached_autoeject(memcached_st *ptr) {
 106   _regen_for_auto_eject(ptr);
 107 }
 108
 109 uint32_t memcached_generate_hash_with_redistribution(memcached_st *ptr, const char *key,
 110                                                      size_t key_length) {
 111   uint32_t hash = _generate_hash_wrapper(ptr, key, key_length);
 112
 113   _regen_for_auto_eject(ptr);
 114
 115   return dispatch_host(ptr, hash);
 116 }
 117
 118 uint32_t memcached_generate_hash(const memcached_st *shell, const char *key, size_t key_length) {
 119   const Memcached *ptr = memcached2Memcached(shell);
 120   if (ptr) {
 121     return dispatch_host(ptr, _generate_hash_wrapper(ptr, key, key_length));
 122   }
 123
 124   return UINT32_MAX;
 125 }
 126
 127 const hashkit_st *memcached_get_hashkit(const memcached_st *shell) {
 128   const Memcached *ptr = memcached2Memcached(shell);
 129   if (ptr) {
 130     return &ptr->hashkit;
 131   }
 132
 133   return NULL;
 134 }
 135
 136 memcached_return_t memcached_set_hashkit(memcached_st *shell, hashkit_st *hashk) {
 137   Memcached *self = memcached2Memcached(shell);
 138   if (self) {
 139     hashkit_free(&self->hashkit);
 140     hashkit_clone(&self->hashkit, hashk);
 141
 142     return MEMCACHED_SUCCESS;
 143   }
 144
 145   return MEMCACHED_INVALID_ARGUMENTS;
 146 }
 147
 148 const char *libmemcached_string_hash(memcached_hash_t type) {
 149   return libhashkit_string_hash((hashkit_hash_algorithm_t) type);
 150 }