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 #if HAVE_SYS_TIME_H
  19 #  include <sys/time.h>
  20 #endif
  21 #include <time.h>
  22
  23 #include "libmemcached/virtual_bucket.h"
  24
  25 uint32_t memcached_generate_hash_value(const char *key, size_t key_length,
  26                                        memcached_hash_t hash_algorithm) {
  27   return libhashkit_digest(key, key_length, (hashkit_hash_algorithm_t) hash_algorithm);
  28 }
  29
  30 static inline uint32_t generate_hash(const Memcached *ptr, const char *key, size_t key_length) {
  31   return hashkit_digest(&ptr->hashkit, key, key_length);
  32 }
  33
  34 static uint32_t dispatch_host(const Memcached *ptr, uint32_t hash) {
  35   switch (ptr->distribution) {
  36   case MEMCACHED_DISTRIBUTION_CONSISTENT:
  37   case MEMCACHED_DISTRIBUTION_CONSISTENT_WEIGHTED:
  38   case MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA:
  39   case MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA_SPY: {
  40     uint32_t num = ptr->ketama.continuum_points_counter;
  41     WATCHPOINT_ASSERT(ptr->ketama.continuum);
  42
  43     memcached_continuum_item_st *begin, *end, *left, *right, *middle;
  44     begin = left = ptr->ketama.continuum;
  45     end = right = ptr->ketama.continuum + num;
  46
  47     while (left < right) {
  48       middle = left + (right - left) / 2;
  49       if (middle->value < hash)
  50         left = middle + 1;
  51       else
  52         right = middle;
  53     }
  54     if (right == end)
  55       right = begin;
  56     return right->index;
  57   }
  58   case MEMCACHED_DISTRIBUTION_MODULA:
  59     return hash % memcached_server_count(ptr);
  60   case MEMCACHED_DISTRIBUTION_RANDOM:
  61     return (uint32_t) random() % memcached_server_count(ptr);
  62   case MEMCACHED_DISTRIBUTION_VIRTUAL_BUCKET: {
  63     return memcached_virtual_bucket_get(ptr, hash);
  64   }
  65   default:
  66   case MEMCACHED_DISTRIBUTION_CONSISTENT_MAX:
  67     WATCHPOINT_ASSERT(0); /* We have added a distribution without extending the logic */
  68     return hash % memcached_server_count(ptr);
  69   }
  70   /* NOTREACHED */
  71 }
  72
  73 /*
  74   One version is public and will not modify the distribution hash, the other will.
  75 */
  76 static inline uint32_t _generate_hash_wrapper(const Memcached *ptr, const char *key,
  77                                               size_t key_length) {
  78   WATCHPOINT_ASSERT(memcached_server_count(ptr));
  79
  80   if (memcached_server_count(ptr) == 1)
  81     return 0;
  82
  83   if (ptr->flags.hash_with_namespace) {
  84     size_t temp_length = memcached_array_size(ptr->_namespace) + key_length;
  85     char temp[MEMCACHED_MAX_KEY];
  86
  87     if (temp_length > MEMCACHED_MAX_KEY - 1)
  88       return 0;
  89
  90     strncpy(temp, memcached_array_string(ptr->_namespace), memcached_array_size(ptr->_namespace));
  91     strncpy(temp + memcached_array_size(ptr->_namespace), key, key_length);
  92
  93     return generate_hash(ptr, temp, temp_length);
  94   } else {
  95     return generate_hash(ptr, key, key_length);
  96   }
  97 }
  98
  99 static inline void _regen_for_auto_eject(Memcached *ptr) {
 100   if (_is_auto_eject_host(ptr) && ptr->ketama.next_distribution_rebuild) {
 101     struct timeval now;
 102
 103     if (gettimeofday(&now, NULL) == 0 and now.tv_sec > ptr->ketama.next_distribution_rebuild) {
 104       run_distribution(ptr);
 105     }
 106   }
 107 }
 108
 109 void memcached_autoeject(memcached_st *ptr) {
 110   _regen_for_auto_eject(ptr);
 111 }
 112
 113 uint32_t memcached_generate_hash_with_redistribution(memcached_st *ptr, const char *key,
 114                                                      size_t key_length) {
 115   uint32_t hash = _generate_hash_wrapper(ptr, key, key_length);
 116
 117   _regen_for_auto_eject(ptr);
 118
 119   return dispatch_host(ptr, hash);
 120 }
 121
 122 uint32_t memcached_generate_hash(const memcached_st *shell, const char *key, size_t key_length) {
 123   const Memcached *ptr = memcached2Memcached(shell);
 124   if (ptr) {
 125     return dispatch_host(ptr, _generate_hash_wrapper(ptr, key, key_length));
 126   }
 127
 128   return UINT32_MAX;
 129 }
 130
 131 const hashkit_st *memcached_get_hashkit(const memcached_st *shell) {
 132   const Memcached *ptr = memcached2Memcached(shell);
 133   if (ptr) {
 134     return &ptr->hashkit;
 135   }
 136
 137   return NULL;
 138 }
 139
 140 memcached_return_t memcached_set_hashkit(memcached_st *shell, hashkit_st *hashk) {
 141   Memcached *self = memcached2Memcached(shell);
 142   if (self) {
 143     hashkit_free(&self->hashkit);
 144     hashkit_clone(&self->hashkit, hashk);
 145
 146     return MEMCACHED_SUCCESS;
 147   }
 148
 149   return MEMCACHED_INVALID_ARGUMENTS;
 150 }
 151
 152 const char *libmemcached_string_hash(memcached_hash_t type) {
 153   return libhashkit_string_hash((hashkit_hash_algorithm_t) type);
 154 }