追踪分布式Memcached默认的一致性hash算法

<?php
/**
*生成100个数据到memcache里。能够思考下，数据会怎么存储
*/
$memClient = new Memcached();
$memClient->addServers(array(’10.21.1.11’,’11233’),array(’10.21.1.12’,’11233’));
for($i = 0;$i < 100;$i++){
     $memClicent->set(“prefix_key_”.$i,$i,3600);
}

<?php
$memClient = new Memcached();
$memClient->addServers(array(’10.21.1.11’,’11233’),array(’10.21.1.12’,’11233’));
for($i = 0;$i < 100;$i++){
     $memClicent->get(“prefix_key_”.$i);
}

PHP_METHOD(Memcached, set)
{
    php_memc_store_impl(INTERNAL_FUNCTION_PARAM_PASSTHRU, MEMC_OP_SET, 0);
}

status = memcached_set(m_obj->memc, key, key_len, payload, payload_len, expiration, flags);

uint32_t server_key= memcached_generate_hash_with_redistribution(ptr, group_key, group_key_length);
memcached_instance_st* instance= memcached_instance_fetch(ptr, server_key);

return hashkit_digest(&ptr->hashkit, key, key_length);

return self->base_hash.function(key, key_length, self->base_hash.context);

status = memcached_set(m_obj->memc, key, key_len, payload, payload_len, expiration, flags);

m_obj->memc->hashkit->base_hash.function(key, key_length, self->base_hash.context);

typedef struct {
	zend_object zo;

	struct memc_obj {
		memcached_st *memc;
		zend_bool compression;
		enum memcached_serializer serializer;
		enum memcached_compression_type compression_type;
#if HAVE_MEMCACHED_SASL
		zend_bool has_sasl_data;
#endif
		long store_retry_count;
	} *obj;

	zend_bool is_persistent;
	zend_bool is_pristine;
	int rescode;
	int memc_errno;
} php_memc_t;

struct hashkit_st
{
  struct hashkit_function_st {
    hashkit_hash_fn function;
    void *context;
  } base_hash, distribution_hash;

  struct {
    bool is_base_same_distributed:1;
  } flags;

  struct {
    bool is_allocated:1;
  } options;

  void *_key;
};

  if (hashkit_create(&self->hashkit) == NULL)
  {
    return false;
  }

static inline void _hashkit_init(hashkit_st *self)
{
  self->base_hash.function= hashkit_one_at_a_time;
  self->base_hash.context= NULL;

  self->distribution_hash.function= hashkit_one_at_a_time;
  self->distribution_hash.context= NULL;

  self->flags.is_base_same_distributed= true;
  self->_key= NULL;
}

#include <libhashkit/common.h>

uint32_t hashkit_one_at_a_time(const char *key, size_t key_length, void *context)
{
  const char *ptr= key;
  uint32_t value= 0;
  (void)context;

  while (key_length--)
  {
    uint32_t val= (uint32_t) *ptr++;
    value += val;
    value += (value << 10);
    value ^= (value >> 6);
  }
  value += (value << 3);
  value ^= (value >> 11);
  value += (value << 15);

  return value;
}