linux c/c++ 单机和集群memcached客户端

memcached 是一个高性能内存缓存，在作为缓存，不需要持久化的场性能稳定，由于现在服务器内存较大，很多应用场景单台memcached就能满足业务需求，普通的官方c API

就能满足需求。

而大型的应用数据量很大，也应该考虑单点故障，集群化可以分散压力，单点故障影响较小。集群的管理通常有两种方式：1.普通hash 2.一致性hash

1.普通hash实现相对简单，效率更高，但是不能动态扩展，这种能满足业务数据不是经常扩展比较固定的场景，单点故障影响不大，这种长期其实很多。通常的mysql + memcached 架构很适合这种方式

2.一致性哈希的优点就是可以动态扩展，适合业务数据持续增长的场景，实现相对复杂，通常需要代理服务器管理

下面是自己实现的基于hash的memcached 集群c++客户端代码，经过线上测试，性能和稳定性没有太大的问题。

/************************************************function: c++ mcached api author:liuyidate:2012.12.31version:3.0modify:2014.10.15*************************************************/#ifndef MULI_MEMCACHE_H#define MULI_MEMCACHE_H#include <iostream>#include <string>#include <vector>#include <map>#include <time.h>#include "libmemcached/memcached.h"using namespace std;typedef unsigned int(*hash_fun)(const char*);unsigned int rs_hash(const char *str)  {  unsigned int b = 378551;  unsigned int a = 63689;  unsigned int hash = 0;       while (*str)  {  hash = hash * a + (*str++);  a *= b;  }return (hash & 0x7FFFFFFF);  }struct memcache_info{string host;int port;};class single_memcached{public:single_memcached(){servers = NULL;memc = NULL;rc = MEMCACHED_SUCCESS;result_buff = NULL;}virtual ~single_memcached(){memcached_free(memc);delete []result_buff;}enum {MAX_VALUE_LEN = 1024*1024};bool init(const char*host, const int& port){result_buff = new char[MAX_VALUE_LEN];if(result_buff == NULL)return false;memc = memcached_create(NULL);servers = memcached_server_list_append(NULL, host, port, &rc);if(servers == NULL)return false;rc = memcached_server_push(memc, servers);if(rc == MEMCACHED_SUCCESS){memcached_server_free(servers);return true;}else{return false;}}//插入或者覆盖原有数据 expiration为有效时间，默认0为一直有效bool set(const char* key, const char* value, time_t expiration = 0){rc = memcached_set(memc, key, strlen(key), value, strlen(value), expiration, 0);return rc == MEMCACHED_SUCCESS;}//删除数据 expiration为有效时间，默认0为立即生效bool delete_k_v(const char* key, time_t expiration = 0){rc = memcached_delete(memc, key, strlen(key), expiration);return  rc == MEMCACHED_SUCCESS;}char *get(const char* key){size_t value_len = 0;uint32_t flag = 0;char *ret = memcached_get(memc, key, strlen(key), &value_len, &flag, &rc);if(ret == NULL){return NULL;}memset(result_buff, 0, MAX_VALUE_LEN);if(value_len < MAX_VALUE_LEN){memcpy(result_buff, ret, value_len);free(ret);}return rc == MEMCACHED_SUCCESS && value_len < MAX_VALUE_LEN  ? result_buff : NULL;}private:memcached_server_st *servers;memcached_st *memc;memcached_return rc;char *result_buff;};class mulit_memcached{public:mulit_memcached(){memcache_servers.clear();memcache_servers_id.clear();}virtual ~mulit_memcached(){}bool init(const vector<memcache_info>& memcache_info_vec, hash_fun hash = rs_hash){m_hash_fun = hash;memcache_servers.resize(memcache_info_vec.size());for(size_t i = 0; i < memcache_info_vec.size(); i++){char value[1024] = {0};snprintf(value, 1023, "%s#%d", memcache_info_vec[i].host.c_str(), memcache_info_vec[i].port);memcache_servers_id.insert(pair<unsigned int, string>(i, value));if(!memcache_servers[i].init(memcache_info_vec[i].host.c_str(), memcache_info_vec[i].port)){return false;}}return true;}bool set(const char* key, const char* value, time_t expiration = 0){unsigned int index = m_hash_fun(key) % memcache_servers.size();return memcache_servers[index].set(key, value, expiration);}bool delete_k_v(const char* key, time_t expiration = 0){unsigned int index = m_hash_fun(key) % memcache_servers.size();return memcache_servers[index].delete_k_v(key, expiration);}char *get(const char* key){unsigned int index = m_hash_fun(key) % memcache_servers.size();return memcache_servers[index].get(key);}string get_memcache_info(const char* key){unsigned int index = m_hash_fun(key) % memcache_servers.size();return memcache_servers_id[index];}private:vector<single_memcached> memcache_servers;map<unsigned int, string> memcache_servers_id;hash_fun m_hash_fun;};#endif

//test 

#include <iostream>#include <string>#include "memcache_api.h"using namespace std;unsigned int user_define_hash(const char *str)  {  unsigned int b = 378551;  unsigned int a = 63689;  unsigned int hash = 0;       while (*str)  {  hash = hash * a + (*str++);  a *= b;  }hash += 1;hash -= 1;return (hash & 0x7FFFFFFF);  }int main(int argc, char *argv[]){single_memcached mc;if(!mc.init("10.101.88.244", 11212)){cout<<"mc init error"<<endl;}char key[1024] = {0};char value[1024] = {"1"};if(!mc.set(key, value)){//cout<<"set error"<<endl;}for(int i = 0; i < 1000; i++){sprintf(key, "%d", i);if(!mc.set(key, key)){cout<<"error"<<endl;}if(mc.get(key))cout<<mc.get(key)<<endl;mc.delete_k_v(key);}memcache_info host_port;host_port.host = "10.101.88.244";host_port.port = 11211;vector<memcache_info> servers;servers.push_back(host_port);host_port.port = 11212;servers.push_back(host_port);mulit_memcached mulit_memcached_servers;if(!mulit_memcached_servers.init(servers))//if(!mulit_memcached_servers.init(servers, user_define_hash)){cout<<"init error"<<endl;}for(int i = 0; i < 1000; i++){char k[16] = {0};sprintf(k, "%d", i);//cout<<k<<endl;cout<<mulit_memcached_servers.set(k, k)<<endl;;cout<<mulit_memcached_servers.set(k, k, 100)<<endl;;if(mulit_memcached_servers.get(k))cout<<mulit_memcached_servers.get(k)<<endl;cout<<mulit_memcached_servers.delete_k_v(k)<<endl;cout<<mulit_memcached_servers.get_memcache_info(key)<<endl;//user for log}return 0;}