Zookeeper实践方案：（4）命名服务

1.基本介绍

命名服务是指通过指定的名字来获取资源或者服务的地址，提供者的信息。利用Zookeeper非常easy创建一个全局的路径，而这个路径就能够作为一个名字。它能够指向集群中的集群。提供的服务的地址，远程对象等。简单来说使用Zookeeper做命名服务就是用路径作为名字，路径上的数据就是其名字指向的实体。

阿里巴巴集团开源的分布式服务框架Dubbo中使用ZooKeeper来作为其命名服务，维护全局的服务地址列表。在Dubbo实现中：

服务提供者在启动的时候，向ZK上的指定节点/dubbo/${serviceName}/providers文件夹下写入自己的URL地址，这个操作就完毕了服务的公布。

服务消费者启动的时候。订阅/dubbo/{serviceName}/providers文件夹下的提供者URL地址， 并向/dubbo/{serviceName} /consumers文件夹下写入自己的URL地址。

注意，全部向ZK上注冊的地址都是暂时节点。这样就行保证服务提供者和消费者可以自己主动感应资源的变化。

另外，Dubbo还有针对服务粒度的监控。方法是订阅/dubbo/{serviceName}文件夹下全部提供者和消费者的信息。

场景实践

上面的介绍已经满具体。实际实现起来也比較easy。以下讲讲模拟程序的主要特点。模拟程序有3个參数

• -m 程序执行的方式，指定是服务提供者provider还是服务消费者consumer,或者是服务监控者monitor
• -n 表示服务名称
• -s 表示Zookeeper的服务地址IP:PORT
  执行命令例如以下：
  服务提供者：
  >nameservice -m provider -n query_bill -s172.17.0.36:2181
  服务消费者：
  >nameservice -m consumer -n query_bill -s172.17.0.36:2181
  服务监控者：
  >nameservice -m monitor -n query_bill -s172.17.0.36:2181

第一条命令是启动一个服务提供进程,它提供了一个名为query_bill的服务。程序首次执行时会创建
/NameService,/NameService/query_bill,/NameService/query_bill/provider,/NameService/query_bill/consumer/等几个路径。然后在服务提供进程在/NameService/query_bill/provider下创建暂时序列节点.

第二条命令是启动一个服务消费进程,它在/NameService/query_bill/consumer/下创建暂时序列节点，并watch/NameService/query_bill/provider的子节点变化事件。及时更新provider列表。

第三条命令是启动一个服务监控进程。它watch /NameService/query_bill/provider,/NameService/query_bill/consumer/两个路径的子节点变化，及时更新provider列表和comsumer列表。

完整的代码例如以下：

#include<stdio.h>  #include<string.h>  #include<unistd.h>#include <netinet/in.h>#include <netdb.h>#include <arpa/inet.h>#include"zookeeper.h"  #include"zookeeper_log.h"  enum MODE{PROVIDER_MODE,CONSUMER_MODE,MONITOR_MODE} g_mode;char g_host[512]= "172.17.0.36:2181";  char g_service[512]={ 0 };char g_path[512]="/NameService";//watch function when child list changedvoid zktest_watcher_g(zhandle_t* zh, int type, int state, const char* path, void* watcherCtx);//show all process ip:pidvoid show_list(zhandle_t *zkhandle,const char *path);//if success,the g_mode will become MODE_MONITORvoid choose_mater(zhandle_t *zkhandle,const char *path);//get localhost ip:pidvoid getlocalhost(char *ip_pid,int len);void print_usage();void get_option(int argc,const char* argv[]);/**********unitl*********************/  void print_usage(){    printf("Usage : [nameservice] [-h] [-m mode] [-n servicename] [-s ip:port] \n");    printf("        -h Show help\n");    printf("        -m set mode:provider,consumer,monitor\n");    printf("        -n set servicename\n");    printf("        -s server ip:port\n");    printf("For example:\n");    printf("    nameservice -m provider -n query_bill -s172.17.0.36:2181 \n");    printf("    nameservice -m consumer -n query_bill -s172.17.0.36:2181 \n");    printf("    nameservice -m monitor  -n query_bill -s172.17.0.36:2181 \n");}void get_option(int argc,const char* argv[]){    extern char    *optarg;    int            optch;    int            dem = 1;    const char    optstring[] = "hm:n:s:";    while((optch = getopt(argc , (char * const *)argv , optstring)) != -1 )    {        switch( optch )        {        case 'h':            print_usage();            exit(-1);        case '?':            print_usage();            printf("unknown parameter: %c\n", optopt);            exit(-1);        case ':':            print_usage();            printf("need parameter: %c\n", optopt);            exit(-1);        case 'm':            if (strcasecmp(optarg,"provider") == 0){                g_mode = PROVIDER_MODE;            }else if (strcasecmp(optarg,"consumer") == 0){                g_mode = CONSUMER_MODE;            }else{                g_mode = MONITOR_MODE;            }            break;        case 'n':            strncpy(g_service,optarg,sizeof(g_service));            break;        case 's':            strncpy(g_host,optarg,sizeof(g_host));            break;        default:            break;        }    }} void zktest_watcher_g(zhandle_t* zh, int type, int state, const char* path, void* watcherCtx)  {  /*      printf("watcher event\n");      printf("type: %d\n", type);      printf("state: %d\n", state);      printf("path: %s\n", path);      printf("watcherCtx: %s\n", (char *)watcherCtx);  */      if(type == ZOO_CHILD_EVENT &&       state == ZOO_CONNECTED_STATE &&       g_mode == CONSUMER_MODE){        printf("providers list changed!\n");        show_list(zh,path);    }else if(type == ZOO_CHILD_EVENT &&             state == ZOO_CONNECTED_STATE &&             g_mode == MONITOR_MODE){        printf("providers or consumers list changed!\n");        char child_path[512];        printf("providers:\n");        sprintf(child_path,"%s/%s/provider",g_path,g_service);        show_list(zh,child_path);        printf("consumers:\n");        sprintf(child_path,"%s/%s/consumer",g_path,g_service);        show_list(zh,child_path);    }}  void getlocalhost(char *ip_pid,int len){    char hostname[64] = {0};    struct hostent *hent ;    gethostname(hostname,sizeof(hostname));    hent = gethostbyname(hostname);    char * localhost = inet_ntoa(*((struct in_addr*)(hent->h_addr_list[0])));    snprintf(ip_pid,len,"%s:%d",localhost,getpid());}void show_list(zhandle_t *zkhandle,const char *path){    struct String_vector procs;    int i = 0;    char localhost[512]={0};    getlocalhost(localhost,sizeof(localhost));    int ret = zoo_get_children(zkhandle,path,1,&procs);    if(ret != ZOK){        fprintf(stderr,"failed to get the children of path %s!\n",path);    }else{        char child_path[512] ={0};        char ip_pid[64] = {0};        int ip_pid_len = sizeof(ip_pid);        printf("--------------\n");        printf("ip\tpid\n");        for(i = 0; i < procs.count; ++i){            sprintf(child_path,"%s/%s",path,procs.data[i]);            //printf("%s\n",child_path);            ret = zoo_get(zkhandle,child_path,0,ip_pid,&ip_pid_len,NULL);            if(ret != ZOK){                fprintf(stderr,"failed to get the data of path %s!\n",child_path);            }else if(strcmp(ip_pid,localhost)==0){                printf("%s(Master)\n",ip_pid);            }else{                printf("%s\n",ip_pid);            }        }    }    for(i = 0; i < procs.count; ++i){        free(procs.data[i]);        procs.data[i] = NULL;    }}int create(zhandle_t *zkhandle,const char *path,const char *ctx,int flag){    char path_buffer[512];      int bufferlen=sizeof(path_buffer);      int ret = zoo_exists(zkhandle,path,0,NULL);     if(ret != ZOK){        ret = zoo_create(zkhandle,path,ctx,strlen(ctx),                            &ZOO_OPEN_ACL_UNSAFE,flag,                            path_buffer,bufferlen);          if(ret != ZOK){            fprintf(stderr,"failed to create the path %s!\n",path);        }else{            printf("create path %s successfully!\n",path);        }    }    return ZOK;}int main(int argc, const char *argv[])  {      int timeout = 30000;      char path_buffer[512];      int bufferlen=sizeof(path_buffer);      int ret = 0;    zoo_set_debug_level(ZOO_LOG_LEVEL_ERROR); //设置日志级别,避免出现一些其它信息      get_option(argc,argv);    zhandle_t* zkhandle = zookeeper_init(g_host,zktest_watcher_g, timeout, 0, (char *)"NameService Test", 0);      if (zkhandle ==NULL)      {          fprintf(stderr, "Error when connecting to zookeeper servers...\n");          exit(EXIT_FAILURE);      }      create(zkhandle,g_path,"NameService Test",0);    sprintf(path_buffer,"%s/%s",g_path,g_service);    create(zkhandle,path_buffer,"NameService Test",0);    sprintf(path_buffer,"%s/%s/provider",g_path,g_service);    create(zkhandle,path_buffer,"NameService Test",0);    sprintf(path_buffer,"%s/%s/consumer",g_path,g_service);    create(zkhandle,path_buffer,"NameService Test",0);    if(g_mode == PROVIDER_MODE){        char localhost[512]={0};        getlocalhost(localhost,sizeof(localhost));        char child_path[512];        sprintf(child_path,"%s/%s/provider/",g_path,g_service);        ret = zoo_create(zkhandle,child_path,localhost,strlen(localhost),                            &ZOO_OPEN_ACL_UNSAFE,ZOO_SEQUENCE|ZOO_EPHEMERAL,                            path_buffer,bufferlen);          if(ret != ZOK){            fprintf(stderr,"failed to create the child_path %s,buffer:%s!\n",child_path,path_buffer);        }else{            printf("create child path %s successfully!\n",path_buffer);        }    }else if (g_mode == CONSUMER_MODE){        char localhost[512]={0};        getlocalhost(localhost,sizeof(localhost));        char child_path[512];        sprintf(child_path,"%s/%s/consumer/",g_path,g_service);        ret = zoo_create(zkhandle,child_path,localhost,strlen(localhost),                            &ZOO_OPEN_ACL_UNSAFE,ZOO_SEQUENCE|ZOO_EPHEMERAL,                            path_buffer,bufferlen);          if(ret != ZOK){            fprintf(stderr,"failed to create the child_path %s,buffer:%s!\n",child_path,path_buffer);        }else{            printf("create child path %s successfully!\n",path_buffer);        }        sprintf(child_path,"%s/%s/provider",g_path,g_service);        show_list(zkhandle,child_path);    }else if(g_mode == MONITOR_MODE){        char child_path[512];        printf("providers:\n");        sprintf(child_path,"%s/%s/provider",g_path,g_service);        show_list(zkhandle,child_path);        printf("consumers:\n");        sprintf(child_path,"%s/%s/consumer",g_path,g_service);        show_list(zkhandle,child_path);    }    getchar();    zookeeper_close(zkhandle);     return 0;}