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 changed
void zktest_watcher_g(zhandle_t* zh, int type, int state, const char* path, void* watcherCtx);
//show all process ip:pid
void show_list(zhandle_t *zkhandle,const char *path);
//if success,the g_mode will become MODE_MONITOR
void choose_mater(zhandle_t *zkhandle,const char *path);
//get localhost ip:pid
void 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;
}

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