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很容易创建一个全局的路径，而这个路径就可以作为一个名字，它可以指向集群中的集群，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目录下写入自己的URL地址，这个操作就完成了服务的发布。
服务消费者启动的时候，订阅/dubbo/{serviceName}/providers目录下的提供者URL地址， 并向/dubbo/{serviceName} /consumers目录下写入自己的URL地址。
注意，所有向ZK上注册的地址都是临时节点，这样就能够保证服务提供者和消费者能够自动感应资源的变化。
另外，Dubbo还有针对服务粒度的监控，方法是订阅/dubbo/{serviceName}目录下所有提供者和消费者的信息。
场景实践
上面的介绍已经满详细，实际实现起来也比较容易。下面讲讲模拟程序的主要特点。模拟程序有3个参数
-
-m程序运行的方式，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
运行命令如下：
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，程序首次运行时会创建/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下创建临时序列节点.
第二条命令是启动一个服务消费进程,它在/NameService/query_bill/consumer/下创建临时序列节点，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。
完整的代码如下：
#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,避免出现一些其他信息
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;
}