大家好，又见面了，我是全栈君，今天给大家准备了Idea注册码。
1.基本介绍
分布式锁是控制分布式系统之间同步訪问共享资源的一种方式,须要相互排斥来防止彼此干扰来保证一致性。
利用Zookeeper的强一致性能够完毕锁服务。Zookeeper的官方文档是列举了两种锁。独占锁和共享锁。
独占锁保证不论什么时候都仅仅有一个进程能或者资源的读写权限。共享锁能够同一时候有多个读，可是同一时刻最多仅仅能有一个写，读和写是相互排斥的。
2.场景分析
我们准备来实现相互排斥的锁，依照官网的思路，给定一个锁的路径，如/Lock,全部要申请这个锁的进程都在/Lock文件夹下创建一个/Lock/lock-的暂时序列节点，并监控/Lock的子节点变化事件。当子节点发送变化时用get_children()获取子节点的列表，假设发现进程发现自己拥有最小的一个序号，则获得锁。
处理业务完成后须要释放锁，此时仅仅须要删除该暂时节点就可以。简单来说就是永远是拥有最小序号的进程获得锁。
3.场景实践
使用锁有两个主要的函数，就是lock或unlock.定义为
Lock *lock(zhandle_t *zkhandle,const char *path)lock函数有两个參数，一个是zookeeper_init返回的句柄zkhandle,还有一个是锁的路径,假设成功则返回一个Lock的结构体指针。并同一时候获得锁，否则返回NULL。int unlock(zhandle_t *zkhandle,Lock * *lock)unlock函数也有两个參数。一个是zookeeper_init返回的句柄zkhandle,还有一个是lock函数返回的结构体指针的指针。
接下来在看详细的实现。
代码语言：javascript复制Lock *lock(zhandle_t *zkhandle,const char *path){ Lock *lock = create_lock(zkhandle,path); if(lock != NULL){ while(try_lock(zkhandle,lock) == 0){ sleep(1); } }else{ fprintf(stderr,"error when create lock %s.n",path); } return lock;}create_lock：负责锁的初始化。主要功能是负责创建{path}的节点已经{path}/lock-的暂时序列节点。 {path}假设存在则不再创建。try_lock：尝试加锁，这个函数不会等待，失败和成功都马上返回。其主要功能是获取{path}的子节点列表，并查看自己是否是拥有最小序列号的节点。假设是则返回1，否则返回0;
lock函数初始化锁后，会持续的尝试加锁，直到成功。尽管我是这样实现的。可是过于简单粗暴（哈哈）。假设拿不到锁的话。持续就会堵塞在lock函数。
int unlock(zhandle_t *zkhandle,Lock * *lock){ if(*lock){ int ret = zoo_delete(zkhandle,(*lock)->selfpath,-1); if(ret != ZOK){ fprintf(stderr,"error when release lock %s.n",(*lock)->selfpath); } free(*lock); *lock = NULL; return ret; } return ZOK;} unlock函数就很easy了。就是将create_lock中创建的暂时序列节点删除就能够了。
接下来在看下模拟程序的功能。
代码语言：javascript复制> ./mylock -hUsage : [mylock] [-h] [-p path][-s ip:port] -h Show help -p lock path -s zookeeper server ip:portFor example: mylock -s 172.17.0.36:2181 -p /Lock模拟程序有3个选项。
当中
-s：为Zookeeper的server的ip：port.
-p: 为锁的路径。
分别同一时候执行多个mylock程序，就能够看到各个程序之间是怎样获取锁的了。
最后是完整的代码：
代码语言：javascript复制/*
* 提示：该行代码过长，系统自动注释不进行高亮。一键复制会移除系统注释
* #include<stdio.h> #include<string.h> #include<unistd.h>#include"zookeeper.h" #include"zookeeper_log.h" char g_host[512]= "172.17.0.36:2181"; char g_path[512]= "/Lock";typedef struct Lock{ char lockpath[1024]; char selfpath[1024];}Lock;void print_usage();void get_option(int argc,const char* argv[]);/**********unitl*********************/ void print_usage(){ printf("Usage : [mylock] [-h] [-p path][-s ip:port] n"); printf(" -h Show helpn"); printf(" -p lock pathn"); printf(" -s zookeeper server ip:portn"); printf("For example:n"); printf(" mylock -s172.17.0.36:2181 -p /Lockn");}void get_option(int argc,const char* argv[]){ extern char *optarg; int optch; int dem = 1; const char optstring[] = "hp:s:"; while((optch = getopt(argc , (char * const *)argv , optstring)) != -1 ) { switch( optch ) { case 'h': print_usage(); exit(-1); case '?': print_usage(); printf("unknown parameter: %cn", optopt); exit(-1); case ':': print_usage(); printf("need parameter: %cn", optopt); exit(-1); case 's': strncpy(g_host,optarg,sizeof(g_host)); break; case 'p': strncpy(g_path,optarg,sizeof(g_path)); break; default: break; } }} Lock *create_lock(zhandle_t *zkhandle,const char *path){ char path_buffer[512]={0}; int bufferlen = sizeof(path_buffer); Lock * lock = NULL; int ret = zoo_exists(zkhandle,path,0,NULL); if(ret != ZOK){ ret = zoo_create(zkhandle,path,"1.0",strlen("1.0"), &ZOO_OPEN_ACL_UNSAFE,0, path_buffer,bufferlen); if(ret != ZOK){ fprintf(stderr,"failed to create the path %s!n",path); }else{ printf("create path %s successfully!n",path); } } if(ret == ZOK){ char child_path[512]; sprintf(child_path,"%s/lock-",path); ret = zoo_create(zkhandle,child_path,"1.0",strlen("1.0"), &ZOO_OPEN_ACL_UNSAFE,ZOO_SEQUENCE|ZOO_EPHEMERAL, path_buffer,bufferlen); if(ret != ZOK){ fprintf(stderr,"failed to create the path %s!n",path); }else{ printf("create path %s successfully!n",path); } } if(ret == ZOK){ lock = (Lock *)malloc(sizeof(Lock)); strcpy(lock->lockpath,path); strcpy(lock->selfpath,path_buffer); } return lock;}int try_lock(zhandle_t *zkhandle,Lock *lock){ struct String_vector children; int i = 0; int ret = zoo_get_children(zkhandle,lock->lockpath,0,&children); if(ret != ZOK){ fprintf(stderr,"error when get children of path %sn",lock->lockpath); ret = -1; }else{ char *myseq = rindex(lock->selfpath,'/'); if (myseq != NULL) myseq = 1; ret = 1; for(i = 0; i < children.count; i){ if(strcmp(children.data[i],myseq) < 0){ ret = 0; break; } } for(i = 0; i < children.count; i){ free(children.data[i]); children.data[i] = NULL; } } return ret;}Lock *lock(zhandle_t *zkhandle,const char *path){ Lock *lock = create_lock(zkhandle,path); if(lock != NULL){ while(try_lock(zkhandle,lock) == 0){ sleep(1); } }else{ fprintf(stderr,"error when create lock %s.n",path); } return lock;}int unlock(zhandle_t *zkhandle,Lock * *lock){ if(*lock){ int ret = zoo_delete(zkhandle,(*lock)->selfpath,-1); if(ret != ZOK){ fprintf(stderr,"error when release lock %s.n",(*lock)->selfpath); } free(*lock); *lock = NULL; return ret; } return ZOK;}int main(int argc, const char *argv[]) { int timeout = 30000; char path_buffer[512]; int bufferlen=sizeof(path_buffer); zoo_set_debug_level(ZOO_LOG_LEVEL_WARN); //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,NULL, timeout, 0, (char *)"lock Test", 0); if (zkhandle ==NULL) { fprintf(stderr, "Error when connecting to zookeeper servers...n"); exit(EXIT_FAILURE); } int ret = zoo_exists(zkhandle,g_path,0,NULL); if(ret != ZOK){ ret = zoo_create(zkhandle,g_path,"1.0",strlen("1.0"), &ZOO_OPEN_ACL_UNSAFE,0, path_buffer,bufferlen); if(ret != ZOK){ fprintf(stderr,"failed to create the path %s!n",g_path); }else{ printf("create path %s successfully!n",g_path); } } if(ret == ZOK ){ Lock *mylock = lock(zkhandle,g_path); if(mylock){ printf("get lock of %s.n",g_path); printf("self path is %s.n",mylock->selfpath); printf("do something....n"); getchar(); unlock(zkhandle,&mylock); } } zookeeper_close(zkhandle); return 0;}
*/版权声明：本文博客原创文章，博客，未经同意，不得转载。
发布者：全栈程序员栈长，转载请注明出处：https://javaforall.cn/117603.html原文链接：https://javaforall.cn
