zk系列-c++下zookeeper使用实例

ZooKeeper是一个分布式的，开放源码的分布式应用程序协调服务。分布式应用可以使用它来实现诸如：统一命名服务、配置管理、分布式锁服务、集群管理等功能。公司常用到的是Java服务集群的管理。

1.函数介绍

//create a handle to used communicate with zookeeperzhandle_t *zookeeper_init(const char *host, watcher_fn fn, int recv_timeout, const clientid_t *clientid, void *context, int flags)//create a node synchronouslyint zoo_create(zhandle_t *zh, const char *path, const char *value,int valuelen,   const struct ACL_vector *acl, int flags,char *path_buffer, int path_buffer_len);//lists the children of a node synchronously.int zoo_wget_children(zhandle_t *zh, const char *path, watcher_fn watcher, void* watcherCtx, struct String_vector *strings)//close the zookeeper handle and free up any resources.int zookeeper_close(zhandle_t *zh)

2.实例

用上面3个函数，就能创建一个简单的集群管理。

数据存储结构为

服务端向Zk注册服务

//连接zkvoid ZkRegistry::ConnectZK() {  if (zhandle_) {    zookeeper_close(zhandle_);  }  int count = 0;  do {    ++count;    zhandle_ = zookeeper_init(zk_hosts_.c_str(),InitWatcher, timeout_, NULL, NULL, 0);  } while (!connected_ && count < ZK_MAX_CONNECT_TIMES);  if (count >= ZK_MAX_CONNECT_TIMES) {    SLOG_WARN("ZkRegistry::Init --> connect host " << zk_hosts_ << " over max times:" << count);    return;  }}//发布服务，建立临时节点void ZkRegistry::PublishService() {  if (zhandle_ == NULL) {    ConnectZK();  }  string server_path = PING_SERVER + "/" + PingConfig::instance().get_index() + "/"    + GetIp() + ":" + PingConfig::instance().get_port();  char res_path[128];  int rc = zoo_create(zhandle_, server_path.c_str(), GetIp().c_str(), GetIp().size(),      &ZOO_OPEN_ACL_UNSAFE, ZOO_EPHEMERAL, res_path, 128);  if (rc) {    SLOG_INFO("ZkRegistry::PublishService --> zoo_create() path=" << server_path << "," << zerror(rc));  }}//每隔10s注册一次服务void ZkRegistry::run() {  while(true) {    SLOG_INFO("publish service");    ConnectZK();    PublishService();    sleep(10);  }}void ZkRegistry::InitWatcher(zhandle_t *zh, int type, int state, const char *path, void *watcher_ctx) {  if (state == ZOO_CONNECTED_STATE) {    connected_ = true;    SLOG_INFO("InitWatcher() ZOO_CONNECTED_STATE");  } else if (state == ZOO_AUTH_FAILED_STATE) {    SLOG_INFO("InitWatcher() ZOO_AUTH_FAILED_STATE");  } else if (state == ZOO_EXPIRED_SESSION_STATE) {    SLOG_INFO("InitWatcher() ZOO_EXPIRED_SESSION_STATE");  } else if (state == ZOO_CONNECTING_STATE) {    SLOG_INFO("InitWatcher() ZOO_CONNECTING_STATE");  } else if (state == ZOO_ASSOCIATING_STATE) {    SLOG_INFO("InitWatcher() ZOO_ASSOCIATING_STATE");  }}

客户端获取服务列表

//连接zk servervoid ZkClient::ConnectZK() {  cout << "ZkClient::ConnectZK" << endl;  if (zhandle_) {    zookeeper_close(zhandle_);  }  zhandle_ = NULL;  connected_ = false;  int count = 0;  do {    ++count;    zhandle_ = zookeeper_init(zk_hosts_.c_str(), InitWatcher, timeout_, NULL, NULL, 0);    sleep(5 * ONE_SECONDS);  } while (!connected_ && count < ZK_MAX_CONNECT_TIMES);  if (count >= ZK_MAX_CONNECT_TIMES){    cout << "ZkClient::Init --> connecting zookeeper host: " << zk_hosts_ << " over times: " << count << endl;  }}//更新服务列表，冷备和热备void ZkClient::Update() {  cout << "ZkClient::Update" << endl;  if (zhandle_ == NULL || connected_ == false) {    Init();  }  //获得服务份数  struct String_vector str_vec;  int ret = zoo_wget_children(zhandle_, PING_SERVER.c_str(), ServiceWatcher, NULL, &str_vec);  if (ret) {    cout << "Update --> read path:" << PING_SERVER << " wrong, " << zerror(ret) << endl;    return;  }  //获得各份服务ip:port  for (int i = 0; i < str_vec.count; ++i) {    struct String_vector node_vec;    string path = PING_SERVER + "/" + str_vec.data[i];    int ret = zoo_wget_children(zhandle_, path.c_str(), ServiceWatcher, NULL, &node_vec);    cout << "Update --> path:" << path << ", ret:" << ret << ", node's size:" << node_vec.count << endl;    if (ret || node_vec.count != 1) {      continue;    }    ....  }}//监控服务变化void ZkClient::ServiceWatcher(zhandle_t *zh, int type, int state, const char *path, void *watcherCtx) {  cout << "type:" << type << endl;  cout << "state:" << state << endl;  cout << "path:" << path << endl;//  cout << "watcherCtx:" << (char*)watcherCtx << endl;  cout << "ZOO_CHILD_EVENT:" << ZOO_CHILD_EVENT << endl;  if (ZOO_CHILD_EVENT == type) {    cout << "ServiceWatcher ZOO_CHILD_EVENT" << endl;    ZkClient::Instance().Update();//更新服务列表      }}

服务端会每隔一段时间重新注册自己；

客户端在第一次与zk建立连接获取服务列表时，注册监听函数。zk当节点发生变化时，通知客户端，客户端重新获取服务列表，并注册事件。