问题1:
JAVA的API的Server和linux上跑的有zkServer有什么区别呢?
我的猜想:
JAVA上跑的只是一种修改Linux上跑的zookeeper的内容的方式,JAVA的API写的Zookeeper的Server只是应用在服务器上用来改数据信息的。而zkServer跑的则是实实在在的在搭建集群环境。
1.客户端连接中可能遇到的问题。
一:KeeperErrorCode = ConnectionLoss for /
请看以下博客(我是第四个错误,所以我的代码修改了等待连接的功能)
https://blog.csdn.net/weixin_41673769/article/details/89385797
2.小技巧:eclipse返回值快捷键
光标放到调用方法分号 ' ; ' 后面 ,使用Ctrl+1,直接回车,
例子:
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package day_one; import java.awt.List; import java.io.IOException; import java.util.Iterator; import org.apache.zookeeper.CreateMode; import org.apache.zookeeper.KeeperException; import org.apache.zookeeper.WatchedEvent; import org.apache.zookeeper.Watcher; import org.apache.zookeeper.ZooDefs.Ids; import org.apache.zookeeper.ZooKeeper; import org.apache.zookeeper.ZooKeeper.States; import org.apache.zookeeper.data.Stat; public class TestZk { private static final String CONN_STRING = "192.168.204.128:2181,192.168.204.129:2181,192.168.204.130:2181"; private static final int sessionTimeOut = 2000; ZooKeeper zkClient = null; // 1 。连接客户端 // 2. 写入注册信息 public void connect_client() throws Exception { // 客户端连接 zkClient = new ZooKeeper(CONN_STRING, sessionTimeOut, new Watcher() { @Override public void process(WatchedEvent event) { // TODO Auto-generated method stub // 收到事件通知后的回调函数 System.out.println(event.getType()+"----"+event.getPath()); try { zkClient.getChildren("/", true); //因为一次监听只能生效一次,所以要一直监听的话就需要,在事件调用的方法里面重新建立 } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } } }); while (true) { /*此处的while 是因为,如果还没有连接好就创建目录的话,就会发生错误*/ if (States.CONNECTING==zkClient.getState()) { System.out.println("i whell sleep"); Thread.sleep(1000); }else { break; } } /** * 数据的增删改查 * */ // 参数1:要创建的节点路径 参数2:节点数据要转换成 bytes类型 参数3:节点的ACL(访问控制列表)权限 参数4:节点的类型 String nodeCreat = zkClient.create("/eclipse_4", "hello_zk".getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT); // 上传的数据可以是任何一种,只要转成bytes就可以 // 查子节点 java.util.List<String> children = zkClient.getChildren("/", true);// "/" 是路径, true是选择是否生成监听 监听器只生效一次,生效就会调用process for (String childreString : children) { System.out.println(childreString); } //判断是否存在 Stat exists = zkClient.exists("/a", false); //获取znode的数据 byte[] data = zkClient.getData("/a", false, null); } public static void main(String[] args) throws Exception { TestZk testZk = new TestZk(); testZk.connect_client(); Thread.sleep(Long.MAX_VALUE); } }
zookeeper 客户端与服务器代码
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package day_one; import java.io.IOException; import java.util.List; import org.apache.zookeeper.CreateMode; import org.apache.zookeeper.KeeperException; import org.apache.zookeeper.WatchedEvent; import org.apache.zookeeper.Watcher; import org.apache.zookeeper.ZooDefs.Ids; import org.apache.zookeeper.ZooKeeper; import org.apache.zookeeper.ZooKeeper.States; public class DistributedServer { private static final String CONN_STRING = "192.168.204.128:2181,192.168.204.129:2181,192.168.204.130:2181"; private static final int sessionTimeOut = 2000; public static final String parenNoteString = "/Servers"; private ZooKeeper zk = null; public void getConnect() throws Exception { zk=new ZooKeeper(CONN_STRING, sessionTimeOut, new Watcher() { @Override public void process(WatchedEvent event) { // TODO Auto-generated method stub System.out.println(event.getType()+"----"+event.getPath()); try { zk.getChildren("/", true); //因为一次监听只能生效一次,所以要一直监听的话就需要,在事件调用的方法里面重新建立 } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } } }); while (true) { /*此处的while 是因为,如果还没有连接好就创建目录的话,就会发生错误*/ if (States.CONNECTING==zk.getState()) { System.out.println("connect..."); Thread.sleep(1000); }else { break; } } } public void registerServer(String hostname) throws Exception, Exception { if (zk.exists(parenNoteString, false) != null){ String create = zk.create(parenNoteString+"/server", hostname.getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL); System.out.println(hostname+" Server is logging"); }else { zk.create(parenNoteString, null, Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT); String create = zk.create(parenNoteString+"/server", hostname.getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL); System.out.println("no "+parenNoteString+" please add node"); } } public void getChild() throws Exception, InterruptedException { List<String> getChildList = zk.getChildren("/", false); for (String child : getChildList) { System.out.println(child); } } public static void main(String[] args) throws Exception { /* * 1.获取zk连接 * 2.利用zk连接注册服务器信息 * 3.启动业务功能 * */ DistributedServer server = new DistributedServer(); server.getConnect(); server.getChild(); server.registerServer(args[0]); Thread.sleep(Long.MAX_VALUE); } }
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package day_one; import java.io.IOException; import java.util.ArrayList; import java.util.List; import org.apache.zookeeper.KeeperException; import org.apache.zookeeper.WatchedEvent; import org.apache.zookeeper.Watcher; import org.apache.zookeeper.ZooKeeper; import org.apache.zookeeper.ZooKeeper.States; public class DistributedClient { private static final String CONN_STRING = "192.168.204.128:2181,192.168.204.129:2181,192.168.204.130:2181"; private static final int sessionTimeOut = 2000; public static final String parenNoteString = "/Servers"; private volatile ArrayList<String> allServerlist; private ZooKeeper zk = null; public void clientConnect() throws Exception { zk = new ZooKeeper(CONN_STRING, sessionTimeOut, new Watcher() { @Override public void process(WatchedEvent event) { // TODO Auto-generated method stub try { getServer(); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } } }); while (true) { /*此处的while 是因为,如果还没有连接好就创建目录的话,就会发生错误*/ if (States.CONNECTING==zk.getState()) { System.out.println("connect..."); Thread.sleep(1000); }else { break; } } } public void getServer() throws Exception, Exception { List<String> children = zk.getChildren(parenNoteString, true); ArrayList<String> nodeDatArrayList = new ArrayList<String>(); for (String childrenString : children) { byte[] data = zk.getData(parenNoteString+"/"+childrenString, false, null); nodeDatArrayList.add(new String(data)); } allServerlist = nodeDatArrayList; System.out.println(allServerlist); } public static void main(String[] args) throws Exception { /* * 1.连接Zookeeper * 2.获取Server信息 * 如果有变化就重新获取(watch) * 3.业务功能 * * */ DistributedClient distributedClient = new DistributedClient(); distributedClient.clientConnect(); distributedClient.getServer(); } }