The zookeeper (API) of big data's ecology

Import the relevant jar packages when writing zookeeper programs using the maven project:

Org.apache.zookeeper zookeeper 3.4.10

1. Create a cluster connection

/ / Cluster node nodes, separated by commas between static String url= "hadoop01:2181,hadoop02:2181,hadoop03:2181"; / / Cluster programming entry static ZooKeeper zk; / / timeout static long time=5000; / / initialize the ZooKeeper object static {try (url, (int) time,null) using a static code block } catch (IOException e) {e.printStackTrace ();}}

two。 Create a nod

Public void createZnode (ZooKeeper zk) {/ / must use the absolute path String path= "/ test/test04"; / / when creating a node, you must specify the node content byte data [] = "I am a good boy!" .getBytes () The four parameters of try {/ * zk.create indicate: * arg1: node path * arg2: content stored by node * arg3: permission setting: default * arg4: node type (permanent no order, permanent order, temporary no order, Temporary order) * / String info = zk.create (path Data, ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL) System.out.println (info==null? "fail": "success");} catch (KeeperException e) {e.printStackTrace ();} catch (InterruptedException e) {e.printStackTrace ();}}

3. View node information

Public void getInfo (ZooKeeper zk,String path) {try {/ * zk.getData (path, null, null) * Parameter 1: absolute path of the node string * parameter 2: node listening * parameter 3: node status object * / byte [] data = zk.getData (path, null, null); System.out.println ("node:" + path+ "message is" + (new String (data) } catch (KeeperException e) {e.printStackTrace ();} catch (InterruptedException e) {e.printStackTrace ();}}

4. Modify node data

Public void updateData (ZooKeeper zk,String path) {try {/ * zk.setData (path, data, version) * path: modified node * data: updated data * version: modified version: if you don't know, write-1, indicating the latest version * / zk.setData (path, "" .getBytes (),-1);} catch (Exception e) {e.printStackTrace ();}}

5. Delete nod

Public void deleteZnode (ZooKeeper zk,String path) {try {/ * zk.delete (path, version); * path: path * version: deleted version. If you don't know, write-1 to delete the latest version int * / zk.delete (path,-1). } catch (Exception e) {e.printStackTrace ();}}

6. Get permission information of znode node

Public void getACL (ZooKeeper zk,String path) {try {/ * * zk.getACL (path,stat) * path: path * stat: status information * / List acls = zk.getACL (path, null); for (ACL acl:acls) {System.out.println (acl.getPerms ()) } catch (Exception e) {e.printStackTrace ();}}

7. Get child node

Public void getChildren (ZooKeeper zk, String path) {try {/ / determine whether a node exists if (zk.exists (path, null) = = null) {List childrens = zk.getChildren (path, null) For (String children:childrens) {/ / Note that what is received is the relative path System.out.println (children) of the child nodes under the current node;} catch (Exception e) {e.printStackTrace ();}}

Test monitoring of 8.znode

Public class testZKWatcher {static String url= "hadoop01:2181,hadoop02:2181,hadoop03:2181"; static ZooKeeper zk; static long time=5000; static {try {zk=new ZooKeeper (url, (int) time,null);} catch (Exception) {e.printStackTrace () }} / / set listening public static void liisten (String path,ZooKeeper zk) {try {zk.exists (path) New Watcher () {@ Override / / WatchedEvent event listening event object public void process (WatchedEvent event) {/ / Node trigger type (add, modify, create...) Event.EventType type = event.getType () / / get the path of the triggered node event.getPath (); System.out.println ("path to trigger event" + path+ ", type of triggered event" + type ";}});} catch (Exception e) {e.printStackTrace () }} public static void main (String [] args) {String path= "/ test/test01"; liisten (path,zk); try {/ / trigger snooping zk.create ("jj", "zzy" .getBytes (), ZooDefs.Ids.OPEN_ACL_UNSAFE,CreateMode.EPHEMERAL) } catch (Exception e) {e.printStackTrace ();}

| it should be noted that listening events are one-time. If you need to monitor all the time, you need to set cyclic listening.