Liu, Looks like you have just one server. The client does not expire the session unless its able to talk to a server. Also, please take a look at some examples/tests on better understanding of event handling and session expiry for ZK.
2011/6/22 lei liu <[email protected]>: > I create "group" znode, and add "A","B","C" three children to the znode. I > want to print all children of "group" znode periodically，example below code: > public class ListGroup extends ConnectionWatcher { > > private static Random random = new Random(); > > public void register(Watcher watcher) { > zk.register(watcher); > } > > public void nodify(String groupName) throws KeeperException, > InterruptedException { > String path = "/" + groupName; > List<String> children = zk.getChildren(path, true); > } > > public void list(String groupName) throws KeeperException, > InterruptedException { > String path = "/" + groupName; > try { > Stat stat = new Stat(); > > List<String> children = zk.getChildren(path, true); > if (children.isEmpty()) { > System.out.printf("No members in group %s\n", groupName); > > } > for (String child : children) { > System.out.println(child); > } > } catch (KeeperException.NoNodeException e) { > System.out.printf("Group %s does not exist\n", groupName); > //System.exit(1); > } > } > > public static void main(String[] args) throws Exception { > ListGroup listGroup = new ListGroup(); > String connectString = "localhost:2181"; > listGroup.connect(connectString); > listGroup.list("test"); > while(true) { > try { > listGroup.list("test"); > } catch(Exception e) { > e.printStackTrace(); > } > TimeUnit.SECONDS.sleep(random.nextInt(10)); > } > //listGroup.close(); > } > } > > I run the ListGroup class then It output :"A B C" information, and then I > close the zookeeper server, the ListGroup class output below exception: > org.apache.zookeeper.KeeperException$ConnectionLossException: > KeeperErrorCode = ConnectionLoss for /test > at org.apache.zookeeper.KeeperException.create(KeeperException.java:90) > at org.apache.zookeeper.KeeperException.create(KeeperException.java:42) > at org.apache.zookeeper.ZooKeeper.getChildren(ZooKeeper.java:1243) > at org.apache.zookeeper.ZooKeeper.getChildren(ZooKeeper.java:1271) > at hadoop.definitive.guide.ListGroup.list(ListGroup.java:30) > at hadoop.definitive.guide.ListGroup.main(ListGroup.java:51) > > when I restart the zookeeper server, the ListGroup class continue to output > "A B C" information. > > I think the session is expiry before I restart the zookeeper server, I have > two questions: > 1. Why ListGroup class don't throw the SessionExpiredException. > 2. I think client can automatically reconnect to server , after the > reconnection is successfull, the session whether is still valid? > > thanks, > > > LiuLei > -- thanks mahadev @mahadevkonar
