[CURATOR-339] CuratorFramework misses session expired events

[jira-importer]

I was using CuratorFramework and was unable to see some expected session expiration events.

Here's a simpler demonstration of these missed events (without using CuratorFramework)

---

Code that works:
This code doesn't misses any events, note that here I am holding onto a particular zk instance through out.

import org.apache.curator.CuratorZookeeperClient;
import org.apache.curator.retry.RetryOneTime;
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;
import org.apache.zookeeper.ZooKeeper;
public class CuClient implements Watcher {
public static void main(String[] args) throws Exception {
CuClient zkc = new CuClient();
zkc.connect(args[0]);
}
private void connect(String zkConnect) throws Exception {
CuratorZookeeperClient czc = new CuratorZookeeperClient(
zkConnect,
4000,
1000,
this,
new RetryOneTime(1000)
);
czc.start();
ZooKeeper zk = czc.getZooKeeper();

<span class="code-keyword">for</span> (<span class="code-object">int</span> i = 0; i < 100; i++) {
  <span class="code-object">Thread</span>.sleep(1000);
  <span class="code-object">System</span>.out.println(<span class="code-quote">"creating "</span> + i);
  <span class="code-keyword">try</span> {

zk.create("/rollup/" + i, null, ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
} catch (KeeperException ke) {
System.out.println(ke.getMessage());
}
}
czc.close();

}
@Override
public void process(WatchedEvent watchedEvent) {
System.out.println(watchedEvent);
}
}

I caused a network partition after node 6 and then healed it after the session expired

WatchedEvent state:SyncConnected type:None path:null
creating 0
creating 1
creating 2
creating 3
creating 4
creating 5
creating 6
WatchedEvent state:Disconnected type:None path:null
creating 7
KeeperErrorCode = ConnectionLoss for /rollup/7
creating 8
KeeperErrorCode = ConnectionLoss for /rollup/8
creating 9
KeeperErrorCode = ConnectionLoss for /rollup/9
creating 10
KeeperErrorCode = ConnectionLoss for /rollup/10
creating 11
WatchedEvent state:Expired type:None path:null
WatchedEvent state:SyncConnected type:None path:null
KeeperErrorCode = Session expired for /rollup/11
creating 12
KeeperErrorCode = Session expired for /rollup/12
creating 13
KeeperErrorCode = Session expired for /rollup/13
creating 14
KeeperErrorCode = Session expired for /rollup/14
^C

---

Code that doesn't work:
This is the same code, except instead of holding onto a zookeeper instance, I am calling getZookeeper again and again.

import org.apache.curator.CuratorZookeeperClient;
import org.apache.curator.retry.RetryOneTime;
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;
import org.apache.zookeeper.ZooKeeper;
public class CuClient implements Watcher {
public static void main(String[] args) throws Exception {
CuClient zkc = new CuClient();
zkc.connect(args[0]);
}
private void connect(String zkConnect) throws Exception {
CuratorZookeeperClient czc = new CuratorZookeeperClient(
zkConnect,
4000,
1000,
this,
new RetryOneTime(1000)
);
czc.start();
<span class="code-keyword">for</span> (<span class="code-object">int</span> i = 0; i < 100; i++) {
  <span class="code-object">Thread</span>.sleep(1000);
  <span class="code-object">System</span>.out.println(<span class="code-quote">"creating "</span> + i);
  <span class="code-keyword">try</span> {

czc.getZooKeeper().create("/rollup/" + i, null, ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
} catch (KeeperException ke) {
System.out.println(ke.getMessage());
}
}
czc.close();

}
@Override
public void process(WatchedEvent watchedEvent) {
System.out.println(watchedEvent);
}
}

Again, network partitioned after node 5 and then healed once the session expired. Note the missing 'WatchedEvent state:Expired type:None path:null' line.

WatchedEvent state:SyncConnected type:None path:null
creating 0
creating 1
creating 2
creating 3
creating 4
creating 5
WatchedEvent state:Disconnected type:None path:null
creating 6
KeeperErrorCode = ConnectionLoss for /rollup/6
creating 7
KeeperErrorCode = ConnectionLoss
creating 8
KeeperErrorCode = ConnectionLoss
creating 9
KeeperErrorCode = ConnectionLoss for /rollup/9
creating 10
KeeperErrorCode = ConnectionLoss
creating 11
KeeperErrorCode = ConnectionLoss
WatchedEvent state:SyncConnected type:None path:null
creating 12
creating 13
creating 14
creating 15
creating 16
creating 17
^C

The same happens when I use CuratorFramework (I get SyncConnected events but no Expired events). Am I doing something wrong? I want to do all the operations in one session (because I am creating some ephemeral nodes etc.) I want a reliable way of getting notified when the session expired.

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Originally reported by ragarwal, imported from: CuratorFramework misses session expired events

• assignee: randgalt
• status: Open
• priority: Major
• resolution: Unresolved
• imported: 2025-01-21

[jira-importer]

[Originally related to: CURATOR-338]