[jira] [Created] (CURATOR-573) No leader is getting selected intermittently

["Viniti (Jira)" <ji...@apache.org>]

Viniti created CURATOR-573:
------------------------------

             Summary: No leader is getting selected intermittently
                 Key: CURATOR-573
                 URL: https://issues.apache.org/jira/browse/CURATOR-573
             Project: Apache Curator
          Issue Type: Bug
          Components: Apache, Framework, Recipes
    Affects Versions: 4.0.1
            Reporter: Viniti


I am using Apache Curator Leader Election Recipe : https://curator.apache.org/curator-recipes/leader-election.html in my application.

Zookeeper version : 3.5.7
Curator : 4.0.1

Below are the sequence of steps:
1. Whenever my tomcat server instance is getting up, I create a single CuratorFramework instance(single instance per tomcat server) and start it : 
```
CuratorFramework client = CuratorFrameworkFactory.newClient(connectionString, retryPolicy);
client.start();
if(!client.blockUntilConnected(10, TimeUnit.MINUTES)){
 LOGGER.error("Zookeeper connection could not establish!");
 throw new RuntimeException("Zookeeper connection could not establish");
}
```

2. Create an instance of LSAdapter and start it:
```
LSAdapter adapter = new LSAdapter(client, <some_metadata>);
adapter.start();
```
Below is my LSAdapter class :
```
public class LSAdapter extends LeaderSelectorListenerAdapter implements Closeable {

//<Class instance variables defined>
 public LSAdapter(CuratorFramework client, <some_metadata>) {
 leaderSelector = new LeaderSelector(client, <path_to_be_used_for_leader_election>, this);
 leaderSelector.autoRequeue();
 }

public void start() throws IOException {
 leaderSelector.start();
 }

@Override
 public void close() throws IOException {
 leaderSelector.close();
 }

@Override
 public void takeLeadership(CuratorFramework client) throws Exception {
 final int waitSeconds = (int) (5 * Math.random()) + 1;

LOGGER.info(name + " is now the leader. Waiting " + waitSeconds + " seconds...");
 LOGGER.debug(name + " has been leader " + leaderCount.getAndIncrement() + " time(s) before.");
 while (true) {
 try {
 Thread.sleep(TimeUnit.SECONDS.toMillis(waitSeconds));
 //do leader tasks
 } catch (InterruptedException e) {
 LOGGER.error(name + " was interrupted.");
 //cleanup
 Thread.currentThread().interrupt();
 } finally {

}
 }
 }
}
```
4. When server instance is getting down, close LSAdapter instance(which application is using) and close CuratorFramework client created
```
CloseableUtils.closeQuietly(lsAdapter);
curatorFrameworkClient.close();
```

The issue I am facing is that at times, when server is restarted, no leader gets elected. I checked that by tracing the log inside takeLeadership(). I have two tomcat server instances with above code, connecting to same zookeeper quorum and most of the times one of the instance becomes leader but when this issue happens, both of them becomes follower. Please suggest what am I doing wrong.

 



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