[CURATOR-439] CuratorFrameworkState STARTED, but ZookeeperClient not connected

I recently ran into an issue on some of our nodes caused by network issues between a service and Zookeeper. I have been unable to recreate them as of yet, but I'm still trying.

Setup

5x services using Curator 3.2.1 to talk to Zookeeper 3.5.3 cluster (also 5 nodes).

Network issues caused the services to disconnect from Zookeeper.

There's a check in our code to see if the Zookeeper connection is available before sending a request:

public boolean isConnected()

Unknown macro: {
return curatorFramework.getZookeeperClient().isConnected();
}

After the network issues resolved, we noticed that all calls to Zookeeper from 4 of the services were still failing (the fifth was fine). Checking the logs, we saw that CuratorFramework.getState() was reporting the state as STARTED, but curatorFramework.getZookeeperClient().isConnected(); was returning false. Restarting the service fixed everything, but I want to obviously avoid this issue in future.

Problem

I couldn't find any documentation stating whether the CuratorZookeeperClient.isConnected() should be used, or if CuratorFramework.getState() == CuratorFrameworkState.STARTED (the functionality of the deprecated CuratorFramework.isConnected()) would be the better check, or if these should both be equivalent, and there's a bug that let one be true while the other was false.

If my own check is wrong, and I shouldn't be using CuratorZookeeperClient.isConnected(), then I can easily fix that. I wanted to check the expected behaviour before diving too deep into this, in case this is normal and I am just using Curator incorrectly.

Edit

This was a misunderstanding on my part. I'm leaving it open so that I can submit a documentation/example update shortly to hopefully clarify things a bit better for others.

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Originally reported by Kenco, imported from: CuratorFrameworkState STARTED, but ZookeeperClient not connected

• status: Open
  
• priority: Minor
  
• resolution: Unresolved
  
• imported: 2025-01-21