[
https://issues.apache.org/jira/browse/ZOOKEEPER-4921?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17946903#comment-17946903
]
Kezhu Wang commented on ZOOKEEPER-4921:
---------------------------------------
{noformat}
"stackTrace" : "o.a.z.ClientCnxn$SessionTimeoutException: Client session
timed out, have not heard from server in 5590ms for session id 0x0
{noformat}
This is the log when client decide to give up retry.
1. This log comes from an unestablished zookeeper session as it prints "session
id 0x0".
2. The server is configured with a small session timeout as the default min
expiration timeout in client is {{8000ms}} (it is {{4/3}} of the default min
session timeout in server which is {{6000ms}}).
> Zookeeper Client 3.9.3 Fails to Reconnect After Network Failures
> ----------------------------------------------------------------
>
> Key: ZOOKEEPER-4921
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-4921
> Project: ZooKeeper
> Issue Type: Bug
> Components: java client
> Affects Versions: 3.9.3
> Reporter: Chuong Tran
> Priority: Critical
>
> After upgrading the Java Zookeeper client to version 3.9.3, we observed that
> it is not resilient to brief network disruptions, such as a short VPN blip.
> In such cases, the client attempts to reconnect only once, and if
> unsuccessful, the session expires.
> {quote}Apr 23, 2025 10:19:23 AM
> com.twitter.finagle.common.zookeeper.ZooKeeperClient$3 process
> INFO: Zookeeper session expired. Event: WatchedEvent state:Expired type:None
> path:null zxid: -1
> {quote}
> In contrast, the previous version (3.9.2) would continuously retry until the
> network connection was restored, maintaining the session more reliably.
> I believe it's a new issue with this change:
> https://issues.apache.org/jira/browse/ZOOKEEPER-4508
>
> Step to repro:
> # Open VPN.
> # Start the application which connects to the Zookeeper server with the VPN.
> # Disable VPN for a couple of minutes.
> # Observe the application.
> # Enable the VPN again.
> {quote}3.9.3:
> "message" : "Session 0x0 for server XXX, Closing socket connection.
> Attempting reconnect except it is a SessionExpiredException or
> SessionTimeoutException.",
> "stackTrace" : "o.a.z.ClientCnxn$SessionTimeoutException: Client session
> timed out, have not heard from server in 5590ms for session id 0x0
> at o.a.z.ClientCnxn$SendThread.run(ClientCnxn.java:1253)
> {quote}
> 3.9.2: Application will be reconnected successfully.
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
