Michael Han commented on ZOOKEEPER-2867:

Yes, you are correct. The node creation was a success. The error logged 
({{Adjusting parent cversion for Txn: 1 path:/cp15/brokers/ids/0 err: -110}}) 
is not unexpected during recovery process and such log does not imply the node 
failed to create, after checking the related code.

So, it seems that the ephemeral nodes associated with the session 
0x25cd1e82c110001 were deleted at quorum level, otherwise creation will not 
succeed. That is a pretty strong evidence that the session *should be* expired 
already otherwise the ephemeral nodes will not get deleted at quorum level (if 
we can find other evidence shows that the close session proposal was committed, 
that's even stronger).

Assuming the session 0x25cd1e82c110001 is closed in this case.. now the problem 
seems to be about watcher triggering - that is the deletion of the ephemerals 
should trigger the watcher so controller would receive notification but 
actually no notifications were received, correct?

bq. do you think not expiring session 0x25cd1e82c110001 after pinging stops is 
a bug in ZK?

Yes it should be a bug, if we prove session 0x25cd1e82c110001 is not closed 
after client was dead.

> an expired ZK session can be re-established
> -------------------------------------------
>                 Key: ZOOKEEPER-2867
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2867
>             Project: ZooKeeper
>          Issue Type: Bug
>    Affects Versions: 3.4.10
>            Reporter: Jun Rao
>         Attachments: zk.0.formatted, zk.1.formatted
> Not sure if this is a real bug, but I found an instance when a ZK client 
> seems to be able to renew a session already expired by the ZK server.
> From ZK server log, session 25cd1e82c110001 was expired at 22:04:39.
> {code:java}
> June 27th 2017, 22:04:39.000  INFO    
> org.apache.zookeeper.server.ZooKeeperServer     Expiring session 
> 0x25cd1e82c110001, timeout of 12000ms exceeded
> June 27th 2017, 22:04:39.001  DEBUG   
> org.apache.zookeeper.server.quorum.Leader       Proposing:: 
> sessionid:0x25cd1e82c110001 type:closeSession cxid:0x0 zxid:0x200000fc4 
> txntype:-11 reqpath:n/a
> June 27th 2017, 22:04:39.001  INFO    
> org.apache.zookeeper.server.PrepRequestProcessor        Processed session 
> termination for sessionid: 0x25cd1e82c110001
> June 27th 2017, 22:04:39.001  DEBUG   
> org.apache.zookeeper.server.quorum.CommitProcessor      Processing request:: 
> sessionid:0x25cd1e82c110001 type:closeSession cxid:0x0 zxid:0x200000fc4 
> txntype:-11 reqpath:n/a
> June 27th 2017, 22:05:20.324  INFO    
> org.apache.zookeeper.server.quorum.Learner      Revalidating client: 
> 0x25cd1e82c110001
> June 27th 2017, 22:05:20.324  INFO    
> org.apache.zookeeper.server.ZooKeeperServer     Client attempting to renew 
> session 0x25cd1e82c110001 at /
> June 27th 2017, 22:05:20.325  INFO    
> org.apache.zookeeper.server.ZooKeeperServer     Established session 
> 0x25cd1e82c110001 with negotiated timeout 12000 for client /
> {code}
> From ZK client's log, it was able to renew the expired session on 22:05:20.
> {code:java}
> June 27th 2017, 22:05:18.590  INFO    org.apache.zookeeper.ClientCnxn Client 
> session timed out, have not heard from server in 4485ms for sessionid 
> 0x25cd1e82c110001, closing socket connection and attempting reconnect      0
> June 27th 2017, 22:05:18.590  WARN    org.apache.zookeeper.ClientCnxn Client 
> session timed out, have not heard from server in 4485ms for sessionid 
> 0x25cd1e82c110001  0
> June 27th 2017, 22:05:19.325  WARN    org.apache.zookeeper.ClientCnxn SASL 
> configuration failed: javax.security.auth.login.LoginException: No JAAS 
> configuration section named 'Client' was found in specified JAAS 
> configuration file: '/opt/confluent/etc/kafka/server_jaas.conf'. Will 
> continue connection to Zookeeper server without SASL authentication, if 
> Zookeeper server allows it. 0
> June 27th 2017, 22:05:19.326  INFO    org.apache.zookeeper.ClientCnxn Opening 
> socket connection to server  0
> June 27th 2017, 22:05:20.324  INFO    org.apache.zookeeper.ClientCnxn Socket 
> connection established to, initiating 
> session 0
> June 27th 2017, 22:05:20.327  INFO    org.apache.zookeeper.ClientCnxn Session 
> establishment complete on server, 
> sessionid = 0x25cd1e82c110001, negotiated timeout = 12000  0
> {code}

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