我参考了旧版本的 Apache Curator 和 Zookeeper（ Apache Curator 无法重置过期会话）问了一个类似的问题，并建议升级。我现在已经更新到最新版本的客户端软件，并且看到了一个非常相似的问题。
似乎当 Zookeeper 会话过期时，在某些情况下客户端连接没有被重置。这导致 Curator 客户端进入指数回退，它反复尝试使用过期会话，每次都失败并出现异常“ org.apache.zookeeper.KeeperException$SessionExpiredException: KeeperErrorCode = Session expired for /zk/path ” .
如果客户端服务完全重新启动，一切都会恢复正常。
客户端日志记录（Apache Curator 4.2.0；Apache Zookeeper 3.4.8）：
2020-08-17 16:25:47.521 [main-SendThread(hostname:2181)] [INFO ] [org.apache.zookeeper.ClientCnxn ] - Client session timed out, have not heard from server in 6037ms for sessionid 0x10003f181c10087, closing socket connection and attempting reconnect
2020-08-17 16:25:50.848 [main-SendThread(hostname:2181)] [INFO ] [org.apache.zookeeper.ClientCnxn ] - Opening socket connection to server hostname:2181. Will not attempt to authenticate using SASL (unknown error)
2020-08-17 16:25:50.848 [main-SendThread(hostname:2181)] [INFO ] [org.apache.zookeeper.ClientCnxn ] - Socket connection established to hostname:2181, initiating session
2020-08-17 16:25:50.851 [main-SendThread(hostname:2181)] [DEBUG] [org.apache.zookeeper.ClientCnxn ] - Session establishment request sent on hostname:2181
2020-08-17 16:25:50.853 [main-SendThread(hostname:2181)] [TRACE] [org.apache.zookeeper.ClientCnxnSocket ] - readConnectResult 37 0x[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,10,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,]
2020-08-17 16:25:50.853 [main-SendThread(hostname:2181)] [WARN ] [org.apache.zookeeper.ClientCnxn ] - Unable to reconnect to ZooKeeper service, session 0x10003f181c10087 has expired
2020-08-17 16:25:50.853 [main-SendThread(hostname:2181)] [INFO ] [org.apache.zookeeper.ClientCnxn ] - Unable to reconnect to ZooKeeper service, session 0x10003f181c10087 has expired, closing socket connection
2020-08-17 16:25:50.962 [main-EventThread ] [DEBUG] [org.apache.curator.RetryLoop ] - Retry-able exception received
org.apache.zookeeper.KeeperException$SessionExpiredException: KeeperErrorCode = Session expired for /zk/path
at org.apache.zookeeper.KeeperException.create(KeeperException.java:127)
at org.apache.zookeeper.KeeperException.create(KeeperException.java:51)
at org.apache.zookeeper.ZooKeeper.exists(ZooKeeper.java:1102)
at org.apache.curator.framework.imps.ExistsBuilderImpl$3.call(ExistsBuilderImpl.java:237)
at org.apache.curator.framework.imps.ExistsBuilderImpl$3.call(ExistsBuilderImpl.java:226)
at org.apache.curator.RetryLoop.callWithRetry(RetryLoop.java:109)
at org.apache.curator.framework.imps.ExistsBuilderImpl.pathInForegroundStandard(ExistsBuilderImpl.java:223)
at org.apache.curator.framework.imps.ExistsBuilderImpl.pathInForeground(ExistsBuilderImpl.java:216)
at org.apache.curator.framework.imps.ExistsBuilderImpl.forPath(ExistsBuilderImpl.java:175)
at org.apache.curator.framework.imps.ExistsBuilderImpl.forPath(ExistsBuilderImpl.java:32)
[...]
at org.apache.curator.framework.imps.NamespaceWatcher.process(NamespaceWatcher.java:68)
at org.apache.zookeeper.ClientCnxn$EventThread.processEvent(ClientCnxn.java:530)
at org.apache.zookeeper.ClientCnxn$EventThread.run(ClientCnxn.java:505)
2020-08-17 16:25:51.054 [main-SendThread(hostname:2181)] [TRACE] [org.apache.zookeeper.ClientCnxnSocketNIO] - Doing client selector close
2020-08-17 16:25:51.055 [main-SendThread(hostname:2181)] [TRACE] [org.apache.zookeeper.ClientCnxnSocketNIO] - Closed client selector
2020-08-17 16:25:51.056 [main-SendThread(hostname:2181)] [TRACE] [org.apache.zookeeper.ClientCnxn ] - SendThread exited loop for session: 0x10003f181c10087
2020-08-17 16:25:53.991 [main-EventThread ] [TRACE] [o.a.curator.utils.DefaultTracerDriver ] - Counter retries-allowed: 1
2020-08-17 16:25:53.991 [main-EventThread ] [DEBUG] [org.apache.curator.RetryLoop ] - Retrying operation
2020-08-17 16:25:53.992 [main-EventThread ] [DEBUG] [org.apache.curator.RetryLoop ] - Retry-able exception received
org.apache.zookeeper.KeeperException$SessionExpiredException: KeeperErrorCode = Session expired for /zk/path
at org.apache.zookeeper.KeeperException.create(KeeperException.java:127)
at org.apache.zookeeper.KeeperException.create(KeeperException.java:51)
at org.apache.zookeeper.ZooKeeper.exists(ZooKeeper.java:1102)
at org.apache.curator.framework.imps.ExistsBuilderImpl$3.call(ExistsBuilderImpl.java:237)
at org.apache.curator.framework.imps.ExistsBuilderImpl$3.call(ExistsBuilderImpl.java:226)
at org.apache.curator.RetryLoop.callWithRetry(RetryLoop.java:109)
at org.apache.curator.framework.imps.ExistsBuilderImpl.pathInForegroundStandard(ExistsBuilderImpl.java:223)
at org.apache.curator.framework.imps.ExistsBuilderImpl.pathInForeground(ExistsBuilderImpl.java:216)
at org.apache.curator.framework.imps.ExistsBuilderImpl.forPath(ExistsBuilderImpl.java:175)
at org.apache.curator.framework.imps.ExistsBuilderImpl.forPath(ExistsBuilderImpl.java:32)
[...]
at org.apache.curator.framework.imps.NamespaceWatcher.process(NamespaceWatcher.java:68)
at org.apache.zookeeper.ClientCnxn$EventThread.processEvent(ClientCnxn.java:530)
at org.apache.zookeeper.ClientCnxn$EventThread.run(ClientCnxn.java:505)
服务器日志记录(Zookeeper 3.4.13)
2020-08-17 16:25:47,519 - INFO [SessionTracker:ZooKeeperServer@355] - Expiring session 0x10003f181c10087, timeout of 4000ms exceeded
2020-08-17 16:25:47,521 - INFO [ProcessThread(sid:0 cport:2181)::PrepRequestProcessor@487] - Processed session termination for sessionid: 0x10003f181c10087
2020-08-17 16:25:47,522 - INFO [SyncThread:0:NIOServerCnxn@1056] - Closed socket connection for client which had sessionid 0x10003f181c10087
2020-08-17 16:25:50,849 - INFO [NIOServerCxn.Factory:0.0.0.0/0.0.0.0:2181:NIOServerCnxnFactory@215] - Accepted socket connection from
2020-08-17 16:25:50,851 - INFO [NIOServerCxn.Factory:0.0.0.0/0.0.0.0:2181:ZooKeeperServer@942] - Client attempting to renew session 0x10003f181c10087 at
2020-08-17 16:25:50,852 - INFO [NIOServerCxn.Factory:0.0.0.0/0.0.0.0:2181:ZooKeeperServer@687] - Invalid session 0x10003f181c10087 for client, probably expired
2020-08-17 16:25:50,852 - INFO [NIOServerCxn.Factory:0.0.0.0/0.0.0.0:2181:NIOServerCnxn@1056] - Closed socket connection for client which had sessionid 0x10003f181c10087
没有与“KeeperErrorCode = Session expired”客户端错误对应的服务器日志记录。
非常感谢您对此问题的任何见解。谢谢！