[ZOOKEEPER-1809] ephemeral node not deleted (or recreated?) after session expiry

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Not A Problem
• Affects Version/s: 3.4.5, 3.5.0
• Assignee: Unassigned
• Reporter: Shaun Senecal
• Created: 06/Nov/13 05:06
• Updated: 06/Dec/13 21:32
• Resolved: 07/Nov/13 03:54

Description

We have been running into a situation where we attempt to recreate our ephemeral nodes after a session expiry, only to find that the node already exists. Admittedly, this is only happening when we are aggresively killing and recreating sessions in a tight loop, but I thought it might point to a larger issue which may need to be addressed.

Attached is a small app which demonstrates the issue, and a log file (client and server in the same log) which shows the issue as it occured. Reproducing the bug is a tedious process of rerunning the test over and over again, but I have typically been able to reproduce it within 15mins of trying. The test app is using Curator, however, I think the issue is occuring at the ZK level since the logs clearly indicate the ephermal node is deleted after the session expiry.

Interesting bits from the log

...
2013/11/06 13:46:03,065 INFO  [ConnectionStateManager-0] Recreating node: /test
...
2013/11/06 13:46:03,070 DEBUG [SyncThread:0] Processing request:: sessionid:0x1422bbb36d10002 type:create cxid:0x2 zxid:0x8 txntype:1 reqpath:n/a
...
2013/11/06 13:46:03,071 DEBUG [main] Closing client for session: 0x1422bbb36d10002
2013/11/06 13:46:03,075 INFO  [ProcessThread(sid:0 cport:-1):] Processed session termination for sessionid: 0x1422bbb36d10002
2013/11/06 13:46:03,079 DEBUG [SyncThread:0] Processing request:: sessionid:0x1422bbb36d10002 type:closeSession cxid:0x1 zxid:0x9 txntype:-11 reqpath:n/a
2013/11/06 13:46:03,080 DEBUG [SyncThread:0] Deleting ephemeral node /test for session 0x1422bbb36d10002
2013/11/06 13:46:03,080 DEBUG [SyncThread:0] sessionid:0x1422bbb36d10002 type:closeSession cxid:0x1 zxid:0x9 txntype:-11 reqpath:n/a
...
2013/11/06 13:46:04,459 INFO  [NIOServerCxn.Factory:0.0.0.0/0.0.0.0:43462] Client attempting to renew session 0x1422bbb36d10002 at /127.0.0.1:59559
2013/11/06 13:46:04,459 INFO  [NIOServerCxn.Factory:0.0.0.0/0.0.0.0:43462] Invalid session 0x1422bbb36d10002 for client /127.0.0.1:59559, probably expired
2013/11/06 13:46:04,460 INFO  [main-SendThread(localhost:43462)] Unable to reconnect to ZooKeeper service, session 0x1422bbb36d10002 has expired, closing socket connection
2013/11/06 13:46:04,460 DEBUG [NIOServerCxn.Factory:0.0.0.0/0.0.0.0:43462] Dropping request: No session with sessionid 0x1422bbb36d10002 exists, probably expired and removed
...
2013/11/06 13:46:04,463 INFO  [NIOServerCxn.Factory:0.0.0.0/0.0.0.0:43462] Client attempting to establish new session at /127.0.0.1:59560
2013/11/06 13:46:04,466 DEBUG [SyncThread:0] Processing request:: sessionid:0x1422bbb36d10003 type:createSession cxid:0x0 zxid:0xa txntype:-10 reqpath:n/a
2013/11/06 13:46:04,466 DEBUG [SyncThread:0] sessionid:0x1422bbb36d10003 type:createSession cxid:0x0 zxid:0xa txntype:-10 reqpath:n/a
2013/11/06 13:46:04,467 INFO  [SyncThread:0] Established session 0x1422bbb36d10003 with negotiated timeout 30000 for client /127.0.0.1:59560
...
2013/11/06 13:46:04,473 INFO  [ConnectionStateManager-0] Recreating node: /test
2013/11/06 13:46:04,474 DEBUG [SyncThread:0] Processing request:: sessionid:0x1422bbb36d10003 type:exists cxid:0x2 zxid:0xfffffffffffffffe txntype:unknown reqpath:/___CURATOR_KILL_SESSION___15970538640754
2013/11/06 13:46:04,474 DEBUG [SyncThread:0] sessionid:0x1422bbb36d10003 type:exists cxid:0x2 zxid:0xfffffffffffffffe txntype:unknown reqpath:/___CURATOR_KILL_SESSION___15970538640754
2013/11/06 13:46:04,475 INFO  [ProcessThread(sid:0 cport:-1):] Got user-level KeeperException when processing sessionid:0x1422bbb36d10003 type:create cxid:0x3 zxid:0xc txntype:-1 reqpath:n/a Error Path:/test Error:KeeperErrorCode = NodeExists for /test
2013/11/06 13:46:04,475 DEBUG [main-SendThread(localhost:43462)] Reading reply sessionid:0x1422bbb36d10003, packet:: clientPath:null serverPath:null finished:false header:: 2,3  replyHeader:: 2,11,-101  request:: '/___CURATOR_KILL_SESSION___15970538640754,T  response::  
2013/11/06 13:46:04,476 INFO  [main] Initiating client connection, connectString=127.0.0.1:43462 sessionTimeout=10000 watcher=com.netflix.curator.test.KillSession$2@4067d00a sessionId=1422bbb36d10003 sessionPasswd=<hidden>
...
2013/11/06 13:46:04,479 ERROR [ConnectionStateManager-0] Failed to recreate ephemeral node
org.apache.zookeeper.KeeperException$NodeExistsException: KeeperErrorCode = NodeExists for /test
	at org.apache.zookeeper.KeeperException.create(KeeperException.java:119)
	at org.apache.zookeeper.KeeperException.create(KeeperException.java:51)
	at org.apache.zookeeper.ZooKeeper.create(ZooKeeper.java:783)
	at com.netflix.curator.framework.imps.CreateBuilderImpl$10.call(CreateBuilderImpl.java:625)
	at com.netflix.curator.framework.imps.CreateBuilderImpl$10.call(CreateBuilderImpl.java:609)
	at com.netflix.curator.RetryLoop.callWithRetry(RetryLoop.java:106)
	at com.netflix.curator.framework.imps.CreateBuilderImpl.pathInForeground(CreateBuilderImpl.java:605)
	at com.netflix.curator.framework.imps.CreateBuilderImpl.forPath(CreateBuilderImpl.java:428)
	at com.netflix.curator.framework.imps.CreateBuilderImpl.forPath(CreateBuilderImpl.java:408)
	at com.netflix.curator.framework.imps.CreateBuilderImpl.forPath(CreateBuilderImpl.java:41)
	at com.rakuten.sandbox.sessionexpiry.nodeexists.SessionExpiryTest$2.stateChanged(SessionExpiryTest.java:72)
	at com.netflix.curator.framework.state.ConnectionStateManager$2.apply(ConnectionStateManager.java:184)
	at com.netflix.curator.framework.state.ConnectionStateManager$2.apply(ConnectionStateManager.java:180)
	at com.netflix.curator.framework.listen.ListenerContainer$1.run(ListenerContainer.java:92)
	at com.google.common.util.concurrent.MoreExecutors$SameThreadExecutorService.execute(MoreExecutors.java:262)
	at com.netflix.curator.framework.listen.ListenerContainer.forEach(ListenerContainer.java:83)
	at com.netflix.curator.framework.state.ConnectionStateManager.processEvents(ConnectionStateManager.java:177)
	at com.netflix.curator.framework.state.ConnectionStateManager.access$000(ConnectionStateManager.java:40)
	at com.netflix.curator.framework.state.ConnectionStateManager$1.call(ConnectionStateManager.java:104)
	at java.util.concurrent.FutureTask.run(FutureTask.java:262)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
	at java.lang.Thread.run(Thread.java:744)
...

Issue Links

• is related to: ZOOKEEPER-1740 Zookeeper 3.3.4 loses ephemeral nodes under stress