Jonathan Park created ZOOKEEPER-3280:
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Summary: ClientCnxn xid rollover can break sessions
Key: ZOOKEEPER-3280
URL: https://issues.apache.org/jira/browse/ZOOKEEPER-3280
Project: ZooKeeper
Issue Type: Bug
Components: java client
Affects Versions: 3.4.12, 3.4.6
Reporter: Jonathan Park
Attachments: ZKOutOfOrder.java
{code:java}
181, unexpected error, closing socket connection and attempting reconnect
java.io.IOException: Xid out of order. Got Xid -3 with err 0 expected Xid -4
for a packet with details: clientPath:null serverPath:null finished:false
header:: -4,8 replyHeader:: 0,0,-4 request:: '/,F response:: v{}
at org.apache.zookeeper.ClientCnxn$SendThread.readResponse(ClientCnxn.java:828)
at org.apache.zookeeper.ClientCnxnSocketNIO.doIO(ClientCnxnSocketNIO.java:94)
at
org.apache.zookeeper.ClientCnxnSocketNIO.doTransport(ClientCnxnSocketNIO.java:366)
at org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1143)
2019-02-15 13:40:22,520 [myid:] - INFO
[main-SendThread(localhost:2181):ClientCnxn$SendThread@1027] - Opening socket
connection to server localhost/127.0.0.1:2181. Will not attempt to authenticate
using SASL (unknown error)
2019-02-15 13:40:22,521 [myid:] - INFO
[main-SendThread(localhost:2181):ClientCnxn$SendThread@877] - Socket connection
established to localhost/127.0.0.1:2181, initiating session
2019-02-15 13:40:22,521 [myid:] - DEBUG
[main-SendThread(localhost:2181):ClientCnxn$SendThread@950] - Session
establishment request sent on localhost/127.0.0.1:2181
2019-02-15 13:40:22,522 [myid:] - INFO
[main-SendThread(localhost:2181):ClientCnxn$SendThread@1301] - Session
establishment complete on server localhost/127.0.0.1:2181, sessionid =
0x168f2c5e9c60017, negotiated timeout = 30000
2019-02-15 13:40:22,525 [myid:] - DEBUG
[main-SendThread(localhost:2181):ClientCnxn$SendThread@742] - Got ping response
for sessionid: 0x168f2c5e9c60017 after 235329552ms
{code}
ClientCnxn xid's are tracked as java int's. For long-lived ZK clients this can
lead to rollover into the negative xid space. Xid = -4 is treated as a special
xid reserved for auth requests. With xid rollover, a normal ZK request can also
have xid = -4 but the response will be treated as an auth response making
subsequent packet processing error with the exception above. We can reproduce
this more readily by changing the starting xid in ClientCnxn from 1 to -100.
The ZK client will transparently reconnect and establish a new session but
features that depended on the same session persisting will unnecessarily
experience a disconnected event.
I've attached simple class with a main() method that reproduces the failure
quickly against a local ZK server after modifying the initial value of
ClientCnxn.xid from 1 to -100.
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