[ZOOKEEPER-2623] CheckVersion outside of Multi causes NullPointerException

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 3.10.0
• Labels: pull-request-available
• Assignee: Kezhu Wang
• Reporter: Diego Ongaro
• Created: 28/Oct/16 02:29
• Updated: 09/Jan/24 15:54
• Resolved: 10/Sep/23 14:37

Description

I wasn't sure if check version (opcode 13) was permitted outside of a multi op, so I tried it. My server crashed with a NullPointerException and became unusable until restarted. I guess it's not allowed, but perhaps the server should handle this more gracefully?

Here are the server logs:

Accepted socket connection from /0:0:0:0:0:0:0:1:51737
Session establishment request from client /0:0:0:0:0:0:0:1:51737 client's lastZxid is 0x0
Connection request from old client /0:0:0:0:0:0:0:1:51737; will be dropped if server is in r-o mode
Client attempting to establish new session at /0:0:0:0:0:0:0:1:51737
:Fsessionid:0x10025651faa0000 type:createSession cxid:0x0 zxid:0xfffffffffffffffe txntype:unknown reqpath:n/a
Processing request:: sessionid:0x10025651faa0000 type:createSession cxid:0x0 zxid:0xfffffffffffffffe txntype:unknown reqpath:n/a
Got zxid 0x60000065e expected 0x1
Creating new log file: log.60000065e
Committing request:: sessionid:0x10025651faa0000 type:createSession cxid:0x0 zxid:0x60000065e txntype:-10 reqpath:n/a
Processing request:: sessionid:0x10025651faa0000 type:createSession cxid:0x0 zxid:0x60000065e txntype:-10 reqpath:n/a
:Esessionid:0x10025651faa0000 type:createSession cxid:0x0 zxid:0x60000065e txntype:-10 reqpath:n/a
sessionid:0x10025651faa0000 type:createSession cxid:0x0 zxid:0x60000065e txntype:-10 reqpath:n/a
Add a buffer to outgoingBuffers, sk sun.nio.ch.SelectionKeyImpl@28e9f397 is valid: true
Established session 0x10025651faa0000 with negotiated timeout 20000 for client /0:0:0:0:0:0:0:1:51737
:Fsessionid:0x10025651faa0000 type:check cxid:0x1 zxid:0xfffffffffffffffe txntype:unknown reqpath:/
Processing request:: sessionid:0x10025651faa0000 type:check cxid:0x1 zxid:0xfffffffffffffffe txntype:unknown reqpath:/
Processing request:: sessionid:0x10025651faa0000 type:check cxid:0x1 zxid:0xfffffffffffffffe txntype:unknown reqpath:/
Exception causing close of session 0x10025651faa0000: Connection reset by peer
:Esessionid:0x10025651faa0000 type:check cxid:0x1 zxid:0xfffffffffffffffe txntype:unknown reqpath:/
IOException stack trace
java.io.IOException: Connection reset by peer
	at sun.nio.ch.FileDispatcherImpl.read0(Native Method)
	at sun.nio.ch.SocketDispatcher.read(SocketDispatcher.java:39)
	at sun.nio.ch.IOUtil.readIntoNativeBuffer(IOUtil.java:223)
	at sun.nio.ch.IOUtil.read(IOUtil.java:197)
	at sun.nio.ch.SocketChannelImpl.read(SocketChannelImpl.java:380)
	at org.apache.zookeeper.server.NIOServerCnxn.doIO(NIOServerCnxn.java:320)
	at org.apache.zookeeper.server.NIOServerCnxnFactory$IOWorkRequest.doWork(NIOServerCnxnFactory.java:530)
	at org.apache.zookeeper.server.WorkerService$ScheduledWorkRequest.run(WorkerService.java:162)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at java.lang.Thread.run(Thread.java:745)
Unexpected exception
java.lang.NullPointerException
	at org.apache.zookeeper.server.ZKDatabase.addCommittedProposal(ZKDatabase.java:252)
	at org.apache.zookeeper.server.FinalRequestProcessor.processRequest(FinalRequestProcessor.java:127)
	at org.apache.zookeeper.server.quorum.CommitProcessor$CommitWorkRequest.doWork(CommitProcessor.java:362)
	at org.apache.zookeeper.server.WorkerService$ScheduledWorkRequest.run(WorkerService.java:162)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at java.lang.Thread.run(Thread.java:745)
Committing request:: sessionid:0x10025651faa0000 type:error cxid:0x1 zxid:0x60000065f txntype:-1 reqpath:n/a
Unregister MBean [org.apache.ZooKeeperService:name0=ReplicatedServer_id1,name1=replica.1,name2=Follower,name3=Connections,name4="0:0:0:0:0:0:0:1",name5=0x10025651faa0000]
Exception thrown by downstream processor, unable to continue.
CommitProcessor exited loop!
Closed socket connection for client /0:0:0:0:0:0:0:1:51737 which had sessionid 0x10025651faa0000

And here's a one-liner to repro, which does a ConnectRequest followed by a CheckVersion(path="/", version=89235}:

echo AAAALAAAAAAAAAAAAAAAAAAAJxAAAAAAAAAAAAAAABAAAAAAAAAAAAAAAAAAAAAAAAAAEQAAAAEAAAANAAAAAS8AAVyT | base64 --decode | nc localhost 2181 >/dev/null

This is against master as of a couple of weeks ago (f78061a). I haven't checked to see which versions are affected.

Issue Links

• is duplicated by: ZOOKEEPER-4680 OpCode.check is treated as a quorum write operation white it is not
• links to: GitHub Pull Request #1988
• links to: GitHub Pull Request #2067
• links to: GitHub Pull Request #2104
• links to: GitHub Pull Request #2105