WARN [NIOWorkerThread-2:NIOServerCnxn@373] - Close of session 0x0

[Dhirendra Singh <dh...@gmail.com>]

I have setup zookeeper ensemble with quorum size of 3 in kubernetes.
zookeeper version i am using is 3.6.1
i see following warning message logged in the log approximately every 4
seconds in the log of all zookeeper server. what is the cause of these
warning messages ?

2020-08-25 05:17:40,265 [myid:1] - WARN
[NIOWorkerThread-2:NIOServerCnxn@373] - Close of session 0x0
java.io.IOException: Len error 369295618
at
org.apache.zookeeper.server.NIOServerCnxn.readLength(NIOServerCnxn.java:541)
at org.apache.zookeeper.server.NIOServerCnxn.doIO(NIOServerCnxn.java:332)
at
org.apache.zookeeper.server.NIOServerCnxnFactory$IOWorkRequest.doWork(NIOServerCnxnFactory.java:522)
at
org.apache.zookeeper.server.WorkerService$ScheduledWorkRequest.run(WorkerService.java:154)
at
java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
at
java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
at java.base/java.lang.Thread.run(Thread.java:834)

-dsingh

Re: WARN [NIOWorkerThread-2:NIOServerCnxn@373] - Close of session 0x0

[Szalay-Bekő Máté <sz...@gmail.com>]

there should be some process / script that is sending malformed packages to
the ZooKeeper client port.

The first 4 bytes sent by the client is interpreted as the length of the
message (or as a 4 letter word command), but ZooKeeper is unable to parse
this. (most probably it is not a real ZooKeeper message, unless the client
really wants to send ~370MB in a single message) Sometimes what happens is
that some security scanners are periodically checking the ZooKeeper client
port. Or maybe some misconfigured client is trying to connect using TLS/SSL
to an unsecure ZooKeeper port, that doesn't expect an SSL handshake?

Best Regards,
Mate

On Tue, Aug 25, 2020 at 8:25 AM Dhirendra Singh <dh...@gmail.com>
wrote:

> I have setup zookeeper ensemble with quorum size of 3 in kubernetes.
> zookeeper version i am using is 3.6.1
> i see following warning message logged in the log approximately every 4
> seconds in the log of all zookeeper server. what is the cause of these
> warning messages ?
>
> 2020-08-25 05:17:40,265 [myid:1] - WARN
> [NIOWorkerThread-2:NIOServerCnxn@373] - Close of session 0x0
> java.io.IOException: Len error 369295618
> at
>
> org.apache.zookeeper.server.NIOServerCnxn.readLength(NIOServerCnxn.java:541)
> at org.apache.zookeeper.server.NIOServerCnxn.doIO(NIOServerCnxn.java:332)
> at
>
> org.apache.zookeeper.server.NIOServerCnxnFactory$IOWorkRequest.doWork(NIOServerCnxnFactory.java:522)
> at
>
> org.apache.zookeeper.server.WorkerService$ScheduledWorkRequest.run(WorkerService.java:154)
> at
>
> java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
> at
>
> java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
> at java.base/java.lang.Thread.run(Thread.java:834)
>
> -dsingh
>