Unexpected packet from client, disconnecting the client

[olafz]

We are experiencing a reproducible bug in ProxySQL with our setup and data. We have an application connecting to a ProxySQL instance and issuing lots of queries. This all works just fine, until a certain point where the ProxySQL logs

MySQL_Session.cpp:2427:handler(): [ERROR] Unexpected packet from client, disconnecting the client

At the same moment, the application logs an error because it's client connection is killed.

We are running ProxySQL version 1.4.9 on Debian linux.

We have a TCPDump of the specific TCP flow, but so far nothing seems wrong there and similar queries work on other places. That seems to suggest it's in some state of the proxy or maybe even in the data.

I can send the full TCPDump file.

[Reiner030]

Looks like same problem as #1600
which seems to be finally same problem as issue i answered there:

it could be that you also have multiplexing off and your backend is perhaps disconnected?
Then it could be a problem that the backend connection is "sticky" and therefore ProxySQL must hook off the connection to the client like here explained:
#1632 (comment) / #1632 (comment)

(I have this problem also in our environment from time to time if there is some network stuck in WAN connection...)