[ERROR] Unexpected packet from client <IP> . Session_status: 6 , client_status: 0 Disconnecting it

[Lubomir Budzak]

Hello,

I'm experiencing very strange behavior from ProxySQL.

I've got application which have to connect to MariaDB but app can't connect through proxysql as connections are keep killed by proxysql. 

If I point app directly to MariaDB server, it works fine without dropped connections.

I also tried to switch on fast_forward and in this case app works fine. 

Multiplexing has been switched off and on but without any difference in behavior.

Does any of you gurus experienced such behavior?

ProxySQL ver.: 3.0.1

MariaDB ver.: 10.3.

Below messages are repeating in the logs. 

Proxysql.log

2025-07-30 10:29:28 MySQL_Session.cpp:3688:handler___status_NONE_or_default(): [ERROR] Unexpected packet from client <IP> . Session_status: 6 , client_status: 0 Disconnecting it
2025-07-30 10:29:33 MySQL_Session.cpp:3688:handler___status_NONE_or_default(): [ERROR] Unexpected packet from client  <IP>  . Session_status: 6 , client_status: 0 Disconnecting it
2025-07-30 10:29:33 MySQL_Session.cpp:3688:handler___status_NONE_or_default(): [ERROR] Unexpected packet from client  <IP>  . Session_status: 10 , client_status: 0 Disconnecting it
2025-07-30 10:29:33 MySQL_Session.cpp:269:kill_query_thread(): [WARNING] KILL CONNECTION 55202 on db-server-01:3306 

MariaDB.log

2025-07-30 10:31:56 55295 [Warning] Aborted connection 55295 to db: 'dev' user: 'dev' host: 'proxy-01' (Got an error reading communication packets)
2025-07-30 10:31:56 55295 [Warning] Aborted connection 55295 to db: 'dev' user: 'dev' host: 'proxy-01' (CLOSE_CONNECTION)

Thank you in advance.

Best Regards

Lubo

[René Cannaò]

Hi Lubo,

Thank you for using ProxySQL.

ProxySQL internally has a state machine, and the error you are seeing means that proxysql received a packet from the client while it was not expecting it (according to its state machine).

In the past we identified multiple scenarios when this happened, for example:
* haproxy sends a QUIT command before authentication is completed : proxysql handles this

* a client can send a QUIT command while waiting for a query to complete: proxysql handles this

* a client can send a query before authentication is completed: we have seen this with mariadb connector/J and it is a configuration setting (I don't remember the name), proxysql doesn't handle this

* mariadb connector/J with useBatchMultiSend enabled , where multiple queries can be sent without waiting for them to complete : proxysql doesn't support it

Can you share the output of tcpdump (or equivalent) so we can understand what is happening?

Thanks,

René

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[Lubomir Budzak]

Hi Rene,

Thank you for your answer.

I'm suspecting that the problem is described in your last point.

I'm in touch with vendor of the application to clarify this.

Are there plans for ProxySQL to support those batchmultisend transactions?

Thanks,

Lubo

[René Cannaò]

Hi Lubo,

No, there is no plan to support useBatchMultiSend, as we believe it is a good practice and we don't want to encourage it.

Setting useBatchMultiSend can make sending data to the server (or ProxySQL in this case) more efficient, but it is a nightmare for error handling.

A query may fail, and the client would have already sent more data without knowing that a previous query failed.

We have seen useBatchMultiSend being used mostly for INSERT statements. In that case, using multi-rows INSERT statements would be way more efficient in term of performance (1 INSERT with 100 rows is more efficient than 100 INSERTs with 1 row each even if useBatchMultiSend is used), and it completely remove the error handling nightmare.

For reference:

https://dev.mysql.com/doc/refman/8.4/en/insert-optimization.html

To view this discussion visit https://groups.google.com/d/msgid/proxysql/ccd5d297-9db6-4fd0-90bf-bf5bdecde034n%40googlegroups.com.

[René Cannaò]

Typo in my previous email:

as we believe it is not a good practice and we don't want to encourage it.

[Lubomir Budzak]

Hi Rene,

I had a meeting with software vendor and they will fix this issue with useBatchMultiSend.

One question arise during meeting. How should be preset continueBatchOnError as it is enabled by default.

My understanding is that, this option should be disabled. Am I right?

Is the option continueBatchOnError restricted by ProxySQL?

Best Regards

Lubo