vtgate does not support killing queries

[aquarapid]

This would be non-trivial to support, but adding here to track:

• For long-running queries against vtgate, issuing a CTRL-C in the mysql client will generate a "KILL QUERY X" against vtgate, where "X" is the mysql process list id.
• vtgate does not support this, and sends back an mysql ERR packet (0xff) with error code 1105 and SQL state HY000, and error message "vtgate: http://localhost:15001/: unrecognized statement: KILL QUERY 8"
• This does not mean anything to the mysql client, which just continues waiting (hanging), besides printing something like " -- query aborted".

It would be ideal if we could somehow map the kill query to the running backend (vttablet) query and issue a (real) kill.

[aquarapid]

As a generalization of this; this also means that JDBC Statement.cancel() will not work with Vitess (it does with MySQL with any recent MySQL Connector/J driver).

Note that since the MySQL Connector/J implementation of cancel() uses a second database connection to issue a KILL QUERY command for the query being canceled, this introduces an additional problem in that we can't necessarily guarantee that the initial connection and the second connection are to the same vtgate instance...

[derekperkins]

This does work correctly with the gRPC client though, right?

[aquarapid]

This does work correctly with the gRPC client though, right?

Yes it does; to clarify: I meant all of the above in the context of the MySQL protocol interface of vtgate.