TiDB can't close connection immediately after killing client process

[pcqz]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

Run a tidb instance locally, and execute select sleep(300); in a connection.
Then kill this client process ps aux | grep -i mysql | grep -v grep | awk '{print $2}' | xargs kill

2. What did you expect to see? (Required)

The connection is closed immediately like mysql.

3. What did you see instead (Required)

The connection is still in processlist and closed after 300s of execution.

4. What is your TiDB version? (Required)

v8.2.0

[pcqz]

/report customer

[yibin87]

The sleep command can be killed by "kill" command. It seems the killing of client doesn't send kill signal to the target sleep process. I think this should be a sql infra issue.

[yibin87]

/sig infra

[ti-chi-bot]

@yibin87: The label(s) sig/infra cannot be applied, because the repository doesn't have them.

In response to this:

/sig infra

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the ti-community-infra/tichi repository.

[yibin87]

/sig sql-infra

[yibin87]

/remove-sig execution

[Defined2014]

The biggest different is MySQL could sense the tcp connect closed which TiDB can't.

MySQL, it replied a response after the kill processed:

If we want do it, we can monitor the fd of conn in the background and terminate SQL when a read signal is received and EOF is read.

A very hack way to acheive it

diff --git a/pkg/server/conn.go b/pkg/server/conn.go
index e201ff3cb4..05c6e5085a 100644
--- a/pkg/server/conn.go
+++ b/pkg/server/conn.go
@@ -1375,6 +1375,14 @@ func (cc *clientConn) dispatch(ctx context.Context, data []byte) error {
                        data = data[:len(data)-1]
                        dataStr = string(hack.String(data))
                }
+               go func(cc *clientConn) {
+                       b := make([]byte, 100)
+                       if idx := strings.Index(dataStr, "sleep"); idx >= 0 {
+                               if _, err := cc.bufReadConn.Conn.Read(b); err != nil {
+                                       killQuery(cc, false, false)
+                               }
+                       }
+               }(cc)
                return cc.handleQuery(ctx, dataStr)
        case mysql.ComFieldList:
                return cc.handleFieldList(ctx, dataStr)

[dveeden]

This is what go-sql-driver/mysql uses: https://github.com/go-sql-driver/mysql/blob/v1.8.1/conncheck.go