Revert "server: Set default drainClientWait as 15s (pingcap#42134) (p…

…ingcap#48944)"

This reverts commit 877198d.

server/conn.go

@@ -1111,8 +1111,6 @@ func (cc *clientConn) Run(ctx context.Context) {
 	// by CAS operation, it would then take some actions accordingly.
 	for {
 		// Close connection between txn when we are going to shutdown server.
-		// Note the current implementation when shutting down, for an idle connection, the connection may block at readPacket()
-		// consider provider a way to close the connection directly after sometime if we can not read any data.
 		if cc.server.inShutdownMode.Load() {
 			if !cc.ctx.GetSessionVars().InTxn() {
 				return

tidb-server/main.go

@@ -836,15 +836,17 @@ func closeDomainAndStorage(storage kv.Storage, dom *domain.Domain) {
 	terror.Log(errors.Trace(err))
 }
 
-// The amount of time we wait for the ongoing txt to finished.
-// We should better provider a dynamic way to set this value.
 var gracefulCloseConnectionsTimeout = 15 * time.Second
 
-func cleanup(svr *server.Server, storage kv.Storage, dom *domain.Domain, _ bool) {
+func cleanup(svr *server.Server, storage kv.Storage, dom *domain.Domain, graceful bool) {
 	dom.StopAutoAnalyze()
 
-	drainClientWait := gracefulCloseConnectionsTimeout
-
+	var drainClientWait time.Duration
+	if graceful {
+		drainClientWait = 1<<63 - 1
+	} else {
+		drainClientWait = gracefulCloseConnectionsTimeout
+	}
 	cancelClientWait := time.Second * 1
 	svr.DrainClients(drainClientWait, cancelClientWait)