Fix: reset transaction session when no reserved connection

go/test/endtoend/cluster/cluster_process.go

@@ -854,7 +854,7 @@ func (cluster *LocalProcessCluster) ExecOnTablet(ctx context.Context, vttablet *
 		return nil, err
 	}
 
-	tablet, err := cluster.vtctlclientGetTablet(vttablet)
+	tablet, err := cluster.VtctlclientGetTablet(vttablet)
 	if err != nil {
 		return nil, err
 	}
@@ -897,7 +897,7 @@ func (cluster *LocalProcessCluster) ExecOnVTGate(ctx context.Context, addr strin
 // returns the responses. It returns an error if the stream ends with fewer than
 // `count` responses.
 func (cluster *LocalProcessCluster) StreamTabletHealth(ctx context.Context, vttablet *Vttablet, count int) (responses []*querypb.StreamHealthResponse, err error) {
-	tablet, err := cluster.vtctlclientGetTablet(vttablet)
+	tablet, err := cluster.VtctlclientGetTablet(vttablet)
 	if err != nil {
 		return nil, err
 	}
@@ -929,7 +929,7 @@ func (cluster *LocalProcessCluster) StreamTabletHealth(ctx context.Context, vtta
 	return responses, nil
 }
 
-func (cluster *LocalProcessCluster) vtctlclientGetTablet(tablet *Vttablet) (*topodatapb.Tablet, error) {
+func (cluster *LocalProcessCluster) VtctlclientGetTablet(tablet *Vttablet) (*topodatapb.Tablet, error) {
 	result, err := cluster.VtctlclientProcess.ExecuteCommandWithOutput("GetTablet", "--", tablet.Alias)
 	if err != nil {
 		return nil, err

go/test/endtoend/reparent/prssettingspool/main_test.go

@@ -0,0 +1,148 @@
+/*
+Copyright 2023 The Vitess Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package misc
+
+import (
+	"context"
+	_ "embed"
+	"flag"
+	"os"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+
+	"vitess.io/vitess/go/mysql"
+	"vitess.io/vitess/go/test/endtoend/cluster"
+	rutils "vitess.io/vitess/go/test/endtoend/reparent/utils"
+	"vitess.io/vitess/go/test/endtoend/utils"
+)
+
+var (
+	clusterInstance *cluster.LocalProcessCluster
+	vtParams        mysql.ConnParams
+	keyspaceName    = "ks"
+	cell            = "test"
+
+	//go:embed schema.sql
+	schemaSQL string
+)
+
+func TestMain(m *testing.M) {
+	defer cluster.PanicHandler(nil)
+	flag.Parse()
+
+	exitCode := func() int {
+		clusterInstance = cluster.NewCluster(cell, "localhost")
+		defer clusterInstance.Teardown()
+
+		// Start topo server
+		err := clusterInstance.StartTopo()
+		if err != nil {
+			return 1
+		}
+
+		// Start keyspace
+		keyspace := &cluster.Keyspace{
+			Name:      keyspaceName,
+			SchemaSQL: schemaSQL,
+		}
+		clusterInstance.VtTabletExtraArgs = append(clusterInstance.VtTabletExtraArgs,
+			"--queryserver-enable-settings-pool")
+		err = clusterInstance.StartUnshardedKeyspace(*keyspace, 2, false)
+		if err != nil {
+			return 1
+		}
+
+		// Start vtgate
+		clusterInstance.VtGateExtraArgs = append(clusterInstance.VtGateExtraArgs,
+			"--planner-version", "gen4")
+		err = clusterInstance.StartVtgate()
+		if err != nil {
+			return 1
+		}
+
+		vtParams = mysql.ConnParams{
+			Host: clusterInstance.Hostname,
+			Port: clusterInstance.VtgateMySQLPort,
+		}
+		return m.Run()
+	}()
+	os.Exit(exitCode)
+}
+
+func TestSettingsPoolWithTXAndPRS(t *testing.T) {
+	ctx := context.Background()
+	conn, err := mysql.Connect(ctx, &vtParams)
+	require.NoError(t, err)
+	defer conn.Close()
+
+	// set a system settings that will trigger reserved connection usage.
+	utils.Exec(t, conn, "set default_week_format = 5")
+
+	// have transaction on the session
+	utils.Exec(t, conn, "begin")
+	utils.Exec(t, conn, "select id1, id2 from t1")
+	utils.Exec(t, conn, "commit")
+
+	tablets := clusterInstance.Keyspaces[0].Shards[0].Vttablets
+
+	// prs should happen without any error.
+	text, err := rutils.Prs(t, clusterInstance, tablets[1])
+	require.NoError(t, err, text)
+	rutils.WaitForTabletToBeServing(t, clusterInstance, tablets[0], 1*time.Minute)
+
+	defer func() {
+		// reset state
+		text, err = rutils.Prs(t, clusterInstance, tablets[0])
+		require.NoError(t, err, text)
+		rutils.WaitForTabletToBeServing(t, clusterInstance, tablets[1], 1*time.Minute)
+	}()
+
+	// no error should occur and it should go to the right tablet.
+	utils.Exec(t, conn, "select id1, id2 from t1")
+}
+
+func TestSettingsPoolWithoutTXAndPRS(t *testing.T) {
+	ctx := context.Background()
+	conn, err := mysql.Connect(ctx, &vtParams)
+	require.NoError(t, err)
+	defer conn.Close()
+
+	// set a system settings that will trigger reserved connection usage.
+	utils.Exec(t, conn, "set default_week_format = 5")
+
+	// execute non-tx query
+	utils.Exec(t, conn, "select id1, id2 from t1")
+
+	tablets := clusterInstance.Keyspaces[0].Shards[0].Vttablets
+
+	// prs should happen without any error.
+	text, err := rutils.Prs(t, clusterInstance, tablets[1])
+	require.NoError(t, err, text)
+	rutils.WaitForTabletToBeServing(t, clusterInstance, tablets[0], 1*time.Minute)
+	defer func() {
+		// reset state
+		text, err = rutils.Prs(t, clusterInstance, tablets[0])
+		require.NoError(t, err, text)
+		rutils.WaitForTabletToBeServing(t, clusterInstance, tablets[1], 1*time.Minute)
+	}()
+
+	// no error should occur and it should go to the right tablet.
+	utils.Exec(t, conn, "select id1, id2 from t1")
+
+}

go/test/endtoend/reparent/prssettingspool/schema.sql

@@ -0,0 +1,5 @@
+create table t1(
+                   id1 bigint,
+                   id2 bigint,
+                   primary key(id1)
+) Engine=InnoDB;

go/test/endtoend/reparent/utils/utils.go

@@ -31,6 +31,9 @@ import (
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
+	querypb "vitess.io/vitess/go/vt/proto/query"
+	"vitess.io/vitess/go/vt/vttablet/tabletconn"
+
 	"vitess.io/vitess/go/json2"
 	"vitess.io/vitess/go/mysql"
 	"vitess.io/vitess/go/sqltypes"
@@ -695,3 +698,24 @@ func CheckReplicationStatus(ctx context.Context, t *testing.T, tablet *cluster.V
 		require.Equal(t, "No", res.Rows[0][11].ToString())
 	}
 }
+
+func WaitForTabletToBeServing(t *testing.T, clusterInstance *cluster.LocalProcessCluster, tablet *cluster.Vttablet, timeout time.Duration) {
+	vTablet, err := clusterInstance.VtctlclientGetTablet(tablet)
+	require.NoError(t, err)
+
+	tConn, err := tabletconn.GetDialer()(vTablet, false)
+	require.NoError(t, err)
+
+	newCtx, cancel := context.WithTimeout(context.Background(), timeout)
+	err = tConn.StreamHealth(newCtx, func(shr *querypb.StreamHealthResponse) error {
+		if shr.Serving {
+			cancel()
+		}
+		return nil
+	})
+
+	// the error should only be because we cancelled the context when the tablet became serving again.
+	if err != nil && !strings.Contains(err.Error(), "context canceled") {
+		t.Fatal(err.Error())
+	}
+}

go/vt/vtgate/safe_session.go

@@ -151,11 +151,22 @@ func (session *SafeSession) ResetTx() {
 	session.mu.Lock()
 	defer session.mu.Unlock()
 	session.resetCommonLocked()
-	if !session.Session.InReservedConn {
-		session.ShardSessions = nil
-		session.PreSessions = nil
-		session.PostSessions = nil
+	// If settings pools is enabled on the vttablet.
+	// This variable will be true but there will not be a shard session with reserved connection id.
+	// So, we should check the shard session and not just this variable.
+	if session.Session.InReservedConn {
+		allSessions := append(session.ShardSessions, append(session.PreSessions, session.PostSessions...)...)
+		for _, ss := range allSessions {
+			if ss.ReservedId != 0 {
+				// found that reserved connection exists.
+				// abort here, we should keep the shard sessions.
+				return
+			}
+		}
 	}
+	session.ShardSessions = nil
+	session.PreSessions = nil
+	session.PostSessions = nil
 }
 
 // Reset clears the session

test/config.json

@@ -1214,6 +1214,15 @@
 			"Shard": "vttablet_prscomplex",
 			"RetryMax": 1,
 			"Tags": [""]
+		},
+		"prssettingspool": {
+			"File": "unused.go",
+			"Args": ["vitess.io/vitess/go/test/endtoend/reparent/prssettingspool"],
+			"Command": [],
+			"Manual": false,
+			"Shard": "vttablet_prscomplex",
+			"RetryMax": 1,
+			"Tags": [""]
 		}
 	}
 }