Prefer replicas that have innodb buffer pool populated in PRS (vitess…

…io#16374)

Signed-off-by: Manan Gupta <manan@planetscale.com>

go/test/endtoend/reparent/plannedreparent/reparent_test.go

@@ -297,17 +297,14 @@ func TestReparentWithDownReplica(t *testing.T) {
 	// Perform a graceful reparent operation. It will fail as one tablet is down.
 	out, err := utils.Prs(t, clusterInstance, tablets[1])
 	require.Error(t, err)
-	var insertVal int
 	// Assert that PRS failed
-	if clusterInstance.VtctlMajorVersion <= 17 {
-		assert.True(t, utils.SetReplicationSourceFailed(tablets[2], out))
-		// insert data into the new primary, check the connected replica work
-		insertVal = utils.ConfirmReplication(t, tablets[1], []*cluster.Vttablet{tablets[0], tablets[3]})
-	} else {
+	if clusterInstance.VtctlMajorVersion <= 20 {
 		assert.Contains(t, out, fmt.Sprintf("TabletManager.PrimaryStatus on %s", tablets[2].Alias))
-		// insert data into the old primary, check the connected replica works. The primary tablet shouldn't have changed.
-		insertVal = utils.ConfirmReplication(t, tablets[0], []*cluster.Vttablet{tablets[1], tablets[3]})
+	} else {
+		assert.Contains(t, out, fmt.Sprintf("TabletManager.GetGlobalStatusVars on %s", tablets[2].Alias))
 	}
+	// insert data into the old primary, check the connected replica works. The primary tablet shouldn't have changed.
+	insertVal := utils.ConfirmReplication(t, tablets[0], []*cluster.Vttablet{tablets[1], tablets[3]})
 
 	// restart mysql on the old replica, should still be connecting to the old primary
 	tablets[2].MysqlctlProcess.InitMysql = false

go/vt/mysqlctl/fakemysqldaemon.go

@@ -96,6 +96,9 @@ type FakeMysqlDaemon struct {
 	// PrimaryStatusError is used by PrimaryStatus.
 	PrimaryStatusError error
 
+	// GlobalStatusVars is used by GetGlobalStatusVars.
+	GlobalStatusVars map[string]string
+
 	// CurrentSourceHost is returned by ReplicationStatus.
 	CurrentSourceHost string
 
@@ -419,9 +422,7 @@ func (fmd *FakeMysqlDaemon) SetSuperReadOnly(ctx context.Context, on bool) (Rese
 
 // GetGlobalStatusVars is part of the MysqlDaemon interface.
 func (fmd *FakeMysqlDaemon) GetGlobalStatusVars(ctx context.Context, variables []string) (map[string]string, error) {
-	return make(map[string]string), fmd.ExecuteSuperQueryList(ctx, []string{
-		"FAKE " + getGlobalStatusQuery,
-	})
+	return fmd.GlobalStatusVars, nil
 }
 
 // StartReplication is part of the MysqlDaemon interface.

go/vt/vtctl/grpcvtctldserver/server_slow_test.go

@@ -25,6 +25,7 @@ import (
 	"github.com/stretchr/testify/require"
 
 	"vitess.io/vitess/go/mysql/replication"
+	"vitess.io/vitess/go/vt/vtctl/reparentutil"
 
 	"vitess.io/vitess/go/mysql"
 	"vitess.io/vitess/go/protoutil"
@@ -402,19 +403,24 @@ func TestPlannedReparentShardSlow(t *testing.T) {
 						Error: nil,
 					},
 				},
-				// This is only needed to verify reachability, so empty results are fine.
-				PrimaryStatusResults: map[string]struct {
-					Status *replicationdatapb.PrimaryStatus
-					Error  error
+				GetGlobalStatusVarsResults: map[string]struct {
+					Statuses map[string]string
+					Error    error
 				}{
 					"zone1-0000000200": {
-						Status: &replicationdatapb.PrimaryStatus{},
+						Statuses: map[string]string{
+							reparentutil.InnodbBufferPoolsDataVar: "123",
+						},
 					},
 					"zone1-0000000101": {
-						Status: &replicationdatapb.PrimaryStatus{},
+						Statuses: map[string]string{
+							reparentutil.InnodbBufferPoolsDataVar: "123",
+						},
 					},
 					"zone1-0000000100": {
-						Status: &replicationdatapb.PrimaryStatus{},
+						Statuses: map[string]string{
+							reparentutil.InnodbBufferPoolsDataVar: "123",
+						},
 					},
 				},
 				PrimaryPositionResults: map[string]struct {
@@ -519,19 +525,24 @@ func TestPlannedReparentShardSlow(t *testing.T) {
 						Error: nil,
 					},
 				},
-				// This is only needed to verify reachability, so empty results are fine.
-				PrimaryStatusResults: map[string]struct {
-					Status *replicationdatapb.PrimaryStatus
-					Error  error
+				GetGlobalStatusVarsResults: map[string]struct {
+					Statuses map[string]string
+					Error    error
 				}{
 					"zone1-0000000200": {
-						Status: &replicationdatapb.PrimaryStatus{},
+						Statuses: map[string]string{
+							reparentutil.InnodbBufferPoolsDataVar: "123",
+						},
 					},
 					"zone1-0000000101": {
-						Status: &replicationdatapb.PrimaryStatus{},
+						Statuses: map[string]string{
+							reparentutil.InnodbBufferPoolsDataVar: "123",
+						},
 					},
 					"zone1-0000000100": {
-						Status: &replicationdatapb.PrimaryStatus{},
+						Statuses: map[string]string{
+							reparentutil.InnodbBufferPoolsDataVar: "123",
+						},
 					},
 				},
 				PrimaryPositionResults: map[string]struct {

go/vt/vtctl/grpcvtctldserver/server_test.go

@@ -29,6 +29,7 @@ import (
 	"time"
 
 	_flag "vitess.io/vitess/go/internal/flag"
+	"vitess.io/vitess/go/vt/vtctl/reparentutil"
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -8296,19 +8297,24 @@ func TestPlannedReparentShard(t *testing.T) {
 						Error: nil,
 					},
 				},
-				// This is only needed to verify reachability, so empty results are fine.
-				PrimaryStatusResults: map[string]struct {
-					Status *replicationdatapb.PrimaryStatus
-					Error  error
+				GetGlobalStatusVarsResults: map[string]struct {
+					Statuses map[string]string
+					Error    error
 				}{
 					"zone1-0000000200": {
-						Status: &replicationdatapb.PrimaryStatus{},
+						Statuses: map[string]string{
+							reparentutil.InnodbBufferPoolsDataVar: "123",
+						},
 					},
 					"zone1-0000000101": {
-						Status: &replicationdatapb.PrimaryStatus{},
+						Statuses: map[string]string{
+							reparentutil.InnodbBufferPoolsDataVar: "123",
+						},
 					},
 					"zone1-0000000100": {
-						Status: &replicationdatapb.PrimaryStatus{},
+						Statuses: map[string]string{
+							reparentutil.InnodbBufferPoolsDataVar: "123",
+						},
 					},
 				},
 				PrimaryPositionResults: map[string]struct {
@@ -8425,19 +8431,22 @@ func TestPlannedReparentShard(t *testing.T) {
 				},
 			},
 			tmc: &testutil.TabletManagerClient{
-				// This is only needed to verify reachability, so empty results are fine.
-				PrimaryStatusResults: map[string]struct {
-					Status *replicationdatapb.PrimaryStatus
-					Error  error
+				GetGlobalStatusVarsResults: map[string]struct {
+					Statuses map[string]string
+					Error    error
 				}{
 					"zone1-0000000200": {
-						Error: fmt.Errorf("primary status failed"),
+						Error: fmt.Errorf("global status vars failed"),
 					},
 					"zone1-0000000101": {
-						Status: &replicationdatapb.PrimaryStatus{},
+						Statuses: map[string]string{
+							reparentutil.InnodbBufferPoolsDataVar: "123",
+						},
 					},
 					"zone1-0000000100": {
-						Status: &replicationdatapb.PrimaryStatus{},
+						Statuses: map[string]string{
+							reparentutil.InnodbBufferPoolsDataVar: "123",
+						},
 					},
 				},
 			},
@@ -8451,7 +8460,7 @@ func TestPlannedReparentShard(t *testing.T) {
 				WaitReplicasTimeout: protoutil.DurationToProto(time.Millisecond * 10),
 			},
 			expectEventsToOccur: true,
-			expectedErr:         "primary status failed",
+			expectedErr:         "global status vars failed",
 		},
 	}
 

go/vt/vtctl/grpcvtctldserver/testutil/test_tmclient.go

@@ -250,6 +250,7 @@ type TabletManagerClient struct {
 		Schema *tabletmanagerdatapb.SchemaDefinition
 		Error  error
 	}
+	GetGlobalStatusVarsDelays  map[string]time.Duration
 	GetGlobalStatusVarsResults map[string]struct {
 		Statuses map[string]string
 		Error    error
@@ -742,6 +743,17 @@ func (fake *TabletManagerClient) GetGlobalStatusVars(ctx context.Context, tablet
 	}
 
 	key := topoproto.TabletAliasString(tablet.Alias)
+	if fake.GetGlobalStatusVarsDelays != nil {
+		if delay, ok := fake.GetGlobalStatusVarsDelays[key]; ok {
+			select {
+			case <-ctx.Done():
+				return nil, ctx.Err()
+			case <-time.After(delay):
+				// proceed to results
+			}
+		}
+	}
+
 	if result, ok := fake.GetGlobalStatusVarsResults[key]; ok {
 		return result.Statuses, result.Error
 	}

go/vt/vtctl/reparentutil/emergency_reparenter.go

@@ -390,7 +390,7 @@ func (erp *EmergencyReparenter) findMostAdvanced(
 	}
 
 	// sort the tablets for finding the best intermediate source in ERS
-	err = sortTabletsForReparent(validTablets, tabletPositions, opts.durability)
+	err = sortTabletsForReparent(validTablets, tabletPositions, nil, opts.durability)
 	if err != nil {
 		return nil, nil, err
 	}

go/vt/vtctl/reparentutil/planned_reparenter.go

@@ -19,6 +19,7 @@ package reparentutil
 import (
 	"context"
 	"fmt"
+	"strconv"
 	"sync"
 	"time"
 
@@ -44,6 +45,7 @@ var (
 	prsCounter = stats.NewCountersWithMultiLabels("PlannedReparentCounts", "Number of times Planned Reparent Shard has been run",
 		[]string{"Keyspace", "Shard", "Result"},
 	)
+	InnodbBufferPoolsDataVar = "Innodb_buffer_pool_pages_data"
 )
 
 // PlannedReparenter performs PlannedReparentShard operations.
@@ -158,6 +160,7 @@ func (pr *PlannedReparenter) preflightChecks(
 	ctx context.Context,
 	ev *events.Reparent,
 	tabletMap map[string]*topo.TabletInfo,
+	innodbBufferPoolData map[string]int,
 	opts *PlannedReparentOptions, // we take a pointer here to set NewPrimaryAlias
 ) (isNoop bool, err error) {
 	// We don't want to fail when both NewPrimaryAlias and AvoidPrimaryAlias are nil.
@@ -178,7 +181,7 @@ func (pr *PlannedReparenter) preflightChecks(
 	}
 
 	event.DispatchUpdate(ev, "electing a primary candidate")
-	opts.NewPrimaryAlias, err = ElectNewPrimary(ctx, pr.tmc, &ev.ShardInfo, tabletMap, opts.NewPrimaryAlias, opts.AvoidPrimaryAlias, opts.WaitReplicasTimeout, opts.TolerableReplLag, opts.durability, pr.logger)
+	opts.NewPrimaryAlias, err = ElectNewPrimary(ctx, pr.tmc, &ev.ShardInfo, tabletMap, innodbBufferPoolData, opts.NewPrimaryAlias, opts.AvoidPrimaryAlias, opts.WaitReplicasTimeout, opts.TolerableReplLag, opts.durability, pr.logger)
 	if err != nil {
 		return true, err
 	}
@@ -523,13 +526,13 @@ func (pr *PlannedReparenter) reparentShardLocked(
 		return err
 	}
 
-	err = pr.verifyAllTabletsReachable(ctx, tabletMap)
+	innodbBufferPoolData, err := pr.verifyAllTabletsReachable(ctx, tabletMap)
 	if err != nil {
 		return err
 	}
 
 	// Check invariants that PlannedReparentShard depends on.
-	if isNoop, err := pr.preflightChecks(ctx, ev, tabletMap, &opts); err != nil {
+	if isNoop, err := pr.preflightChecks(ctx, ev, tabletMap, innodbBufferPoolData, &opts); err != nil {
 		return err
 	} else if isNoop {
 		return nil
@@ -730,18 +733,30 @@ func (pr *PlannedReparenter) reparentTablets(
 }
 
 // verifyAllTabletsReachable verifies that all the tablets are reachable when running PRS.
-func (pr *PlannedReparenter) verifyAllTabletsReachable(ctx context.Context, tabletMap map[string]*topo.TabletInfo) error {
+func (pr *PlannedReparenter) verifyAllTabletsReachable(ctx context.Context, tabletMap map[string]*topo.TabletInfo) (map[string]int, error) {
 	// Create a cancellable context for the entire set of RPCs to verify reachability.
 	verifyCtx, verifyCancel := context.WithTimeout(ctx, topo.RemoteOperationTimeout)
 	defer verifyCancel()
 
+	innodbBufferPoolsData := make(map[string]int)
+	var mu sync.Mutex
 	errorGroup, groupCtx := errgroup.WithContext(verifyCtx)
-	for _, info := range tabletMap {
+	for tblStr, info := range tabletMap {
 		tablet := info.Tablet
 		errorGroup.Go(func() error {
-			_, err := pr.tmc.PrimaryStatus(groupCtx, tablet)
-			return err
+			statusValues, err := pr.tmc.GetGlobalStatusVars(groupCtx, tablet, []string{InnodbBufferPoolsDataVar})
+			if err != nil {
+				return err
+			}
+			// We are ignoring the error in conversion because some MySQL variants might not have this
+			// status variable like MariaDB.
+			val, _ := strconv.Atoi(statusValues[InnodbBufferPoolsDataVar])
+			mu.Lock()
+			defer mu.Unlock()
+			innodbBufferPoolsData[tblStr] = val
+			return nil
 		})
 	}
-	return errorGroup.Wait()
+	err := errorGroup.Wait()
+	return innodbBufferPoolsData, err
 }