Add GetServerStatus RPC to use in PRS (#16022)

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

go/test/endtoend/tabletmanager/main_test.go

@@ -185,6 +185,11 @@ func tmcPrimaryPosition(ctx context.Context, tabletGrpcPort int) (string, error)
 	return tmClient.PrimaryPosition(ctx, vtablet)
 }
 
+func tmcGetGlobalStatusVars(ctx context.Context, tabletGrpcPort int, variables []string) (map[string]string, error) {
+	vtablet := getTablet(tabletGrpcPort)
+	return tmClient.GetGlobalStatusVars(ctx, vtablet, variables)
+}
+
 func tmcStartReplicationUntilAfter(ctx context.Context, tabletGrpcPort int, positon string, waittime time.Duration) error {
 	vtablet := getTablet(tabletGrpcPort)
 	return tmClient.StartReplicationUntilAfter(ctx, vtablet, positon, waittime)

go/test/endtoend/tabletmanager/tablet_test.go

@@ -19,6 +19,7 @@ package tabletmanager
 import (
 	"context"
 	"fmt"
+	"strconv"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -100,3 +101,31 @@ func TestResetReplicationParameters(t *testing.T) {
 	require.NoError(t, err)
 	require.Len(t, res.Rows, 0)
 }
+
+// TestGetGlobalStatusVars tests the GetGlobalStatusVars RPC
+func TestGetGlobalStatusVars(t *testing.T) {
+	ctx := context.Background()
+	statusValues, err := tmcGetGlobalStatusVars(ctx, replicaTablet.GrpcPort, []string{"Innodb_buffer_pool_pages_data", "unknown_value"})
+	require.NoError(t, err)
+	require.Len(t, statusValues, 1)
+	checkValueGreaterZero(t, statusValues, "Innodb_buffer_pool_pages_data")
+
+	statusValues, err = tmcGetGlobalStatusVars(ctx, replicaTablet.GrpcPort, []string{"Uptime", "Innodb_buffer_pool_pages_data"})
+	require.NoError(t, err)
+	require.Len(t, statusValues, 2)
+	checkValueGreaterZero(t, statusValues, "Innodb_buffer_pool_pages_data")
+	checkValueGreaterZero(t, statusValues, "Uptime")
+
+	statusValues, err = tmcGetGlobalStatusVars(ctx, replicaTablet.GrpcPort, nil)
+	require.NoError(t, err)
+	require.Greater(t, len(statusValues), 250)
+	checkValueGreaterZero(t, statusValues, "Innodb_buffer_pool_pages_data")
+	checkValueGreaterZero(t, statusValues, "Innodb_buffer_pool_pages_free")
+	checkValueGreaterZero(t, statusValues, "Uptime")
+}
+
+func checkValueGreaterZero(t *testing.T, statusValues map[string]string, val string) {
+	valInMap, err := strconv.Atoi(statusValues[val])
+	require.NoError(t, err)
+	require.Greater(t, valInMap, 0)
+}

go/vt/mysqlctl/fakemysqldaemon.go

@@ -417,6 +417,13 @@ func (fmd *FakeMysqlDaemon) SetSuperReadOnly(ctx context.Context, on bool) (Rese
 	return nil, nil
 }
 
+// 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,
+	})
+}
+
 // StartReplication is part of the MysqlDaemon interface.
 func (fmd *FakeMysqlDaemon) StartReplication(ctx context.Context, hookExtraEnv map[string]string) error {
 	if fmd.StartReplicationError != nil {

go/vt/mysqlctl/mysql_daemon.go

@@ -53,6 +53,10 @@ type MysqlDaemon interface {
 	// GetServerUUID returns the servers UUID
 	GetServerUUID(ctx context.Context) (string, error)
 
+	// GetGlobalStatusVars returns the server's global status variables asked for.
+	// An empty/nil variable name parameter slice means you want all of them.
+	GetGlobalStatusVars(ctx context.Context, variables []string) (map[string]string, error)
+
 	// replication related methods
 	StartReplication(ctx context.Context, hookExtraEnv map[string]string) error
 	RestartReplication(ctx context.Context, hookExtraEnv map[string]string) error

go/vt/mysqlctl/replication.go

@@ -32,12 +32,20 @@ import (
 	"vitess.io/vitess/go/mysql"
 	"vitess.io/vitess/go/mysql/replication"
 	"vitess.io/vitess/go/netutil"
+	"vitess.io/vitess/go/sqltypes"
 	"vitess.io/vitess/go/vt/hook"
 	"vitess.io/vitess/go/vt/log"
 	"vitess.io/vitess/go/vt/proto/replicationdata"
+	vtrpcpb "vitess.io/vitess/go/vt/proto/vtrpc"
+	"vitess.io/vitess/go/vt/sqlparser"
 	"vitess.io/vitess/go/vt/vterrors"
 )
 
+const (
+	// Queries used for RPCs
+	getGlobalStatusQuery = "SELECT variable_name, variable_value FROM performance_schema.global_status"
+)
+
 type ResetSuperReadOnlyFunc func() error
 
 // WaitForReplicationStart waits until the deadline for replication to start.
@@ -228,6 +236,38 @@ func (mysqld *Mysqld) GetServerUUID(ctx context.Context) (string, error) {
 	return conn.Conn.GetServerUUID()
 }
 
+// GetGlobalStatusVars returns the server's global status variables asked for.
+// An empty/nil variable name parameter slice means you want all of them.
+func (mysqld *Mysqld) GetGlobalStatusVars(ctx context.Context, variables []string) (map[string]string, error) {
+	query := getGlobalStatusQuery
+	if len(variables) != 0 {
+		// The format specifier is for any optional predicates.
+		statusBv, err := sqltypes.BuildBindVariable(variables)
+		if err != nil {
+			return nil, err
+		}
+		query, err = sqlparser.ParseAndBind(getGlobalStatusQuery+" WHERE variable_name IN %a",
+			statusBv,
+		)
+		if err != nil {
+			return nil, err
+		}
+	}
+	qr, err := mysqld.FetchSuperQuery(ctx, query)
+	if err != nil {
+		return nil, err
+	}
+
+	finalRes := make(map[string]string, len(qr.Rows))
+	for _, row := range qr.Rows {
+		if len(row) != 2 {
+			return nil, vterrors.New(vtrpcpb.Code_INTERNAL, "incorrect number of fields in the row")
+		}
+		finalRes[row[0].ToString()] = row[1].ToString()
+	}
+	return finalRes, nil
+}
+
 // IsReadOnly return true if the instance is read only
 func (mysqld *Mysqld) IsReadOnly(ctx context.Context) (bool, error) {
 	qr, err := mysqld.FetchSuperQuery(ctx, "SHOW VARIABLES LIKE 'read_only'")