*: implement the INSPECTION_SCHEMA to provide snapshot of inspection tables

infoschema/infoschema.go

@@ -370,16 +370,6 @@ func init() {
 	RegisterVirtualTable(infoSchemaDB, createInfoSchemaTable)
 }
 
-// IsMemoryDB checks if the db is in memory.
-func IsMemoryDB(dbName string) bool {
-	for _, driver := range drivers {
-		if driver.DBInfo.Name.L == dbName {
-			return true
-		}
-	}
-	return false
-}
-
 // HasAutoIncrementColumn checks whether the table has auto_increment columns, if so, return true and the column name.
 func HasAutoIncrementColumn(tbInfo *model.TableInfo) (bool, string) {
 	for _, col := range tbInfo.Columns {

infoschema/infoschema_test.go

@@ -123,13 +123,13 @@ func (*testSuite) TestT(c *C) {
 	is := handle.Get()
 
 	schemaNames := is.AllSchemaNames()
-	c.Assert(schemaNames, HasLen, 4)
-	c.Assert(testutil.CompareUnorderedStringSlice(schemaNames, []string{util.InformationSchemaName.O, util.MetricSchemaName.O, util.PerformanceSchemaName.O, "Test"}), IsTrue)
+	c.Assert(schemaNames, HasLen, 5)
+	c.Assert(testutil.CompareUnorderedStringSlice(schemaNames, []string{util.InformationSchemaName.O, util.MetricSchemaName.O, util.PerformanceSchemaName.O, "Test", util.InspectionSchemaName.O}), IsTrue)
 
 	schemas := is.AllSchemas()
-	c.Assert(schemas, HasLen, 4)
+	c.Assert(schemas, HasLen, 5)
 	schemas = is.Clone()
-	c.Assert(schemas, HasLen, 4)
+	c.Assert(schemas, HasLen, 5)
 
 	c.Assert(is.SchemaExists(dbName), IsTrue)
 	c.Assert(is.SchemaExists(noexist), IsFalse)

infoschema/inspection_schema.go

@@ -0,0 +1,127 @@
+// Copyright 2019 PingCAP, Inc.
+//
+// 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,
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package infoschema
+
+import (
+	"fmt"
+
+	"github.com/pingcap/errors"
+	"github.com/pingcap/parser/model"
+	"github.com/pingcap/parser/mysql"
+	"github.com/pingcap/tidb/kv"
+	"github.com/pingcap/tidb/meta/autoid"
+	"github.com/pingcap/tidb/sessionctx"
+	"github.com/pingcap/tidb/sessionctx/variable"
+	"github.com/pingcap/tidb/table"
+	"github.com/pingcap/tidb/util"
+)
+
+// The `inspection_schema` is used to provide a consistent view of `information_schema` tables,
+// so the related table should have the same table name within `information_schema`.
+// The data will be obtained lazily from `information_schema` and cache in `SessionVars`, and
+// the cached data will be cleared at `InspectionExec` closing.
+var inspectionTables = map[string][]columnInfo{
+	tableClusterInfo:       tableClusterInfoCols,
+	TableClusterConfig:     tableClusterConfigCols,
+	TableClusterLoad:       tableClusterLoadCols,
+	TableClusterHardware:   tableClusterHardwareCols,
+	TableClusterSystemInfo: tableClusterSystemInfoCols,
+}
+
+type inspectionSchemaTable struct {
+	infoschemaTable
+}
+
+// IterRecords implements table.Table IterRecords interface.
+func (it *inspectionSchemaTable) IterRecords(ctx sessionctx.Context, startKey kv.Key, cols []*table.Column,
+	fn table.RecordIterFunc) error {
+	sessionVars := ctx.GetSessionVars()
+	// The `InspectionTableCache` will be assigned in `InspectionExec.Open` and be
+	// cleaned at `InspectionExec.Close`, so nil represents currently in non-inspection mode.
+	if sessionVars.InspectionTableCache == nil {
+		return errors.New("not currently in inspection mode")
+	}
+
+	if len(startKey) != 0 {
+		return table.ErrUnsupportedOp
+	}
+
+	// Obtain data from cache first.
+	cached, found := sessionVars.InspectionTableCache[it.meta.Name.L]
+	if !found {
+		// We retrieve data from `information_schema` if can found in cache.
+		rows, err := it.getRows(ctx, cols)
+		cached = variable.TableSnapshot{
+			Rows: rows,
+			Err:  err,
+		}
+		sessionVars.InspectionTableCache[it.meta.Name.L] = cached
+	}
+	if cached.Err != nil {
+		return cached.Err
+	}
+
+	for i, row := range cached.Rows {
+		more, err := fn(int64(i), row, cols)
+		if err != nil {
+			return err
+		}
+		if !more {
+			break
+		}
+	}
+	return nil
+}
+
+func init() {
+	// Initialize the inspection schema database and register the driver to `drivers`.
+	dbID := autoid.InspectionSchemaDBID
+	tables := make([]*model.TableInfo, 0, len(inspectionTables))
+	for name, cols := range inspectionTables {
+		tableInfo := buildTableMeta(name, cols)
+		tables = append(tables, tableInfo)
+		var ok bool
+		tid, ok := tableIDMap[tableInfo.Name.O]
+		if !ok {
+			panic(fmt.Sprintf("get inspection_schema table id failed, unknown system table `%v`", tableInfo.Name.O))
+		}
+		// Reuse information_schema table id serial number.
+		tableInfo.ID = tid - autoid.InformationSchemaDBID + autoid.InspectionSchemaDBID
+		for i, c := range tableInfo.Columns {
+			c.ID = int64(i) + 1
+		}
+	}
+	inspectionSchema := &model.DBInfo{
+		ID:      dbID,
+		Name:    util.InspectionSchemaName,
+		Charset: mysql.DefaultCharset,
+		Collate: mysql.DefaultCollationName,
+		Tables:  tables,
+	}
+	builder := func(_ autoid.Allocators, meta *model.TableInfo) (table.Table, error) {
+		columns := make([]*table.Column, len(meta.Columns))
+		for i, col := range meta.Columns {
+			columns[i] = table.ToColumn(col)
+		}
+		tbl := &inspectionSchemaTable{
+			infoschemaTable{
+				meta: meta,
+				cols: columns,
+				tp:   table.VirtualTable,
+			},
+		}
+		return tbl, nil
+	}
+	RegisterVirtualTable(inspectionSchema, builder)
+}

infoschema/inspection_schema_test.go

@@ -0,0 +1,100 @@
+// Copyright 2019 PingCAP, Inc.
+//
+// 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,
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package infoschema_test
+
+import (
+	"strings"
+
+	. "github.com/pingcap/check"
+	"github.com/pingcap/failpoint"
+	"github.com/pingcap/tidb/domain"
+	"github.com/pingcap/tidb/kv"
+	"github.com/pingcap/tidb/session"
+	"github.com/pingcap/tidb/sessionctx/variable"
+	"github.com/pingcap/tidb/store/mockstore"
+	"github.com/pingcap/tidb/util/testkit"
+	"github.com/pingcap/tidb/util/testleak"
+)
+
+type inspectionSuite struct {
+	store kv.Storage
+	dom   *domain.Domain
+}
+
+var _ = SerialSuites(&inspectionSuite{})
+
+func (s *inspectionSuite) SetUpSuite(c *C) {
+	testleak.BeforeTest()
+
+	var err error
+	s.store, err = mockstore.NewMockTikvStore()
+	c.Assert(err, IsNil)
+	session.DisableStats4Test()
+	s.dom, err = session.BootstrapSession(s.store)
+	c.Assert(err, IsNil)
+}
+
+func (s *inspectionSuite) TearDownSuite(c *C) {
+	s.dom.Close()
+	s.store.Close()
+	testleak.AfterTest(c)()
+}
+
+func (s *inspectionSuite) TestInspectionTables(c *C) {
+	tk := testkit.NewTestKit(c, s.store)
+	instances := []string{
+		"pd,127.0.0.1:11080,127.0.0.1:10080,mock-version,mock-githash",
+		"tidb,127.0.0.1:11080,127.0.0.1:10080,mock-version,mock-githash",
+		"tikv,127.0.0.1:11080,127.0.0.1:10080,mock-version,mock-githash",
+	}
+	fpName := "github.com/pingcap/tidb/infoschema/mockClusterInfo"
+	fpExpr := `return("` + strings.Join(instances, ";") + `")`
+	c.Assert(failpoint.Enable(fpName, fpExpr), IsNil)
+	defer func() { c.Assert(failpoint.Disable(fpName), IsNil) }()
+
+	tk.MustQuery("select * from information_schema.cluster_info").Check(testkit.Rows(
+		"pd 127.0.0.1:11080 127.0.0.1:10080 mock-version mock-githash",
+		"tidb 127.0.0.1:11080 127.0.0.1:10080 mock-version mock-githash",
+		"tikv 127.0.0.1:11080 127.0.0.1:10080 mock-version mock-githash",
+	))
+
+	// enable inspection mode
+	inspectionTableCache := map[string]variable.TableSnapshot{}
+	tk.Se.GetSessionVars().InspectionTableCache = inspectionTableCache
+	tk.MustQuery("select * from inspection_schema.cluster_info").Check(testkit.Rows(
+		"pd 127.0.0.1:11080 127.0.0.1:10080 mock-version mock-githash",
+		"tidb 127.0.0.1:11080 127.0.0.1:10080 mock-version mock-githash",
+		"tikv 127.0.0.1:11080 127.0.0.1:10080 mock-version mock-githash",
+	))
+	c.Assert(inspectionTableCache["cluster_info"].Err, IsNil)
+	c.Assert(len(inspectionTableCache["cluster_info"].Rows), DeepEquals, 3)
+
+	// should invisible to other sessions
+	tk2 := testkit.NewTestKitWithInit(c, s.store)
+	err := tk2.QueryToErr("select * from inspection_schema.cluster_info")
+	c.Assert(err, ErrorMatches, "not currently in inspection mode")
+
+	// check whether is obtain data from cache at the next time
+	inspectionTableCache["cluster_info"].Rows[0][0].SetString("modified-pd")
+	tk.MustQuery("select * from inspection_schema.cluster_info").Check(testkit.Rows(
+		"modified-pd 127.0.0.1:11080 127.0.0.1:10080 mock-version mock-githash",
+		"tidb 127.0.0.1:11080 127.0.0.1:10080 mock-version mock-githash",
+		"tikv 127.0.0.1:11080 127.0.0.1:10080 mock-version mock-githash",
+	))
+	tk.Se.GetSessionVars().InspectionTableCache = nil
+
+	// disable inspection mode
+	err = tk.QueryToErr("select * from inspection_schema.cluster_info")
+	c.Assert(err, ErrorMatches, "not currently in inspection mode")
+}

infoschema/tables_test.go

@@ -999,8 +999,10 @@ func (s *testClusterTableSuite) TestForClusterServerInfo(c *C) {
 
 func (s *testTableSuite) TestSystemSchemaID(c *C) {
 	uniqueIDMap := make(map[int64]string)
-	s.checkSystemSchemaTableID(c, "information_schema", autoid.SystemSchemaIDFlag|1, 1, 10000, uniqueIDMap)
-	s.checkSystemSchemaTableID(c, "performance_schema", autoid.SystemSchemaIDFlag|10000, 10000, 20000, uniqueIDMap)
+	s.checkSystemSchemaTableID(c, "information_schema", autoid.InformationSchemaDBID, 1, 10000, uniqueIDMap)
+	s.checkSystemSchemaTableID(c, "performance_schema", autoid.PerformanceSchemaDBID, 10000, 20000, uniqueIDMap)
+	s.checkSystemSchemaTableID(c, "metric_schema", autoid.MetricSchemaDBID, 20000, 30000, uniqueIDMap)
+	s.checkSystemSchemaTableID(c, "inspection_schema", autoid.InspectionSchemaDBID, 30000, 40000, uniqueIDMap)
 }
 
 func (s *testTableSuite) checkSystemSchemaTableID(c *C, dbName string, dbID, start, end int64, uniqueIDMap map[int64]string) {

meta/autoid/autoid.go

@@ -43,6 +43,8 @@ const (
 	PerformanceSchemaDBID int64 = SystemSchemaIDFlag | 10000
 	// MetricSchemaDBID is the metric_schema schema id, it's exported for test.
 	MetricSchemaDBID int64 = SystemSchemaIDFlag | 20000
+	// InspectionSchemaDBID is the inspection_schema id, it's exports for test.
+	InspectionSchemaDBID int64 = SystemSchemaIDFlag | 30000
 )
 
 const (

server/http_handler_test.go

@@ -688,7 +688,7 @@ func (ts *HTTPHandlerTestSuite) TestGetSchema(c *C) {
 	var dbs []*model.DBInfo
 	err = decoder.Decode(&dbs)
 	c.Assert(err, IsNil)
-	expects := []string{"information_schema", "metric_schema", "mysql", "performance_schema", "test", "tidb"}
+	expects := []string{"information_schema", "inspection_schema", "metric_schema", "mysql", "performance_schema", "test", "tidb"}
 	names := make([]string, len(dbs))
 	for i, v := range dbs {
 		names[i] = v.Name.L

sessionctx/variable/session.go

@@ -204,6 +204,12 @@ func (ib *WriteStmtBufs) clean() {
 	ib.IndexKeyBuf = nil
 }
 
+// TableSnapshot represents a data snapshot of the table contained in `inspection_schema`.
+type TableSnapshot struct {
+	Rows [][]types.Datum
+	Err  error
+}
+
 // SessionVars is to handle user-defined or global variables in the current session.
 type SessionVars struct {
 	Concurrency
@@ -484,6 +490,12 @@ type SessionVars struct {
 	MetricSchemaStep int64
 	// MetricSchemaRangeDuration indicates the step when query metric schema.
 	MetricSchemaRangeDuration int64
+
+	// Some data of cluster-level memory tables will be retrieved many times in different inspection rules,
+	// and the cost of retrieving some data is expensive. We use the `TableSnapshot` to cache those data
+	// and obtain them lazily, and provide a consistent view of inspection tables for each inspection rules.
+	// All cached snapshots will be released at the `InspectionExec` executor closing.
+	InspectionTableCache map[string]TableSnapshot
 }
 
 // PreparedParams contains the parameters of the current prepared statement when executing it.

util/misc.go

@@ -139,17 +139,23 @@ func SyntaxWarn(err error) error {
 
 var (
 	// InformationSchemaName is the `INFORMATION_SCHEMA` database name.
-	InformationSchemaName = model.CIStr{O: "INFORMATION_SCHEMA", L: "information_schema"}
+	InformationSchemaName = model.NewCIStr("INFORMATION_SCHEMA")
 	// PerformanceSchemaName is the `PERFORMANCE_SCHEMA` database name.
-	PerformanceSchemaName = model.CIStr{O: "PERFORMANCE_SCHEMA", L: "performance_schema"}
+	PerformanceSchemaName = model.NewCIStr("PERFORMANCE_SCHEMA")
 	// MetricSchemaName is the `METRIC_SCHEMA` database name.
-	MetricSchemaName = model.CIStr{O: "METRIC_SCHEMA", L: "metric_schema"}
+	MetricSchemaName = model.NewCIStr("METRIC_SCHEMA")
+	// InspectionSchemaName is the `INSPECTION_SCHEMA` database name
+	InspectionSchemaName = model.NewCIStr("INSPECTION_SCHEMA")
 )
 
 // IsMemOrSysDB uses to check whether dbLowerName is memory database or system database.
 func IsMemOrSysDB(dbLowerName string) bool {
 	switch dbLowerName {
-	case InformationSchemaName.L, PerformanceSchemaName.L, mysql.SystemDB, MetricSchemaName.L:
+	case InformationSchemaName.L,
+		InspectionSchemaName.L,
+		PerformanceSchemaName.L,
+		mysql.SystemDB,
+		MetricSchemaName.L:
 		return true
 	}
 	return false