Add a write-cache to the database interface options

database/database_test.go

@@ -22,6 +22,24 @@ import (
 	_ "github.com/safing/portbase/database/storage/hashmap"
 )
 
+func TestMain(m *testing.M) {
+	testDir, err := ioutil.TempDir("", "portbase-database-testing-")
+	if err != nil {
+		panic(err)
+	}
+
+	err = InitializeWithPath(testDir)
+	if err != nil {
+		panic(err)
+	}
+
+	exitCode := m.Run()
+
+	os.RemoveAll(testDir) // clean up
+
+	os.Exit(exitCode)
+}
+
 func makeKey(dbName, key string) string {
 	return fmt.Sprintf("%s:%s", dbName, key)
 }
@@ -220,23 +238,19 @@ func testDatabase(t *testing.T, storageType string, shadowDelete bool) { //nolin
 func TestDatabaseSystem(t *testing.T) {
 
 	// panic after 10 seconds, to check for locks
-	go func() {
-		time.Sleep(10 * time.Second)
-		fmt.Println("===== TAKING TOO LONG - PRINTING STACK TRACES =====")
-		_ = pprof.Lookup("goroutine").WriteTo(os.Stdout, 1)
-		os.Exit(1)
+	finished := make(chan struct{})
+	defer func() {
+		close(finished)
+	}()
+	go func() {
+		select {
+		case <-finished:
+		case <-time.After(10 * time.Second):
+			fmt.Println("===== TAKING TOO LONG - PRINTING STACK TRACES =====")
+			_ = pprof.Lookup("goroutine").WriteTo(os.Stdout, 1)
+			os.Exit(1)
+		}
 	}()
-
-	testDir, err := ioutil.TempDir("", "portbase-database-testing-")
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	err = InitializeWithPath(testDir)
-	if err != nil {
-		t.Fatal(err)
-	}
-	defer os.RemoveAll(testDir) // clean up
 
 	for _, shadowDelete := range []bool{false, true} {
 		testDatabase(t, "bbolt", shadowDelete)
@@ -246,7 +260,7 @@ func TestDatabaseSystem(t *testing.T) {
 		// TODO: Fix badger tests
 	}
 
-	err = MaintainRecordStates(context.TODO())
+	err := MaintainRecordStates(context.TODO())
 	if err != nil {
 		t.Fatal(err)
 	}

database/interface.go

@@ -4,11 +4,11 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"sync"
 	"time"
 
-	"github.com/tevino/abool"
-
 	"github.com/bluele/gcache"
+	"github.com/tevino/abool"
 
 	"github.com/safing/portbase/database/accessor"
 	"github.com/safing/portbase/database/iterator"
@@ -24,6 +24,10 @@ const (
 type Interface struct {
 	options *Options
 	cache   gcache.Cache
+
+	writeCache        map[string]record.Record
+	writeCacheLock    sync.Mutex
+	triggerCacheWrite chan struct{}
 }
 
 // Options holds options that may be set for an Interface instance.
@@ -34,7 +38,22 @@ type Options struct {
 	AlwaysMakeCrownjewel      bool
 	AlwaysSetRelativateExpiry int64
 	AlwaysSetAbsoluteExpiry   int64
-	CacheSize                 int
+
+	// CacheSize defines that a cache should be used for this interface and
+	// defines it's size.
+	// Caching comes with an important caveat: If database records are changed
+	// from another interface, the cache will not be invalidated for these
+	// records. It will therefore serve outdated data until that record is
+	// evicted from the cache.
+	CacheSize int
+
+	// DelayCachedWrites defines a database storage for which cache writes should
+	// be cached and batched. The database backend must support the Batcher
+	// interface. This option is only valid if used with a cache.
+	// Additionally, this may only be used for internal and local interfaces.
+	// Please note that this means that other interfaces will not be able to
+	// guarantee to serve the latest record if records are written this way.
+	DelayCachedWrites string
 }
 
 // Apply applies options to the record metadata.
@@ -63,57 +82,40 @@ func NewInterface(opts *Options) *Interface {
 		options: opts,
 	}
 	if opts.CacheSize > 0 {
-		new.cache = gcache.New(opts.CacheSize).ARC().Expiration(time.Hour).Build()
+		cacheBuilder := gcache.New(opts.CacheSize).ARC()
+		if len(opts.DelayCachedWrites) > 0 {
+			cacheBuilder.EvictedFunc(new.cacheEvictHandler)
+			new.writeCache = make(map[string]record.Record)
+			new.triggerCacheWrite = make(chan struct{})
+		}
+		new.cache = cacheBuilder.Build()
 	}
 	return new
 }
 
-func (i *Interface) checkCache(key string) (record.Record, bool) {
-	if i.cache != nil {
-		cacheVal, err := i.cache.Get(key)
-		if err == nil {
-			r, ok := cacheVal.(record.Record)
-			if ok {
-				return r, true
-			}
-		}
-	}
-	return nil, false
-}
-
-func (i *Interface) updateCache(r record.Record) {
-	if i.cache != nil {
-		_ = i.cache.Set(r.Key(), r)
-	}
-}
-
 // Exists return whether a record with the given key exists.
 func (i *Interface) Exists(key string) (bool, error) {
-	_, _, err := i.getRecord(getDBFromKey, key, false, false)
+	_, err := i.Get(key)
 	if err != nil {
-		if err == ErrNotFound {
+		switch err {
+		case ErrNotFound:
 			return false, nil
+		case ErrPermissionDenied:
+			return true, nil
+		default:
+			return false, err
 		}
-		return false, err
 	}
 	return true, nil
 }
 
 // Get return the record with the given key.
 func (i *Interface) Get(key string) (record.Record, error) {
-	r, ok := i.checkCache(key)
-	if ok {
-		if !r.Meta().CheckPermission(i.options.Local, i.options.Internal) {
-			return nil, ErrPermissionDenied
-		}
-		return r, nil
-	}
-
-	r, _, err := i.getRecord(getDBFromKey, key, true, false)
+	r, _, err := i.getRecord(getDBFromKey, key, false)
 	return r, err
 }
 
-func (i *Interface) getRecord(dbName string, dbKey string, check bool, mustBeWriteable bool) (r record.Record, db *Controller, err error) {
+func (i *Interface) getRecord(dbName string, dbKey string, mustBeWriteable bool) (r record.Record, db *Controller, err error) {
 	if dbName == "" {
 		dbName, dbKey = record.ParseKey(dbKey)
 	}
@@ -124,19 +126,24 @@ func (i *Interface) getRecord(dbName string, dbKey string, check bool, mustBeWri
 	}
 
 	if mustBeWriteable && db.ReadOnly() {
-		return nil, nil, ErrReadOnly
+		return nil, db, ErrReadOnly
+	}
+
+	r = i.checkCache(dbName + ":" + dbKey)
+	if r != nil {
+		if !r.Meta().CheckPermission(i.options.Local, i.options.Internal) {
+			return nil, db, ErrPermissionDenied
+		}
+		return r, db, nil
 	}
 
 	r, err = db.Get(dbKey)
 	if err != nil {
-		if err == ErrNotFound {
-			return nil, db, err
-		}
-		return nil, nil, err
+		return nil, db, err
 	}
 
-	if check && !r.Meta().CheckPermission(i.options.Local, i.options.Internal) {
-		return nil, nil, ErrPermissionDenied
+	if !r.Meta().CheckPermission(i.options.Local, i.options.Internal) {
+		return nil, db, ErrPermissionDenied
 	}
 
 	return r, db, nil
@@ -144,7 +151,7 @@ func (i *Interface) getRecord(dbName string, dbKey string, check bool, mustBeWri
 
 // InsertValue inserts a value into a record.
 func (i *Interface) InsertValue(key string, attribute string, value interface{}) error {
-	r, db, err := i.getRecord(getDBFromKey, key, true, true)
+	r, db, err := i.getRecord(getDBFromKey, key, true)
 	if err != nil {
 		return err
 	}
@@ -177,7 +184,40 @@ func (i *Interface) Put(r record.Record) (err error) {
 	// get record or only database
 	var db *Controller
 	if !i.options.Internal || !i.options.Local {
-		_, db, err = i.getRecord(r.DatabaseName(), r.DatabaseKey(), true, true)
+		_, db, err = i.getRecord(r.DatabaseName(), r.DatabaseKey(), true)
+		if err != nil && err != ErrNotFound {
+			return err
+		}
+	} else {
+		db, err = getController(r.DatabaseName())
+		if err != nil {
+			return err
+		}
+	}
+
+	// Check if database is read only before we add to the cache.
+	if db.ReadOnly() {
+		return ErrReadOnly
+	}
+
+	r.Lock()
+	defer r.Unlock()
+	i.options.Apply(r)
+
+	written := i.updateCache(r, true)
+	if written {
+		return nil
+	}
+
+	return db.Put(r)
+}
+
+// PutNew saves a record to the database as a new record (ie. with new timestamps).
+func (i *Interface) PutNew(r record.Record) (err error) {
+	// get record or only database
+	var db *Controller
+	if !i.options.Internal || !i.options.Local {
+		_, db, err = i.getRecord(r.DatabaseName(), r.DatabaseKey(), true)
 		if err != nil && err != ErrNotFound {
 			return err
 		}
@@ -191,36 +231,16 @@ func (i *Interface) Put(r record.Record) (err error) {
 	r.Lock()
 	defer r.Unlock()
 
-	i.options.Apply(r)
-
-	i.updateCache(r)
-	return db.Put(r)
-}
-
-// PutNew saves a record to the database as a new record (ie. with new timestamps).
-func (i *Interface) PutNew(r record.Record) (err error) {
-	// get record or only database
-	var db *Controller
-	if !i.options.Internal || !i.options.Local {
-		_, db, err = i.getRecord(r.DatabaseName(), r.DatabaseKey(), true, true)
-		if err != nil && err != ErrNotFound {
-			return err
-		}
-	} else {
-		db, err = getController(r.DatabaseKey())
-		if err != nil {
-			return err
-		}
-	}
-
-	r.Lock()
-	defer r.Unlock()
-
 	if r.Meta() != nil {
 		r.Meta().Reset()
 	}
 	i.options.Apply(r)
-	i.updateCache(r)
+
+	written := i.updateCache(r, true)
+	if written {
+		return nil
+	}
+
 	return db.Put(r)
 }
 
@@ -316,7 +336,7 @@ func (i *Interface) PutMany(dbName string) (put func(record.Record) error) {
 
 // SetAbsoluteExpiry sets an absolute record expiry.
 func (i *Interface) SetAbsoluteExpiry(key string, time int64) error {
-	r, db, err := i.getRecord(getDBFromKey, key, true, true)
+	r, db, err := i.getRecord(getDBFromKey, key, true)
 	if err != nil {
 		return err
 	}
@@ -331,7 +351,7 @@ func (i *Interface) SetAbsoluteExpiry(key string, time int64) error {
 
 // SetRelativateExpiry sets a relative (self-updating) record expiry.
 func (i *Interface) SetRelativateExpiry(key string, duration int64) error {
-	r, db, err := i.getRecord(getDBFromKey, key, true, true)
+	r, db, err := i.getRecord(getDBFromKey, key, true)
 	if err != nil {
 		return err
 	}
@@ -346,7 +366,7 @@ func (i *Interface) SetRelativateExpiry(key string, duration int64) error {
 
 // MakeSecret marks the record as a secret, meaning interfacing processes, such as an UI, are denied access to the record.
 func (i *Interface) MakeSecret(key string) error {
-	r, db, err := i.getRecord(getDBFromKey, key, true, true)
+	r, db, err := i.getRecord(getDBFromKey, key, true)
 	if err != nil {
 		return err
 	}
@@ -361,7 +381,7 @@ func (i *Interface) MakeSecret(key string) error {
 
 // MakeCrownJewel marks a record as a crown jewel, meaning it will only be accessible locally.
 func (i *Interface) MakeCrownJewel(key string) error {
-	r, db, err := i.getRecord(getDBFromKey, key, true, true)
+	r, db, err := i.getRecord(getDBFromKey, key, true)
 	if err != nil {
 		return err
 	}
@@ -376,7 +396,7 @@ func (i *Interface) MakeCrownJewel(key string) error {
 
 // Delete deletes a record from the database.
 func (i *Interface) Delete(key string) error {
-	r, db, err := i.getRecord(getDBFromKey, key, true, true)
+	r, db, err := i.getRecord(getDBFromKey, key, true)
 	if err != nil {
 		return err
 	}

database/interface_cache.go

@@ -0,0 +1,171 @@
+package database
+
+import (
+	"context"
+	"errors"
+	"time"
+
+	"github.com/safing/portbase/database/record"
+	"github.com/safing/portbase/log"
+)
+
+// DelayedCacheWriter must be run by the caller of an interface that uses delayed cache writing.
+func (i *Interface) DelayedCacheWriter(ctx context.Context) error {
+	// Check if the DelayedCacheWriter should be run at all.
+	if i.options.CacheSize <= 0 || len(i.options.DelayCachedWrites) == 0 {
+		return errors.New("delayed cache writer is not applicable to this database interface")
+	}
+
+	// Check if backend support the Batcher interface.
+	batchPut := i.PutMany(i.options.DelayCachedWrites)
+	// End batchPut immediately and check for an error.
+	err := batchPut(nil)
+	if err != nil {
+		return err
+	}
+
+	for {
+		// Wait for trigger for writing the cache.
+		select {
+		case <-ctx.Done():
+			// Module is shutting down, flush write cache to database.
+			i.flushWriteCache()
+			return nil
+
+		case <-i.triggerCacheWrite:
+		case <-time.After(5 * time.Second):
+		}
+
+		i.flushWriteCache()
+	}
+}
+
+func (i *Interface) flushWriteCache() {
+	i.writeCacheLock.Lock()
+	defer i.writeCacheLock.Unlock()
+
+	// Check if there is anything to do.
+	if len(i.writeCache) == 0 {
+		return
+	}
+
+	// Write the full cache in a batch operation.
+	batchPut := i.PutMany(i.options.DelayCachedWrites)
+	for _, r := range i.writeCache {
+		err := batchPut(r)
+		if err != nil {
+			log.Warningf("database: failed to write write-cached entry to %q database: %s", i.options.DelayCachedWrites, err)
+		}
+	}
+	// Finish batch.
+	err := batchPut(nil)
+	if err != nil {
+		log.Warningf("database: failed to finish flushing write cache to %q database: %s", i.options.DelayCachedWrites, err)
+	}
+
+	// Optimized map clearing following the Go1.11 recommendation.
+	for key := range i.writeCache {
+		delete(i.writeCache, key)
+	}
+}
+
+// cacheEvictHandler is run by the cache for every entry that gets evicted
+// from the cache.
+func (i *Interface) cacheEvictHandler(keyData, _ interface{}) {
+	// Transform the key into a string.
+	key, ok := keyData.(string)
+	if !ok {
+		return
+	}
+
+	// Check if the evicted record is one that is to be written.
+	i.writeCacheLock.Lock()
+	r, ok := i.writeCache[key]
+	if ok {
+		delete(i.writeCache, key)
+	}
+	i.writeCacheLock.Unlock()
+	if !ok {
+		return
+	}
+
+	// Write record to database in order to mitigate race conditions where the record would appear
+	// as non-existent for a short duration.
+	db, err := getController(r.DatabaseName())
+	if err != nil {
+		log.Warningf("database: failed to write evicted cache entry %q: database %q does not exist", key, r.DatabaseName())
+		return
+	}
+	err = db.Put(r)
+	if err != nil {
+		log.Warningf("database: failed to write evicted cache entry %q to database: %s", key, err)
+	}
+
+	// Finally, trigger writing the full write cache because a to-be-written
+	// entry was just evicted from the cache, and this makes it likely that more
+	// to-be-written entries will be evicted shortly.
+	select {
+	case i.triggerCacheWrite <- struct{}{}:
+	default:
+	}
+}
+
+func (i *Interface) checkCache(key string) record.Record {
+	// Check if cache is in use.
+	if i.cache == nil {
+		return nil
+	}
+
+	// Check if record exists in cache.
+	cacheVal, err := i.cache.Get(key)
+	if err == nil {
+		r, ok := cacheVal.(record.Record)
+		if ok {
+			return r
+		}
+	}
+	return nil
+}
+
+func (i *Interface) updateCache(r record.Record, write bool) (written bool) {
+	// Check if cache is in use.
+	if i.cache == nil {
+		return false
+	}
+
+	// Check if record should be deleted
+	if r.Meta().IsDeleted() {
+		// Remove entry from cache.
+		i.cache.Remove(r.Key())
+		// Let write through to database storage.
+		return false
+	}
+
+	// Update cache with record.
+	ttl := r.Meta().GetRelativeExpiry()
+	if ttl >= 0 {
+		_ = i.cache.SetWithExpire(
+			r.Key(),
+			r,
+			time.Duration(ttl)*time.Second,
+		)
+	} else {
+		_ = i.cache.Set(
+			r.Key(),
+			r,
+		)
+	}
+
+	// Add record to write cache instead if:
+	// 1. The record is being written.
+	// 2. Write delaying is active.
+	// 3. Write delaying is active for the database of this record.
+	if write && len(i.options.DelayCachedWrites) > 0 && r.DatabaseName() == i.options.DelayCachedWrites {
+		i.writeCacheLock.Lock()
+		defer i.writeCacheLock.Unlock()
+		i.writeCache[r.Key()] = r
+		return true
+	}
+
+	return false
+}

database/interface_cache_test.go

@@ -0,0 +1,158 @@
+package database
+
+import (
+	"context"
+	"fmt"
+	"strconv"
+	"sync"
+	"testing"
+)
+
+func benchmarkCacheWriting(b *testing.B, storageType string, cacheSize int, sampleSize int, delayWrites bool) { //nolint:gocognit,gocyclo
+	b.Run(fmt.Sprintf("CacheWriting_%s_%d_%d_%v", storageType, cacheSize, sampleSize, delayWrites), func(b *testing.B) {
+		// Setup Benchmark.
+
+		// Create database.
+		dbName := fmt.Sprintf("cache-w-benchmark-%s-%d-%d-%v", storageType, cacheSize, sampleSize, delayWrites)
+		_, err := Register(&Database{
+			Name:        dbName,
+			Description: fmt.Sprintf("Cache Benchmark Database for %s", storageType),
+			StorageType: storageType,
+		})
+		if err != nil {
+			b.Fatal(err)
+		}
+
+		// Create benchmark interface.
+		options := &Options{
+			Local:     true,
+			Internal:  true,
+			CacheSize: cacheSize,
+		}
+		if cacheSize > 0 && delayWrites {
+			options.DelayCachedWrites = dbName
+		}
+		db := NewInterface(options)
+
+		// Start
+		ctx, cancelCtx := context.WithCancel(context.Background())
+		var wg sync.WaitGroup
+		if cacheSize > 0 && delayWrites {
+			wg.Add(1)
+			go func() {
+				err := db.DelayedCacheWriter(ctx)
+				if err != nil {
+					panic(err)
+				}
+				wg.Done()
+			}()
+		}
+
+		// Start Benchmark.
+		b.ResetTimer()
+		for i := 0; i < b.N; i++ {
+			testRecordID := i % sampleSize
+			r := NewExample(
+				dbName+":"+strconv.Itoa(testRecordID),
+				"A",
+				1,
+			)
+			err = db.Put(r)
+			if err != nil {
+				b.Fatal(err)
+			}
+		}
+
+		// End cache writer and wait
+		cancelCtx()
+		wg.Wait()
+
+	})
+}
+
+func benchmarkCacheReadWrite(b *testing.B, storageType string, cacheSize int, sampleSize int, delayWrites bool) { //nolint:gocognit,gocyclo
+	b.Run(fmt.Sprintf("CacheReadWrite_%s_%d_%d_%v", storageType, cacheSize, sampleSize, delayWrites), func(b *testing.B) {
+		// Setup Benchmark.
+
+		// Create database.
+		dbName := fmt.Sprintf("cache-rw-benchmark-%s-%d-%d-%v", storageType, cacheSize, sampleSize, delayWrites)
+		_, err := Register(&Database{
+			Name:        dbName,
+			Description: fmt.Sprintf("Cache Benchmark Database for %s", storageType),
+			StorageType: storageType,
+		})
+		if err != nil {
+			b.Fatal(err)
+		}
+
+		// Create benchmark interface.
+		options := &Options{
+			Local:     true,
+			Internal:  true,
+			CacheSize: cacheSize,
+		}
+		if cacheSize > 0 && delayWrites {
+			options.DelayCachedWrites = dbName
+		}
+		db := NewInterface(options)
+
+		// Start
+		ctx, cancelCtx := context.WithCancel(context.Background())
+		var wg sync.WaitGroup
+		if cacheSize > 0 && delayWrites {
+			wg.Add(1)
+			go func() {
+				err := db.DelayedCacheWriter(ctx)
+				if err != nil {
+					panic(err)
+				}
+				wg.Done()
+			}()
+		}
+
+		// Start Benchmark.
+		b.ResetTimer()
+		writing := true
+		for i := 0; i < b.N; i++ {
+			testRecordID := i % sampleSize
+			key := dbName + ":" + strconv.Itoa(testRecordID)
+
+			if i > 0 && testRecordID == 0 {
+				writing = !writing // switch between reading and writing every samplesize
+			}
+
+			if writing {
+				r := NewExample(key, "A", 1)
+				err = db.Put(r)
+			} else {
+				_, err = db.Get(key)
+			}
+			if err != nil {
+				b.Fatal(err)
+			}
+		}
+
+		// End cache writer and wait
+		cancelCtx()
+		wg.Wait()
+
+	})
+}
+
+func BenchmarkCache(b *testing.B) {
+	for _, storageType := range []string{"bbolt", "hashmap"} {
+		benchmarkCacheWriting(b, storageType, 32, 8, false)
+		benchmarkCacheWriting(b, storageType, 32, 8, true)
+		benchmarkCacheWriting(b, storageType, 32, 1024, false)
+		benchmarkCacheWriting(b, storageType, 32, 1024, true)
+		benchmarkCacheWriting(b, storageType, 512, 1024, false)
+		benchmarkCacheWriting(b, storageType, 512, 1024, true)
+
+		benchmarkCacheReadWrite(b, storageType, 32, 8, false)
+		benchmarkCacheReadWrite(b, storageType, 32, 8, true)
+		benchmarkCacheReadWrite(b, storageType, 32, 1024, false)
+		benchmarkCacheReadWrite(b, storageType, 32, 1024, true)
+		benchmarkCacheReadWrite(b, storageType, 512, 1024, false)
+		benchmarkCacheReadWrite(b, storageType, 512, 1024, true)
+	}
+}

database/record/base.go

@@ -2,7 +2,6 @@ package record
 
 import (
 	"errors"
-	"fmt"
 
 	"github.com/safing/portbase/container"
 	"github.com/safing/portbase/database/accessor"
@@ -18,7 +17,7 @@ type Base struct {
 
 // Key returns the key of the database record.
 func (b *Base) Key() string {
-	return fmt.Sprintf("%s:%s", b.dbName, b.dbKey)
+	return b.dbName + ":" + b.dbKey
 }
 
 // KeyIsSet returns true if the database key is set.

database/record/meta.go

@@ -31,9 +31,10 @@ func (m *Meta) GetAbsoluteExpiry() int64 {
 }
 
 // GetRelativeExpiry returns the current relative expiry time - ie. seconds until expiry.
+// A negative value signifies that the record does not expire.
 func (m *Meta) GetRelativeExpiry() int64 {
-	if m.Deleted < 0 {
-		return -m.Deleted
+	if m.Expires == 0 {
+		return -1
 	}
 
 	abs := m.Expires - time.Now().Unix()

database/storage/hashmap/map.go

@@ -66,11 +66,7 @@ func (hm *HashMap) PutMany(shadowDelete bool) (chan<- record.Record, <-chan erro
 	// start handler
 	go func() {
 		for r := range batch {
-			if !shadowDelete && r.Meta().IsDeleted() {
-				delete(hm.db, r.DatabaseKey())
-			} else {
-				hm.db[r.DatabaseKey()] = r
-			}
+			hm.putOrDelete(shadowDelete, r)
 		}
 		errs <- nil
 	}()
@@ -78,6 +74,17 @@ func (hm *HashMap) PutMany(shadowDelete bool) (chan<- record.Record, <-chan erro
 	return batch, errs
 }
 
+func (hm *HashMap) putOrDelete(shadowDelete bool, r record.Record) {
+	hm.dbLock.Lock()
+	defer hm.dbLock.Unlock()
+
+	if !shadowDelete && r.Meta().IsDeleted() {
+		delete(hm.db, r.DatabaseKey())
+	} else {
+		hm.db[r.DatabaseKey()] = r
+	}
+}
+
 // Delete deletes a record from the database.
 func (hm *HashMap) Delete(key string) error {
 	hm.dbLock.Lock()