Fix dataraces in memqdb

Makefile

@@ -68,7 +68,7 @@ pooler_run:
 ####################### TESTS #######################
 
 unittest:
-	go test ./cmd/... ./pkg/... ./router/... ./qdb/... ./coordinator/...
+	go test -race ./cmd/... ./pkg/... ./router/... ./qdb/... ./coordinator/...
 
 regress_local: proxy_2sh_run
 	./script/regress_local.sh

pkg/coord/local/clocal.go

@@ -202,16 +202,9 @@ func (qr *LocalCoordinator) Unite(ctx context.Context, req *kr.UniteKeyRange) er
 	}(qr.qdb, ctx, req.KeyRangeIDLeft)
 
 	// TODO: krRight seems to be empty.
-	if krright, err = qr.qdb.LockKeyRange(ctx, req.KeyRangeIDRight); err != nil {
+	if krright, err = qr.qdb.GetKeyRange(ctx, req.KeyRangeIDRight); err != nil {
 		return err
 	}
-	defer func(qdb qdb.QDB, ctx context.Context, keyRangeID string) {
-		err := qdb.UnlockKeyRange(ctx, keyRangeID)
-		if err != nil {
-			spqrlog.Zero.Error().Err(err).Msg("")
-			return
-		}
-	}(qr.qdb, ctx, req.KeyRangeIDRight)
 
 	if err = qr.qdb.DropKeyRange(ctx, krright.KeyRangeID); err != nil {
 		return err

qdb/command.go

@@ -1,8 +1,14 @@
 package qdb
 
+import (
+	"fmt"
+
+	"github.com/pg-sharding/spqr/pkg/spqrlog"
+)
+
 type Command interface {
-	Do()
-	Undo()
+	Do() error
+	Undo() error
 }
 
 func NewDeleteCommand[T any](m map[string]T, key string) *DeleteCommand[T] {
@@ -16,17 +22,19 @@ type DeleteCommand[T any] struct {
 	present bool
 }
 
-func (c *DeleteCommand[T]) Do() {
+func (c *DeleteCommand[T]) Do() error {
 	c.value, c.present = c.m[c.key]
 	delete(c.m, c.key)
+	return nil
 }
 
-func (c *DeleteCommand[T]) Undo() {
+func (c *DeleteCommand[T]) Undo() error {
 	if !c.present {
 		delete(c.m, c.key)
 	} else {
 		c.m[c.key] = c.value
 	}
+	return nil
 }
 
 func NewUpdateCommand[T any](m map[string]T, key string, value T) *UpdateCommand[T] {
@@ -41,17 +49,19 @@ type UpdateCommand[T any] struct {
 	present   bool
 }
 
-func (c *UpdateCommand[T]) Do() {
+func (c *UpdateCommand[T]) Do() error {
 	c.prevValue, c.present = c.m[c.key]
 	c.m[c.key] = c.value
+	return nil
 }
 
-func (c *UpdateCommand[T]) Undo() {
+func (c *UpdateCommand[T]) Undo() error {
 	if !c.present {
 		delete(c.m, c.key)
 	} else {
 		c.m[c.key] = c.prevValue
 	}
+	return nil
 }
 
 func NewDropCommand[T any](m map[string]T) *DropCommand[T] {
@@ -63,47 +73,71 @@ type DropCommand[T any] struct {
 	copy map[string]T
 }
 
-func (c *DropCommand[T]) Do() {
+func (c *DropCommand[T]) Do() error {
 	c.copy = make(map[string]T)
 	for k, v := range c.m {
 		c.copy[k] = v
 	}
 	for k := range c.m {
 		delete(c.m, k)
 	}
+	return nil
 }
 
-func (c *DropCommand[T]) Undo() {
+func (c *DropCommand[T]) Undo() error {
 	for k, v := range c.copy {
 		c.m[k] = v
 	}
+	return nil
 }
 
-func NewCustomCommand(do func(), undo func()) *CustomCommand {
+func NewCustomCommand(do func() error, undo func() error) *CustomCommand {
 	return &CustomCommand{do: do, undo: undo}
 }
 
 type CustomCommand struct {
-	do   func()
-	undo func()
+	do   func() error
+	undo func() error
 }
 
-func (c *CustomCommand) Do() {
-	c.do()
+func (c *CustomCommand) Do() error {
+	return c.do()
 }
 
-func (c *CustomCommand) Undo() {
-	c.undo()
+func (c *CustomCommand) Undo() error {
+	return c.undo()
 }
 
-func ExecuteCommands(saver func() error, commands ...Command) error {
+func doCommands(commands ...Command) (int, error) {
+	for i, c := range commands {
+		err := c.Do()
+		if err != nil {
+			return i, err
+		}
+	}
+	return len(commands), nil
+}
+
+func undoCommands(commands ...Command) error {
+	spqrlog.Zero.Info().Msg("memqdb: undo commands")
 	for _, c := range commands {
-		c.Do()
+		err := c.Undo()
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func ExecuteCommands(saver func() error, commands ...Command) error {
+	completed, err := doCommands(commands...)
+	if err == nil {
+		err = saver()
 	}
-	err := saver()
 	if err != nil {
-		for _, c := range commands {
-			c.Undo()
+		undoErr := undoCommands(commands[:completed]...)
+		if undoErr != nil {
+			return fmt.Errorf("failed to undo command %s while: %s", undoErr.Error(), err.Error())
 		}
 		return err
 	}