Experiment of forced clean of old history items for the case wqhen se…

…rver is about to reach max object limit on the client.

Must not be merged as-is.

command/command.go

@@ -14,8 +14,16 @@ import (
 
 var (
 	// Could be modified in tests.
-	maxGUBatchSize       = 500
-	maxClientObjectQuota = 85000
+	// Original:
+	// maxGUBatchSize       = 500
+	// maxClientObjectQuota = 85000
+
+	// Test with small values
+	maxGUBatchSize       = 5
+	maxClientObjectQuota = 30
+	// new
+	clientObjectsToStartCleanup = 20
+	historyObjectsToCleanup     = 5
 )
 
 const (
@@ -214,6 +222,20 @@ func handleCommitRequest(cache *cache.Cache, commitMsg *sync_pb.CommitMessage, c
 		return &errCode, fmt.Errorf("error getting client's item count: %w", err)
 	}
 
+	deletedHistoryEntriesCount := 0
+
+	if itemCount >= clientObjectsToStartCleanup {
+		_, historySyncEntities, err3 :=
+			db.GetUpdatesForType(historyTypeID, 0/*clientToken*/, false/*fetchFolders*/, clientID, int64(historyObjectsToCleanup)/*maxSize int64*/)
+		if err3 == nil && len(historySyncEntities) > 0 {
+			err4 := db.DeleteThese(historySyncEntities)
+			if err4 == nil {
+				deletedHistoryEntriesCount = len(historySyncEntities);
+				itemCount -= deletedHistoryEntriesCount
+			}
+		}
+	}
+
 	commitRsp.Entryresponse = make([]*sync_pb.CommitResponse_EntryResponse, len(commitMsg.Entries))
 
 	// Map client-generated ID to its server-generated ID.
@@ -315,7 +337,7 @@ func handleCommitRequest(cache *cache.Cache, commitMsg *sync_pb.CommitMessage, c
 		cache.SetTypeMtime(context.Background(), clientID, dataType, mtime)
 	}
 
-	err = db.UpdateClientItemCount(clientID, count)
+	err = db.UpdateClientItemCount(clientID, count - deletedHistoryEntriesCount)
 	if err != nil {
 		// We only impose a soft quota limit on the item count for each client, so
 		// we only log the error without further actions here. The reason of this

datastore/datastore.go

@@ -15,6 +15,8 @@ type Datastore interface {
 	GetUpdatesForType(dataType int, clientToken int64, fetchFolders bool, clientID string, maxSize int64) (bool, []SyncEntity, error)
 	// Check if a server-defined unique tag is in the datastore.
 	HasServerDefinedUniqueTag(clientID string, tag string) (bool, error)
+	// Deletes some entries
+	DeleteThese(entities []SyncEntity) error;
 	// Get the count of sync items for a client.
 	GetClientItemCount(clientID string) (int, error)
 	// Update the count of sync items for a client.

datastore/datastoretest/mock_datastore.go

@@ -45,6 +45,12 @@ func (m *MockDatastore) HasItem(clientID string, ID string) (bool, error) {
 	return args.Bool(0), args.Error(1)
 }
 
+// DeleteThese mocks calls to DeleteThese
+func (m *MockDatastore) DeleteThese(entities []datastore.SyncEntity) error {
+	args := m.Called(entities)
+	return args.Error(0)
+}
+
 // GetClientItemCount mocks calls to GetClientItemCount
 func (m *MockDatastore) GetClientItemCount(clientID string) (int, error) {
 	args := m.Called(clientID)

datastore/instrumented_datastore.go

@@ -65,6 +65,20 @@ func (_d DatastoreWithPrometheus) DisableSyncChain(clientID string) (err error)
 	return _d.base.DisableSyncChain(clientID)
 }
 
+ // DeleteThese implements Datastore
+ func (_d DatastoreWithPrometheus) DeleteThese(entities []SyncEntity) (err error) {
+	_since := time.Now()
+	defer func() {
+		result := "ok"
+		if err != nil {
+			result = "error"
+		}
+
+		datastoreDurationSummaryVec.WithLabelValues(_d.instanceName, "DeleteThese", result).Observe(time.Since(_since).Seconds())
+	}()
+	return _d.base.DeleteThese(entities)
+}
+
 // GetClientItemCount implements Datastore
 func (_d DatastoreWithPrometheus) GetClientItemCount(clientID string) (i1 int, err error) {
 	_since := time.Now()

datastore/sync_entity.go

@@ -469,6 +469,69 @@ func (dynamo *Dynamo) ClearServerData(clientID string) ([]SyncEntity, error) {
 	return syncEntities, nil
 }
 
+// Code is taken mostly from ClearServerData function
+func (dynamo *Dynamo) DeleteThese(entities []SyncEntity) error {
+	if len(entities) == 0 {
+		return fmt.Errorf("error deleting sync entities - none requested")
+	}
+
+	items := []*dynamodb.TransactWriteItem{}
+
+	for _, item := range entities {
+		// Fail delete if race condition detected (modified time has changed).
+		if item.Version != nil {
+			cond := expression.Name("Mtime").Equal(expression.Value(*item.Mtime))
+			expr, err := expression.NewBuilder().WithCondition(cond).Build()
+			if err != nil {
+				return fmt.Errorf("error deleting sync entities for client <???>: %w", err)
+			}
+
+			writeItem := dynamodb.TransactWriteItem{
+				Delete: &dynamodb.Delete{
+					ConditionExpression:       expr.Condition(),
+					ExpressionAttributeNames:  expr.Names(),
+					ExpressionAttributeValues: expr.Values(),
+					TableName:                 aws.String(Table),
+					Key: map[string]*dynamodb.AttributeValue{
+						pk: {
+							S: aws.String(item.ClientID),
+						},
+						sk: {
+							S: aws.String(item.ID),
+						},
+					},
+				},
+			}
+
+			items = append(items, &writeItem)
+		} else {
+			// If row doesn't hold Mtime, delete as usual.
+			writeItem := dynamodb.TransactWriteItem{
+				Delete: &dynamodb.Delete{
+					TableName: aws.String(Table),
+					Key: map[string]*dynamodb.AttributeValue{
+						pk: {
+							S: aws.String(item.ClientID),
+						},
+						sk: {
+							S: aws.String(item.ID),
+						},
+					},
+				},
+			}
+
+			items = append(items, &writeItem)
+		}
+	}
+	_, err := dynamo.TransactWriteItems(&dynamodb.TransactWriteItemsInput{TransactItems: items})
+
+	if err != nil {
+		return fmt.Errorf("error deleting sync entities for client <???>: %w", err)
+	}
+
+	return nil
+}
+
 // IsSyncChainDisabled checks whether a given sync chain has been deleted
 func (dynamo *Dynamo) IsSyncChainDisabled(clientID string) (bool, error) {
 	key, err := dynamodbattribute.MarshalMap(DisabledMarkerItemQuery{