Supporting MongoDB streaming part 1

sources/mongo/message.go

@@ -12,12 +12,13 @@ import (
 	"go.mongodb.org/mongo-driver/bson"
 )
 
-type mgoMessage struct {
+type Message struct {
 	jsonExtendedString string
+	operation          string
 	pkMap              map[string]any
 }
 
-func (m *mgoMessage) ToRawMessage(collection config.Collection, database string) (lib.RawMessage, error) {
+func (m *Message) ToRawMessage(collection config.Collection, database string) (lib.RawMessage, error) {
 	evt := &mongo.SchemaEventPayload{
 		Schema: debezium.Schema{},
 		Payload: mongo.Payload{
@@ -27,7 +28,7 @@ func (m *mgoMessage) ToRawMessage(collection config.Collection, database string)
 				Collection: collection.Name,
 				TsMs:       time.Now().UnixMilli(),
 			},
-			Operation: "r",
+			Operation: m.operation,
 		},
 	}
 
@@ -38,7 +39,7 @@ func (m *mgoMessage) ToRawMessage(collection config.Collection, database string)
 	return lib.NewRawMessage(collection.TopicSuffix(database), pkMap, evt), nil
 }
 
-func ParseMessage(result bson.M) (*mgoMessage, error) {
+func ParseMessage(result bson.M, op string) (*Message, error) {
 	jsonExtendedBytes, err := bson.MarshalExtJSON(result, false, false)
 	if err != nil {
 		return nil, fmt.Errorf("failed to marshal document to JSON extended: %w", err)
@@ -58,8 +59,10 @@ func ParseMessage(result bson.M) (*mgoMessage, error) {
 	if err != nil {
 		return nil, fmt.Errorf("failed to marshal ext json: %w", err)
 	}
-	return &mgoMessage{
+
+	return &Message{
 		jsonExtendedString: string(jsonExtendedBytes),
+		operation:          op,
 		pkMap: map[string]any{
 			"id": string(pkBytes),
 		},

sources/mongo/message_test.go

@@ -18,7 +18,7 @@ import (
 func TestParseMessagePartitionKey(t *testing.T) {
 	objId, err := primitive.ObjectIDFromHex("507f1f77bcf86cd799439011")
 	assert.NoError(t, err)
-	msg, err := ParseMessage(bson.M{"_id": objId})
+	msg, err := ParseMessage(bson.M{"_id": objId}, "r")
 	assert.NoError(t, err)
 	assert.Equal(t, `{"$oid":"507f1f77bcf86cd799439011"}`, msg.pkMap["id"])
 
@@ -61,7 +61,7 @@ func TestParseMessage(t *testing.T) {
 			"trueValue":  true,
 			"falseValue": false,
 			"nullValue":  nil,
-		})
+		}, "r")
 	assert.NoError(t, err)
 
 	rawMsg, err := msg.ToRawMessage(config.Collection{}, "database")

sources/mongo/mongo.go

@@ -59,8 +59,7 @@ func (s *Source) Run(ctx context.Context, writer writers.Writer) error {
 			slog.Any("batchSize", collection.GetBatchSize()),
 		)
 
-		iterator := newIterator(s.db, collection, s.cfg)
-		count, err := writer.Write(ctx, iterator)
+		count, err := writer.Write(ctx, newSnapshotIterator(s.db, collection, s.cfg))
 		if err != nil {
 			return fmt.Errorf("failed to snapshot collection %q: %w", collection.Name, err)
 		}

sources/mongo/collection.go → sources/mongo/snapshot.go

@@ -11,7 +11,7 @@ import (
 	"go.mongodb.org/mongo-driver/mongo/options"
 )
 
-type collectionScanner struct {
+type snapshotIterator struct {
 	db         *mongo.Database
 	cfg        config.MongoDB
 	collection config.Collection
@@ -21,62 +21,62 @@ type collectionScanner struct {
 	done   bool
 }
 
-func newIterator(db *mongo.Database, collection config.Collection, cfg config.MongoDB) *collectionScanner {
-	return &collectionScanner{
+func newSnapshotIterator(db *mongo.Database, collection config.Collection, cfg config.MongoDB) *snapshotIterator {
+	return &snapshotIterator{
 		db:         db,
 		cfg:        cfg,
 		collection: collection,
 	}
 }
 
-func (c *collectionScanner) HasNext() bool {
-	return !c.done
+func (s *snapshotIterator) HasNext() bool {
+	return !s.done
 }
 
-func (c *collectionScanner) Next() ([]lib.RawMessage, error) {
-	if !c.HasNext() {
+func (s *snapshotIterator) Next() ([]lib.RawMessage, error) {
+	if !s.HasNext() {
 		return nil, fmt.Errorf("no more rows to scan")
 	}
 
 	ctx := context.Background()
-	if c.cursor == nil {
+	if s.cursor == nil {
 		findOptions := options.Find()
-		findOptions.SetBatchSize(c.collection.GetBatchSize())
-		cursor, err := c.db.Collection(c.collection.Name).Find(ctx, bson.D{}, findOptions)
+		findOptions.SetBatchSize(s.collection.GetBatchSize())
+		cursor, err := s.db.Collection(s.collection.Name).Find(ctx, bson.D{}, findOptions)
 		if err != nil {
 			return nil, fmt.Errorf("failed to find documents: %w", err)
 		}
 
-		c.cursor = cursor
+		s.cursor = cursor
 	}
 
 	var rawMsgs []lib.RawMessage
-	for c.collection.GetBatchSize() > int32(len(rawMsgs)) && c.cursor.Next(ctx) {
+	for s.collection.GetBatchSize() > int32(len(rawMsgs)) && s.cursor.Next(ctx) {
 		var result bson.M
-		if err := c.cursor.Decode(&result); err != nil {
+		if err := s.cursor.Decode(&result); err != nil {
 			return nil, fmt.Errorf("failed to decode document: %w", err)
 		}
 
-		mgoMsg, err := ParseMessage(result)
+		mgoMsg, err := ParseMessage(result, "r")
 		if err != nil {
 			return nil, fmt.Errorf("failed to parse message: %w", err)
 		}
 
-		rawMsg, err := mgoMsg.ToRawMessage(c.collection, c.cfg.Database)
+		rawMsg, err := mgoMsg.ToRawMessage(s.collection, s.cfg.Database)
 		if err != nil {
 			return nil, fmt.Errorf("failed to create raw message: %w", err)
 		}
 
 		rawMsgs = append(rawMsgs, rawMsg)
 	}
 
-	if err := c.cursor.Err(); err != nil {
+	if err := s.cursor.Err(); err != nil {
 		return nil, fmt.Errorf("failed to iterate over documents: %w", err)
 	}
 
 	// If the number of fetched documents is less than the batch size, we are done
-	if c.collection.GetBatchSize() > int32(len(rawMsgs)) {
-		c.done = true
+	if s.collection.GetBatchSize() > int32(len(rawMsgs)) {
+		s.done = true
 	}
 
 	return rawMsgs, nil

writers/transfer/writer_test.go

@@ -22,7 +22,7 @@ func TestWriter_MessageToEvent(t *testing.T) {
 		"string": "Hello, world!",
 		"int64":  int64(1234567890),
 		"double": 3.14159,
-	})
+	}, "r")
 	assert.NoError(t, err)
 
 	message, err := msg.ToRawMessage(config.Collection{Name: "collection"}, "database")