- Better comments on what MaxMessageBytes is used for

- Also sets the size the consumer may use

dendrite-config.yaml

@@ -74,8 +74,11 @@ global:
     # Kafka.
     use_naffka: true
 
-    # The maximal size of messages passed between Kafka producers and consumers
-    max_message_bytes: 1048576
+    # The max size a Kafka message is allowed to use.
+    # You only need to change this value, if you encounter issues with too large messages.
+    # Must be less than/equal to "max.message.bytes" configured in Kafka.
+    # Defaults to 8388608 bytes.
+    # max_message_bytes: 8388608
 
     # Naffka database options. Not required when using Kafka.
     naffka_database:

internal/config/config_kafka.go

@@ -24,7 +24,8 @@ type Kafka struct {
 	UseNaffka bool `yaml:"use_naffka"`
 	// The Naffka database is used internally by the naffka library, if used.
 	Database DatabaseOptions `yaml:"naffka_database"`
-	// The max size a message can have
+	// The max size a Kafka message passed between consumer/producer can have
+	// Equals roughly max.message.bytes / fetch.message.max.bytes in Kafka
 	MaxMessageBytes *int `yaml:"max_message_bytes"`
 }
 
@@ -39,7 +40,7 @@ func (c *Kafka) Defaults() {
 	c.Database.ConnectionString = DataSource("file:naffka.db")
 	c.TopicPrefix = "Dendrite"
 
-	maxBytes := 2 << 22 // about 8MB
+	maxBytes := 1024 * 1024 * 8 // about 8MB
 	c.MaxMessageBytes = &maxBytes
 }
 

internal/setup/kafka/kafka.go

@@ -20,6 +20,7 @@ func setupKafka(cfg *config.Kafka) (sarama.Consumer, sarama.SyncProducer) {
 	sCfg := sarama.NewConfig()
 	sCfg.Producer.MaxMessageBytes = *cfg.MaxMessageBytes
 	sCfg.Producer.Return.Successes = true
+	sCfg.Consumer.Fetch.Default = int32(*cfg.MaxMessageBytes)
 
 	consumer, err := sarama.NewConsumer(cfg.Addresses, sCfg)
 	if err != nil {