How to send Large Messages in Apache Kafka?

The Kafka max message size is 1MB. In this lesson we will look at two approaches for handling larger messages in Kafka.

Kafka has a default limit of 1MB per message in the topic. This is because very large messages are considered inefficient and an anti-pattern in Apache Kafka.

Yet, you may need to send large messages in Apache Kafka.

There are two approaches to sending large messages in Apache Kafka:

Option 1: using an external store (GB-size messages)

Modify your client to send large messages (example video files) outside of Kafka and only send to Kafka a reference to these message. This involves extra logic on your end but could prove quite efficient.

The store of your large message could be a cloud store such as Amazon S3, or an on-premise large file storage system such as a network system or HDFS.

Large Kafka Message Diagram showing how you can send large messages in Apache Kafka using an external store and metadata messages that keep within the 1MB message limit recommended for Apache  Kafka.

To date there is no library that exists that performs this functionality out of the box, but it shouldn't be too complicated to engineer. Ensure you have written both a custom producer and consumer.

Option 2: sending larger messages to Kafka (ex less than 10MB but over 1MB)

Here we need to modify topic, producer and consumer configurations to allow for a bigger message size.

Broker Side

It is recommended to leave the max message size default for the Kafka brokers and only override this at the topic level through topic-level configurations.

Confusing setting

The broker-side setting is message.max.bytesand the topic-side setting is max.message.bytes

Let's create a topic named large-message

1 --bootstrap-server localhost:9092 --create --topic large-message --partitions 3 --replication-factor 1

And add the necessary max.message.bytes configuration for 10MB

1 2 3 4 --bootstrap-server localhost:9092 \ --alter --entity-type topics \ --entity-name configured-topic \ --add-config max.message.bytes=10485880

Now our topic is created and configured to receive large messages, but this is not enough/

You must also set the setting replica.fetch.max.bytes=10485880 so that your brokers can replicate the large messages correctly. This setting can only be set in the Kafka config files and must require a broker restart.

Consumer Side

You must also change the max.partition.fetch.bytes configuration on the consumer side and your consumer clients. If this value is smaller than message.max.bytes the consumer will fail to fetch these messages and will get stuck on processing, which is very undesirable.

To set this in your CLI, you can use --consumer-property:

1 2 3 4 --bootstrap-server localhost:9092 \ --topic large-message \ --from-beginning \ --consumer-property max.partition.fetch.bytes=10485880

Or in your Java code:

1 properties.setProperty(ConsumerConfig.FETCH_MAX_BYTES_CONFIG, "10485880");

Producer Side

You must change the property max.request.size producer-side to ensure large messages can be sent.

To set this in your CLI, you can use --producer-property:

1 2 3 --bootstrap-server localhost:9092 \ --topic large-message \ --producer-property max.request.size=10485880

Or in your Java code:

1 properties.setProperty(ProducerConfig.MAX_REQUEST_SIZE_CONFIG, "10485880");

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PreviousKafka Topics Choosing the Replication Factor and Partition Count
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Conduktor & Advanced Topic Configuration

Now that you have seen how to perform all these tasks using the Kafka Configs CLI, you may wonder how you can achieve this using a graphical UI tool.

Using Conduktor you can configure your topics and brokers without a lot of effort, documentation included!

Screenshot of Kafka min.insync.replicas dialog in Conduktor
Dynamic Configuration
Conduktor screenshot of Kafka Topic config
Kafka Topic Configuration in Conduktor