![]() When the consumer processes this message, it will communicate with the Schema Registry using the schema ID it received from the producer and deserialize it using the same schema. Once the producer gets the schema, it will serialize the data with the schema and send it to Kafka in binary format prepended with a unique schema ID. If it doesn’t find the schema then it registers and caches it in the Schema Registry. With the Schema Registry in place, the producer, before sending the data to Kafka, talks to the Schema Registry first and checks if the schema is available. Schema Example in JSON formatįigure 6: Schema Registry in Apache Kafka (1) You could also consider it the “contract” between producers and consumers that the clients involved have agreed to send and receive messages. There can be a multitude of reasons why you choose a certain data format: depending on legacy systems, choices on latency & throughput, and your company's own knowledge and experience.Ī data schema is really the structure or shape of how your messages are sent. binary, CSV, JSON, AVRO, Protobuf, etc and the schema that you will use. The data format is how the data is parsed, i.e. In any process involving integration of data, the two main challenges to consider are the data format and the data schema. the more topics you have the more potential cases where producers and consumers deviate due to serialization incompatibility. The issue is more prominent in Kafka clusters which have many topics, i.e. Depending on what the application is doing you could have a serious problem. So what happens if a producer starts sending data to Kafka that your consumer doesn't know how to deserialize (sometimes known as a “poison pill”) or if the data format is changed without changing the consumer? If this were to happen your consumer(s) downstream will start breaking as they can't properly read the messages, which could mean any applications involved will not work correctly. Kafka message deserialization for a message with a Integer Key and a String Valueįigure 4: Kafka message deserialization for a message with an Integer Key and a String Value (5)
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