Is key required as part of sending messages to Kafka?

Question

KeyedMessage keyedMessage = new KeyedMessage(request.getRequestTopicName(), Seri         


        

Answer 1

The key with a message is basically sent to get the message ordering for a specific field.

• If key=null, data is sent round-robin (to a different partition and to a different broker in a distributed env. and of course to the same topic.).
• If a key is sent, then all messages for that key will always go to the same partition.

Explain and example

• key can be any string or integer, etc.. take an example of an integer employee_id as key.
• So emplyee_id 123 will always go to partition 0, employee_id 345 will always go to partition 1. This is decided by the key hashing algorithm which depends on the number of partitions.
• if you don't send any key then the message can go to any partition using a round-robin technique.