Difference between poll and consume in Kafka Confluent library

Question

The github examples page for the Confluent Kafka library lists two methods, namely poll and consume. What is the difference between the two.

I did look at the Consumer implementation in the Confluent Kafka library here , and feel they're functionally the same, and differ only in terms of what they return.

Poll() calls consume() to see if there is a message ready to be picked up, and if yes, invokes the OnMessage event. Whereas, consume, saves the message in one of it's parameters, and returns a boolean. I feel difference is in implementation, and functionally they're the same https://github.com/confluentinc/confluent-kafka-dotnet/blob/master/src/Confluent.Kafka/Consumer.cs

Tabb

Seems like Consume just fills the output and return true/false if message are returned, and poll does the same but also trigger an event when there are messages... – Rosebud

Answer 1

You are right. https://github.com/confluentinc/confluent-kafka-dotnet/blob/3f48e8944242abf631ea8d2cd5698f6e149e0731/src/Confluent.Kafka/Consumer.cs#L1147

Poll is the same as Consume, just expose message with different semantic. Consume will return message in out parameter whereas Poll return null and will fire OnMessage event.

Edit: in v1 there is only Consume call left, no more confusion.

Handhold

Just an FYI: more recent versions (eg 1.0 beta) no longer have the Poll function w/OnMessage event - it's all just through the Consume function. – Forte