Relation between Window size and unack messages in message consumer service

Tilak

Hi,

The page nicely summarises from publisher acknowledgment point of view https://solace.com/blog/understanding-guaranteed-message-publish-window-sizes-and-acknowledgement/

Is there something similar for consumer acknowledgment? We see window size often dropping to 0 when unack messages are around 255.

The listener/consumer service is built using Spring Cloud Stream.

Thanks

Tilak

giri

@Tilak Curious, are you using batch acknowledgement? Checkout this blog and see if it helps https://solace.com/blog/batch-processing-with-spring-cloud-stream-binder-for-solace-pubsub/

Tilak

Thanks Giri for the response.

Yes, messages are consumed in batch. The service consumes messages in batch and uploads to S3 one by one (S3 does not support batch upload).

What is batch acknowledgement?

we are using auto ack which ack when no errors returned from consumer.

Batch size is 15, not sure why unack messages reaches around 255 and window size drops to 0. When there is no error in consumer, unack messages should be less than or equal to batch size right?

derrick_solace

Hey @Tilak this is Derrick from Melbourne. I assume you're using the Solace JMS API?

derrick_solace

Actually I see you're using the SCS binder. I think these two links would help with your understanding of flow management and API and Application acknowledgements in Solace.

https://docs.solace.com/API/API-Developer-Guide/Acknowledging-Messages.htm
https://docs.solace.com/API/API-Developer-Guide/Creating-Flows.htm#Importan