Delay Kafka processor reading from source topic

Question

I have a topology that consists of two source topics which are read and processed by two different processors in a Kafka Streams app. The one processor A reads its corresponding topic and creates a persistent local store which is shared with the other processor B in the topology.

My issue is that I need somehow after a restart to pause processor B processing for a very small amount of time and give processor A the time to read some events from its topic updating its local store before processor B starts with its processing.

Since both processors belong to the same sub-topology I can't use Thread.sleep in init() for example because this will cause the whole app to stall.

So is there a way to make processor B in topology wait/stall for a very small amount of time when restarting the application before starting reading from the source topic and begin processing events?

Answer 1

Processing order is base on record timestamps. Hence, if the timestamps of the record processed by A are smaller than the timestamps of the record processed by B, those "A records" will be processed first.

Explicitly pausing one side does not make sense, as it may violate the processing order. Just make sure that your input data is properly timestamped and you don't have to worry about manual pausing.