A combination of `BoundedMultiInput` and `InputSelectable` could help. You could see `org.apache.flink.table.runtime.operators.join.HashJoinOperator` for an usage example. The control topic have not to be bounded.
There are maybe other approaches from later responses. I could not tell whether it is canonical or not. Best, Kezhu Wang On February 17, 2021 at 13:03:42, Salva Alcántara (salcantara...@gmail.com) wrote: What is the canonical way to accomplish this: >Given a ConnectedStreams, e.g., a CoFlatMap UDF, how to prevent any processing of the data stream until >the control stream is "ready", so to speak My particular use case is as follows: I have a CoFlatMap function. The data stream contains elements that need to be enriched with additional information (they come with some fields empty). The missing information is taken from the control stream, whose elements come through a kafka source. Essentially, what I want is to pause any processing until having read the full (control) topic, otherwise (at least initially) the output elements will not be enriched as expected. -- Sent from: http://apache-flink-user-mailing-list-archive.2336050.n4.nabble.com/
