Hi, I wrote a proof of concept for a Java version of mapWithState with time-based state eviction https://github.com/juanrh/flink-state-eviction/blob/a6bb0d4ca0908d2f4350209a4a41e381e99c76c5/src/main/java/com/github/juanrh/streaming/MapWithStateIterPoC.java. The idea is:
- Convert an input KeyedStream with key K and value V into a KeyedStream of Either<V, K>, with the original values as Left. - Replace a ValueState<S> by a ValueState for a POJO that besides S it stores the timestamp of the last time that state was accessed. - Define a IterativeStream from the Either stream, and apply a transformation function that periorically sends "tombstone" events as Right events in the closeWith of the IterativeStream. When a tombstone is received, delete the state with clear if it the time since it was last accessed is bigger than a configured time to live. This seems to work so far, but there are some things that look weird to me: - The program never seems to stop, event though I Ihave defined the IterativeStream with https://ci.apache.org/projects/flink/flink-docs-master/api/java/org/apache/flink/streaming/api/datastream/DataStream.html#iterate-long- . The value of seems to be ignored. I'm using a custom source function, but it seems like the method SourceFunction.cancel() it's not being called. - I'm getting several messages "WARN MetricGroup: Name collision: Group already contains a Metric with the name 'numRecordsOut'. Metric will not be reported. (null)". What does that mean? Thanks, Juan
