Hello folks, As we are approaching the feature freeze deadline of 0.11.0.0, one thing I realized is that currently the Streams public APIs are still marked as "Unstable", which is to indicate that the API itself does not provide guarantees about backward compatibility across releases. On the other hand, since Streams have now been widely adopted in production use cases by many organizations, we are in fact evolving its APIs in a much stricter manner than "Unstable" allows us: for all the current Streams related KIP proposals under discussions right now [1], people have been working hard to make sure none of them are going to break backward compatibility in the coming releases. So I think it would be a good timing to change the Streams API annotations.
My proposal would be the following: 1. For "o.a.k.streams.errors" and "o.a.k.streams.state" packages: remove the annotations except `StreamsMetrics`. 2. For "o.a.k.streams.kstream": remove the annotations except "KStream", "KTable", "GroupedKStream", "GroupedKTable", "GlobalKTable" and "KStreamBuilder". 3. For all the other public classes, including "o.a.k.streams.processor" and the above mentioned classes, change the annotation to "Evolving", which means "we might break compatibility at minor releases (i.e. 0.12.x, 0.13.x, 1.0.x etc) only". The ultimate goal is to make sure we won't break anything going forward, hence in the future we should remove all the annotations to make that clear. The above changes in 0.11.0.0 is to give us some "buffer time" in case there are some major API change proposals after the release. Would love to hear your thoughts. [1] KIP-95: Incremental Batch Processing for Kafka Streams <https://cwiki.apache.org/confluence/display/KAFKA/KIP-95%3A+Incremental+Batch+Processing+for+Kafka+Streams> KIP-120: Cleanup Kafka Streams builder API <https://cwiki.apache.org/confluence/display/KAFKA/KIP-120%3A+Cleanup+Kafka+Streams+builder+API> KIP-123: Allow per stream/table timestamp extractor <https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=68714788> KIP 130: Expose states of active tasks to KafkaStreams public API <https://cwiki.apache.org/confluence/display/KAFKA/KIP+130%3A+Expose+states+of+active+tasks+to+KafkaStreams+public+API> KIP-132: Augment KStream.print to allow extra parameters in the printed string <https://cwiki.apache.org/confluence/display/KAFKA/KIP-132+-+Augment+KStream.print+to+allow+extra+parameters+in+the+printed+string> KIP-138: Change punctuate semantics <https://cwiki.apache.org/confluence/display/KAFKA/KIP-138%3A+Change+punctuate+semantics> KIP-147: Add missing type parameters to StateStoreSupplier factories and KGroupedStream/Table methods <https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=69408481> KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner <https://cwiki.apache.org/confluence/display/KAFKA/KIP-149%3A+Enabling+key+access+in+ValueTransformer%2C+ValueMapper%2C+and+ValueJoiner#KIP-149:EnablingkeyaccessinValueTransformer,ValueMapper,andValueJoiner-RejectedAlternatives> KIP-150 - Kafka-Streams Cogroup <https://cwiki.apache.org/confluence/display/KAFKA/KIP-150+-+Kafka-Streams+Cogroup> KIP 155 - Add range scan for windowed state stores <https://cwiki.apache.org/confluence/display/KAFKA/KIP+155+-+Add+range+scan+for+windowed+state+stores> KIP 156 Add option "dry run" to Streams application reset tool <https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=69410150> -- -- Guozhang
