Dear all, The following describes KIP-132, which I just created. See: https://cwiki.apache.org/confluence/display/KAFKA/KIP-132+-+Augment+KStream.print+to+allow+extra+parameters+in+the+printed+string
Motivation As for now, KStream#print leads to a predefined output where key and value are printed with comma separation. KAFKA-4830 <https://issues.apache.org/jira/browse/KAFKA-4830> suggests to extend print in a way that it takes KeyValueMapper as a parameter. This will allow a user to change outputs according to the users demand. Public Interfaces The affected interface is KStream, which needs to be extended with another overloaded version of print: void print(final Serde<K> keySerde, final Serde<V> valSerde, final String streamName, final KeyValueMapper<K, V, String> mapper); Proposed Changes See pull request GH-2669 <https://github.com/apache/kafka/pull/2669>. This PR contains a discussion regarding KAFKA-4830 <https://issues.apache.org/jira/browse/KAFKA-4830> as well as KAFKA-4772 <https://issues.apache.org/jira/browse/KAFKA-4772>. Compatibility, Deprecation, and Migration Plan The extension of print will not introduce compatibility issues – we can maintain the current output by keeping the current output format as a default (if mapper was not set): if(mapper == null) { printStream.println("[" + streamName + "]: " + keyToPrint + " , " + valueToPrint); } else { printStream.println("[" + streamName + "]: " + mapper.apply(keyToPrint, valueToPrint)); } Kind regards, Marc
