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ASF GitHub Bot commented on TWILL-199: -------------------------------------- Github user chtyim commented on a diff in the pull request: https://github.com/apache/twill/pull/16#discussion_r94911854 --- Diff: twill-core/src/main/java/org/apache/twill/kafka/client/KafkaConsumer.java --- @@ -33,14 +33,16 @@ /** * Invoked when new messages is available. + * @param startOffset Offset of the first {@link FetchedMessage} in the iterator of new messages. --- End diff -- Is it? Or shall it return the offset of the first message being read? Other, e.g. if `-1L` was specified, and the latest message was read, but not being consumed by the `onReceived` method. If it returns `-1L`, then that particular message won't get fetched again if there is a newer message available. Is that the intention? > Get next offset and handle offset error in KafkaConsumer.MessageCallback > ------------------------------------------------------------------------ > > Key: TWILL-199 > URL: https://issues.apache.org/jira/browse/TWILL-199 > Project: Apache Twill > Issue Type: Improvement > Reporter: Chengfeng Mao > > The method {{void onReceived(Iterator<FetchedMessage> messages)}} in > {{KafkaConsumer.MessageCallback}} can be more flexible with the change to > {{Long onReceived(Iterator<FetchedMessage> messages)}} so that it can provide > additional functionalities: > 1. To return the next offset to be fetched > 2. To handle offset non-existence or offset mismatch error and take action on > the error > This method will return null for backward compatibility when it doesn't need > to provide the next offset. > In concrete implementation, a class of a new interface > {{KafkaOffsetProvider}} can be added as a member in > {{KafkaConsumer.MessageCallback}} to perform the offset error handling and > provide the next offset. Besides, {{KafkaOffsetProvider}} also has methods to > provide the following functionalities: > 1. To fetch earliest/latest offset in Kafka > 2. To find the offset of a message with timestamp equal to the given > timestamp in Kafka > For backward compatibility, if {{KafkaOffsetProvider}} instance is not > provided, its default value will be null and none of its methods will be > called. -- This message was sent by Atlassian JIRA (v6.3.4#6332)