[jira] [Created] (FLINK-8410) Kafka consumer's commitedOffsets gauge metric is prematurely set

["Tzu-Li (Gordon) Tai (JIRA)" <ji...@apache.org>]

Tzu-Li (Gordon) Tai created FLINK-8410:
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             Summary: Kafka consumer's commitedOffsets gauge metric is prematurely set
                 Key: FLINK-8410
                 URL: https://issues.apache.org/jira/browse/FLINK-8410
             Project: Flink
          Issue Type: Bug
          Components: Kafka Connector, Metrics
    Affects Versions: 1.3.2, 1.4.0, 1.5.0
            Reporter: Tzu-Li (Gordon) Tai
            Assignee: Tzu-Li (Gordon) Tai
             Fix For: 1.3.3, 1.5.0, 1.4.1


The {{committedOffset}} metric gauge value is set too early. It is set here:
https://github.com/apache/flink/blob/master/flink-connectors/flink-connector-kafka-0.9/src/main/java/org/apache/flink/streaming/connectors/kafka/internal/Kafka09Fetcher.java#L236

This sets the committed offset before the actual commit happens, which varies depending on whether the commit mode is auto periodically, or committed on checkpoints. Moreover, in the 0.9+ consumers, the {{KafkaConsumerThread}} may choose to supersede some commit attempts if the commit takes longer than the commit interval.

While the committed offset back to Kafka is not a critical value used by the consumer, it will be best to have more accurate values as a Flink-shipped metric.



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