[FLINK-24542] Expose the freshness metrics for kafka connector

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Invalid
• Affects Version/s: 1.12.2, 1.14.0, 1.13.1
• Component/s: Connectors / Kafka
• Assignee: Unassigned
• Reporter: zlzhang0122
• Created: 14/Oct/21 08:00
• Updated: 16/Oct/23 06:46
• Resolved: 16/Oct/23 06:46

Description

When we start a flink job to consume apache kafka, we usually use offsetLag, which can be calulated by current-offsets minus committed-offsets, but sometimes the offsetLag is hard to understand, we can hardly to judge wether the value is normal or not. Kafka have proposed a new metric: freshness(see a-guide-to-kafka-consumer-freshness).

So we can also expose the freshness metric for kafka connector to improve the user experience.From this freshness metric, user can easily know wether the kafka message is backlog and need to deal with it.