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Status

Current state: Under Discussion

Discussion thread: here [Change the link from the KIP proposal email archive to your own email thread]

JIRA: here 

Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).

Motivation

Currently, the consumer reports a metric of the lag between the high watermark of a log and the consumer offset. It will be useful to report a similar lead metric between the consumer offset and the start offset of the log. If this number gets close to 0, it's an indication that the consumer may stall or lose data soon. It would be useful to know per partition lead as well.

Public Interfaces

There is no programmatic public interface change. We are only adding new metrics.

Proposed Changes

Add min lead metric across all partitions to KafkaConsumer.the metric name would be:

"records-lead-min"

Also, add per partition lead metrics to KafkaConsumer. The metric names would be:

"TOPIC-PARTITION_ID.record-lead"
"TOPIC-PARTITION_ID.record-lead-avg"
"TOPIC-PARTITION_ID.record-lead-min"

Compatibility, Deprecation, and Migration Plan

• What impact (if any) will there be on existing users?
• If we are changing behavior how will we phase out the older behavior?
• If we need special migration tools, describe them here.
• When will we remove the existing behavior?

Rejected Alternatives

If there are alternative ways of accomplishing the same thing, what were they? The purpose of this section is to motivate why the design is the way it is and not some other way.