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https://issues.apache.org/jira/browse/KAFKA-9430?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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John Roesler updated KAFKA-9430:
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Description:
Right now, we use _endOffsets_ of the source topic for the computation. For
"optimized" changelogs, this will be wrong, strictly speaking, but it's an
over-estimate (which seems better than an under-estimate), and it's also still
an apples-to-apples comparison, since all replicas would use the same upper
bound to compute their lags, so the "pick the freshest" replica is still going
to pick the right one.
The current implementation is technically correct, within the documented
behavior that the result is an "estimate", but I marked it as a blocker to be
sure that we revisit it after ongoing work to refactor the task management in
Streams is complete. If it becomes straightforward to tighten up the estimate,
we should go ahead and do it. Otherwise, we can downgrade the priority of the
ticket.
was:
Right now, we use _endOffsets_ of the source topic for the computation. Since
the source topics can also have user event produces, this is an over estimate
>From John:
For "optimized" changelogs, this will be wrong, strictly speaking, but it's an
over-estimate (which seems better than an under-estimate), and it's also still
an apples-to-apples comparison, since all replicas would use the same upper
bound to compute their lags, so the "pick the freshest" replica is still going
to pick the right one.
> Tighten up lag estimates when source topic optimization is on
> --------------------------------------------------------------
>
> Key: KAFKA-9430
> URL: https://issues.apache.org/jira/browse/KAFKA-9430
> Project: Kafka
> Issue Type: Sub-task
> Components: streams
> Affects Versions: 2.5.0
> Reporter: Vinoth Chandar
> Assignee: Vinoth Chandar
> Priority: Blocker
>
> Right now, we use _endOffsets_ of the source topic for the computation. For
> "optimized" changelogs, this will be wrong, strictly speaking, but it's an
> over-estimate (which seems better than an under-estimate), and it's also
> still an apples-to-apples comparison, since all replicas would use the same
> upper bound to compute their lags, so the "pick the freshest" replica is
> still going to pick the right one.
> The current implementation is technically correct, within the documented
> behavior that the result is an "estimate", but I marked it as a blocker to be
> sure that we revisit it after ongoing work to refactor the task management in
> Streams is complete. If it becomes straightforward to tighten up the
> estimate, we should go ahead and do it. Otherwise, we can downgrade the
> priority of the ticket.
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