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https://issues.apache.org/jira/browse/KAFKA-6376?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16427321#comment-16427321
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John Roesler commented on KAFKA-6376:
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Hey [~guozhang], I'm chasing down those possible skip areas you noted.
About 1) deserialization errors on Consumer, I don't think this could possibly
result in a skip.
I'm looking at
org.apache.kafka.clients.consumer.internals.Fetcher.PartitionRecords#fetchRecords,
and it will only increment `nextFetchOffset` after successfully deserializing
the record. If there's an exception, it does *not* increment the next fetch
offset (so it'll fetch the same record next time), and it returns any records
it has already deserialized. If there are no successful deserializations, it
just throws a SerializationException.
Did I misread the code, or were you perhaps talking about a different condition?
> Improve Streams metrics for skipped records
> -------------------------------------------
>
> Key: KAFKA-6376
> URL: https://issues.apache.org/jira/browse/KAFKA-6376
> Project: Kafka
> Issue Type: Improvement
> Components: metrics, streams
> Affects Versions: 1.0.0
> Reporter: Matthias J. Sax
> Assignee: John Roesler
> Priority: Major
> Labels: kip
>
> Copy this from KIP-210 discussion thread:
> {quote}
> Note that currently we have two metrics for `skipped-records` on different
> levels:
> 1) on the highest level, the thread-level, we have a `skipped-records`,
> that records all the skipped records due to deserialization errors.
> 2) on the lower processor-node level, we have a
> `skippedDueToDeserializationError`, that records the skipped records on
> that specific source node due to deserialization errors.
> So you can see that 1) does not cover any other scenarios and can just be
> thought of as an aggregate of 2) across all the tasks' source nodes.
> However, there are other places that can cause a record to be dropped, for
> example:
> 1) https://issues.apache.org/jira/browse/KAFKA-5784: records could be
> dropped due to window elapsed.
> 2) KIP-210: records could be dropped on the producer side.
> 3) records could be dropped during user-customized processing on errors.
> {quote}
> [~guozhang] Not sure what you mean by "3) records could be dropped during
> user-customized processing on errors."
> Btw: we also drop record with {{null}} key and/or value for certain DSL
> operations. This should be included as well.
> KIP: :
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-274%3A+Kafka+Streams+Skipped+Records+Metrics
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