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https://issues.apache.org/jira/browse/KAFKA-12713?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17331590#comment-17331590
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Ming Liu edited comment on KAFKA-12713 at 4/27/21, 12:17 AM:
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The idea is:
# Add waitTimeMs in FetchResponse
# In processResponseCallback() of handleFetchRequest, set the waitTimeMs as
the time spent in purgatory.
# In FetcherStats, we will add a new meter to track the fetch latency, by
deduct the waitTimeMs from the latency.
Also, in FetchLatency, we should also report a time called TotalEffectiveTime =
TotalTime-RemoteTime.
Let me know for any suggestion/feedback. I like to propose a KIP on that
change.
was (Author: mingaliu):
The idea is:
0. Add waitTimeMs in Request()
1. In delayedOperation DelayedFetch class, add some code to track the actual
wait time.
2. In processResponseCallback() of handleFetchRequest, we can add additional
parameter of waitTimeMs invoked from DelayedFetch. It will set
request.waitTimeMs.
3. In updateRequestMetrics() function, if waitTimeMs is not zero, we will
deduct that out of RemoteTime and TotalTime.
Let me know for any suggestion/feedback. I like to propose a KIP on that
change.
> Report "REAL" follower/consumer fetch latency
> ---------------------------------------------
>
> Key: KAFKA-12713
> URL: https://issues.apache.org/jira/browse/KAFKA-12713
> Project: Kafka
> Issue Type: Bug
> Reporter: Ming Liu
> Priority: Major
>
> The fetch latency is an important metrics to monitor for the cluster
> performance. With ACK=ALL, the produce latency is affected primarily by
> broker fetch latency.
> However, currently the reported fetch latency didn't reflect the true fetch
> latency because it sometimes need to stay in purgatory and wait for
> replica.fetch.wait.max.ms when data is not available. This greatly affect the
> real P50, P99 etc.
> I like to propose a KIP to be able track the real fetch latency for both
> broker follower and consumer.
>
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