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https://issues.apache.org/jira/browse/KAFKA-48?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13247409#comment-13247409
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Jun Rao commented on KAFKA-48:
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Thanks for patch v3. Some comments:
31. DelayedFetch is keyed off topic. It should be keyed off (topic, partition)
since a consumer may be interested in only a subset of partitions within a
topic.
32. KafkaApis: The following 3 lines are duplicated in 2 places.
val topicData = readMessageSets(delayed.fetch.offsetInfo)
val response = new FetchResponse(FetchRequest.CurrentVersion,
delayed.fetch.correlationId, topicData)
requestChannel.sendResponse(new RequestChannel.Response(delayed.request,
new FetchResponseSend(response, ErrorMapping.NoError), -1))
Should we put them in a private method and share the code?
33. ExpiredRequestReaper.purgeExpired(): We need to decrement unsatisfied count
here.
34. FetchRequest: Can we have the default constants for correlationId,
clientid, etc defined and shared btw the constructor and the request builder?
35. MessageSetSend.empty is unused. Should we remove it?
> Implement optional "long poll" support in fetch request
> -------------------------------------------------------
>
> Key: KAFKA-48
> URL: https://issues.apache.org/jira/browse/KAFKA-48
> Project: Kafka
> Issue Type: Bug
> Reporter: Jun Rao
> Assignee: Jay Kreps
> Attachments: KAFKA-48-v2.patch, KAFKA-48-v3.patch, KAFKA-48.patch
>
>
> Currently, the fetch request is non-blocking. If there is nothing on the
> broker for the consumer to retrieve, the broker simply returns an empty set
> to the consumer. This can be inefficient, if you want to ensure low-latency
> because you keep polling over and over. We should make a blocking version of
> the fetch request so that the fetch request is not returned until the broker
> has at least one message for the fetcher or some timeout passes.
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