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https://issues.apache.org/jira/browse/KAFKA-12776?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17345836#comment-17345836
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Guozhang Wang commented on KAFKA-12776:
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I think KIP-739 is relatively orthogonal to the scenario we just described
here..
The reason Kafka does not try to enforce ordering at the gate of `send` call is
that, in practice there are many other factors that can cause out-of-order.
Note that even in telecom scenarios, from the time an HTTP request gets
received and to the time `producer.send` is triggered, there could also be
skewness between threads, such that a request arrives first but ended up
calling `producer.send` second compared to another.
> Producer sends messages out-of-order inspite of enabling idempotence
> --------------------------------------------------------------------
>
> Key: KAFKA-12776
> URL: https://issues.apache.org/jira/browse/KAFKA-12776
> Project: Kafka
> Issue Type: Bug
> Components: producer
> Affects Versions: 2.6.0, 2.7.0
> Environment: Linux RHEL 7.9 and Ubuntu 20.04
> Reporter: NEERAJ VAIDYA
> Priority: Major
> Attachments: mocker.zip
>
>
> I have an Apache Kafka 2.6 Producer which writes to topic-A (TA).
> My application is basically a Spring boot web-application which accepts JSON
> payloads via HTTP and then pushes each to a Kafka topic. I also use Spring
> Cloud Stream Kafka in the application to create and use a Producer.
> For one of my failure handling test cases, I shutdown the Kafka cluster while
> my applications are running. (Note : No messages have been published to the
> Kafka cluster before I stop the cluster)
> When the producer application tries to write messages to TA, it cannot
> because the cluster is down and hence (I assume) buffers the messages. Let's
> say it receives 4 messages m1,m2,m3,m4 in increasing time order. (i.e. m1 is
> first and m4 is last).
> When I bring the Kafka cluster back online, the producer sends the buffered
> messages to the topic, but they are not in order. I receive for example, m2
> then m3 then m1 and then m4.
> Why is that ? Is it because the buffering in the producer is multi-threaded
> with each producing to the topic at the same time ?
> My project code is attached herewith.
> I can confirm that I have enabled idempotence. I have also tried with
> ```max.in.flight.requests=1```
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