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https://issues.apache.org/jira/browse/KAFKA-14156?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jose Armando Garcia Sancio updated KAFKA-14156:
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Fix Version/s: 3.3.0
> Built-in partitioner may create suboptimal batches with large linger.ms
> -----------------------------------------------------------------------
>
> Key: KAFKA-14156
> URL: https://issues.apache.org/jira/browse/KAFKA-14156
> Project: Kafka
> Issue Type: Improvement
> Components: producer
> Affects Versions: 3.3.0
> Reporter: Artem Livshits
> Priority: Major
> Fix For: 3.3.0
>
>
> The new built-in "sticky" partitioner switches partitions based on the amount
> of bytes produced to a partition. It doesn't use batch creation as a switch
> trigger. The previous "sticky" DefaultPartitioner switched partition when a
> new batch was created and with small linger.ms (default is 0) could result in
> sending larger batches to slower brokers potentially overloading them. See
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-794%3A+Strictly+Uniform+Sticky+Partitioner
> for more detail.
> However, the with large linger.ms, the new built-in partitioner may create
> suboptimal batches. Let's consider an example, suppose linger.ms=500,
> batch.size=16KB (default) and we produce 24KB / sec, i.e. every 500ms we
> produce 12KB worth of data. The new built-in partitioner would switch
> partition on every 16KB, so we could get into the following batching pattern:
> * produce 12KB to one partition in 500ms, hit linger, send 12KB batch
> * produce 4KB more to the same partition, now we've produced 16KB of data,
> switch partition
> * produce 12KB to the second partition in 500ms, hit linger, send 12KB batch
> * in the mean time the 4KB produced to the first partition would hit linger
> as well, sending 4KB batch
> * produce 4KB more to the second partition, now we've produced 16KB of data
> to the second partition, switch to 3rd partition
> so in this scenario the new built-in partitioner produces a mix of 12KB and
> 4KB batches, while the previous DefaultPartitioner would produce only 12KB
> batches -- it switches on new batch creation, so there is no "mid-linger"
> leftover batches.
> To avoid creation of batch fragmentation on partition switch, we can wait
> until the batch is ready before switching the partition, i.e. the condition
> to switch to a new partition would be "produced batch.size bytes" AND "batch
> is not lingering". This may potentially introduce some non-uniformity into
> data distribution, but unlike the previous DefaultPartitioner, the
> non-uniformity would not be based on broker performance and won't
> re-introduce the bad pattern of sending more data to slower brokers.
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