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Date: Mon, 16 May 2016 15:35:13 +0000 (UTC)
From: "Ismael Juma (JIRA)" <jira@apache.org>
To: dev@kafka.apache.org
Message-ID: <JIRA.12968050.1463002918000.197569.1463412913013@Atlassian.JIRA>
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Subject: [jira] [Updated] (KAFKA-3704) Use default block size in
 KafkaProducer
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archived-at: Mon, 16 May 2016 15:35:15 -0000


     [ https://issues.apache.org/jira/browse/KAFKA-3704?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Ismael Juma updated KAFKA-3704:
-------------------------------
    Description: 
As discovered in https://issues.apache.org/jira/browse/KAFKA-3565, the current default block size (1K) used in Snappy and GZIP may cause a sub-optimal compression ratio for Snappy, and hence reduce throughput. Because we no longer recompress data in the broker, it also impacts what gets stored on disk.

A solution might be to use the default block size, which is 64K in LZ4, 32K in Snappy and 0.5K in GZIP. The downside is that this solution will require more memory allocated outside of the buffer pool and hence users may need to bump up their JVM heap size, especially for MirrorMakers. Using Snappy as an example, it's an additional 2x32k per batch (as Snappy uses two buffers) and one would expect at least one batch per partition. However, the number of batches per partition can be much higher if the broker is slow to acknowledge producer requests (depending on `buffer.memory`, `batch.size`, message size, etc.).

Given the above, it seems like a configuration may be needed as the there is no one size fits all. An alternative to a new config is to allocate buffers from the buffer pool and pass them to the compression library. This is possible with Snappy and we could adapt our LZ4 code. It's not possible with GZIP, but it uses a very small buffer by default.

Note that we decided that this change was too risky for 0.10.0.0 and reverted the original attempt.

  was:
As discovered in https://issues.apache.org/jira/browse/KAFKA-3565, the current default block size (1K) used in Snappy and GZIP may cause sub-optimal compression ratio for Snappy, and hence reduce throughput.

A better solution would be using the default block size, which is 32K in Snappy and 0.5K in GZIP. A notable side-effect is that with Snappy, this solution will require more extra memory allocated out side of the bufferpoll, by {{(32 - 1)K * num.total.partitions}} and hence users may need to bump up their JVM heap size, especially for MirrorMakers.


> Use default block size in KafkaProducer
> ---------------------------------------
>
>                 Key: KAFKA-3704
>                 URL: https://issues.apache.org/jira/browse/KAFKA-3704
>             Project: Kafka
>          Issue Type: Bug
>            Reporter: Guozhang Wang
>            Assignee: Guozhang Wang
>             Fix For: 0.10.1.0
>
>
> As discovered in https://issues.apache.org/jira/browse/KAFKA-3565, the current default block size (1K) used in Snappy and GZIP may cause a sub-optimal compression ratio for Snappy, and hence reduce throughput. Because we no longer recompress data in the broker, it also impacts what gets stored on disk.
> A solution might be to use the default block size, which is 64K in LZ4, 32K in Snappy and 0.5K in GZIP. The downside is that this solution will require more memory allocated outside of the buffer pool and hence users may need to bump up their JVM heap size, especially for MirrorMakers. Using Snappy as an example, it's an additional 2x32k per batch (as Snappy uses two buffers) and one would expect at least one batch per partition. However, the number of batches per partition can be much higher if the broker is slow to acknowledge producer requests (depending on `buffer.memory`, `batch.size`, message size, etc.).
> Given the above, it seems like a configuration may be needed as the there is no one size fits all. An alternative to a new config is to allocate buffers from the buffer pool and pass them to the compression library. This is possible with Snappy and we could adapt our LZ4 code. It's not possible with GZIP, but it uses a very small buffer by default.
> Note that we decided that this change was too risky for 0.10.0.0 and reverted the original attempt.


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