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Status

Current state: Draft

Discussion thread: here [Change the link from the KIP proposal email archive to your own email thread]

JIRA: KAFKA-7722

Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).

Motivation

The ProducerPerformance tool is the standard for benchmarking Kafka producer send performance. The tool uses sampling and Java’s System.currentTimeMillis() to record latencies and provide percentiles at the end of each run. This method works well in most cases but results in a lack of precision.

This is a problem in low-latency environments in which sending a message takes at most a couple milliseconds. For example, if a user wants to run a benchmark test comparing two different Kafka cluster setups, it is hard to compare results if low latency values are observed.

Example Scenario:

Benchmark #1: average latency = 2 ms

Benchmark #2: average latency = 3 ms

Since System.currentTimeMillis() gives values with millisecond precision:

• A result of 2 ms can have a true value between [1.5, 2.5) before rounding
• A result of 3 ms can have a true value between [2.5, 3.5) before rounding

If we want to calculate the increase in latency observed, then we have a big spread of either:

• (1) Smallest spread: 2.5 - (2.5) or ~0, resulting in approximately ~0% increase in latency
• (2) Largest spread: (3.5) - 1.5 or ~2, resulting in approximately 2/2 or ~100% increase in latency

This means we cannot effectively compare these two benchmark results as the latency in #2 is anywhere from 0 to 100% higher than in #1, which is a big spread and results in very different implications. 

Public Interfaces

Briefly list any new interfaces that will be introduced as part of this proposal or any existing interfaces that will be removed or changed. The purpose of this section is to concisely call out the public contract that will come along with this feature.

A public interface is any change to the following:

• Binary log format

• The network protocol and api behavior

• Any class in the public packages under clientsConfiguration, especially client configuration

  • org/apache/kafka/common/serialization

  • org/apache/kafka/common

  • org/apache/kafka/common/errors

  • org/apache/kafka/clients/producer

  • org/apache/kafka/clients/consumer (eventually, once stable)

• Monitoring

• Command line tools and arguments

• Anything else that will likely break existing users in some way when they upgrade

Proposed Changes

Describe the new thing you want to do in appropriate detail. This may be fairly extensive and have large subsections of its own. Or it may be a few sentences. Use judgement based on the scope of the change.

Compatibility, Deprecation, and Migration Plan

• What impact (if any) will there be on existing users?
• If we are changing behavior how will we phase out the older behavior?
• If we need special migration tools, describe them here.
• When will we remove the existing behavior?

Rejected Alternatives

If there are alternative ways of accomplishing the same thing, what were they? The purpose of this section is to motivate why the design is the way it is and not some other way.