Status

Current state: "Under Discussion"

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

JIRA: here [Change the link from KAFKA-1 to your own ticket]

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

Motivation

Kafka has a dependency on Zookeeper 3.6.3, which reached its end of life in December 2022. We would like to upgrade Zookeeper to version 3.8.1 which is the latest release of the 3.8.x versions.

Zookeeper 3.8.1 server supports clients no older than 3.5.x and Zookeeper 3.8.1. clients support server versions no older than 3.5.x.

ZooKeeper clients from 3.5.x onwards are fully compatible with 3.8.x servers.
The upgrade from 3.6.x and 3.7.x can be executed as usual, no particular additional upgrade procedure is needed.
ZooKeeper 3.8.x clients are compatible with 3.5.x, 3.6.x and 3.7.x servers as long as you are not using new APIs not present these versions.

In comparison, Zookeeper 3.6.3 server supports clients no older than 3.4.x and Zookeeper 3.6.3 clients support server versions no older than 3.5.x

ZooKeeper clients from 3.4 and 3.5 branch are fully compatible with 3.6 servers.
The upgrade from 3.5.7 to 3.6.0 can be executed as usual, no particular additional upgrade procedure is needed.
ZooKeeper 3.6.0 clients are compatible with 3.5 servers as long as you are not using new APIs not present in 3.5.

Public Interfaces

No public interfaces are being changed.

Proposed Changes

Similarly to https://github.com/apache/kafka/pull/12620/files we would like to upgrade to 3.8.1.

Compatibility, Deprecation, and Migration Plan

• What impact (if any) will there be on existing users? Users who use Kafka clusters with Zookeeper clients older than 3.5.x won't be able to communicate with a Zookeeper cluster using 3.8.1
• If we are changing behavior how will we phase out the older behavior? It should gradually be phased out as users update their Kafka versions
• If we need special migration tools, describe them here. N/A
• When will we remove the existing behavior? N/A

Test Plan

We ran the following test on the latest trunk of Kafka with Zookeeper 3.6.3 and Zookeeper 3.8.1:

1) Start 1 Zookeeper node on an m5.4xlarge machine

2) Start 1 Kafka broker on a different m5.4xlarge machine

3) Using 4 admin clients sequentially create up to 2000 topics with 1 partition

4) Using 4 admin clients sequentially change the number of partitions on all 2000 topics to 2

5) Using 4 admin clients sequentially delete all topics

Zookeeper 3.8.1 request latency

<TO-BE-ADDED>

Zookeeper 3.6.3 request latency

<TO-BE-ADDED>

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. N/A