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Zookeeper 3.8.1 server supports clients no older than 3.5.x (i.e. Apache Kafka version 2.4.0) and Zookeeper 3.8.1. clients support server versions no older than 3.5.x (i.e. Apache Kafka version 2.4.0).
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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. |
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A Zookeeper cluster is separate from a Kafka cluster.For example, a user wanting to migrate from a Kafka cluster with version 2.3 and a Zookeeper cluster with version 3.4 to a Kafka cluster with version 3.X (where X is the Kafka version containing this KIP) and Zookeeper cluster with version 3.8.1 would first have to upgrade their Kafka cluster to 3.4.0 (latest version of the time of writing), then update their Zookeeper cluster to 3.8.1 and lastly update their Kafka cluster again from 3.4.0 to 3.X.As another example, a user wanting to migrate from a Kafka cluster with version 2.4 and a Zookeeper cluster with version 3.5 to a Kafka cluster with version 3.X and Zookeeper cluster with version 3.8.1 could upgrade their Kafka cluster to 3.X and then their Zookeeper cluster to 3.8.1 or vice versa.
It is worth mentioning that Kafka is still tested for cluster upgrades between versions 0.8.2 and 3.4.
The table below makes the assumption you want to carry out the upgrades using a rolling restart
Zookeeper cluster (< 3.5) | Zookeeper cluster (>= 3.5) | |
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Kafka cluster (< 2.4) |
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Kafka client (< 2.4) |
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Kafka cluster (>= 2.4) |
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Kafka client (>= 2.4) |
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Below is an analysis of changes introduced in 3.7.0 and 3.8.0 and whether they will introduce breaking changes in Kafka or not.
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