nixos/apache-kafka: Add manual chapter

        SuccessExitStatus = "0 143";

      };

    };

  };

  meta.doc = ./kafka.md;

  meta.maintainers = with lib.maintainers; [

    srhb

  ];

}

# Apache Kafka {#module-services-apache-kafka}

[Apache Kafka](https://kafka.apache.org/) is an open-source distributed event

streaming platform

## Basic Usage {#module-services-apache-kafka-basic-usage}

The Apache Kafka service is configured almost exclusively through its

[settings](#opt-services.apache-kafka.settings) option, with each attribute

corresponding to the [upstream configuration

manual](https://kafka.apache.org/documentation/#configuration) broker settings.

## KRaft {#module-services-apache-kafka-kraft}

Unlike in Zookeeper mode, Kafka in

[KRaft](https://kafka.apache.org/documentation/#kraft) mode requires each log

dir to be "formatted" (which means a cluster-specific a metadata file must

exist in each log dir)

The upstream intention is for users to execute the [storage

tool](https://kafka.apache.org/documentation/#kraft_storage) to achieve this,

but this module contains a few extra options to automate this:

- [](#opt-services.apache-kafka.clusterId)

- [](#opt-services.apache-kafka.formatLogDirs)

- [](#opt-services.apache-kafka.formatLogDirsIgnoreFormatted)

## Migrating to settings {#module-services-apache-kafka-migrating-to-settings}

Migrating a cluster to the new `settings`-based changes requires adapting removed options to the corresponding upstream settings.

This means that the upstream [Broker Configs documentation](https://kafka.apache.org/documentation/#brokerconfigs) should be followed closely.

Note that dotted options in the upstream docs do _not_ correspond to nested Nix attrsets, but instead as quoted top level `settings` attributes, as in `services.apache-kafka.settings."broker.id"`, *NOT* `services.apache-kafka.settings.broker.id`.

Care should be taken, especially when migrating clusters from the old module, to ensure that the same intended configuration is reproduced faithfully via `settings`.

To assist in the comparison, the final config can be inspected by building the config file itself, ie. with: `nix-build <nixpkgs/nixos> -A config.services.apache-kafka.configFiles.serverProperties`.

Notable changes to be aware of include:

- Removal of `services.apache-kafka.extraProperties` and `services.apache-kafka.serverProperties`

  - Translate using arbitrary properties using [](#opt-services.apache-kafka.settings)

  - [Upstream docs](https://kafka.apache.org/documentation.html#brokerconfigs)

  - The intention is for all broker properties to be fully representable via [](#opt-services.apache-kafka.settings).

  - If this is not the case, please do consider raising an issue.

  - Until it can be remedied, you *can* bail out by using [](#opt-services.apache-kafka.configFiles.serverProperties) to the path of a fully rendered properties file.

- Removal of `services.apache-kafka.hostname` and `services.apache-kafka.port`

  - Translate using: `services.apache-kafka.settings.listeners`

  - [Upstream docs](https://kafka.apache.org/documentation.html#brokerconfigs_listeners)

- Removal of `services.apache-kafka.logDirs`

  - Translate using: `services.apache-kafka.settings."log.dirs"`

  - [Upstream docs](https://kafka.apache.org/documentation.html#brokerconfigs_log.dirs)

- Removal of `services.apache-kafka.brokerId`

  - Translate using: `services.apache-kafka.settings."broker.id"`

  - [Upstream docs](https://kafka.apache.org/documentation.html#brokerconfigs_broker.id)

- Removal of `services.apache-kafka.zookeeper`

  - Translate using: `services.apache-kafka.settings."zookeeper.connect"`

  - [Upstream docs](https://kafka.apache.org/documentation.html#brokerconfigs_zookeeper.connect)