Brokers should be able to pull from a meta data store to get their configurations.
Current state: Superseded by KIP-21
Discussion thread: here
JIRA: here
Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).
It is dangerous to have the possibility of different configuration on different brokers. Even if folks use orchestration system it could be disastrous for a Kafka cluster if that system didn't work/update right. It takes an unnecessary amount of effort making builds for every target platform to help keep changes consistent throughout the cluster(s). Instead we can provide a way for Kafka brokers to handle their own configurations.
Command line tools and arguments
You can keep using properties as you do today. If you decide to use the global configuration feature then only a few properties will be able to be overridden e.g. host and port. All other properties will either be default or set in the central meta store for retrieving the settings.
These changes use and are based on KAFKA-1845 (KafkaConfig should use ConfigDef).
The new proposed workflow is the following:
The global configuration is stored in the same format as a topic-level configuration:
{ "version" : "1", "config" : { "message.max.bytes" : "200000", "num.network.threads" : "5" } } |
Dedicated zookeeper path to store global configuration: /brokers/config
To change global configuration the new Wire Protocol message is introduced. Proposed schema:
Request:
ConfigChangeRequest => [ConfigData] ConfigData => ConfigKey ConfigValue ConfigKey => string ConfigValue => string |
Response:
ConfigChangeResponse => ErrorCode ErrorCode => int16 |
To change global configuration:
In 0.8.3 we will still support the property files but it will be deprecated and we will then remove support for property files in 0.9.0.
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.