Status

Current state: Under Discussion

Discussion thread: here

JIRA: KAFKA-6793 - Getting issue details... STATUS

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

Motivation

Kafka clients report warning for config options that were not used during initialization, for example, a default set of warnings you get when starting Streams application:

The configuration 'admin.retries' was supplied but isn't a known config.
The configuration 'auto.register.schemas' was supplied but isn't a known config.
The configuration 'schema.registry.url' was supplied but isn't a known config.

This list can be extended if you use some extra configuration, required by your internal infrastructure or if you use some 3rd party plugins. While these config options are valid they create a lot of noise in monitoring. This KIP proposes to suppress this warning by changing its log level to DEBUG.

Public Interfaces

None.

Proposed Changes

Change log level from WARN to DEBUG for unused config message.

Compatibility, Deprecation, and Migration Plan

None. Hard to imagine a scenario where anyone relies on this message to be a warning.

Rejected Alternatives

Adding interface to control message log level

There are no strong reasons to keep it as a warning, so introducing an extra interface would be an overkill. 

Remove the message

The warning should stay, as it could save time debugging issues related to incorrect configuration.

Add whitelist property

A comma-separated list of properties, that should be ignored. Requires extra property, but less flexible, that proposed approach.

User config prefix

The idea would be to add a "user config prefix" to allow users to tell clients about additional configs they should ignore. There are maybe some 3rd party libraries, that not comply with a prefix rule and then users stay with a warning and can do nothing about it.