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Status

Current state: draft [One of "Under Discussion", "Accepted", "Rejected"]

Discussion thread: here

JIRA: here

Released: <Kafka Version>

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

Motivation

From  Unable to render Jira issues macro, execution error. , certain datasets require modifications to the messages either coming into Kafka (source) or going to another data store (sink). For example, we may require to remove user identifiable information like SSN from Kafka while exporting data into a Hadoop cluster for analysis.

Currently, the "data transfer" logic is locked within a single function, thus Kafka Connect API is inflexible for making such modifications. This is more so when a Kafka Connect API is provided via third party where the user cannot modify the source. Custom modifications from user to user would require modifying the source of Connect API. 

Public Interfaces

For the transformers, we require to introduce an abstract class which others can extend to create their own custom Transformer.

public abstract class Transformer<T1, T2> {
    public abstract T2 transform(T1 t1);
    public void initialize(Map<String, String> props) {}
}

Also, this would need a :

transformers=org.AbcTransformer,org2.XyzTransformer

property in the Kafka Connect config files to initialise the transformers, in the order specified in the above property. 

Proposed Changes

Describe the new thing you want to do in appropriate detail. This may be fairly extensive and have large subsections of its own. Or it may be a few sentences. Use judgement based on the scope of the change.

Compatibility, Deprecation, and Migration Plan

• What impact (if any) will there be on existing users?
• If we are changing behavior how will we phase out the older behavior?
• If we need special migration tools, describe them here.
• When will we remove the existing behavior?

Test Plan

Describe in few sentences how the KIP will be tested. We are mostly interested in system tests (since unit-tests are specific to implementation details). How will we know that the implementation works as expected? How will we know nothing broke?

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.