KAFKA-18409: ShareGroupStateMessageFormatter should use ApiMessageFormatter

[brandboat]

related to https://issues.apache.org/jira/browse/KAFKA-18409

ShareGroupStateMessageFormatter should extend ApiMessageFormatter in order to have a consistent handling of records of coordinators.

Committer Checklist (excluded from commit message)

• Verify design and implementation
• Verify test coverage and CI build status
• Verify documentation (including upgrade notes)

[m1a2st]

Thanks for the PR, left few comments. PTAL

[m1a2st]

I think we should use the modifier protected.

[brandboat]

Sure, thanks.

[m1a2st]

Since the keyVersion parameter is only used by the ShareGroupStateMessageFormatter class, we should refactor this to make the method less abstract. Instead of requiring all subclasses to implement the keyVersion parameter, we could:

1. Move keyVersion out of the abstract definition
2. Provide a default implementation in the base class

WDYT?

[brandboat]

Yes, I've thought about that before, but that means we need to add below methods to ApiMessageFormatter.java.

    protected abstract JsonNode readToValueJson(ByteBuffer byteBuffer);

    protected JsonNode readToValueJson(ByteBuffer byteBuffer, short keyVersion) {
        return readToValueJson(byteBuffer);
    }

But doing that means I need to override two methods in ShareGroupStateMessageFormatter.java, particularly readToValueJson(ByteBuffer byteBuffer). This method will essentially be a dummy method, which feels somewhat awkward to implement, so I decided to add an extra parameter to it instead.

    @Override
    protected JsonNode readToValueJson(ByteBuffer byteBuffer, short keyVersion) {
        short valueVersion = byteBuffer.getShort();
        return readToSnapshotMessageValue(byteBuffer, keyVersion, valueVersion)
            .map(logValue -> transferValueMessageToJsonNode(logValue, valueVersion))
            .orElseGet(() -> new TextNode(UNKNOWN));
    }

    @Override
    protected JsonNode readToValueJson(ByteBuffer byteBuffer) {
        return null;
    }

Or you have other ideas? Let me know if you'd like any further adjustments!

[m1a2st]

I propose changing the JsonNode readToValueJson signature to accept a ConsumerRecord<byte[], byte[]>parameter. This would standardize the method signature across all subclasses. WDYT?

protected JsonNode readToValueJson(ConsumerRecord<byte[], byte[]> consumerRecord)

[brandboat]

Not sure if this is a good idea, perhaps we can wait for others opinion.

[dajac]

@brandboat What do you think about this one: #18695?