Status

Current state: Under Discussion

Discussion thread: here (<- link to https://mail-archives.apache.org/mod_mbox/flink-dev/)

JIRA: here (<- link to https://issues.apache.org/jira/browse/FLINK-XXXX)

Released: <Flink Version>

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

Motivation

This FLIP proposes to promote the Unified Sink API V2 from PublicEvolving to Public and to mark the SinkFunction as Deprecated. Since its introduction in Flink 1.12, the Unified Sink API has undergone extensive development and testing, evidenced by its evolution across multiple FLIPs and its adoption in major connectors like Kafka, Cassandra, and Elasticsearch since Flink 1.14 and beyond. Over more then four release cycles, the API has demonstrated stability and robustness, aligning with the criteria set forth in FLIP-197 for API stability graduation. This promotion is expected to encourage wider adoption by signaling the API’s maturity and reliability to the user base. This step is essential for standardizing Flink’s API landscape, much like the transition from SourceFunction to Source API, thereby enhancing the framework's overall functionality and maintainability.

The following table shows the relevant FLIPs that lead to the SinkV2 API as it has been released with Flink 1.19

The following table shows the state of migration to SinkV2 for ASF supported and released connectors:

Status	Connector	Used Sink/SinkV2 since
	FileSystem	Flink 1.12 FLINK-19758 - Getting issue details... STATUS
	Kafka / Upsert-Kafka	Flink 1.14 FLINK-22902 - Getting issue details... STATUS
	Cassandra	FLINK-26821 - Getting issue details... STATUS
	DynamoDB	AWS Connector v3.0 (via ASync API) FLINK-24229 - Getting issue details... STATUS
	Elasticsearch	Flink 1.15 FLINK-24323 - Getting issue details... STATUS
	Firehose	Flink 1.15 (via ASync API) FLINK-24228 - Getting issue details... STATUS
	Kinesis	Flink 1.15 (via ASync API) FLINK-24227 - Getting issue details... STATUS
	MongoDB	MongoDB v1.0 (via ASync API) FLINK-6573 - Getting issue details... STATUS
	Opensearch	Opensearch v1.0 (via ASync API) FLINK-25756 - Getting issue details... STATUS
	RabbitMQ	FLINK-21373 - Getting issue details... STATUS
	Google Cloud PubSub	FLINK-24296 - Getting issue details... STATUS / FLINK-24298 - Getting issue details... STATUS
	Pulsar	Flink 1.15 FLINK-26022 - Getting issue details... STATUS
	JDBC	JDBC v3.2.0 FLINK-25421 - Getting issue details... STATUS
	HBase	FLINK-35280 - Getting issue details... STATUS

This topic has also been previously discussed on the Dev mailing list in https://lists.apache.org/thread/q62nj89rrz0t5xtggy5n65on95f2rmmx

Public Interfaces

Briefly list any new interfaces that will be introduced as part of this proposal or any existing interfaces that will be removed or changed. The purpose of this section is to concisely call out the public contract that will come along with this feature.

A public interface is any change to the following:

• DataStream and DataSet API, including classes related to that, such as StreamExecutionEnvironment

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 FLIP 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.