Status

Current state: Released

Discussion thread: https://lists.apache.org/thread/hod6bg421bzwhbfv60lwsck7r81dvo59

JIRA: FLINK-35378 - Getting issue details... STATUS

Released: 1.20

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, FileSystem, and AWS 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

• The following interfaces will be marked as @Deprecated 
  • org.apache.flink.streaming.api.functions.sink#SinkFunction
  • org.apache.flink.streaming.api.functions.sink#SocketClientSink
  • org.apache.flink.streaming.api.functions.sink#TwoPhaseCommitSinkFunction
• The following interfaces will be marked as @Public 
  • org.apache.flink.api.connector.sink2#Committer
  • org.apache.flink.api.connector.sink2#CommitterInitContext
  • org.apache.flink.api.connector.sink2#CommittingSinkWriter
  • org.apache.flink.api.connector.sink2#Sink
  • org.apache.flink.api.connector.sink2#SinkWriter
  • org.apache.flink.api.connector.sink2#StatefulSinkWriter
  • org.apache.flink.api.connector.sink2#SupportsCommitter
  • org.apache.flink.api.connector.sink2#SupportsWriterState
  • org.apache.flink.api.connector.sink2#WriterInitContext

Proposed Changes

Properly annotate the above interfaces with the designated annotation. 

Compatibility, Deprecation, and Migration Plan

• We need to include in the next release notes that these interfaces are deprecated / designated to by annotated as Public
• Change the existing org.apache.flink.streaming.api.functions.sink#DiscardingSink, org.apache.flink.streaming.api.functions.sink#PrintSink and org.apache.flink.streaming.api.functions.sink#PrintSinkFunction to use the new interfaces

Test Plan

Existing tests

Rejected Alternatives

N/A