Jan Westphal created FLINK-20628:
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Summary: Port RabbitMQ Sources to FLIP-27 API
Key: FLINK-20628
URL: https://issues.apache.org/jira/browse/FLINK-20628
Project: Flink
Issue Type: Improvement
Components: Connectors/ RabbitMQ
Reporter: Jan Westphal
Fix For: 1.12.0
*Structure*
The new RabbitMQ Source will have three components:
* RabbitMQ enumerator that receives one RabbitMQ Channel Config.
* RabbitMQ splits contain the RabbitMQ Channel Config
* RabbitMQ Readers which subscribe to the same RabbitMQ channel and receive
the messages (automatically load balanced by RabbitMQ).
*Checkpointing Enumerators*
The enumerator only needs to checkpoint the RabbitMQ channel config since the
continuous discovery of new unread/unhandled messages is taken care of by the
subscribed RabbitMQ readers and RabbitMQ itself.
*Checkpointing Readers*
The new RabbitMQ Source needs to ensure that every reader can be checkpointed.
Since RabbitMQ is non-persistent and cannot be read by offset, a combined usage
of checkpoints and message acknowledgments is necessary. Until a received
message is checkpointed by a reader, it will stay in an un-acknowledge state.
As soon as the checkpoint is created, the messages from the last checkpoint can
be acknowledged as handled against RabbitMQ and thus will be deleted only then.
Messages need to be acknowledged one by one as messages are handled by each
SourceReader individually.
When deserializing the messages we will make use of the implementation in the
existing RabbitMQ Source.
*Message Delivery Guarantees*
Unacknowledged messages of a reader will be redelivered by RabbitMQ
automatically to other consumers of the same channel if the reader goes down.
This Source is going to only support at-least-once as this is the default
RabbitMQ behavior and thus everything else would require changes to RabbitMQ
itself or would impair the idea of parallelizing SourceReaders.
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