Hi Basanth,
Given the fact that Flink put failure recovery garantee on checkpointing and source rewinding.
I can imagine a lossless rpc source would be tricky. In essence, any rpc source needs to provide rewind api which can buffer at least to last success checkpoint.
In production use cases, put your data received from rpc server to a distributed queue and consume from queue might be better idea.
Thanks,
Chen