Producer retries

 1. In case of transient failures, developers are expected to handle exceptions, otherwise the data will be lost.

2. Example of transient failure:

    - NotEnoughReplicasException

3. There is a "retries" setting

    - defaults to 0

    - You can increase to a high number, ex Integer.MAX_VALUE

- In case of retries, by default there is a chance that messages will be sent out of order (if a batch has failed to be sent).

- If yolu rely on key-based ordering, that can be an issue.

- For this, you can set the setting while controls how many produce requests can be made in parallel: max.in.flight.requests.per.connection

    - Default: 5 

    - Set it to I if you need to ensure ordering (may impact throughput)

- In Kafka >= 1.0.0, there's a better solution!