• [Refactor] Introduce a counter-based locking approach to make sure, that we close the producer safely but at the same time not to limit messages production with producing lock.
• [Refactor] Make private methods private.
• [Refactor] Validate that producer is not closed only when attempting to produce.
• [Refactor] Improve one 5 minute long spec to run in 10 seconds.
• [Refactor] clear client assignment after closing.