The PartialValueStrategy component attempts to clone via BSON parsing on both the key and value of the kafka message. At this time, bson parsing is attempted for the key value, resulting in a parsing error if the key is an unsupported value. This error completely stops consuming messages. I think this is an unintended strategy implementation. PartialValueStrategy should try bson parsing only for the value.

For example, kafka's key type is string type. When I try to clone the key, the key is converted to a bson type. But it's just a string, so the conversion(bson parsing) fails.

Just cloning the value in PartialValueStrategy is clear and enough. 

The same goes for PartialKeyStrategy.