KIP-425 adds SASL support to the KafkaLog4jAppender however it does not include the credential handling improvements added with KIP-86. This is a proposal is to expose `sasl.login.callback.handler.class` for use by the underlying producer.
KIP-473 https://cwiki.apache.org/confluence/display/KAFKA/KIP-473%3A+Enable+KafkaLog4JAppender+to+use+SASL+Authentication+Callback+Handlers KIP-425 https://cwiki.apache.org/confluence/display/KAFKA/KIP-425%3A+Add+some+Log4J+Kafka+Appender+Properties+for+Producing+to+Secured+Brokers KIP-86 https://cwiki.apache.org/confluence/display/KAFKA/KIP-86%3A+Configurable+SASL+callback+handlers
