The Kafka appender uses the Kafka client library, and that client library does it's own logging through SLF4J, it always emits a few log messages at DEBUG level on each message sent.
If you have log4j-slf4j-impl in classpath and enable DEBUG logging through KafkaAppender, you will get recursive logging, and the application gets stuck. The recursive logging prevention in AppenderControl does not protect against this as far as I can see. I have put in some protection in KafkaAppender: https://github.com/apache/logging-log4j2/blob/master/log4j-core/src/main/java/org/apache/logging/log4j/core/appender/mom/kafka/KafkaAppender.java#L133 Without this, you get recursive logging. -- [image: MagineTV] *Mikael Ståldal* Senior software developer *Magine TV* [email protected] Grev Turegatan 3 | 114 46 Stockholm, Sweden | www.magine.com Privileged and/or Confidential Information may be contained in this message. If you are not the addressee indicated in this message (or responsible for delivery of the message to such a person), you may not copy or deliver this message to anyone. In such case, you should destroy this message and kindly notify the sender by reply email.
