Confluent Docker log4j logger level configurations - docker

Question

I am running locally Kafka using the confluentinc/cp-kafka Docker image and I am setting the following logging container environment variables:
KAFKA_LOG4J_ROOT_LOGLEVEL: ERROR
KAFKA_LOG4J_LOGGERS: >-
org.apache.zookeeper=ERROR,
org.apache.kafka=ERROR,
kafka=ERROR,
kafka.cluster=ERROR,
kafka.controller=ERROR,
kafka.coordinator=ERROR,
kafka.log=ERROR,
kafka.server=ERROR,
kafka.zookeeper=ERROR,
state.change.logger=ERROR
and I see in the Kafka logs that Kafka is starting with the following configuration:
===> ENV Variables ...
ALLOW_UNSIGNED=false
COMPONENT=kafka
CONFLUENT_DEB_VERSION=1
CONFLUENT_PLATFORM_LABEL=
CONFLUENT_VERSION=5.4.1
...
KAFKA_LOG4J_LOGGERS=org.apache.zookeeper=ERROR, org.apache.kafka=ERROR, kafka=ERROR, kafka.cluster=ERROR, kafka.controller=ERROR, kafka.coordinator=ERROR, kafka.log=ERROR, kafka.server=ERROR, kafka.zookeeper=ERROR, state.change.logger=ERROR
KAFKA_LOG4J_ROOT_LOGLEVEL=ERROR
...
Still I see further down in the logs the INFO and TRACE log levels. For example:
[2020-03-26 16:22:12,838] INFO [Controller id=1001] Ready to serve as the new controller with epoch 1 (kafka.controller.KafkaController)
[2020-03-26 16:22:12,848] INFO [Controller id=1001] Partitions undergoing preferred replica election: (kafka.controller.KafkaController)
[2020-03-26 16:22:12,849] INFO [Controller id=1001] Partitions that completed preferred replica election: (kafka.controller.KafkaController)
[2020-03-26 16:22:12,855] INFO [Controller id=1001] Skipping preferred replica election for partitions due to topic deletion: (kafka.controller.KafkaController)
How can I really deactivate the logs below a certain level? In the example above, I really want only ERROR logs.
The approach above is the way described in the Confluent documentation.
And the Apache Kafka source code lists all sorts of loggers that I could not influence using the KAFKA_LOG4J_LOGGERS Docker environment variable.

Answer 1

I went and troubleshot the Dockerfile's and inspected the Kafka container. The cause of this behaviour was the YAML multiline string folding.
Hence the provided environment variable (using a YAML multiline value) is at runtime:
KAFKA_LOG4J_LOGGERS=org.apache.zookeeper=ERROR, org.apache.kafka=ERROR, kafka=ERROR, kafka.cluster=ERROR, kafka.controller=ERROR, kafka.coordinator=ERROR, kafka.log=ERROR, kafka.server=ERROR, kafka.zookeeper=ERROR, state.change.logger=ERROR
instead of (no spaces in between):
KAFKA_LOG4J_LOGGERS=org.apache.zookeeper=ERROR,org.apache.kafka=ERROR, kafka=ERROR, kafka.cluster=ERROR,kafka.controller=ERROR, kafka.coordinator=ERROR,kafka.log=ERROR,kafka.server=ERROR,kafka.zookeeper=ERROR,state.change.logger=ERROR
And this was visible inside the container in the generated /etc/kafka/log4j.properties file:
log4j.rootLogger=ERROR, stdout
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=[%d] %p %m (%c)%n
log4j.logger.kafka.authorizer.logger=WARN
log4j.logger.kafka.cluster=ERROR
log4j.logger.kafka.producer.async.DefaultEventHandler=DEBUG
log4j.logger.kafka.zookeeper=ERROR
log4j.logger.org.apache.kafka=ERROR
log4j.logger.kafka.coordinator=ERROR
log4j.logger.org.apache.zookeeper=ERROR
log4j.logger.kafka.log.LogCleaner=INFO
log4j.logger.kafka.controller=ERROR
log4j.logger.kafka=INFO
log4j.logger.kafka.log=ERROR
log4j.logger.state.change.logger=ERROR
log4j.logger.kafka=ERROR
log4j.logger.kafka.server=ERROR
log4j.logger.kafka.controller=TRACE
log4j.logger.kafka.network.RequestChannel$=WARN
log4j.logger.kafka.request.logger=WARN
log4j.logger.state.change.logger=TRACE
If you really need to split the long line in a YAML multiline value, you would have to use this YAML syntax.
More hints from the code:
here is where the log4j.properties file is generated when a confluent container is run.
these are the default log levels that Kafka will start with.
these should be all the loggers supported by Kafka