Configure Docker Logging
==========================

log4j log levels
~~~~~~~~~~~~~~~~

To change the default logging levels or add new logging levels:

1. Change the ``{COMPONENT}_LOG4J_ROOT_LOGLEVEL`` to change ``rootLogger`` loglevel.
2. Add or override default loggers by using ``{COMPONENT}_LOG4J_LOGGERS`` environment variable. This variable accepts the comma separated values of the logger config. For example, to override the log levels of controller and request loggers , use ``KAFKA_LOG4J_LOGGERS="kafka.controller=WARN,kafka.foo.bar=DEBUG"``.
3. To change the logging levels for the tools, use the ``{COMPONENT}_LOG4J_TOOLS_ROOT_LOGLEVEL``.

Replace ``{COMPONENT}`` as below for the component you are changing the log level for:

.. csv-table::
   :header: "Component", "``{COMPONENT}``"
   :widths: 20, 20

   "ZooKeeper", "``ZOOKEEPER``"
   "Kafka", "``KAFKA``"
   "Confluent Control Center", "``CONTROL_CENTER``"
   "Schema Registry", "``SCHEMA_REGISTRY``"
   "REST Proxy", "``KAFKA_REST``"
   "Kafka Connect", "``CONNECT``"
   "ksqlDB", "``KSQL``"
   
An example command to change the log level for Kafka is:

.. codewithvars:: bash

    docker run -d \
      --name=kafka-log-example \
      --net=host \
      -e KAFKA_BROKER_ID=1 \
      -e KAFKA_ZOOKEEPER_CONNECT=localhost:32181/jmx \
      -e KAFKA_ADVERTISED_LISTENERS=PLAINTEXT://localhost:39092 \
      -e KAFKA_JMX_PORT=39999 \
      -e KAFKA_LOG4J_LOGGERS="kafka.controller=WARN,kafka.foo.bar=DEBUG" \
      -e KAFKA_LOG4J_ROOT_LOGLEVEL=WARN \
      -e KAFKA_TOOLS_LOG4J_LOGLEVEL=ERROR \
      -e KAFKA_OFFSETS_TOPIC_REPLICATION_FACTOR=1 \
      confluentinc/cp-kafka:|release|

Change log outputs
~~~~~~~~~~~~~~~~~~

All logs are sent to ``stdout`` by default. You can change this by
:ref:`extending the images <log-to-external-volumes>`.