Logging
Guardian for Apache Kafka uses logback to perform logging. This means if you are using the modules as libraries you need to provide a logback.xml in your classpath (typically this is done by putting the logback.xml in your /src/main/resources folder). Note that the Guardian modules do not provide a default logback.xml for deployed artifacts since this is typically the responsibility of an application to configure and provide.
If you want examples of logback.xml configuration you can have a look at the official logback page but you can also use existing logback.xml’s from either the cli or the tests as a reference.
As documented at pekko logback configuration it is highly recommended to use an AsyncAppender in your configuration as this offsets the logging to a background thread otherwise you will end up blocking the core pekko/pekko-streams library whenever a log is made.
Logback adapter for pekko/pekko-streams
By default, pekko/pekko-streams uses its own asynchronous logger however they provide a logging adapter which has already been preconfigured for use in Guardian.
CLI/Application
Note that unlike the core libraries, the CLI application does provide a default logback.xml. For more details read application logging.