Quarkus - Logging Logback

This extension allows you to use Logback to configure Quarkus logging via logback.xml. This extension parses the config file at build time, and then bridges the resulting config with jboss-logmanager.


If you want to use this extension, you need to add the io.quarkiverse.logging.logback:quarkus-logging-logback extension first. In your pom.xml file, add:


Technical Details

This extension does not actually replace jboss-logmanager as the default logging engine, instead it bridges to the two, to allow them to co-exist. JBoss Logging is still the core logmanager for Quarkus, however any logging events it receives are also sent to the logback and will be sent through any logback appenders.

Log levels for loggers are also parsed, and are used to set the default log level for the corresponding jboss-logmanager loggers. These defaults can still be overriden however, so if you set a log level in application.properties it will take precidence.

If a console appender is detected in logback.xml then the standard Quarkus console logging is disabled, to prevent double logging of messages, otherwise it is left enabled and will work as normal.

Common Problems

Duplicate SLF4J bindings

You may see an error similar to below:

SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/home/stuart/.m2/repository/ch/qos/logback/logback-classic/1.2.3/logback-classic-1.2.3.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/home/stuart/.m2/repository/org/jboss/slf4j/slf4j-jboss-logmanager/1.1.0.Final/slf4j-jboss-logmanager-1.1.0.Final.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.
SLF4J: Actual binding is of type [ch.qos.logback.classic.util.ContextSelectorStaticBinder]

To get around this you need to exclude the ch.qos.logback:logback-classic artifact from your project. Quarkus will automatically bring in a modified version at runtime that has had the SLF4J binding removed. Run mvn dependency:tree to figure out what is bringing in the artifact, and then exclude it from the pom.xml.