How to log FATAL (or any custom log level) with SLF4J and Log4j2

Question

I have those specific requirements :

• Need to be able to log in FATAL level
• Need to use SLF4J<

Answer 1

Here's the closest working solution I came with some colleagues :

1. Create a Fatal Marker class using SLF4J Markers.
2. Using a RoutingAppender, use the Marker as the routing pattern: "$${marker:}"
3. Configure a Fatal-specific appender that has its own PatternLayout that doesn't include the LogLevel but a hardcoded FATAL level.

Here's the Java sample :

Marker fatal = MarkerFactory.getMarker("FATAL");
// Usage example
final Logger logger = LoggerFactory.getLogger(FatalLogger.class);
logger.log(fatal, "this is a fatal message");

// Log sample : 
20150514T115144,279  FATAL [main] FatalLogger - this is a fatal message

Here's the YAML sample :

Configuration:
  status: debug

  Appenders:
    RandomAccessFile:
      - name: APPLICATION_APPENDER
        fileName: logs/application.log
        PatternLayout:
          Pattern: "%d{ISO8601_BASIC} %-5level %msg%n"
      - name: FATAL_APPENDER
        fileName: logs/application.log
        PatternLayout:
          Pattern: "%d{ISO8601_BASIC} FATAL %msg%n"

    Routing:
      name: ROUTING_APPENDER
      Routes:
        pattern: "$${marker:}"
        Route:
        - key: FATAL
          ref: FATAL_APPENDER
        - ref: APPLICATION_APPENDER #DefaultRoute

  Loggers:
    Root:
      level: trace
      AppenderRef:
        - ref: ROUTING_APPENDER