Log4j2 Composite config

Composite Configuration

Log4j allows multiple configuration files to be used by specifying them as a list of comma separated file paths on log4j.configurationFile. The merge logic can be controlled by specifying a class that implements the MergeStrategy interface on the log4j.mergeStrategy property. The default merge strategy will merge the files using the following rules:

1. The global configuration attributes are aggregated with those in later configurations replacing those in previous configurations, with the exception that the highest status level and the lowest monitorInterval greater than 0 will be used.
2. Properties from all configurations are aggregated. Duplicate properties replace those in previous configurations.
3. Filters are aggregated under a CompositeFilter if more than one Filter is defined. Since Filters are not named duplicates may be present.
4. Scripts and ScriptFile references are aggregated. Duplicate definiations replace those in previous configurations.
5. Appenders are aggregated. Appenders with the same name are replaced by those in later configurations, including all of the Appender's subcomponents.
6. Loggers are all aggregated. Logger attributes are individually merged with duplicates being replaced by those in later configurations. Appender references on a Logger are aggregated with duplicates being replaced by those in later configurations. Filters on a Logger are aggregated under a CompositeFilter if more than one Filter is defined. Since Filters are not named duplicates may be present. Filters under Appender references included or discarded depending on whether their parent Appender reference is kept or discarded.