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This project employs the logging utility facade SLF4J, using Apache Log4j , accordingly 2.x as its backend. Accordingly, levels of detail can be specified as follows:
OFF: The highest possible rank and is intended to turn off logging.
FATAL: Designates very severe error events that will presumably lead the application to abort.
ERROR: Designates error events that might still allow the application to continue running.
WARN: Designates potentially harmful situations.
INFO: Designates informational messages that highlight the progress of the application at coarse-grained level.
DEBUG: Designates fine-grained informational events that are most useful to debug an application.
TRACE: Designates finer-grained informational events than the DEBUG.
ALL: All levels including custom levels.
For more guidance on which level to use, see Coding Conventions#Logging
For modifying One mechanism of globally effecting the log output of a running client is though modification the file /besu/src/main/resources/log4j2.xml, where it can be specified under the <Property name="root.log.level">. As such, corresponding instances of information logs throughout the codebase, e.g. log.fatal("Fatal Message!");, will be rendered to the console while the client is in use, you may use a custom log4j config file by setting a system property at startup. Besu's logging doc provides good documentation on how to configure logging in Besu.