java - What does threshold mean in Log4J?

Question

I have a log4j properties something like below. Everything that is logged in TextProcessor.log is something above WARN level. I don't understand the threshold that is set here to debug. Can someone explain what the threshold does?

log4j.logger.TextProcessor=warn,TextProcessor 

log4j.appender.TextProcessor=org.apache.log4j.RollingFileAppender
log4j.appender.TextProcessor.File=C:/project/logs/TextProcessor.log
log4j.appender.TextProcessor.MaxFileSize=10MB
log4j.appender.TextProcessor.MaxBackupIndex=10
log4j.appender.TextProcessor.Threshold=debug
log4j.appender.TextProcessor.layout=org.apache.log4j.PatternLayout
log4j.appender.TextProcessor.layout.ConversionPattern=[%d] [%5p] (%F:%L) - %m%n

Answer 1

You have two things here : a logger, and an appender. Unfortunately, you chose the same name for both, which doesn't make it very clear.

The logger's minimum level is set to warn, which means everything you log with this logger which doesn't have at least the warn level will be ignored.

Once a message is accepted by the logger, it's sent to one or several appenders (to a file, to the console, to a mail server, etc.). Each of these appenders may define a threshold. You could for example limit the messages in the console to errors, but accept warn messages in the log file.