Java – log4j rootLogger seems to inherit log level of other logger. Why

javalog4j

I've got a log4J setup in which the root logger is supposed to log ERROR level messages and above to the console and another logger logs everything to syslog.

log4j.properties is:

# Root logger option
log4j.rootLogger=ERROR,R

log4j.appender.R=org.apache.log4j.ConsoleAppender
log4j.appender.R.layout=org.apache.log4j.PatternLayout
log4j.appender.R.layout.ConversionPattern=%d %p %t %c - %m%n

log4j.logger.SGSearch=DEBUG,SGSearch
log4j.appender.SGSearch=org.apache.log4j.net.SyslogAppender
log4j.appender.SGSearch.SyslogHost=localhost
log4j.appender.SGSearch.Facility=LOCAL6
log4j.appender.SGSearch.layout=org.apache.log4j.PatternLayout
log4j.appender.SGSearch.layout.ConversionPattern=[%-5p] %m%n

In code I do

private static final Logger logger = Logger.getLogger("SGSearch");
.
.
.
logger.info("Commencing snapshot index [" + args[1] + " -> " + args[2] + "]");

What is happening is that I get the console logging for all logging levels. What seems to be happening is that the level for SGSearch overrides the level set for the root logger somehow. I can't figure it out.

I have confirmed that Log4J is reading the properties file I think it is, and no other (via the -Dlog4j.debug option)

Best Answer

The way Log4j chaining works is a bit counter intuitive (to me at least). See the log4j manual. If the request level is equal to or above the threshold of the most specific matching logger, it is accepted. Once the request is accepted, it gets handled by the complete chain of ancestors regardless of their thresholds!

To suppress the chaining behavior, add:

log4j.additivity.SGSearch=false

This will cause requests handled by logger SGSearch to no longer be passed up the chain.

One other suggestion: don't name your logger and appender the same, because at some point in the future you, or a colleague will mix them up. The logger name should indicate which type of logging is handled, the appender name should specify where the logging goes. So in this case I would think 'SGSearch' could be the logger name, and the appender should be called something like 'LocalSysLog'.

BTW: In my opinion you are doing the right thing by restricting the root logger with a high threshold, and lowering it for specific loggers. This avoids clutter from loud libraries (Apache has a few notorious ones).

Related Solutions

Java – Log4j: Why is the root logger collecting all log types regardless the configuration

The root logger resides at the top of the logger hierarchy. It is exceptional in three ways:

it always exists,
its level cannot be set to null
it cannot be retrieved by name.

The rootLogger is the father of all appenders. Each enabled logging request for a given logger will be forwarded to all the appenders in that logger as well as the appenders higher in the hierarchy (including rootLogger)

For example, if the console appender is added to the root logger, then all enabled logging requests will at least print on the console. If in addition a file appender is added to a logger, say L, then enabled logging requests for L and L's children will print on a file and on the console. It is possible to override this default behavior so that appender accumulation is no longer additive by setting the additivity flag to false.

From the log4j manual

To sum up:

If you want not to propagate a logging event to the parents loggers (say rootLogger) then add the additivity flag to false in those loggers. In your case:

<logger name="org.springframework.ws.server.endpoint.interceptor"
        additivity="false">
        <level value="DEBUG" />
        <appender-ref ref="payloadAppender" />
</logger>

In standard log4j config style (which I prefer to XML):

log4j.logger.org.springframework.ws.server.endpoint.interceptor = INFO, payloadAppender
log4j.additivity.org.springframework.ws.server.endpoint.interceptor = false

Hope this helps.

Java – Turning off hibernate logging console output

Important notice: the property (part of hibernate configuration, NOT part of logging framework config!)

hibernate.show_sql

controls the logging directly to STDOUT bypassing any logging framework (which you can recognize by the missing output formatting of the messages). If you use a logging framework like log4j, you should always set that property to false because it gives you no benefit at all.

That circumstance irritated me quite a long time because I never really cared about it until I tried to write some benchmark regarding Hibernate.

Best Answer

Related Solutions

Java – Log4j: Why is the root logger collecting all log types regardless the configuration

Java – Turning off hibernate logging console output

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