Di Shang created LOG4J2-1585:
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Summary: Logger.getParent gives warning about MessageFactory
mismatch
Key: LOG4J2-1585
URL: https://issues.apache.org/jira/browse/LOG4J2-1585
Project: Log4j 2
Issue Type: Bug
Affects Versions: 2.6.2
Reporter: Di Shang
Hi
I just noticed a lot of warning spam in my log like this:
2016-09-15 14:59:16,322 main WARN The Logger was created with the message
factory org.apache.logging.log4j.message.ReusableMessageFactory@51e2adc7 and is
now requested with the message factory
org.apache.logging.log4j.message.ReusableMessageFactory@1a8a8f7c, which may
create log events with unexpected formatting.
The root cause of this is in Logger.getParent() :
final MessageFactory messageFactory = getMessageFactory();
if (context.hasLogger(lcName, messageFactory)) { // <=====
return context.getLogger(lcName, messageFactory); // <=====
}
return new Logger(context, lcName, messageFactory);
It is trying to fetch the parent logger using the child's messageFactory, which
will cause the warning from context.getLogger. To me this looks like a bug
since the parent and child can have different messageFactory instance. (or are
they supposed to be the same?)
Easy way to reproduce this:
LogManager.getRootLogger();
Logger logger = LogManager.getLogger("foo");
((org.apache.logging.log4j.core.Logger) logger).getParent();
I was thinking about a fix like this:
if (context.hasLogger(lcName)) {
return context.getLogger(lcName);
}
return new Logger(context, lcName, getMessageFactory());
But it doesn't look quite right because the LoggerRegistry seems to identify
unique logger by (MF_class_name, logger_name) meaning there can be multiple
loggers of the same name but different MF class.
So the real question is if the parent-child relationship is determined by the
name only but there are multiple loggers of the same name, how can we uniquely
determine the parent logger?
Reviewing the log4j 2 architecture documentation, I realized that it only
mentions about parent-child relationship between LoggerConfig, not Loggers.
Does this mean that the parent-child hierarchy is only determined by the
underlying LoggerConfig and for a particular LoggerConfig there can be multiple
loggers of the same name but different MF. So Logger.getParent() doesn't make
much sense any more and should not be used. Is my understanding here correct?
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