Log4j2 add logger at runtime - what's wrong with this code?

Issue

while migrating a project from log4j to log4j2 I encountered a situation when a logger that logs events to a separate file (let's call it uu.log) has to be added at runtime - all other loggers are configured in properties file. The below code is almost doing the job - namely, uu.log contains events from all existing loggers, not just from new one. This is what I try so far: How can I fix the code below to achieve the desired state in simplest way?

public class MultipleLoggersExample {

    public static void main(String[] args) throws InterruptedException {

        // this logger is configured in properties file and is logging to own file
        Logger aud = LogManager.getLogger("aud");

        // class B is logging to separate file (logger also defined in properties)
        B b = new B();

        // below classes should log to common file NormalLog.log defined in properties
        C c = new C();
        D d = new D();
        E e = new E();

        addLoggerAtRuntime();

        // this logger needs to log only its OWN messages to uu.log file
        Logger runtimeLogger = LogManager.getLogger("my runtime logger");

        int counter = 2;
        while(true) {
            if(counter % 2 == 0){
                aud.info("message from \"aud\" logger no. "+ (counter-1));
            } else{
                b.logger.info("message from class B no. " + (counter-1));
            }
            c.logger.info("message from class C");
            e.logger.info("message from class E");

            if(counter % 4 == 0) {
                runtimeLogger.info("message from logger added at runtime");
            }
            counter++;
            Thread.sleep(5_000);
        }
    }

    private static void addLoggerAtRuntime() {
        final String fileName = "C:\\Users\\Damian\\Desktop\\uu.log";

        LoggerContext lc = (LoggerContext) LogManager.getContext(false);
        RollingFileAppender rfa = RollingFileAppender.newBuilder()
                .withName("my runtime logger").withAppend(true)
                .withFileName(fileName)
                .withLayout(PatternLayout.newBuilder().withPattern("%-5p %d [%t] %C{2} - %m%n").build())
                .withPolicy(TimeBasedTriggeringPolicy.newBuilder().withModulate(true).withInterval(2).build())
                .withFilePattern(fileName + "." + "%d{yyyy-MM-dd-HH-mm}")
                .setConfiguration(lc.getConfiguration()).build();
        rfa.start();
        lc.getConfiguration().addAppender(rfa);
        lc.getRootLogger().addAppender(lc.getConfiguration().getAppender(rfa.getName()));
        lc.updateLoggers();
    }

}

Solution

Appender names have no relationship to logger names, so this:

.withName("my runtime logger")

is pointless. You might as well use "My appender" or something.

The problem is this:

lc.getRootLogger().addAppender(

You’re adding your Appender to the root logger, from which all other loggers inherit, so of course all loggers are using it. Try adding the Appender to just your logger:

lc.getLogger("my runtime logger").addAppender(

Answered By - VGR