Best practices for Java logging from multiple threads?

Question

I want to have a diagnostic log that is produced by several tasks managing data. These tasks may be in multiple threads. Each task needs to write an element (possibly with s

Answer 1

This is an old question but here's my solution using Log4J programmatically.

LogFactory class

import org.apache.log4j.Logger;
import org.apache.log4j.PropertyConfigurator;

import java.util.Properties;

public class LogFactory {

    private final static ThreadLocal logFactory = new ThreadLocal<>();

    public static void createNewLogger(String className) {

        Logger log = Logger.getLogger("Thread" + className);

        Properties props = new Properties();
        props.setProperty("log4j.appender.file", "org.apache.log4j.RollingFileAppender");

        props.setProperty("log4j.appender.file.maxFileSize", "100MB");
        props.setProperty("log4j.appender.file.Append", "false");
        props.setProperty("log4j.", "100MB");
        props.setProperty("log4j.appender.file.maxBackupIndex", "100");
        props.setProperty("log4j.appender.file.File", "logs/" + className + ".log");
        props.setProperty("log4j.appender.file.threshold", "info");
        props.setProperty("log4j.appender.file.layout", "org.apache.log4j.PatternLayout");
        props.setProperty("log4j.appender.file.layout.ConversionPattern", "%d{yyyy-MM-dd HH-mm-ss} | %-5p | %C{1}:%L | %m%n");
        props.setProperty("log4j.appender.stdout", "org.apache.log4j.ConsoleAppender");
        props.setProperty("log4j.appender.stdout.Target", "System.out");
        props.setProperty("log4j.logger." + "Thread" + className, "INFO, file");
        PropertyConfigurator.configure(props);
        logFactory.set(log);
    }

    public static Logger getLogger() {
        return logFactory.get();
    }

}

Then to initialise the the logger use the following approach

logFactory.createNewLogger(String.valueOf(Thread.currentThread().getId()));
logFactory.getLogger().info(" TEST . Thread id is: " + id);