how to use log4j in Multithread using java?

Question

I want to write log for each thread using log4j and log file name will be "workthread..log",first thread print log on file "workthread-1.log" and second thread on "workthread-2.log" and so on.

class MyRunnable implements Runnable 
  {
       private Logger logger=null;

       public MyRunnable()
        {
            DOMConfigurator.configure(this.getClass().getClassLoader().getResource(LOG4J_FILEPATH));
            logger =Logger.getLogger(classname);
        }

        public void run() 
        {
          logger.info("Important job running in MyRunnable"+Thread.currentThread().getName());
        }
   }


public class TestThreads 
{
    public static void main (String [] args) 
     {
        Thread[] worker=new Thread[3];
        MyRunnable r = new MyRunnable();

        for(int i=0;i<3;i++) {
           worker[i]=new Thread(r);
           worker[i].start();
        }


    }
}//class

please help me?

Regards

and what is your problem? what is the code doing? is there any error? — Thomas Uhrig
– Thomas Uhrig, Commented Nov 22, 2011 at 12:14

Shamis Shukoor · Accepted Answer · 2011-11-22 12:19:55Z

4

you could use MDC

MDC.put(key,value); --in the code

and %X{key}-- in the file name field in the log4j configuration file

answered Nov 22, 2011 at 12:19

Shamis Shukoor

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Thomas Uhrig · Accepted Answer · 2011-11-22 12:19:57Z

2

perhaps you could try somezthing like this:

logger = Logger.getLogger(classname);
logger.removeAllAppenders();                                        
logger.addAppender(new FileAppender(layout, "your-thread-name.log", true));

you could get the name of your thread with something like "thread.getName()" i think ;)

answered Nov 22, 2011 at 12:19

Thomas Uhrig

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Matthias Meid · Accepted Answer · 2011-11-22 12:20:06Z

1

You can initialize each logger field with an instance by using LogManager.getLogger(Class) method. By using different text file appenders, you can dump the log lines to an appropriately names text file.

In case each thread used an own Runnable implementation (?), this should work. If it doesn't, try using a ThreadLocal<Logger> as logger and fill it by using LogManager.getLogger(String) with a Thread-widely unique name.

See also Short introduction to log4j: Ceki Gülcü, March 2002 in case you need an example of how to configure appenders.

answered Nov 22, 2011 at 12:20

Matthias Meid

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Dmitry Ginzburg · Accepted Answer · 2015-06-16 10:20:24Z

Implement a new log appender which manages FileAppender for different thread and files. Use AppenderSkeleton to do this, maintain a map for FileAppenders.

public MultiThreadAppender extends AppenderSkeleton {
    public final static String THREAD_KEY = "THREAD_NO";
    private Map<String, FileAppender> fileAppenders;
}

Use MDC to identify different threads. Use a key like "THREAD_NO", put to MDC (MDC.put) when a thread invoke logger the first time, and check this key to get the FileAppender for it. Here's the example:

protected void append(LoggingEvent event) {
    Object value = event.getMDC(THREAD_KEY);
    FileAppender appender;
    if (value instanceof String && ((String) value).length() > 0) {
        appender = fileAppenders.get(value);
    } else {
        value = nextThreadNo();
        fileAppenders.put(value, new FileAppender(...)); //
    }
}

Jorge Campos · Accepted Answer · 2016-03-10 17:56:23Z

this is how I use thread specific logger. Just copy paste and it on top of you run method and should work as is. Don't forget to change the text in caps.

String currenttime = String.valueOf(new Long(new Date().getTime()/1000));
String logFileName = "NAMEHERE_thread" + Thread.currentThread().getId() 
                     + "_" + currenttime+".log";
Logger logger = Logger.getLogger("NAMEHERE_thread" +
                                      Thread.currentThread().getId() + "_"+ currenttime);

Properties prop = new Properties();
prop.setProperty("log4j.logger.NAMEHERE_thread" + Thread.currentThread().getId() 
                 + "_" + currenttime,"DEBUG, file");

prop.setProperty("log4j.appender.file", "org.apache.log4j.RollingFileAppender");
prop.setProperty("log4j.appender.file.maxFileSize", "100MB");
prop.setProperty("log4j.appender.file.maxBackupIndex", "100");
prop.setProperty("log4j.appender.file.File", 
                 REPLACEMEWITHPATH + File.separator + logFileName);
prop.setProperty("log4j.appender.file.threshold","debug");
prop.setProperty("log4j.appender.file.layout", "org.apache.log4j.PatternLayout");
prop.setProperty("log4j.appender.file.layout.ConversionPattern", 
                 "%d [%t] %-5p [%-35F : %-25M : %-6L] %-C -%m%n");
prop.setProperty("log4j.appender.stdout", "org.apache.log4j.ConsoleAppender");
PropertyConfigurator.configure(prop);

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