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 \"work

Answer 1

1. 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;
   }
   

2. 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(...)); //
       }
   }
   

Answer 2

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.

Answer 3

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 ;)

Answer 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

Answer 5

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);