Re: [monolog] LogManager#addLogger breaks classloader isolation (was: Re: Monolog on gcj)

[Serge Lacourte <serge.lacourte@xxxxxxxxxxxxx>]

Hi,

> The problem is that it is currently impossible to have two copies of
> Monolog loaded by two distinct classloaders.  You end up having two
> distinct copies of the
> org.objectweb.util.monolog.wrapper.javaLog.LoggerFactory class, but
> they both talk to the same java.util.logging.LogManager instance.
> This leads to Logger instances being shared between two isolating
> classloaders.
i ran into this problem in using monolog with oscar. I have a separate 
copy of the monolog package within each oscar bundle, and I get an error 
when trying to load the second bundle.

I have implemented a work around, which i submit to your comments. The 
idea is to isolate the name space of the loggers for each class loader. 
This is done by prefixing the names with "root#", where # is obtained as 
the first free name in the shared LogManager.
One drawback of this patch is that the changed logger names are visible 
to the user through the getName() function. I tried to overload it in 
order to remove the prefix, but it failed due to internal calls to this 
function by the LogManager.


--
Serge Lacourte
Directeur general
ScalAgent Distributed Technologies SA

*** ref/LoggerFactory.java      Tue Aug 17 09:15:40 2004
--- ./LoggerFactory.java        Wed Sep  7 08:30:57 2005
***************
*** 45,50 ****
--- 45,85 ----
         */
        protected static Logger rootLogger = null;
  
+   private ArrayList loggers = new ArrayList();
+ 
+   /**
+    * Name of the root logger.
+    * This name intends to isolates the loggers associated to a class loader.
+    */
+   protected static String rootLoggerName = null;
+ 
+   /**
+    * Root logger prefix, i.e. <code>rootLoggerName</code> followed by '.'.
+    */
+   protected static String rootLoggerPrefix = null;
+ 
+   /**
+    * Gets the prefix of the root logger.
+    */
+   public static String getRootLoggerPrefix() {
+     return rootLoggerPrefix;
+   }
+ 
+   /**
+    * isolates the logger hierarchy for a given class loader
+    * by prepending the root logger name.
+    *
+    * @param name      user defined name
+    * @return  internal name
+    */
+   protected String monoLoggerName(String name) {
+     if (name.startsWith(rootLoggerPrefix)) {
+       debug("name already prefixed: " + name);
+       return name;
+     }
+     return rootLoggerPrefix + name;
+   }
+ 
      /**
       * This static code initialize the value of the variable defined into
       * BasicLevel.
***************
*** 71,77 ****
          BasicLevel.LEVEL_FATAL = new LevelImpl("FATAL", BasicLevel.FATAL);
  
          manager = LogManager.getLogManager();
!         rootLogger = new Logger(manager.getLogger(""));
      }
  
      /**
--- 106,132 ----
          BasicLevel.LEVEL_FATAL = new LevelImpl("FATAL", BasicLevel.FATAL);
  
          manager = LogManager.getLogManager();
!         String rootName = null;
!         int i = 1;
!       loop_root:
!         while (true) {
!           rootName = "root" + i;
!           synchronized (manager) {
!             // the manager object is shared between the multiple instances 
of this class
!             if (manager.getLogger(rootName) == null) {
!               rootLogger = new Logger(rootName, null);
!               manager.addLogger(rootLogger);
!               rootLogger.setUseParentHandlers(false);
!             }
!           }
!           if (rootLogger != null) {
!             Monolog.debug("Instanciate the root logger " + rootName);
!             break loop_root;
!           }
!           i ++;
!         }
!         rootLoggerName = rootName;
!         rootLoggerPrefix = rootLoggerName + '.';
      }
  
      /**
***************
*** 140,150 ****
--- 195,208 ----
          if (name.equals("root") || name.length()==0) {
              return rootLogger;
          }
+         // isolates the logger hierarchy
+         name = monoLoggerName(name);
          // Search if the logger already exist.
          Object o = manager.getLogger(name);
          if (o == null) {
              // It doesn't exist => creates and adds it
              Logger result = new Logger(name, resName);
+             loggers.add(result);
              Monolog.debug("Instanciate the logger " + name);
              manager.addLogger(result);
              return result;

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