[Log4cpp-devel] AsyncAppender and others

[LECLERCQ N. <nic...@so...>]

Hi there,
After a preliminary discussion with Bastiaan, I suggest to had to =
following features to log4cpp:

1 - AsyncAppender class.=20

The log4j doc says: <The AsyncAppender lets users log events =
asynchronously. It uses a bounded buffer to store logging events. It =
will collect the events sent to it and then dispatch them to all the =
appenders that are attached to it. You can attach multiple appenders to =
an AsyncAppender. The AsyncAppender uses a separate thread to serve the =
events in its bounded buffer>.

In order to write the AsyncAppender, we first need to implement an =
AppenderAttachable class that could be shared between the Category class =
and the AsyncAppender class (code factorization).  All the existing code =
dedicated to  the Appenders management (i.e. such as addAppender, =
removeAppender, ...) should be encapsulated in the AppenderAttachable =
class.

Then we need a log4cpp::threading::Thread class. That's not a big =
problem but we have to choose an interface compatible with (potentially) =
all underlying implementation of threads. Since the need is basic, only =
the fundamental features are required and the Thread class interface =
could be something like:=20

class Thread  [: private myPreferredThreadingPackage::Thread ] {

public :
=09
 // Define only 3 levels of priority.
 enum {
    THREAD_PRIORITY_LOW =3D 0,
    THREAD_PRIORITY_NORMAL,=09
    THREAD_PRIORITY_HIGH,=09
 } Priority;

  Thread (const char* name);
  Thread (const std::string& name);
  // Ctors

  virtual ~Thread();
  // Dtors

  int start (void);
  // Start the thread.

  virtual void run (void) =3D  0;
  // Override this method to provide functionality to your thread.

  void join (long milli_secs =3D 0);
  // Wait at most milli_secs for this thread to terminate. If milli_secs =
=3D=3D 0 then wait for ever.

  void setPriority (int new_prio);
  // Set the priority of this thread.

  int  getPriority (void) const;   =20
  // Get the priority of this thread.=20

  //... anything else? sleep, yield, ...

};
=20
The last thing we need to implement the AsyncAppender class is something =
similar to the log4j BoundedFIFO. The STL queue is perfectly adapted to =
implement such a class.



2 - Log4Cpp class.

The aim of the Log4Cpp class is to encapsulate the init/shutdown stuffs. =


class Log4Cpp {
public:
    static int init (void);
    // Initializer. Return -1 on error, 0 otherwise.

    static void shutdown (void);
    // Cleanup everything before quitting.=20
};

Some packages (such as Java Threads for C++) need to be initialized to =
work properly. The Log4Cpp::init could be a good place for that. The =
Category::shutdown call could also be moved to  Log4Cpp::shutdown.=20

3 - Logger and Level classes

Just to reflect log4j 1.2 changes.

I'm looking forward to your reactions.

Nicolas
SOLEIL project - http://www.soleil.u-psud.fr.