Re: making Socket(Hub)Appender Java compatible

There was a recent discussion on SocketAppender in log4j and log4net on  
the log4j-dev mailing list:
http://nagoya.apache.org/eyebrowse/ReadMsg?listName=log4j- 
dev@xxxxxxxxxxxxxxxxxx&msgNo=8240.  One of the suggestions in that  
thread is that binary compatibility based on the existing log4j  
serialization is not really important since somebody will eventually  
design a new serialization, but nobody has started work on that either.


On Dec 22, 2004, at 8:39 AM, Sluis, Minto van der wrote:

> Hi its me again,
>
> The extent of the log library begins to dawn on me.
> Regrettably, as I understand, the wire protocol for
> the SocketAppender in Log4J and Log4cxx are not
> compatible (maybe this has something to do with the
> subject of my previous mail).
>
> 1) Where is this wire protocol described?

Log4j SocketAppender's "wire format" is the default Java Serialization  
of its org.apache.log4j.spi.LoggingEvent class.  The Java Serialization  
spec is described at  
http://java.sun.com/j2se/1.5.0/docs/guide/serialization/spec/ 
protocol.html.  The use of default serialization makes log4j's wire  
format sensitive to class changes and there have been some breaking  
changes that will cause some log4j 1.2.x message to not be read by a  
1.3.x implementation and vice versa.  See the previous link for the  
gory details.  If we were going to go done the path of compatibility  
with the existing log4j implementation, then it would be very desirable  
to get log4j 1.2.8 and 1.3 compatible with each other.


> 2) What are the plans for making them compatible?

I'd love for to have it happen, but there is nobody currently working  
on it and it isn't near the top of my to-do list.


> 3) How much work would this be?

It is either not very hard or totally impractical.

> 4) And finally, can I be of service?

The key missing starting point would be someone serializing sample  
log4j LoggingEvent's to a file stream and analyzing the serialized  
events using the source code, the serialization spec and a hex editor.   
It would be great to have a detailed field by field analysis of what  
log4j currently produces.  The analysis would also be useful to log4net  
in case they want to follow us in making their SocketAppender binary  
compatible.  You'd want to start out with the simpliest LoggingEvent  
before adding MDC, NDC, LocationInfo and the like.  If something in the  
internal structure is really nasty, we could rework log4j 1.3 to  
simplify it.

Other possible contributions would be to analyze or address the binary  
incompatibility between log4j 1.2.x and 1.3.