Am 09.03.2010 12:20, schrieb Joern Huxhorn:
Much like an ordinary stack-trace, the NDC is actually a stack. The stacking of messages is the key here.
I know. But looking at your examples, I don't see something that the current Java stack trace wouldn't give me already. The logging of method arguments might be key here but a stack only really makes sense if you use recursion. Another issue is that the API usage is quite complicated for clients. They need to wrap each usage into try/finally blocks. However, I can see some value in having both - a simple to use MDC as well as an NDC. I wonder if it's possible to merge both into a central API "DiagnoseContext" or just DC.
The main difference between the MDC and (my implementation of) the NDC is that NDC is also supporting the same Message as the one I proposed for logging in general. This means, that the actual formatting of the message isn't performed if it's not really needed (for example, if the Appenders in Logback are not printing the NDC but choose to ignore it).
That's just an implementation detail. MDC can be changed as well. Remember, we are talking about a version 2.0 which means breaking API changes anyway.
With MDC, on the other hand, one would have to format the message anyway.
Deferring formatting is good (performance wise). I think such a message class (under the covers) should be a key concept in SLF4J 2.0. -Gunnar -- Gunnar Wagenknecht gunnar@wagenknecht.org http://wagenknecht.org/