[slf4j-user] basic MDC support for java.util.logging

[Ceki Gulcu]

Hi Maarteen,

Just had a look at your contribution.

I have a question in relation with Log4jXmlFormatter. It formats its output 
exactly as the XMLLayout in log4j does. This implies that output logging events 
appears as log4j logging events. Do you have any thoughts on that?

Moreover, who is going to use this output?

Incidentally, including the Log4jXmlFormatter in SLF4J implicitly anoints 
log4j's XML layout as an "official" exchange format.

Would it be worthwhile to develop a logging-system neutral XMLLayout which can 
be adapted to JUL, log4j and logback? Wouldn't this mean a scope-creep as far as 
SLF4J is concerned. SLF4J is about the Logger interface and not about what 
happens behind loggers but SLF4J is also about bridging logging systems.

Don't get me wrong, I am not saying that XMLLayout in SLF4J would necessarily be 
bad. However, there is certainly a change in scope. It's not a step that should 
not be taken lightly.

Maarten Bosteels wrote:
> Hello Ceki et al.
> 
> Have you had time to look at  http://bugzilla.slf4j.org/show_bug.cgi?id=63 ?
> AFAICS the patch is complete.
> 
> The included Log4jXmlFormatter has one important limit: the MDC
> properties will only be correct when format() is called from the same
> thread that generated the LogRecord. (as indicated by the javadoc).
> 
> We are getting close to MINA-2.0-M1 and it would be great if we could
> simply drop our IoSessionLogger
> in favor of the much more poweful MDC mechanism.
> 
> Thanks,
> Maarten
> 
> On Oct 19, 2007 2:15 PM, Ceki Gulcu <listid at qos.ch> wrote:
>> Hi Maarteen,
>>
>> Comments inline.
>>
>> Maarten Bosteels wrote:
>>  > Hello Ceki,
>>  >
>>  > I started coding a BasicMDCAdapter that could be used by java.util.logging
>>  > Had a look at the log4j MDC implementation and also at LogbackMDCAdapter code.
>>  >
>>  > Currently my implementation is roughly the same as the LogbackMDCAdapter
>>  > without the generics (since SLF4J should run on 1.4 right ?)
>>
>> Yes, SLF4J must run under JDK 1.4 or later.
>>
>>  > I didn't quite understand this remark in the code:
>>  > * Each time a value is added, a new instance of the map is created. This is
>>  > * to be certain that the serialization process will operate on the updated map
>>  > * and not send a reference to the old map, thus not allowing the remote
>>  > logback
>>  > * component to see the latest changes.
>>
>> That's an implementation detail in logback. You can safely ignore it
>> for JUL.
>>
>>  > Can you describe a scenario where serialization would fail if one just add a
>> value to the map ?
>>  > Is it a threading issue ?
>>
>> No, it's not a threading issue. As mentioned previously, you can ignore the
>> aforementioned comments in logback code.
>>
>> [snip]
>>
>>  > It would be cool if logback would also have an Log4jXmlLayout. I think the
>> xml layout has several advantages over serialization:
>>  > * it's more compact (much to me surprise) certainly when combined with a
>> GZipOutputStream
>>  > * human readable
>>  > * easier to implement in other languages (eg. log4cxx)
>>  > * no need to depend on log4j's LoggingEvent
>>  > * protected against changes to the serialized form of log4j's LoggingEvent
>>  > for example, Chainsaw currently only displays the MDC when the sender is
>> using log4j 1.3
>>  >
>>  > It would be trivial to write, I am willing to implement it, if there's a
>> chance you will add it to logback.
>>
>> In light of what you describe, I think using XML as an exchange format is quite
>> reasonable. More importantly, it remains aligned with SLF4J's goal of
>> abstracting/bridging logging systems.
>>
>> You mention performance related results comparing XML formatting and Java
>> serialization. I'd be interested in the figures.
>>
>> ps: I'll be away for two weeks and without internet access.
>>
>>  > regards,
>>
>>  > Maarten
>>  >
>>
>> --
>> Ceki Gülcü
>> Logback: The reliable, generic, fast and flexible logging framework for Java.
>> http://logback.qos.ch
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-- 
Ceki Gülcü
Logback: The reliable, generic, fast and flexible logging framework for Java.
http://logback.qos.ch