[logback-user] Separating the logging-output of libraries in tomcat/shared

Achim Wiedemann awn at inxmail.de
Tue Mar 2 16:00:45 CET 2010 

Hi Ceki,

that seems like a good idea. I'll try it out. Thanks again for taking 
the time.


greetz,
achim



Ceki Gülcü schrieb:
> 
> I think the short answer is yes. The nested appenders will have the
> same configuration differentiated by the value returned by the
> discriminator. You could add properties to the logger context and
> since logger context properties are seen as variables, you could in
> principle use the value of the property to filter events. Here is an
> example using a ThresholdFilter and the variable myLevel with a
> default substitution value (see [1]).
> 
>  <appender name="SIFT" class="ch.qos.logback.classic.sift.SiftingAppender">
>     <discriminator
>       class="ch.qos.logback.classic.sift.JNDIBasedContextDiscriminator">
>       <Key>context</Key>
>       <DefaultValue>unknown</DefaultValue>
>     </discriminator>
>     <sift>
>       <appender name="FILE-${context}" 
> class="ch.qos.logback.core.FileAppender">
>         <File>${context}.log</File>
>         <Append>true</Append>
>         <filter class="ch.qos.logback.classic.filter.ThresholdFilter">
>           <level>${myLevel:-DEBUG}</level>
>         </filter>
>         <layout>
>           <pattern>%d [%thread] %level %mdc %logger{35} - %msg%n</pattern>
>         </layout>
>       </appender>
>     </sift>
>   </appender>
> 
> You could set the myLevel property at the start of each
> application. Here is the sample code for web-app A:
> 
> 
>    LoggerContext lc = (LoggerContext) LoggerFactory.getILoggerFactory();
>    lc.putProperty("myLevel", some level value as appropriate for web-app 
> A);
> 
> For web-app B, the code is similar:
> 
>    LoggerContext lc = (LoggerContext) LoggerFactory.getILoggerFactory();
>    lc.putProperty("myLevel", some level value as appropriate for web-app 
> B);
> 
> You need to make sure that the "myLevel" property is set before the
> logger context is configured which means that you need to override
> default logback configuration by invoking joran directly. Search for
> "Invoking JoranConfigurator directly" in [2]. The code then becomes:
> 
>    LoggerContext lc = (LoggerContext) LoggerFactory.getILoggerFactory();
> 
>    JoranConfigurator configurator = new JoranConfigurator();
>    configurator.setContext(lc);
>    // the context was probably already configured by default configuration
>    // rules
>    lc.reset();
>    lc.putProperty("myLevel", some level value as appropriate for the 
> web-app);
>    configurator.doConfigure(args[0]);
> 
> HTH,
> 
> [1] 
> http://logback.qos.ch/manual/configuration.html#defaultValuesForVariables
> [2] http://logback.qos.ch/manual/configuration.html
> 
> 
> On 02/03/2010 1:52 PM, Achim Wiedemann wrote:
>> Hi Ceki,
>>
>> I just implemented your suggestion and it works like a charm. :)
>> So it seems like there's a workaround for LBLCLASSIC-166 with your new
>> discriminator-class now. Great work and thanks a lot!
>>
>> By the way: Is there any possibility to have different logging-levels
>> for the nested appenders of a SiftingAppender?
>>
>>
>> greetz,
>> achim
>>
>>
>>
>>
>> Ceki Gülcü schrieb:
>>> You are right. ContextBasedDiscriminator will not help you because the
>>> context name is retreived from the LoggingEvent which ultimately gets
>>> its value from the calling logger. If the calling logger is attached
>>> to the wrong context, ContextBasedDiscriminator will give you the
>>> wrong context name. Sorry for misleading you.
>>>
>>> However, I've written a new discriminator which should work assuming
>>> you have installed ContextJNDISelector as explained in
>>>
>>> http://logback.qos.ch/manual/loggingSeparation.html
>>>
>>> JNDIBasedContextDiscriminator can be found at
>>>
>>>
>>> http://github.com/ceki/logback/blob/90e50c/logback-classic/src/main/java/ch/qos/logback/classic/sift/JNDIBasedContextDiscriminator.java 
>>>
>>>
>>>
>>> or the same in tiny-speak
>>>
>>> http://tinyurl.com/yb6pdj2
>>>
>>> Getting values from JNDIBasedContextDiscriminator, SiftingAppender
>>> will get the correct context name and things should work much better.
>>> Give it a try.
>>>
>>>
>>>
>>> On 01/03/2010 9:38 AM, Achim Wiedemann wrote:
>>>> Hey Ceki,
>>>>
>>>> thanks for your fast reply. I tested your tip with the SiftingAppender,
>>>> but couldn't see how this gets me further compared to the
>>>> logging-separation described in Ch8 of the manual (separation via
>>>> JNDIContextSelector). The problem is still the same: The context of the
>>>> logger, once initialized, remains the same in shared libraries. Since
>>>> SiftingAppender has to sieve based on some criteria (in my case the
>>>> context), it also can't solve this issue.
>>>>
>>>> So I see, as you already stated, it's not possible to get this scenario
>>>> to work. However, thanks for your time and all your work.
>>>>
>>>>
>>>> greetz,
>>>> achim
>>>>
>>>>
>>>> Ceki Gulcu schrieb:
>>>>>
>>>>> Hello Achim,
>>>>>
>>>>> Thank you for your message.
>>>>>
>>>>>
>>>>> The only way to solve this issue transparently and perfectly would be
>>>>> to introduce another level of indirection inside loggers so that each
>>>>> logger-shell somehow delegate work to an inner logger attached to the
>>>>> appropriate context. This is quite a difficult problem technically and
>>>>> would generate significant computational overhead. I don't see the
>>>>> problem fixed via such indirection any time soon. Read, as a logback
>>>>> user, don't expect this problem to be solved without a little work on
>>>>> your side.
>>>>>
>>>>> As far as I can see, you have two options:
>>>>>
>>>>> 1) move shared classes whose loggers you care about to the web-app
>>>>> (unshare them)
>>>>>
>>>>> If 1) is not an option, there is:
>>>>>
>>>>> 2) Use a single shared logback.xml file with separation done by
>>>>> SiftingAppender [1] using the context as separation criteria [2]. In
>>>>> conjunction with prudent mode of FileAppender, you will be able to
>>>>> separate logging by context.
>>>>>
>>>>> Let me know if the above does not make sense.
>>>>>
>>>>>
>>>>> [1] http://logback.qos.ch/manual/appenders.html#SiftingAppender
>>>>> [2]
>>>>> http://logback.qos.ch/xref/ch/qos/logback/classic/sift/ContextBasedDiscriminator.html 
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> On 26.02.2010 08:21, Achim Wiedemann wrote:
>>>>>> Hey everybody,
>>>>>>
>>>>>> just wanted to port our application from commons-logging / log4j to
>>>>>> slf4j / logback. Unfortunately I stumbled upon some problems when
>>>>>> separating the logging-output from different webapps (using the
>>>>>> JNDIContextSelector). As long as you only use logging from classes
>>>>>> inside the webapp, everything works fine. But as soon as you've got
>>>>>> classes in tomcat/shared which use logging, you run into trouble: All
>>>>>> logging output of the shared classes (e.g. Spring) are directed to 
>>>>>> the
>>>>>> logger-context of the webapp which first loads the (shared) class.
>>>>>>
>>>>>> Example: Let's say you've got webbapp [A], webbapp [B], and Spring in
>>>>>> tomcat/shared. Now both webapps use Spring. If webapp [B] first
>>>>>> accesses
>>>>>> any classes of Spring, all output of Spring will be directed to the
>>>>>> log-file of [B], no matter from which webapp Spring is used. This is
>>>>>> because static Logger references are used in Spring (which is
>>>>>> commonplace) and are initialized with the context of webapp [B].
>>>>>>
>>>>>> The issue is already described very well in the logback JIRA:
>>>>>> http://jira.qos.ch/browse/LBCLASSIC-166
>>>>>>
>>>>>> I wondered if anyone can make a suggestion how to deal with this. Any
>>>>>> advice, tricks or magic is welcome. ;)
>>>>>>
>>>>>>
>>>>>> Thanks a lot,
>>>>>> Achim
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