Cheryl,

Just thinking out loud, Log4j 2 has the ability to start logging to a new log 
file that is not explicitly defined in configuration with the RoutingAppender. 
See https://logging.apache.org/log4j/2.x/faq.html#separate_log_files

You may be able to use this feature, perhaps in combination with a custom 
Filter. The Filter would usually DENY all log events, but would start to ACCEPT 
events for certain products when these products were selected in some admin 
gui. 

This solution would require that all log events have the relevant product ID or 
something in their context map. Currently the only way to put data in the 
LogEvent's context map is via the ThreadContext. (There is a ticket to make 
this customizable: https://issues.apache.org/jira/browse/LOG4J2-1010). 

Can you think about whether these together can form a solution? Maybe 
experiment a little with a test program, to see what obstacles come up. 

Remko

Sent from my iPhone

> On 2016/07/08, at 4:26, <cheryl_mrozien...@dell.com> 
> <cheryl_mrozien...@dell.com> wrote:
> 
> Dell - Internal Use - Confidential
> Hi,
> 
> I am currently using Log4j version 2.3, but might be able to update to a 
> newer version if that would help.
> 
> I have a log4j2.xml file containing more than thirty RollingFileAppenders 
> (one per product component).  Most of these RollingFileAppenders will not be 
> written to until the user turns on logging via our product's user interface.  
> By default, the AppenderRefs that reference these RollingFileAppenders have 
> the "level" attribute set to a value of "OFF".  Once the user turns on 
> logging from the user interface, the "level" attribute will be updated with a 
> value of "INFO", "DEBUG", etc.  And, once the updated log4j2.xml file is 
> persisted, the code will then call LoggerContext.reconfigure() to get Log4j 
> to read in the new log4j2.xml file, so the new log levels take effect.
> 
> My question is whether there is a way to tell Log4j to defer log file 
> creation when nothing will initially write to the file (e.g. all references 
> to the Appender have a level of "OFF")?  Having lots of zero sized log files 
> is not that big of an issue, although not completely optimal.  However, 
> having too many open file handles that are not doing anything, could 
> potentially become an issue.  Note that I do not have control over the number 
> of Appenders configured for the product.  Each product component team 
> contributes its Appender and Loggers to log4j2.xml.
> 
> To work around the open file handle issue at server startup time, I am 
> currently using the Log4j2 private core API calls to loop through the 
> AppenderRefs to determine which ones are "OFF", and then I'm calling the 
> RollingFileAppender.stop() method to close the output stream.  If anyone has 
> any ideas that would avoid creating and opening the log files in the first 
> place, I'd love to hear your thoughts.
> 
> Thanks and regards,
> 
> -Cheryl
> 
> p.s. for reference, the relevant log4j2.xml snippets follow:
> 
> <Appenders>
>    <RollingFile
>      
> fileName="${sys:com.compellent.msaserviceDir}/etc/compservices/debuglogs/Scheduler/Scheduler.debuglog"
>      
> filePattern="${sys:com.compellent.msaserviceDir}/etc/compservices/debuglogs/Scheduler/Scheduler_%i.debuglog.gz"
>      name="debug.Scheduler">
>      <PatternLayout>
>        <Pattern>%d{yyyy-MM-dd HH:mm:ss,SSS} %-5p {%C:%M} [%marker] (%t) - 
> %msg%n</Pattern>
>      </PatternLayout>
>      <Policies>
>        <SizeBasedTriggeringPolicy size="50 MB"/>
>      </Policies>
>      <DefaultRolloverStrategy max="10"/>
>      <Filters>
>        <MarkerFilter marker="Scheduler" onMatch="ACCEPT" onMismatch="DENY"/>
>      </Filters>
>    </RollingFile>
> </Appenders>
> 
> <Loggers>
>    <Logger includeLocation="true" level="TRACE" name="debugLogger">
>      <AppenderRef level="DEBUG" ref="debug.ModuleManager"/>
>      <AppenderRef level="OFF" ref="debug.Scheduler"/>
>    </Logger>
> </Loggers>
> 

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