how to log only one level with log4j2?

Question

I'm using log4j2 in my application.

What I want is everything up to 'debug' to go to console, everything up to 'info' to go to myapp.log, and ONLY 'info' to go to 'myapp-audit.log'.

The reason is, INFO mostly consists of successful modifications to data (ex. 'user created', 'user updated', 'user deleted', and so on). If is effectively an audit log of data modifications.

But I can't get figure out how to do it.

How do I get ONLY 'info' to get logged to 'myapp-audit.log'? Here's my current configuration ...

<?xml version="1.0" encoding="UTF-8"?>
<configuration status="WARN">
    <appenders>
        <Console name="Console" target="SYSTEM_OUT">
            <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n" />
        </Console>

        <File name="LogFile" fileName="myapp.log">
            <PatternLayout
                pattern="%d{yyyy-mm-dd HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n" />
        </File>

        <File name="AuditFile" fileName="myapp-audit.log">
            <PatternLayout
                pattern="%d{yyyy-mm-dd HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n" />
        </File>
    </appenders>

    <loggers>
        <root level="debug">
            <appender-ref ref="Console" level="debug" />
            <appender-ref ref="LogFile" level="info" />
            <appender-ref ref="AuditFile" level="info" /> <!-- I want ONLY 'info' here -->
        </root>
    </loggers>
</configuration>

Answer 1

You can't do that directly since the info level includes everything "above" - warn, error, fatal. What you can do is create a separate audit logger.

in the class:

Logger log = LogManager.getLogger("audit");

in the xml:

<Logger name="audit" level="info">
   <Appender-ref ref="AuditFile" level="info" />
</Logger>

Or you can use the RoutingAppender (you can use something other than ThreadContext):

ThreadContext.put("ROUTINGFLAG", "audit");
log.info("...");
ThreadContext.remove("ROUTINGFLAG");

in the xml:

...
    <Routing name="Routing">
        <Routes pattern="$${ctx:ROUTINGFLAG}">
            <Route AppenderRef="LogFile"/>              
            <Route AppenderRef="AuditFile" key="audit"/>                  
        </Routes>
    </Routing>
</Appenders>
<Loggers>
    <Root level="debug">
        <Appender-ref ref="Console" level="debug"/>
        <AppenderRef ref="Routing" level="info"/>
    </Root>
</Loggers>

Answer 2

If you specify INFO in the appender-ref, the appender will receive INFO, WARN, ERROR and FATAL events. You can further restrict to only INFO by filtering out WARN, ERROR and FATAL level events:

<File name="AuditFile" fileName="myapp-audit.log">
    <PatternLayout 
       pattern="%d{yyyy-mm-dd HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%nZ" />
    <Filters>

        <!-- First deny warn, error and fatal messages -->
        <ThresholdFilter level="warn"  onMatch="DENY" onMismatch="NEUTRAL"/>
        <ThresholdFilter level="error" onMatch="DENY" onMismatch="NEUTRAL"/>
        <ThresholdFilter level="fatal" onMatch="DENY" onMismatch="NEUTRAL"/>

        <!-- Then accept info, warn, error, fatal and deny debug/trace -->
        <ThresholdFilter level="info"  onMatch="ACCEPT" onMismatch="DENY"/>
    </Filters>
</File>