[jira] [Commented] (LOG4J2-1578) RoutingAppender can be configured with scripts

["Gary Gregory (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/LOG4J2-1578?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15486772#comment-15486772 ] 

Gary Gregory commented on LOG4J2-1578:
--------------------------------------

That was easier than I thought; I have a first version working for the "simple" use case:
{code:xml}
<Configuration status="WARN" name="RoutingTest">
  <Appenders>
    <Routing name="Routing">
      <Script name="RoutingInit" language="JavaScript"><![CDATA[
         "OSNameFoo".search("Foo") > -1 ? "Service2" : "Service1";]]>
      </Script>
      <Routes>
        <Route key="Service1">
          <List name="List1" />
        </Route>
        <Route key="Service2">
          <List name="List2" />
        </Route>
      </Routes>
    </Routing>
  </Appenders>
  <Loggers>
    <Root level="error">
      <AppenderRef ref="Routing" />
    </Root>
  </Loggers>
</Configuration>
{code}

In this case, the appender {{"List2"}} is created and {{"List1"}} never sees the light of day, which is exactly what I need. 

Please see the new unit test {{org.apache.logging.log4j.core.appender.routing.DefaultRouteScriptAppenderTest}}.

Note the XML element to initialize the default routing script MUST be called {{"Script"}}; calling it {{"DefaultRouteScript"}} does not work.

*If I could get a code review on that, we can continue with the more complex cases.*

There also something funky going on with starting and stopping logger contexts from the unit test, which it does for every {{@Test}} method, nice and clean. The new test case has {{@Ignore}} on {{DefaultRouteScriptAppenderTest.testRoutingPresence2()}} because it fails when it runs after {{DefaultRouteScriptAppenderTest.testRoutingPresence1()}}. This is not a common use case but it should still work. The Appender Control map is empty somehow.

The real test is to remove the {{@Ignore}} and comment in the other config file in the {{@Parameters}} method.

> RoutingAppender can be configured with scripts
> ----------------------------------------------
>
>                 Key: LOG4J2-1578
>                 URL: https://issues.apache.org/jira/browse/LOG4J2-1578
>             Project: Log4j 2
>          Issue Type: New Feature
>            Reporter: Gary Gregory
>            Assignee: Gary Gregory
>
> RoutingAppender can be configured with scripts. 
> h2. Use Case
> What I need to do is only add a specific appender when running on a specific OS (USS on OS/390 if you must know). Then only add a different appender when not running on that OS.
> h2. Solution
> Posted by [~ralphgoers] on the dev ML:
> After reviewing what I wrote below and looking at the Routing Appender I think the best thing to do is just to add script support to it.  It already has support for a default Route. The init script, if present, could override which Route to use as I described below. Then we could add a script attribute to the Routes plugin which could be used to select the Route instead of only matching on the ThreadContext key.
> With that I think you would have everything you want, plus it could be used as a more intelligent way to route to existing appenders.
> The configuration would then look like:
> {code:xml}
>   <Appenders>
>     <Console name="STDOUT" target="SYSTEM_OUT">
>       <PatternLayout pattern="%m%n"/>
>     </Console>
>     <Flume name="AuditLogger" compress="true">
>       <Agent host="192.168.10.101" port="8800"/>
>       <Agent host="192.168.10.102" port="8800"/>
>       <RFC5424Layout enterpriseNumber="18060" includeMDC="true" appName="MyApp"/>
>     </Flume>
>     <Routing name="Routing">
>       <InitScript name="RoutingInit" language="groovy"><![CDATA[
>          if (System.getProperty(?os.name?).contains(?OS/390") {
>             return "OS390";
>          }
>          return null;]]>
>       </InitScript>
>       <Routes>     
>         <Script name="Router" language="groovy"><![CDATA[
>             if (logEvent.getMarker() != null && logEvent.getMarker().isInstanceOf("AUDIT")) {
>                 return "AUDIT";
>             } else if (logEvent.getContextMap().containsKey("UserId")) { 
>                 return logEvent.getContextMap().get("UserId");
>             }
>             return "STDOUT";
>             ]]>
>           </Script> 
>         <Route>
>           <OS390Appender name="OS390-${mdc:UserId"/> 
>           <RollingFile name="Rolling-${mdc:UserId}" fileName="${mdc:UserId}.log"
>                        filePattern="${mdc:UserId}.%i.log.gz">
>             <PatternLayout>
>               <pattern>%d %p %c{1.} [%t] %m%n</pattern>
>             </PatternLayout>
>             <SizeBasedTriggeringPolicy size="500" />
>           </RollingFile>
>         </Route>
>         <Route ref="AuditLogger" key="Audit"/>
>         <Route ref="STDOUT" key="STDOUT"/>
>       </Routes>
>       <IdlePurgePolicy timeToLive="15" timeUnit="minutes"/>
>     </Routing>
>   </Appenders>
> {code}
> First, the init script changes the default route based on the OS.
> Second, notice that "Routes" has a new Script element and does not have a pattern specified, so the script is determining the key instead of the pattern. 
> Third, the real default route is now "STDOUT" since the actual default Route is only referenced when a UserId is present in the thread context map.
> What would also be nice is if there was a way to have the returned value be usable as a Lookup value in the default Appender definition, instead of relying on the MDC as the code above does. I should be able to pick something out of the message itself and use that as the key. That should be doable but I am still pondering how I would implement that.



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