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Major Description
I recently updated to using beta4 and ran into a problem upon startup where I received numerous errors such as this:
2013-02-14 12:27:40,139 ERROR No Appender was configured for route null
Everything was working great up though beta3. After tracing it back, I think I found that it relates to the change Ralph alluded to in LOG4J2-129...
"The problem was that the code was treating the Appender being created under the default Route as the default. That is incorrect. The code has been modified to just keep track of the default route."
I think my setup was relying on that incorrect behavior, and that it's somewhat similar to what William is trying to accomplish.
(His comment: https://issues.apache.org/jira/browse/LOG4J2-129?focusedCommentId=13553008&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-13553008 )
I have several appenders created, and a routing appender to map events to them using static definitions. I also have a catch-all appender where I want all non-matched events to be sent. The [abbreviated] configuration is like this:
<appenders>
<RollingFile name="apples" fileName="logs/apples" filePattern="logs/apples.%d{yyyy-MM-dd}">
<PatternLayout pattern="${commonLayout}"/>
<Policies>
<TimeBasedTriggeringPolicy interval="1" modulate="true"/>
</Policies>
</RollingFile>
<RollingFile name="oranges" fileName="logs/oranges" filePattern="logs/oranges.%d{yyyy-MM-dd}">
<PatternLayout pattern="${commonLayout}"/>
<Policies>
<TimeBasedTriggeringPolicy interval="1" modulate="true"/>
</Policies>
</RollingFile>
<RollingFile name="other" fileName="logs/other" filePattern="logs/other.%d{yyyy-MM-dd}">
<PatternLayout pattern="${commonLayout}"/>
<Policies>
<TimeBasedTriggeringPolicy interval="1" modulate="true"/>
</Policies>
</RollingFile>
<Routing name="Routing">
<Routes pattern="$${ctx:fruit}">
<Route key="apples" ref="apples"/>
<Route key="oranges" ref="oranges"/>
<Route ref="other"/>
</Routes>
</Routing>
</appenders>
So the idea is that anything which has a ctx:fruit value of apples/oranges goes into the specific files, any everything else (regardless of ctx:fruit being defined or not) going into the "other" file.
At startup time, most (if not all) events fall into the case of not having ctx:fruit defined at all. And during my debugging, I saw that "...the replacement won't occur if the context value isn't present.." as William mentioned.
In RoutingAppender.java on line 107 there is:
final String key = config.getSubst().replace(event, routes.getPattern());
The value that ends up being assigned is the literal string "${ctx:fruit}" instead of null. As a result, it chooses the default Route entry of "other" which hasn't been created yet, so it proceeds to create that appender. So far so good, until...
In RoutingAppender.java on lines 142-144 there is:
final Node routeNode = route.getNode(); for (final Node node : routeNode.getChildren()) { if (node.getType().getElementName().equals("appender")) {
I traced the execution and routeNode.getChildren() returns an empty list. I believe this is due to the <Route/> entries in the config...they don't have any child nodes because they are just referencing some existing appenders.