Recursive call to appender error using Log4j2 with Flume - log4j

Question

I am using Log4j2 with the Flume appender with the following configuration:
<?xml version="1.0" encoding="UTF-8"?>
<configuration status="debug" name="ALI" packages="">
<appenders>
<Flume name="eventLogger" suppressExceptions="false" compress="false">
<Agent host="localhost" port="4141"/>
<RFC5424Layout enterpriseNumber="18060" includeMDC="true" appName="com.weather.ali"/>
</Flume>
<RollingFile name="VTECs" fileName="logs/vtecs.log"
filePattern="logs/$${date:yyyy-MM}/app-%d{MM-dd-yyyy}-%i.log.gz">
<PatternLayout>
<pattern>[%d{ISO8601}] %m%n</pattern>
</PatternLayout>
<Policies>
<TimeBasedTriggeringPolicy />
<SizeBasedTriggeringPolicy size="250 MB"/>
</Policies>
</RollingFile>
</appenders>
<loggers>
<root level="debug">
<appender-ref ref="eventLogger"/>
</root>
<logger name="VTEC" level="debug">
<appender-ref ref="VTECs"/>
</logger>
</loggers>
</configuration>
This works as expected on a couple nodes, but the remaining nodes produce the following error:
ERROR Recursive call to appender eventLogger
Here is the full output of the Log4j bootstrap:
2013-05-07 09:21:59,033 DEBUG Calling createAgent on class org.apache.logging.log4j.flume.appender.Agent for element Agent with params(host="localhost", port="4141")
2013-05-07 09:21:59,040 DEBUG Calling createLayout on class org.apache.logging.log4j.core.layout.RFC5424Layout for element RFC5424Layout with params(facility="null", id="null", enterpriseNumber="18060", includeMDC="true", mdcId="null", mdcPrefix="null", eventPrefix="null", newLine="null", newLineEscape="null", appName="com.weather.ali", messageId="null", mdcExcludes="null", mdcIncludes="null", mdcRequired="null", charset="null", exceptionPattern="null", Configuration(MyApp))
2013-05-07 09:22:02,148 DEBUG Generated plugins in 3.106963125 seconds
2013-05-07 09:22:02,156 DEBUG Calling createAppender on class org.apache.logging.log4j.flume.appender.FlumeAppender for element Flume with params(agents={host=localhost port=4141}, properties={}, embedded="null", type="null", dataDir="null", connectTimeout="null", requestTimeout="null", agentRetries="null", maxDelay="null", name="eventLogger", suppressExceptions="false", mdcExcludes="null", mdcIncludes="null", mdcRequired="null", mdcPrefix="null", eventPrefix="null", compress="false", batchSize="null", null, RFC5424Layout(facility=LOCAL0 appName=com.weather.ali defaultId=Audit enterpriseNumber=18060 newLine=false includeMDC=true messageId=null), null)
2013-05-07 09:22:02,159 DEBUG Starting FlumeAvroManager FlumeAvro[localhost:4141]
2013-05-07 09:22:02,552 DEBUG Calling createAppenders on class org.apache.logging.log4j.core.config.plugins.AppendersPlugin for element appenders with params(appenders={eventLogger})
2013-05-07 09:22:06,774 DEBUG Generated plugins in 4.221008626 seconds
2013-05-07 09:22:06,776 DEBUG Calling createAppenderRef on class org.apache.logging.log4j.core.config.AppenderRef for element appender-ref with params(ref="eventLogger", level="null", null)
2013-05-07 09:22:06,778 DEBUG Calling createLogger on class org.apache.logging.log4j.core.config.LoggerConfig$RootLogger for element root with params(additivity="null", level="debug", includeLocation="null", appender-ref={org.apache.logging.log4j.core.config.AppenderRef#55ed34f1}, properties={}, Configuration(MyApp), null)
2013-05-07 09:22:06,779 DEBUG Calling createLoggers on class org.apache.logging.log4j.core.config.plugins.LoggersPlugin for element loggers with params(loggers={root})
2013-05-07 09:22:06,779 DEBUG Shutting down OutputStreamManager SYSTEM_OUT
2013-05-07 09:22:06,779 DEBUG Reconfiguration completed
2013-05-07 09:22:07,237 ERROR Recursive call to appender eventLogger
So two questions:
Why would this work on some nodes and not on others?
I have looked at the code where this error is generated, and it appears to get called whenever the appender code gets called more than once. I see no reason why this should happen. Can someone explain this to me?

Answer 1

This turned out (not surprisingly) to be a flume configuration issue on the affected nodes. The Flume agents on those nodes were not starting properly, and this resulted in the fairly cryptic recursion error.

Answer 2

FYI, for others chasing similar log4j recursion warnings:
https://issues.apache.org/jira/browse/LOG4J2-2738