Modified Graylog log4j2.xml file that (in addition to the default config) sends Graylog logs to itself via GELF UDP (we have a GELF UDP input active on port 10002). 💣 this can lead to nasty loops breaking your Graylog setup.

log4j2.xml

<?xml version="1.0" encoding="UTF-8"?>
<Configuration packages="org.graylog2.log4j" shutdownHook="disable">
    <Appenders>
        <RollingFile name="rolling-file" fileName="/var/log/graylog-server/server.log" filePattern="/var/log/graylog-server/server.log.%i.gz">
            <PatternLayout pattern="%d{yyyy-MM-dd'T'HH:mm:ss.SSSXXX} %-5p [%c{1}] %m%n"/>
            <Policies>
                <SizeBasedTriggeringPolicy size="50MB"/>
            </Policies>
            <DefaultRolloverStrategy max="10" fileIndex="min"/>
        </RollingFile>

        <Socket name="graylog-gelf-udp" protocol="udp" host="localhost" port="10002">
            <GelfLayout host="${hostName}" compressionType="GZIP" compressionThreshold="1024">
            </GelfLayout>
        </Socket>

        <!-- Internal Graylog log appender. Please do not disable. This makes internal log messages available via REST calls. -->
        <Memory name="graylog-internal-logs" bufferSize="500"/>
    </Appenders>
    <Loggers>
        <!-- Application Loggers -->
        <Logger name="org.graylog2" level="info"/>
        <Logger name="com.github.joschi.jadconfig" level="warn"/>
        <!-- This emits a harmless warning for ActiveDirectory every time which we can't work around :( -->
        <Logger name="org.apache.directory.api.ldap.model.message.BindRequestImpl" level="error"/>
        <!-- Prevent DEBUG message about Lucene Expressions not found. -->
        <Logger name="org.elasticsearch.script" level="warn"/>
        <!-- Disable messages from the version check -->
        <Logger name="org.graylog2.periodical.VersionCheckThread" level="off"/>
        <!-- Silence chatty natty -->
        <Logger name="com.joestelmach.natty.Parser" level="warn"/>
        <!-- Silence Kafka log chatter -->
        <Logger name="kafka.log.Log" level="warn"/>
        <Logger name="kafka.log.OffsetIndex" level="warn"/>
        <!-- Silence useless session validation messages -->
        <Logger name="org.apache.shiro.session.mgt.AbstractValidatingSessionManager" level="warn"/>
        <Root level="warn">
            <AppenderRef ref="rolling-file"/>
            <AppenderRef ref="graylog-internal-logs"/>
            <AppenderRef ref="graylog-gelf-udp"/>
        </Root>
    </Loggers>
</Configuration>