How-To: Configure Tomcat 9 to log via Log4j2

Question

How can you redirect Tomcat 9's internal logging (catalina and localhost) to Log4j2?

the Apache Tomcat 9 documentation<\/a> points to "the instructions provided by the alternative logging framework", and theApache Log4j documentation<\/a> states (jar names in 2. corrected):

This support is implemented automatically by including the log4j-api, log4j-core, and log4j-appserver jars in the boot classpath. A file named log4j2-tomcat.xml, log4j2-tomcat.json, log4j2-tomcat.yaml, log4j2-tomcat.yml, or log4j2-tomcat.properties must also be placed in the boot classpath. This is most easily done by:

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   But what to put in that log4j2-tomcat.* config file?

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Answer 1

I found a sample properties file in the Apache Tomcat 7 documentation , but since this is meant for use with Log4j 1.x, I had to adapt it to the Log4j2 properties file syntax. This is the result:

# 'status' refers to log messages from Log4j2 itself
monitorInterval = 30
status = warn

property.loglevel.catalina = info
property.loglevel.localhost = info

property.layoutPattern.catalina = %d %-5p [%t] %-22.22c{1} %m%n
property.layoutPattern.localhost = %d %-5p [%t] %-30.30c{1} %m%n

# Roll-over the logs once per month using CronTriggerPolicy.

property.fileDatePattern.catalina = %d{yyyy-MM}
property.fileDatePattern.localhost = %d{yyyy-MM}

property.cronTriggerSchedule.catalina = 0 0 0 1 * ?
property.cronTriggerSchedule.localhost = 0 0 0 1 * ?

## Appenders

# N.B.: - No need to specify 'appenders = CATALINA, LOCALHOST, CONSOLE'
#         since these identifiers do not contain '.' characters.
#       - The sub-component identifiers 'policies' and 'cron' are arbitrarily
#         chosen; the actual type is specified via the 'type' attribute.
#       - 'DirectWriteRolloverStrategy' is used automatically since no 'fileName' specified.

appender.CATALINA.type = RollingFile
appender.CATALINA.name = RollingFile-CATALINA
appender.CATALINA.filePattern = ${sys:catalina.base}/logs/catalina.${fileDatePattern.catalina}.log
appender.CATALINA.layout.type = PatternLayout
appender.CATALINA.layout.pattern = ${layoutPattern.catalina}
appender.CATALINA.policies.type = Policies
appender.CATALINA.policies.cron.type = CronTriggeringPolicy
appender.CATALINA.policies.cron.schedule = ${cronTriggerSchedule.catalina}
appender.CATALINA.policies.cron.evaluateOnStartup = true
appender.CATALINA.filePermissions = rw-r-----
appender.CATALINA.fileOwner = tomcat
appender.CATALINA.fileGroup = adm

appender.LOCALHOST.type = RollingFile
appender.LOCALHOST.name = RollingFile-LOCALHOST
appender.LOCALHOST.filePattern = ${sys:catalina.base}/logs/localhost.${fileDatePattern.localhost}.log
appender.LOCALHOST.layout.type = PatternLayout
appender.LOCALHOST.layout.pattern = ${layoutPattern.localhost}
appender.LOCALHOST.policies.type = Policies
appender.LOCALHOST.policies.cron.type = CronTriggeringPolicy
appender.LOCALHOST.policies.cron.schedule = ${cronTriggerSchedule.localhost}
appender.LOCALHOST.policies.cron.evaluateOnStartup = true
appender.LOCALHOST.filePermissions = rw-r-----
appender.LOCALHOST.fileOwner = tomcat
appender.LOCALHOST.fileGroup = adm

# Uncomment if you want to keep logging to catalina.out after Log4j2 takes over.

#appender.CONSOLE.type = Console
#appender.CONSOLE.name = STDOUT
#appender.CONSOLE.layout.type = PatternLayout

## Configure which loggers log to which appenders

rootLogger.level = ${loglevel.catalina}
rootLogger.appenderRef.CATALINA.ref = RollingFile-CATALINA
#rootLogger.appenderRef.stdout.ref = STDOUT

# Here, the identifier does contain '.' characters, so we must specify the list.
loggers = org.apache.catalina.core.ContainerBase.[Catalina].[localhost]

logger.org.apache.catalina.core.ContainerBase.[Catalina].[localhost].name = LOCALHOST
logger.org.apache.catalina.core.ContainerBase.[Catalina].[localhost].level = ${loglevel.localhost}
logger.org.apache.catalina.core.ContainerBase.[Catalina].[localhost].appenderRef.LOCALHOST.ref = RollingFile-LOCALHOST

The main reason for me to use Log4j2 was to be able get monthly log rotation, but you can easily adjust everything how you like, even without restarting Tomcat.

Answer 2

In order to work Tomcat 9.0.54+ setup with log4j2 please complete following:

1. Activate JDK JUL bridge - https://logging.apache.org/log4j/2.x/log4j-jul/

To use the JDK Logging Adapter, you must set the system property java.util.logging.manager to org.apache.logging.log4j.jul.LogManager This must be done either through the command line (ie, using the -Djava.util.logging.manager=org.apache.logging.log4j.jul.LogManager argument) or by using System.setProperty() before any calls are made to LogManager or Logger.

2. Copy all necessary log4j2 jars into classpath or /lib
3. Configure -Dlog4j.configurationFile=/your/path/logger.xml like below example

<?xml version="1.0" encoding="utf-8"?>
<!-- ================================================ -->
<!--               Tomcat log4j2 logger               -->
<!-- ================================================ -->
<Configuration status="INFO" monitorInterval="60">
    <Properties>
        <Property name="logdir">${sys:catalina.base}/logs</Property>
        <Property name="layout">[%d][%p][%c:%L:%M] - %m%n</Property>
    </Properties>
    <Appenders>
        <Console name="DEFAULT" target="SYSTEM_OUT">
            <PatternLayout pattern="${layout}"/>
        </Console>
        <Async name="ASYNC-DEFAULT" includeLocation="true">
            <AppenderRef ref="DEFAULT"/>
            <AppenderRef ref="INTOFILE"/>
        </Async>
        <RollingFile name="INTOFILE"
                     fileName="${logdir}/worker.log"
                     filePattern="${logdir}/catalina.%d{yyyy-MM-dd}-%i.log">
            <PatternLayout pattern="${layout}"/>
            <Policies>
                <TimeBasedTriggeringPolicy/>
                <SizeBasedTriggeringPolicy size="10 MB"/>
            </Policies>
            <DefaultRolloverStrategy max="100"/>
        </RollingFile>
    </Appenders>
    <Loggers>
        <!-- OFF -->

        <!-- ERROR -->

        <!-- WARN -->

        <!-- INFO -->
        <logger name="org.apache.catalina" level="INFO"/>
        <logger name="org.apache.catalina.core" level="INFO"/>
        <logger name="org.apache.tomcat" level="INFO"/>
        <logger name="org.apache.coyote" level="INFO"/>
        <logger name="org.apache.jasper" level="INFO"/>

        <!-- DEBUG -->
        <logger name="org.apache.catalina.startup" level="DEBUG"/>
        <logger name="org.apache.tomcat1" level="DEBUG"/>


        <Root level="TRACE">
            <AppenderRef ref="ASYNC-DEFAULT"/>
        </Root>
    </Loggers>
</Configuration>