Logging

CAS provides a logging facility that logs important informational events like authentication success and failure; it can be customized to produce additional information for troubleshooting. CAS uses the Slf4j Logging framework as a facade for the Log4j engine by default.

The default log4j configuration file is located in src/main/resources/log4j2.xml. By default logging is set to INFO for all functionality related to org.apereo.cas code. For debugging and diagnostic purposes you may want to set these levels to DEBUG.

Configuration

It is often helpful to externalize the log4j2.xml file to a system path to preserve settings between upgrades. The location of log4j2.xml file by default is on the runtime classpath and can be controlled via the CAS properties.

To see the relevant list of CAS properties, please review this guide.

Log Levels

While log levels can directly be massaged via the native log4j2.xml syntax, they may also be modified using the usual CAS properties. To see the relevant list of CAS properties, please review this guide.

Refresh Interval

The log4j2.xml itself controls the refresh interval of the logging configuration. Log4j has the ability to automatically detect changes to the configuration file and reconfigure itself. If the monitorInterval attribute is specified on the configuration element and is set to a non-zero value then the file will be checked the next time a log event is evaluated and/or logged and the monitorInterval has elapsed since the last check. This will allow you to adjust the log levels and configuration without restarting the server environment.

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<!-- Specify the refresh internal in seconds. -->
<Configuration monitorInterval="15" ...>
    ...
</Configuration>

Appenders

Appenders are responsible for delivering log events to their destination. Appenders usually are only responsible for writing the event data to the target destination. In most cases they delegate responsibility for formatting the event to a layout. Some appenders wrap other appenders so that they can modify the log event, handle a failure in an Appender, route the event to a subordinate Appender based on advanced filtering criteria or provide similar functionality that does not directly format the event for viewing. Appenders always have a name so that they can be referenced from Loggers.

The following Appender elements are only a partial collection of available options.

For full details, please review the official Log4j documentation

Log Patterns

By default most appenders that are provided via the log4j2.xml file use pattern-based layouts to format log messages. The following alternative layouts may also be used:

To learn more about nuances and configuration settings for each, please refer to the official Log4J guides.

Log File Rotation

The default configuration specifies triggering policies for rolling over logs, at startup, size or at specific times. These policies apply to RollingFile appenders.

For example, the following XML fragment defines policies that rollover the log when the JVM starts, when the log size reaches 10 megabytes, and when the current date no longer matches the log’s start date.

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<RollingFile name="file" fileName="${baseDir}/cas.log" append="true"
                    filePattern="${baseDir}/cas-%d{yyyy-MM-dd-HH}-%i.log">
    ...
    <Policies>
        <OnStartupTriggeringPolicy />
        <SizeBasedTriggeringPolicy size="10 MB"/>
        <TimeBasedTriggeringPolicy interval="24" />
    </Policies>
    ...
</RollingFile>

The triggering policies determines if a rollover should be performed and rollover strategy can also be design to indicate how that should be done. If no strategy is configured, the default will be used.

To find more a comprehensive documentation, please review the guides here.

Rollover Strategy

Customized rollover strategies provide a delete action that gives users more control over what files are deleted at rollover time than what was possible with the DefaultRolloverStrategy max attribute. The delete action lets users configure one or more conditions that select the files to delete relative to a base directory.

For example, the following appender at rollover time deletes all files under the base directory that match the */*.log glob and are 7 days old or older.

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<RollingFile name="file" fileName="${baseDir}/cas.log" append="true"
             filePattern="${baseDir}/cas-%d{yyyy-MM-dd-HH}-%i.log">
    ...
    <DefaultRolloverStrategy max="5">
        <Delete basePath="${baseDir}" maxDepth="2">
            <IfFileName glob="*/*.log" />
            <IfLastModified age="7d" />
        </Delete>
    </DefaultRolloverStrategy>
    ...
</RollingFile>

To find more a comprehensive documentation, please review the guides here.

Log Data Sanitation

For security purposes, CAS by default will attempt to remove ticket-granting ticket and proxy-granting ticket ids from all log data. This will of course include messages that are routed to a log destination by the logging framework as well as all audit messages.

A sample follows below:

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WHO: audit:unknown
WHAT: TGT-******************123456-cas01.example.org
ACTION: TICKET_GRANTING_TICKET_DESTROYED
APPLICATION: CAS
WHEN: Sat Jul 12 04:10:35 PDT 2014
CLIENT IP ADDRESS: ...
SERVER IP ADDRESS: ...

Certain number of characters are left at the trailing end of the ticket id to assist with troubleshooting and diagnostics.

To see the relevant list of CAS properties, please review this guide.