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 of the cas-server-webapp-resources source module. In the cas.war it is found at the root of the cas-server-webapp-resources*.jar. The cas-overlay comes with an external log42.xml in etc/cas/config and a property logging.config=file:/etc/cas/config/log4j2.xml set to reference it. 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 or TRACE.

:warning: Production

You should always run everything under WARN. In production warnings and errors are things you care about. Everything else is just diagnostics. Only turn up DEBUG or INFO if you need to research a particular issue.

Actuator Endpoints

The following endpoints are provided:

 Fetch the last X number of log entries from all CAS appenders configured to capture logs.

 Get logging configuration report.

 Logger configuration and levels.

 Logger configuration and levels.

 Logger configuration and levels.

 Returns the log file content if `logging.file` or `logging.path` are set with support for HTTP `Range` header.


CAS Plugins

The log4j2.xml file use by CAS includes custom Log4j2 plugins:

  • CasAppender: The CasAppender wraps another regular appender and removes sensitive values from the log entries such as Ticket Granting Tickets or Proxy Granting Tickets. It may be used via the following Log4j2 configuration template:


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<?xml version="1.0" encoding="UTF-8" ?>
<Configuration monitorInterval="2">
  <!-- Wrap the console appender inside -->
  <CasAppender name="casConsole" maxEntries="50">
      <AppenderRef ref="console" />
  </CasAppender>
</Configuration>

The maxEntries attribute indicates the maximum number of latest log entries to keep in an in-memory cache. When the cache is full, the oldest entries are removed. By default, nothing is kept in the cache. This ability is useful when you want to stream the latest log entries via actuator endpoints, etc.

  • ExceptionOnlyFilter: In order to allow CAS to freely log unexpected errors at WARN and ERROR without obscuring everything with stacktraces, exceptions in the logs are disabled by default but there are log4j2.xml properties that can turn them back on. By default, all exceptions are written to a dedicated stacktrace rolling log file and this is done using a custom ExceptionOnlyFilter nested in the CasAppender.

Log4j2 Properties

The log4j2.xml file includes properties for various settings and those can be set in the properties section of the log4j2.xml file, in a property file called log4j2.component.properties on the classpath, or as system properties. If setting properties in a log4j2.component.properties, be sure to include:



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log4j2.contextSelector=org.apache.logging.log4j.core.async.AsyncLoggerContextSelector

in order to keep using asynchronous logging which CAS sets by default. To turn off asynchronous logging, include the following in log4j2.component.properites or as a system property:



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log4j2.contextSelector=org.apache.logging.log4j.core.selector.BasicContextSelector

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.

The following settings and properties are available from the CAS configuration catalog:

The configuration settings listed below are tagged as Required in the CAS configuration metadata. This flag indicates that the presence of the setting may be needed to activate or affect the behavior of the CAS feature and generally should be reviewed, possibly owned and adjusted. If the setting is assigned a default value, you do not need to strictly put the setting in your copy of the configuration, but should review it nonetheless to make sure it matches your deployment expectations.

The configuration settings listed below are tagged as Optional in the CAS configuration metadata. This flag indicates that the presence of the setting is not immediately necessary in the end-user CAS configuration, because a default value is assigned or the activation of the feature is not conditionally controlled by the setting value. In other words, you should only include this field in your configuration if you need to modify the default value or if you need to turn on the feature controlled by the setting.

The configuration settings listed below are tagged as Third Party in the CAS configuration metadata. This flag indicates that the configuration setting is not controlled, owned or managed by the CAS ecosystem, and affects functionality that is offered by a third-party library, such as Spring Boot or Spring Cloud to CAS. For additional info, you might have to visit the third-party source to find more details.

Configuration Metadata

The collection of configuration properties listed in this section are automatically generated from the CAS source and components that contain the actual field definitions, types, descriptions, modules, etc. This metadata may not always be 100% accurate, or could be lacking details and sufficient explanations.

Be Selective

This section is meant as a guide only. Do NOT copy/paste the entire collection of settings into your CAS configuration; rather pick only the properties that you need. Do NOT enable settings unless you are certain of their purpose and do NOT copy settings into your configuration only to keep them as reference. All these ideas lead to upgrade headaches, maintenance nightmares and premature aging.

YAGNI

Note that for nearly ALL use cases, declaring and configuring properties listed here is sufficient. You should NOT have to explicitly massage a CAS XML/Java/etc configuration file to design an authentication handler, create attribute release policies, etc. CAS at runtime will auto-configure all required changes for you. If you are unsure about the meaning of a given CAS setting, do NOT turn it on without hesitation. Review the codebase or better yet, ask questions to clarify the intended behavior.

Naming Convention

Property names can be specified in very relaxed terms. For instance cas.someProperty, cas.some-property, cas.some_property are all valid names. While all forms are accepted by CAS, there are certain components (in CAS and other frameworks used) whose activation at runtime is conditional on a property value, where this property is required to have been specified in CAS configuration using kebab case. This is both true for properties that are owned by CAS as well as those that might be presented to the system via an external library or framework such as Spring Boot, etc.

:information_source: Note

When possible, properties should be stored in lower-case kebab format, such as cas.property-name=value. The only possible exception to this rule is when naming actuator endpoints; The name of the actuator endpoints (i.e. ssoSessions) MUST remain in camelCase mode.

Settings and properties that are controlled by the CAS platform directly always begin with the prefix cas. All other settings are controlled and provided to CAS via other underlying frameworks and may have their own schemas and syntax. BE CAREFUL with the distinction. Unrecognized properties are rejected by CAS and/or frameworks upon which CAS depends. This means if you somehow misspell a property definition or fail to adhere to the dot-notation syntax and such, your setting is entirely refused by CAS and likely the feature it controls will never be activated in the way you intend.

Validation

Configuration properties are automatically validated on CAS startup to report issues with configuration binding, specially if defined CAS settings cannot be recognized or validated by the configuration schema. Additional validation processes are also handled via Configuration Metadata and property migrations applied automatically on startup by Spring Boot and family.

Indexed Settings

CAS settings able to accept multiple values are typically documented with an index, such as cas.some.setting[0]=value. The index [0] is meant to be incremented by the adopter to allow for distinct multiple configuration blocks.

To disable log sanitization, start the container with the system property CAS_TICKET_ID_SANITIZE_SKIP=true.

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.

The following settings and properties are available from the CAS configuration catalog:

The configuration settings listed below are tagged as Optional in the CAS configuration metadata. This flag indicates that the presence of the setting is not immediately necessary in the end-user CAS configuration, because a default value is assigned or the activation of the feature is not conditionally controlled by the setting value. In other words, you should only include this field in your configuration if you need to modify the default value or if you need to turn on the feature controlled by the setting.

The configuration settings listed below are tagged as Third Party in the CAS configuration metadata. This flag indicates that the configuration setting is not controlled, owned or managed by the CAS ecosystem, and affects functionality that is offered by a third-party library, such as Spring Boot or Spring Cloud to CAS. For additional info, you might have to visit the third-party source to find more details.

Configuration Metadata

The collection of configuration properties listed in this section are automatically generated from the CAS source and components that contain the actual field definitions, types, descriptions, modules, etc. This metadata may not always be 100% accurate, or could be lacking details and sufficient explanations.

Be Selective

This section is meant as a guide only. Do NOT copy/paste the entire collection of settings into your CAS configuration; rather pick only the properties that you need. Do NOT enable settings unless you are certain of their purpose and do NOT copy settings into your configuration only to keep them as reference. All these ideas lead to upgrade headaches, maintenance nightmares and premature aging.

YAGNI

Note that for nearly ALL use cases, declaring and configuring properties listed here is sufficient. You should NOT have to explicitly massage a CAS XML/Java/etc configuration file to design an authentication handler, create attribute release policies, etc. CAS at runtime will auto-configure all required changes for you. If you are unsure about the meaning of a given CAS setting, do NOT turn it on without hesitation. Review the codebase or better yet, ask questions to clarify the intended behavior.

Naming Convention

Property names can be specified in very relaxed terms. For instance cas.someProperty, cas.some-property, cas.some_property are all valid names. While all forms are accepted by CAS, there are certain components (in CAS and other frameworks used) whose activation at runtime is conditional on a property value, where this property is required to have been specified in CAS configuration using kebab case. This is both true for properties that are owned by CAS as well as those that might be presented to the system via an external library or framework such as Spring Boot, etc.

:information_source: Note

When possible, properties should be stored in lower-case kebab format, such as cas.property-name=value. The only possible exception to this rule is when naming actuator endpoints; The name of the actuator endpoints (i.e. ssoSessions) MUST remain in camelCase mode.

Settings and properties that are controlled by the CAS platform directly always begin with the prefix cas. All other settings are controlled and provided to CAS via other underlying frameworks and may have their own schemas and syntax. BE CAREFUL with the distinction. Unrecognized properties are rejected by CAS and/or frameworks upon which CAS depends. This means if you somehow misspell a property definition or fail to adhere to the dot-notation syntax and such, your setting is entirely refused by CAS and likely the feature it controls will never be activated in the way you intend.

Validation

Configuration properties are automatically validated on CAS startup to report issues with configuration binding, specially if defined CAS settings cannot be recognized or validated by the configuration schema. Additional validation processes are also handled via Configuration Metadata and property migrations applied automatically on startup by Spring Boot and family.

Indexed Settings

CAS settings able to accept multiple values are typically documented with an index, such as cas.some.setting[0]=value. The index [0] is meant to be incremented by the adopter to allow for distinct multiple configuration blocks.

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.

Layout Description
AsyncAppender Accepts references to other Appenders and causes LogEvents to be written to them on a separate Thread.
CassandraAppender Writes its output to an Apache Cassandra database. A keyspace and table must be configured ahead of time, and the columns should be mapped in a configuration file.
ConsoleAppender Writes its output to either System.out or System.err with System.out being the default target.
FailoverAppender Wraps a set of appenders. If the primary Appender fails the secondary appenders will be tried in order until one succeeds or there are no more secondaries to try.
FileAppender Writes to the File named in the fileName parameter.
CsvParameterLayout Converts an event’s parameters into a CSV record, ignoring the message.
JDBCAppender Writes log events to a relational database table using standard JDBC.
JPAAppender Writes log events to a relational database table using the Java Persistence API 2.1.
HttpAppender Sends log events over HTTP. A Layout must be provided to format the log event.
KafkaAppender Logs events to an Apache Kafka topic. Each log event is sent as a Kafka record.
NoSQLAppender Writes log events to a NoSQL database; Provider implementations exist for MongoDB and Apache CouchDB.
RoutingAppender Evaluates log events and then routes them to a subordinate Appender.
SMTPAppender Sends an e-mail when a specific logging event occurs, typically on errors or fatal errors.
JeroMQ The ZeroMQ appender uses the JeroMQ library to send log events to one or more ZeroMQ endpoints.
RollingFileAppender Writes to the File named in the fileName parameter and rolls the file over according the TriggeringPolicy and the RolloverPolicy.
RewriteAppender Allows the log event to be manipulated before it is processed by another Appender. This can be used to mask sensitive information such as passwords or to inject information into each event.

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:

Layout Description
CsvParameterLayout Converts an event’s parameters into a CSV record, ignoring the message.
GelfLayout Lays out events in the Graylog Extended Log Format (GELF).
HTMLLayout Generates an HTML page and adds each LogEvent to a row in a table
JSONLayout Creates log events in well-formed or fragmented JSON.
PatternLayout Formats the log even based on a conversion pattern.
RFC5424Layout Formats log events in accordance with RFC 5424, the enhanced Syslog specification.
SerializedLayout Log events are transformed into byte arrays useful in JMS or socket connections.
SyslogLayout Formats log events as BSD Syslog records.
XMLLayout Creates log events in well-formed or fragmented XML.
YamlLayout Creates log events in YAML.

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.gz">
    ...
    <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.gz">
    ...
    <DefaultRolloverStrategy max="5" compressionLevel="9">
        <Delete basePath="${baseDir}" maxDepth="2">
            <IfFileName glob="*/*.log.gz" />
            <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.

Log Message Summaries

By default, logged stacktraces are summarized and only the first few lines of the stacktrace are displayed in the output to reduce noise. If you wish to see the full stacktrace and disable the summary mode, you can consider changing the log level for the appropriate package to DEBUG. This behavior can be replaced and customized via your implementation of the LogMessageSummarizer, that should be registered with CAS using the Java ServiceLoader API. In doing so and at a minimum, you need to create a src/main/resources/META-INF/services/org.apereo.cas.util.LogMessageSummarizer file with the following contents:



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org.sso.example.MyLogMessageSummarizer

If you need to disable summary mode altogether, the following contents should be used instead in the above file:



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org.apereo.cas.util.logging.DisabledLogMessageSummarizer