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<!DOCTYPE document [
  <!ENTITY project SYSTEM "project.xml">
]>
<document url="logging.html">

    &project;

  <properties>
    <title>Logging in Tomcat</title>
    <author>Allistair Crossley</author>
    <author email="yoavs@apache.org">Yoav Shapira</author>
  </properties>

<body>

<section name="Table of Contents">
<toc/>
</section>

  <section name="Introduction">
    <p>
      Logging in Apache Tomcat is implemented with the help of
      <a href="http://commons.apache.org/logging">Apache Commons Logging</a>
      library. That library is a thin wrapper above different logging
      frameworks. It provides Tomcat with the ability to log
      hierarchically across various log levels without the need to rely on a
      particular logging implementation.
    </p>

    <p>
      Since Tomcat 6.0, Tomcat uses a private package-renamed implementation of
      Apache Commons Logging, to allow web applications to use their own
      independent copies of the original Apache Commons Logging library.
      In the default distribution this private copy of the library
      is simplified and hardcoded to use the <code>java.util.logging</code> framework.
    </p>

    <p>
      To configure Tomcat to use alternative logging frameworks for its internal
      logging, one has to replace the logging library with the one that is built
      with the full implementation. Such library is provided as an <a href="extras.html">extras</a>
      component. Instructions on how to configure Tomcat to use Log4j framework
      for its internal logging may be found below.
    </p>

    <p>
      A web application running on Apache Tomcat can:
    </p>
    <ul>
      <li>
        Use logging API provided by the Java Servlets specification,
        <code>javax.servlet.ServletContext.log(...)</code>
      </li>
      <li>
        Use system logging API, <code>java.util.logging</code>.
      </li>
      <li>
        Use any logging framework of its choice.
      </li>
    </ul>

    <p>
      The logging frameworks used by different web applications run independently
      of each other. See <a href="class-loader-howto.html">class loading</a>
      for more details.
      The exception to this rule is <code>java.util.logging</code>, if it used
      directly or indirectly by your logging library. That is because it is loaded
      by the system and is shared across web applications.
    </p>

    <p>
      Apache Tomcat has its own implementation of several key elements of
      <code>java.util.logging</code> API. This implementation is called "JULI".
      The key component there is a custom LogManager implementation,
      that is aware of different web applications running on Tomcat (and
      their different class loaders). It supports private per-application
      logging configurations. It is also notified by Tomcat when a web application
      is unloaded from memory, so that the references to its classes can be
      cleared, preventing memory leaks.
      This <code>java.util.logging</code> implementation is enabled by providing
      certain system properties when starting Java. The Apache Tomcat startup
      scripts do this for you, but if you are using different tools to run
      Tomcat (such as jsvc, or running Tomcat from within an IDE), you should
      take care of them by yourself.
      More details about Tomcat JULI may be found below.
    </p>

    <p>
      The calls to <code>javax.servlet.ServletContext.log(...)</code> to write
      log messages are handled by internal Tomcat logging. Such messages are
      logged to the category named
    </p>
      <source>org.apache.catalina.core.ContainerBase.[${engine}].[${host}].[${context}]</source>
    <p>
      This logging is performed according to the Tomcat logging configuration. You
      cannot overwrite it in a web application.
    </p>

    <p>
      Old applications that still use <code>System.out</code> or <code>System.err</code>
      can be tricked, by setting <code>swallowOutput</code> attribute on a
      <a href="config/context.html">Context</a>. If the attribute is set to
      <code>true</code>, calls to <code>System.out/err</code> during request
      processing will be intercepted, and their output will be fed to the
      logging subsystem using the
      <code>javax.servlet.ServletContext.log(...)</code> calls.<br />
      <strong>Note</strong>, that this feature is actually a trick,
      and works only with direct calls to <code>System.out/err</code>,
      and only during request processing cycle. It cannot be used to intercept
      logging frameworks that themselves write to the system streams,
      as those start early and may obtain a direct reference to the streams.
    </p>

    <p>
      The default logging configuration in Apache Tomcat writes the same
      messages to the console and to a log file. This is great when using
      Tomcat for development, but usually is not needed in production.
      When running Tomcat on unixes, the console output is usually redirected
      to a file named <code>catalina.out</code>. The name is configurable
      using an environment variable. (See the startup scripts).
      Whatever is written to <code>System.err/out</code> will be logged in
      that file. That may include:
    </p>

    <ul>
      <li>Thread dumps, if you requested them via a system signal</li>
      <li>Uncaught exceptions printed by <code>java.lang.ThreadGroup.uncaughtException(..)</code></li>
    </ul>

    <p>
      When running as a service on Windows, the console output is also caught
      and redirected, but the file names are different.
    </p>

    <p>
      A related, but different feature is access logging. It can be configured
      as a valve at the Context, or Host, or Engine. See <a href="config/valve.html">Valves</a>
      documentation for more details.
    </p>

  </section>

  <section name="Using java.util.logging (default)">

  <p>
    The default implementation of java.util.logging provided in the JDK is too
    limited to be useful. A limitation of JDK Logging appears to be the
    inability to have per-web application logging,  as the configuration is
    per-VM. As a result, Tomcat will, in the default configuration, replace the
    default LogManager implementation with a container friendly implementation
    called JULI, which addresses these shortcomings. It supports the same
    configuration mechanisms as the standard JDK java.util.logging, using either
    a programmatic approach, or properties files. The main difference is that
    per-classloader properties files can be set (which enables easy redeployment
    friendly webapp configuration), and the properties files support slightly
    extended constructs which allows more freedom for defining handlers and
    assigning them to loggers.
  </p>
  <p>
    JULI is enabled by default, and supports per classloader configuration, in
    addition to the regular global java.util.logging configuration. This means
    that logging can be configured at the following layers:
    <ul>
      <li>In the JDK's logging.properties file. Check your JAVA_HOME environment
      setting to see which JDK Tomcat is using. The file will be in 
      <code>$JAVA_HOME/jre/lib</code>.
      Alternately, it can also use a global configuration file located elsewhere
      by using the system property <code>java.util.logging.config.file</code>,
      or programmatic configuration using
      <code>java.util.logging.config.class</code>.</li>
      <li>In each classloader using a logging.properties file. This means that
      it is possible to have a configuration for the Tomcat core, as well as
      separate configurations for each webapps which will  have the same
      lifecycle as the webapps.</li>
    </ul>
  </p>
  <p>
    The default logging.properties specifies a ConsoleHandler for routing
    logging to stdout and also a FileHandler. A handler's log level threshold
    can be set using SEVERE, WARNING, INFO, CONFIG, FINE, FINER, FINEST or ALL.
    The logging.properties shipped with JDK is set to INFO. You can also target
    specific packages to collect logging from and specify a level. Here is how
    you would set debugging from Tomcat. You would need to ensure the
    ConsoleHandler's level is also set to collect this threshold, so FINEST or
    ALL should be set. Please refer to Sun's java.util.logging documentation for
    the complete details.
  </p>
  <p>
    <source>org.apache.catalina.level=FINEST</source>
  </p>
  <p>
    The configuration used by JULI is extremely similar, but uses a few
    extensions to allow better flexibility in assigning loggers. The main
    differences are:
    <ul>
      <li>A prefix may be added to handler names, so that multiple handlers of a
      single class may be instantiated. A prefix is a String which starts with a
      digit, and ends with '.'. For example, <code>22foobar.</code> is a valid
      prefix.</li>
      <li>As in Java 6.0, loggers can define a list of handlers using the
      <code>loggerName.handlers</code> property.</li>
      <li>By default, loggers will not delegate to their parent if they have
      associated handlers. This may be changed per logger using the
      <code>loggerName.useParentHandlers</code> property, which accepts a
      boolean value.</li>
      <li>The root logger can define its set of handlers using a
      <code>.handlers</code> property.</li>
      <li>Logging is not buffered by default. To configure buffering, use the
      <code>bufferSize</code> property of a handler. A value of <code>0</code>
      uses system default buffering (typically an 8K buffer will be used). A
      value of <code>&lt;0</code> forces a writer flush upon each log write. A
      value <code>&gt;0</code> uses a BufferedOutputStream with the defined
      value but note that the system default buffering will also be
      applied.</li>
      <li>System property replacement is performed for property values which
      contain ${systemPropertyName}.</li>
    </ul>
  </p>
  <p>
    Example logging.properties file to be placed in $CATALINA_BASE/conf:
    <source>
handlers = 1catalina.org.apache.juli.FileHandler, \
           2localhost.org.apache.juli.FileHandler, \
           3manager.org.apache.juli.FileHandler, \
           4admin.org.apache.juli.FileHandler, \
           java.util.logging.ConsoleHandler

.handlers = 1catalina.org.apache.juli.FileHandler, java.util.logging.ConsoleHandler

############################################################
# Handler specific properties.
# Describes specific configuration info for Handlers.
############################################################

1catalina.org.apache.juli.FileHandler.level = FINE
1catalina.org.apache.juli.FileHandler.directory = ${catalina.base}/logs
1catalina.org.apache.juli.FileHandler.prefix = catalina.

2localhost.org.apache.juli.FileHandler.level = FINE
2localhost.org.apache.juli.FileHandler.directory = ${catalina.base}/logs
2localhost.org.apache.juli.FileHandler.prefix = localhost.

3manager.org.apache.juli.FileHandler.level = FINE
3manager.org.apache.juli.FileHandler.directory = ${catalina.base}/logs
3manager.org.apache.juli.FileHandler.prefix = manager.

4admin.org.apache.juli.FileHandler.level = FINE
4admin.org.apache.juli.FileHandler.directory = ${catalina.base}/logs
4admin.org.apache.juli.FileHandler.prefix = admin.
4admin.org.apache.juli.FileHandler.bufferSize = 16384

java.util.logging.ConsoleHandler.level = FINE
java.util.logging.ConsoleHandler.formatter = java.util.logging.SimpleFormatter


############################################################
# Facility specific properties.
# Provides extra control for each logger.
############################################################

org.apache.catalina.core.ContainerBase.[Catalina].[localhost].level = INFO
org.apache.catalina.core.ContainerBase.[Catalina].[localhost].handlers = \
   2localhost.org.apache.juli.FileHandler

org.apache.catalina.core.ContainerBase.[Catalina].[localhost].[/manager].level = INFO
org.apache.catalina.core.ContainerBase.[Catalina].[localhost].[/manager].handlers = \
   3manager.org.apache.juli.FileHandler

org.apache.catalina.core.ContainerBase.[Catalina].[localhost].[/admin].level = INFO
org.apache.catalina.core.ContainerBase.[Catalina].[localhost].[/admin].handlers = \
   4admin.org.apache.juli.FileHandler

# For example, set the org.apache.catalina.util.LifecycleBase logger to log
# each component that extends LifecycleBase changing state:
#org.apache.catalina.util.LifecycleBase.level = FINE
    </source>
    </p>
    
    <p>
      Example logging.properties for the servlet-examples web application to be
      placed in WEB-INF/classes inside the web application:
      <source>
handlers = org.apache.juli.FileHandler, java.util.logging.ConsoleHandler

############################################################
# Handler specific properties.
# Describes specific configuration info for Handlers.
############################################################

org.apache.juli.FileHandler.level = FINE
org.apache.juli.FileHandler.directory = ${catalina.base}/logs
org.apache.juli.FileHandler.prefix = servlet-examples.

java.util.logging.ConsoleHandler.level = FINE
java.util.logging.ConsoleHandler.formatter = java.util.logging.SimpleFormatter
      </source>
    </p>

  </section>

  <section name="Using Log4j">
    <p>
      This section explains how to configure Tomcat to use log4j rather than
      java.util.logging for all Tomcat's internal logging. The following steps
      describe configuring log4j to output Tomcat's internal logging to a file
      named tomcat.log.
    </p>

    <ol>
        <li>Create a file called log4j.properties with the following content 
            and save it into $CATALINA_HOME/lib.</li>
    </ol>
    <source>
log4j.rootLogger=INFO, CATALINA

# Define all the appenders
log4j.appender.CATALINA=org.apache.log4j.DailyRollingFileAppender<br />
log4j.appender.CATALINA.file=${catalina.base}/logs/catalina.<br />
log4j.appender.CATALINA.encoding=UTF-8<br />
# Roll-over the log once per day<br />
log4j.appender.CATALINA.DatePattern='.'yyyy-MM-dd'.log'<br />
log4j.appender.CATALINA.conversionPattern = %d [%t] %-5p %c- %m%n<br />
log4j.appender.CATALINA.append=true<br />
<br />
log4j.appender.LOCALHOST=org.apache.log4j.DailyRollingFileAppender<br />
log4j.appender.LOCALHOST.file=${catalina.base}/logs/localhost.<br />
log4j.appender.LOCALHOST.encoding=UTF-8<br />
log4j.appender.LOCALHOST.DatePattern='.'yyyy-MM-dd'.log'<br />
log4j.appender.LOCALHOST.conversionPattern = %d [%t] %-5p %c- %m%n<br />
log4j.appender.LOCALHOST.append=true<br />

log4j.appender.MANAGER=org.apache.log4j.DailyRollingFileAppender<br />
log4j.appender.MANAGER.file=${catalina.base}/logs/manager.<br />
log4j.appender.MANAGER.encoding=UTF-8<br />
log4j.appender.MANAGER.DatePattern='.'yyyy-MM-dd'.log'<br />
log4j.appender.MANAGER.conversionPattern = %d [%t] %-5p %c- %m%n<br />
log4j.appender.MANAGER.append=true<br />

log4j.appender.HOST-MANAGER=org.apache.log4j.DailyRollingFileAppender<br />
log4j.appender.HOST-MANAGER.file=${catalina.base}/logs/host-manager.<br />
log4j.appender.HOST-MANAGER.encoding=UTF-8<br />
log4j.appender.HOST-MANAGER.DatePattern='.'yyyy-MM-dd'.log'<br />
log4j.appender.HOST-MANAGER.conversionPattern = %d [%t] %-5p %c- %m%n<br />
log4j.appender.HOST-MANAGER.append=true<br />

log4j.appender.CONSOLE=org.apache.log4j.ConsoleAppender<br />
log4j.appender.CONSOLE.encoding=UTF-8<br />
log4j.appender.CONSOLE.conversionPattern = %d [%t] %-5p %c- %m%n<br />
<br />
# Configure which loggers log to which appenders<br />
log4j.logger.org.apache.catalina.core.ContainerBase.[Catalina].[localhost]=INFO, LOCALHOST<br />
log4j.logger.org.apache.catalina.core.ContainerBase.[Catalina].[localhost].[/manager]=\<br />
  INFO, MANAGER<br />
log4j.logger.org.apache.catalina.core.ContainerBase.[Catalina].[localhost].[/host-manager]=\<br />
  INFO, HOST-MANAGER<br />
</source>
    <ol start="2">
        <li><a href="http://logging.apache.org/log4j">Download Log4J</a> 
            (v1.2 or later) and place the log4j jar in $CATALINA_HOME/lib.</li>

        <li>Build or download the additional logging components. See the
            <a href="extras.html">extras components</a> documentation for
            details.</li>

        <li>Replace <code>$CATALINA_HOME/bin/tomcat-juli.jar</code> with
            <code>output/extras/tomcat-juli.jar</code>.</li>

        <li>Place <code>output/extras/tomcat-juli-adapters.jar</code> in 
            $CATALINA_HOME/lib.</li>

        <li>Delete <code>$CATALINA_BASE/conf/logging.properties</code> to
            prevent java.util.logging generating zero length log files.</li>
        <li>Start Tomcat</li>
    </ol>

    <p>
      This log4j configuration mirrors the default java.util.logging setup
      that ships with Tomcat: both the manager and host-manager apps get an
      individual log file, and everything else goes to the "catalina.log" log
      file. Each file is rolled-over once per day.
    </p>
        
    <p>
      You can (and should) be more picky about which packages to include 
      in the logging. Tomcat defines loggers by Engine and Host names.
      For example, for a more detailed Catalina localhost log, add this to the
      end of the log4j.properties above. Note that there are known issues with 
      using this naming convention (with square brackets) in log4j XML based
      configuration files, so we recommend you use a properties file as
      described until a future version of log4j allows this convention.
      
      <source>
log4j.logger.org.apache.catalina.core.ContainerBase.[Catalina].[localhost]=DEBUG<br />
log4j.logger.org.apache.catalina.core=DEBUG<br />
log4j.logger.org.apache.catalina.session=DEBUG<br />
      </source>

      Be warned a level of DEBUG will produce megabytes of logging and slow
      startup of Tomcat. This level should be used sparingly when debugging of
      internal Tomcat operations is required.
    </p>
        
    <p>
      Your web applications should certainly use their own log4j configuration. 
      This is valid <i>with</i> the above configuration.  You would place a
      similar log4j.properties file in your web application's WEB-INF/classes
      directory, and log4jx.y.z.jar into WEB-INF/lib. Then specify your package
      level logging. This is a basic setup of log4j which does *not* require
      Commons-Logging, and you should consult the 
      <a href="http://logging.apache.org/log4j/docs/documentation.html">log4j
      documentation</a> for more options. This page is intended only as a
      bootstrapping guide.
    </p>

    <p>
      If you have multiple instances of Tomcat, each with a separate
      <code>$CATALINA_BASE</code> but a shared <code>$CATALINA_HOME</code> then
      you can configure log4j on a per instance basis by replacing references to
      <code>$CATALINA_HOME</code> in the above instructions with
      <code>$CATALINA_BASE</code>. Note that if you do this then you may need to
      make some, or all, of the following additional changes:
      <ul>
        <li>create a <code>$CATALINA_BASE/bin</code> directory</li>
        <li>create a <code>$CATALINA_BASE/lib</code> directory</li>
        <li>if running with a security manager, adjust the codebase for JULI in
            <code>$CATALINA_BASE/conf/catalina.policy</code></li>
      </ul>
    </p>
  </section>

</body>
</document>
