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<html lang="en"><head><META http-equiv="Content-Type" content="text/html; charset=UTF-8"><link href="./images/docs-stylesheet.css" rel="stylesheet" type="text/css"><title>Apache Tomcat 9 (9.0.112) - Logging in Tomcat</title></head><body><div id="wrapper"><header><div id="header"><div><div><div class="logo noPrint"><a href="https://tomcat.apache.org/"><img alt="Tomcat Home" src="./images/tomcat.png"></a></div><div style="height: 1px;"></div><div class="asfLogo noPrint"><a href="https://www.apache.org/" target="_blank"><img src="./images/asf-logo.svg" alt="The Apache Software Foundation" style="width: 266px; height: 83px;"></a></div><h1>Apache Tomcat 9</h1><div class="versionInfo">
3
            Version 9.0.112,
4
            <time datetime="2025-11-06">Nov 6 2025</time></div><div style="height: 1px;"></div><div style="clear: left;"></div></div></div></div></header><div id="middle"><div><div id="mainLeft" class="noprint"><div><nav><div><h2>Links</h2><ul><li><a href="index.html">Docs Home</a></li><li><a href="https://cwiki.apache.org/confluence/display/TOMCAT/FAQ">FAQ</a></li></ul></div><div><h2>User Guide</h2><ul><li><a href="introduction.html">1) Introduction</a></li><li><a href="setup.html">2) Setup</a></li><li><a href="appdev/index.html">3) First webapp</a></li><li><a href="deployer-howto.html">4) Deployer</a></li><li><a href="manager-howto.html">5) Manager</a></li><li><a href="host-manager-howto.html">6) Host Manager</a></li><li><a href="realm-howto.html">7) Realms and AAA</a></li><li><a href="security-manager-howto.html">8) Security Manager</a></li><li><a href="jndi-resources-howto.html">9) JNDI Resources</a></li><li><a href="jndi-datasource-examples-howto.html">10) JDBC DataSources</a></li><li><a href="class-loader-howto.html">11) Classloading</a></li><li><a href="jasper-howto.html">12) JSPs</a></li><li><a href="ssl-howto.html">13) SSL/TLS</a></li><li><a href="ssi-howto.html">14) SSI</a></li><li><a href="cgi-howto.html">15) CGI</a></li><li><a href="proxy-howto.html">16) Proxy Support</a></li><li><a href="mbeans-descriptors-howto.html">17) MBeans Descriptors</a></li><li><a href="default-servlet.html">18) Default Servlet</a></li><li><a href="cluster-howto.html">19) Clustering</a></li><li><a href="balancer-howto.html">20) Load Balancer</a></li><li><a href="connectors.html">21) Connectors</a></li><li><a href="monitoring.html">22) Monitoring and Management</a></li><li><a href="logging.html">23) Logging</a></li><li><a href="apr.html">24) APR/Native</a></li><li><a href="virtual-hosting-howto.html">25) Virtual Hosting</a></li><li><a href="aio.html">26) Advanced IO</a></li><li><a href="maven-jars.html">27) Mavenized</a></li><li><a href="security-howto.html">28) Security Considerations</a></li><li><a href="windows-service-howto.html">29) Windows Service</a></li><li><a href="windows-auth-howto.html">30) Windows Authentication</a></li><li><a href="jdbc-pool.html">31) Tomcat's JDBC Pool</a></li><li><a href="web-socket-howto.html">32) WebSocket</a></li><li><a href="rewrite.html">33) Rewrite</a></li><li><a href="cdi.html">34) CDI 2 and JAX-RS</a></li><li><a href="graal.html">35) AOT/GraalVM Support</a></li></ul></div><div><h2>Reference</h2><ul><li><a href="RELEASE-NOTES.txt">Release Notes</a></li><li><a href="config/index.html">Configuration</a></li><li><a href="api/index.html">Tomcat Javadocs</a></li><li><a href="servletapi/index.html">Servlet 4.0 Javadocs</a></li><li><a href="jspapi/index.html">JSP 2.3 Javadocs</a></li><li><a href="elapi/index.html">EL 3.0 Javadocs</a></li><li><a href="websocketapi/index.html">WebSocket 1.1 Javadocs</a></li><li><a href="jaspicapi/index.html">JASPIC 1.1 Javadocs</a></li><li><a href="annotationapi/index.html">Common Annotations 1.3 Javadocs</a></li><li><a href="https://tomcat.apache.org/connectors-doc/">JK 1.2 Documentation</a></li></ul></div><div><h2>Apache Tomcat Development</h2><ul><li><a href="building.html">Building</a></li><li><a href="changelog.html">Changelog</a></li><li><a href="https://cwiki.apache.org/confluence/display/TOMCAT/Tomcat+Versions">Status</a></li><li><a href="developers.html">Developers</a></li><li><a href="architecture/index.html">Architecture</a></li><li><a href="tribes/introduction.html">Tribes</a></li></ul></div></nav></div></div><div id="mainRight"><div id="content"><h2>Logging in Tomcat</h2><h3 id="Table_of_Contents">Table of Contents</h3><div class="text">
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<ul><li><a href="#Introduction">Introduction</a><ol><li><a href="#Java_logging_API_%E2%80%94_java.util.logging">Java logging API &mdash; java.util.logging</a></li><li><a href="#Servlets_logging_API">Servlets logging API</a></li><li><a href="#Console">Console</a></li><li><a href="#Access_logging">Access logging</a></li></ol></li><li><a href="#Using_java.util.logging_(default)">Using java.util.logging (default)</a><ol><li><a href="#Documentation_references">Documentation references</a></li><li><a href="#Considerations_for_production_usage">Considerations for production usage</a></li></ol></li><li><a href="#Using_Log4j">Using Log4j</a></li></ul>
6
</div><h3 id="Introduction">Introduction</h3><div class="text">
7
    <p>
8
      The internal logging for Apache Tomcat uses JULI, a packaged renamed fork
9
      of <a href="https://commons.apache.org/logging">Apache Commons Logging</a>
10
      that is hard-coded to use the <code>java.util.logging</code> framework.
11
      This ensures that Tomcat's internal logging and any web application
12
      logging will remain independent, even if a web application uses Apache
13
      Commons Logging.
14
    </p>
15
 
16
    <p>
17
      To configure Tomcat to use an alternative logging framework for its
18
      internal logging, follow the instructions provided by the alternative
19
      logging framework for redirecting logging for applications that use
20
      <code>java.util.logging</code>. Links to some of these instructions are
21
      provided towards the end of this page. Keep in mind that the alternative
22
      logging framework will need to be capable of working in an environment
23
      where different loggers with the same name may exist in different class
24
      loaders.
25
    </p>
26
 
27
    <p>
28
      A web application running on Apache Tomcat can:
29
    </p>
30
    <ul>
31
      <li>
32
        Use any logging framework of its choice.
33
      </li>
34
      <li>
35
        Use system logging API, <code>java.util.logging</code>.
36
      </li>
37
      <li>
38
        Use the logging API provided by the Java Servlets specification,
39
        <code>javax.servlet.ServletContext.log(...)</code>
40
      </li>
41
    </ul>
42
 
43
    <p>
44
      The logging frameworks used by different web applications are independent.
45
      See <a href="class-loader-howto.html">class loading</a> for more details.
46
      The exception to this rule is <code>java.util.logging</code>. If it is
47
      used directly or indirectly by your logging library then elements of it
48
      will be shared across web applications because it is loaded by the system
49
      class loader.
50
    </p>
51
 
52
    <div class="subsection"><h4 id="Java_logging_API_&mdash;_java.util.logging">Java logging API &mdash; java.util.logging</h4><div class="text">
53
 
54
    <p>
55
      Apache Tomcat has its own implementation of several key elements of
56
      <code>java.util.logging</code> API. This implementation is called JULI.
57
      The key component there is a custom LogManager implementation,
58
      that is aware of different web applications running on Tomcat (and
59
      their different class loaders). It supports private per-application
60
      logging configurations. It is also notified by Tomcat when a web application
61
      is unloaded from memory, so that the references to its classes can be
62
      cleared, preventing memory leaks.
63
    </p>
64
 
65
    <p>
66
      This <code>java.util.logging</code> implementation is enabled by providing
67
      certain system properties when starting Java. The Apache Tomcat startup
68
      scripts do this for you, but if you are using different tools to run
69
      Tomcat (such as jsvc, or running Tomcat from within an IDE), you should
70
      take care of them by yourself.
71
    </p>
72
 
73
    <p>
74
      More details about java.util.logging may be found in the documentation
75
      for your JDK and on its Javadoc pages for the <code>java.util.logging</code>
76
      package.
77
    </p>
78
 
79
    <p>
80
      More details about Tomcat JULI may be found below.
81
    </p>
82
 
83
    </div></div>
84
 
85
    <div class="subsection"><h4 id="Servlets_logging_API">Servlets logging API</h4><div class="text">
86
 
87
    <p>
88
      The calls to <code>javax.servlet.ServletContext.log(...)</code> to write
89
      log messages are handled by internal Tomcat logging. Such messages are
90
      logged to the category named
91
    </p>
92
      <div class="codeBox"><pre><code>org.apache.catalina.core.ContainerBase.[${engine}].[${host}].[${context}]</code></pre></div>
93
    <p>
94
      This logging is performed according to the Tomcat logging configuration. You
95
      cannot overwrite it in a web application.
96
    </p>
97
 
98
    <p>
99
      The Servlets logging API predates the <code>java.util.logging</code> API
100
      that is now provided by Java. As such, it does not offer you much options.
101
      E.g., you cannot control the log levels. It can be noted, though, that
102
      in Apache Tomcat implementation the calls to <code>ServletContext.log(String)</code>
103
      or <code>GenericServlet.log(String)</code> are logged at the INFO level.
104
      The calls to <code>ServletContext.log(String, Throwable)</code> or
105
      <code>GenericServlet.log(String, Throwable)</code>
106
      are logged at the SEVERE level.
107
    </p>
108
 
109
    </div></div>
110
 
111
    <div class="subsection"><h4 id="Console">Console</h4><div class="text">
112
 
113
    <p>
114
      When running Tomcat on unixes, the console output is usually redirected
115
      to the file named <code>catalina.out</code>. The name is configurable
116
      using an environment variable. (See the startup scripts).
117
      Whatever is written to <code>System.err/out</code> will be caught into
118
      that file. That may include:
119
    </p>
120
 
121
    <ul>
122
      <li>Uncaught exceptions printed by <code>java.lang.ThreadGroup.uncaughtException(..)</code></li>
123
      <li>Thread dumps, if you requested them via a system signal</li>
124
    </ul>
125
 
126
    <p>
127
      When running as a service on Windows, the console output is also caught
128
      and redirected, but the file names are different.
129
    </p>
130
 
131
    <p>
132
      The default logging configuration in Apache Tomcat writes the same
133
      messages to the console and to a log file. This is great when using
134
      Tomcat for development, but usually is not needed in production.
135
    </p>
136
 
137
    <p>
138
      Old applications that still use <code>System.out</code> or <code>System.err</code>
139
      can be tricked by setting <code>swallowOutput</code> attribute on a
140
      <a href="config/context.html">Context</a>. If the attribute is set to
141
      <code>true</code>, the calls to <code>System.out/err</code> during request
142
      processing will be intercepted, and their output will be fed to the
143
      logging subsystem using the
144
      <code>javax.servlet.ServletContext.log(...)</code> calls.<br>
145
      <strong>Note</strong>, that the <code>swallowOutput</code>  feature is
146
      actually a trick, and it has its limitations.
147
      It works only with direct calls to <code>System.out/err</code>,
148
      and only during request processing cycle. It may not work in other
149
      threads that might be created by the application. It cannot be used to
150
      intercept logging frameworks that themselves write to the system streams,
151
      as those start early and may obtain a direct reference to the streams
152
      before the redirection takes place.
153
    </p>
154
 
155
    </div></div>
156
 
157
    <div class="subsection"><h4 id="Access_logging">Access logging</h4><div class="text">
158
 
159
    <p>
160
      Access logging is a related but different feature, which is
161
      implemented as a <code>Valve</code>. It uses self-contained
162
      logic to write its log files. The essential requirement for
163
      access logging is to handle a large continuous stream of data
164
      with low overhead, so it only uses Apache Commons Logging for
165
      its own debug messages. This implementation approach avoids
166
      additional overhead and potentially complex configuration.
167
      Please refer to the <a href="config/valve.html#Access_Logging">Valves</a>
168
      documentation for more details on its configuration, including
169
      the various report formats.
170
    </p>
171
 
172
    </div></div>
173
 
174
  </div><h3 id="Using_java.util.logging_(default)">Using java.util.logging (default)</h3><div class="text">
175
 
176
  <p>
177
    The default implementation of java.util.logging provided in the JDK is too
178
    limited to be useful. The key limitation is the inability to have per-web
179
    application logging, as the configuration is per-VM. As a result, Tomcat
180
    will, in the default configuration, replace the default LogManager
181
    implementation with a container friendly implementation called JULI, which
182
    addresses these shortcomings.
183
  </p>
184
  <p>
185
    JULI supports the same configuration mechanisms as the standard JDK
186
    <code>java.util.logging</code>, using either a programmatic approach, or
187
    properties files. The main difference is that per-classloader properties
188
    files can be set (which enables easy redeployment friendly webapp
189
    configuration), and the properties files support extended constructs which
190
    allows more freedom for defining handlers and assigning them to loggers.
191
  </p>
192
  <p>
193
    JULI is enabled by default, and supports per classloader configuration, in
194
    addition to the regular global java.util.logging configuration. This means
195
    that logging can be configured at the following layers:
196
  </p>
197
    <ul>
198
      <li>Globally. That is usually done in the
199
        <code>${catalina.base}/conf/logging.properties</code> file.
200
        The file is specified by the <code>java.util.logging.config.file</code>
201
        System property which is set by the startup scripts.
202
        If it is not readable or is not configured, the default is to use the
203
        <code>${java.home}/lib/logging.properties</code> file in the JRE.
204
      </li>
205
      <li>In the web application. The file will be
206
        <code>WEB-INF/classes/logging.properties</code>
207
      </li>
208
    </ul>
209
  <p>
210
    The default <code>logging.properties</code> in the JRE specifies a
211
    <code>ConsoleHandler</code> that routes logging to System.err.
212
    The default <code>conf/logging.properties</code> in Apache Tomcat also
213
    adds several <code>AsyncFileHandler</code>s that write to files.
214
  </p>
215
  <p>
216
    A handler's log level threshold is <code>INFO</code> by default and can be set using
217
    <code>SEVERE</code>, <code>WARNING</code>, <code>INFO</code>, <code>CONFIG</code>,
218
    <code>FINE</code>, <code>FINER</code>, <code>FINEST</code> or <code>ALL</code>.
219
    You can also target specific packages to collect logging from and specify
220
    a level.
221
  </p>
222
  <p>
223
    To enable debug logging for part of Tomcat's internals, you should
224
    configure both the appropriate logger(s) and the appropriate handler(s) to
225
    use the <code>FINEST</code> or <code>ALL</code> level. e.g.:
226
  </p>
227
  <div class="codeBox"><pre><code>org.apache.catalina.session.level=ALL
228
java.util.logging.ConsoleHandler.level=ALL</code></pre></div>
229
  <p>
230
    When enabling debug logging it is recommended that it is enabled for the
231
    narrowest possible scope as debug logging can generate large amounts of
232
    information.
233
  </p>
234
  <p>
235
    The configuration used by JULI is the same as the one supported by plain
236
    <code>java.util.logging</code>, but uses a few extensions to allow better
237
    flexibility in configuring loggers and handlers. The main differences are:
238
  </p>
239
  <ul>
240
      <li>A prefix may be added to handler names, so that multiple handlers of a
241
      single class may be instantiated. A prefix is a String which starts with a
242
      digit, and ends with '.'. For example, <code>22foobar.</code> is a valid
243
      prefix.</li>
244
      <li>System property replacement is performed for property values which
245
      contain <code>${systemPropertyName}</code>.</li>
246
      <li>If using a class loader that implements the
247
      <code>org.apache.juli.WebappProperties</code> interface (Tomcat's
248
      web application class loader does) then property replacement is also
249
      performed for <code>${classloader.webappName}</code>,
250
      <code>${classloader.hostName}</code> and
251
      <code>${classloader.serviceName}</code> which are replaced with the
252
      web application name, the host name and the service name respectively.
253
      </li>
254
      <li>By default, loggers will not delegate to their parent if they have
255
      associated handlers. This may be changed per logger using the
256
      <code>loggerName.useParentHandlers</code> property, which accepts a
257
      boolean value.</li>
258
      <li>The root logger can define its set of handlers using the
259
      <code>.handlers</code> property.</li>
260
      <li> By default the log files will be kept on the file system for
261
      <code>90</code> days. This may be changed per handler using the
262
      <code>handlerName.maxDays</code> property. If the specified value for the
263
      property is <code>&le;0</code> then the log files will be kept on the
264
      file system forever, otherwise they will be kept the specified maximum
265
      days.</li>
266
  </ul>
267
  <p>
268
    There are several additional implementation classes, that can be used
269
    together with the ones provided by Java. The notable ones are
270
    <code>org.apache.juli.FileHandler</code> and <code>org.apache.juli.AsyncFileHandler</code>.
271
  </p>
272
  <p>
273
    <code>org.apache.juli.FileHandler</code> supports buffering of the
274
      logs. The buffering is not enabled by default. To configure it, use the
275
      <code>bufferSize</code> property of a handler. The value of <code>0</code>
276
      uses system default buffering (typically an 8K buffer will be used). A
277
      value of <code>&lt;0</code> forces a writer flush upon each log write. A
278
      value <code>&gt;0</code> uses a BufferedOutputStream with the defined
279
      value but note that the system default buffering will also be
280
      applied.
281
  </p>
282
  <p>
283
    <code>org.apache.juli.AsyncFileHandler</code> is a subclass of <code>FileHandler</code>
284
      that queues the log messages and writes them asynchronously to the log files.
285
      Its additional behaviour can be configured by setting some
286
      <a href="config/systemprops.html#Logging">system properties</a>.
287
  </p>
288
  <p>
289
    Example logging.properties file to be placed in $CATALINA_BASE/conf:
290
  </p>
291
  <div class="codeBox"><pre><code>handlers = 1catalina.org.apache.juli.AsyncFileHandler, \
292
           2localhost.org.apache.juli.AsyncFileHandler, \
293
           3manager.org.apache.juli.AsyncFileHandler, \
294
           java.util.logging.ConsoleHandler
295
 
296
.handlers = 1catalina.org.apache.juli.AsyncFileHandler, java.util.logging.ConsoleHandler
297
 
298
############################################################
299
# Handler specific properties.
300
# Describes specific configuration info for Handlers.
301
############################################################
302
 
303
1catalina.org.apache.juli.AsyncFileHandler.level = ALL
304
1catalina.org.apache.juli.AsyncFileHandler.directory = ${catalina.base}/logs
305
1catalina.org.apache.juli.AsyncFileHandler.prefix = catalina.
306
1catalina.org.apache.juli.AsyncFileHandler.maxDays = 90
307
1catalina.org.apache.juli.AsyncFileHandler.encoding = UTF-8
308
 
309
2localhost.org.apache.juli.AsyncFileHandler.level = ALL
310
2localhost.org.apache.juli.AsyncFileHandler.directory = ${catalina.base}/logs
311
2localhost.org.apache.juli.AsyncFileHandler.prefix = localhost.
312
2localhost.org.apache.juli.AsyncFileHandler.maxDays = 90
313
2localhost.org.apache.juli.AsyncFileHandler.encoding = UTF-8
314
 
315
3manager.org.apache.juli.AsyncFileHandler.level = ALL
316
3manager.org.apache.juli.AsyncFileHandler.directory = ${catalina.base}/logs
317
3manager.org.apache.juli.AsyncFileHandler.prefix = manager.
318
3manager.org.apache.juli.AsyncFileHandler.bufferSize = 16384
319
3manager.org.apache.juli.AsyncFileHandler.maxDays = 90
320
3manager.org.apache.juli.AsyncFileHandler.encoding = UTF-8
321
 
322
java.util.logging.ConsoleHandler.level = ALL
323
java.util.logging.ConsoleHandler.formatter = org.apache.juli.OneLineFormatter
324
java.util.logging.ConsoleHandler.encoding = UTF-8
325
 
326
############################################################
327
# Facility specific properties.
328
# Provides extra control for each logger.
329
############################################################
330
 
331
org.apache.catalina.core.ContainerBase.[Catalina].[localhost].level = INFO
332
org.apache.catalina.core.ContainerBase.[Catalina].[localhost].handlers = \
333
   2localhost.org.apache.juli.AsyncFileHandler
334
 
335
org.apache.catalina.core.ContainerBase.[Catalina].[localhost].[/manager].level = INFO
336
org.apache.catalina.core.ContainerBase.[Catalina].[localhost].[/manager].handlers = \
337
   3manager.org.apache.juli.AsyncFileHandler
338
 
339
# For example, set the org.apache.catalina.util.LifecycleBase logger to log
340
# each component that extends LifecycleBase changing state:
341
#org.apache.catalina.util.LifecycleBase.level = FINE</code></pre></div>
342
 
343
    <p>
344
      Example logging.properties for the servlet-examples web application to be
345
      placed in WEB-INF/classes inside the web application:
346
    </p>
347
    <div class="codeBox"><pre><code>handlers = org.apache.juli.AsyncFileHandler, java.util.logging.ConsoleHandler
348
 
349
############################################################
350
# Handler specific properties.
351
# Describes specific configuration info for Handlers.
352
############################################################
353
 
354
org.apache.juli.AsyncFileHandler.level = ALL
355
org.apache.juli.AsyncFileHandler.directory = ${catalina.base}/logs
356
org.apache.juli.AsyncFileHandler.prefix = ${classloader.webappName}.
357
org.apache.juli.AsyncFileHandler.encoding = UTF-8
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java.util.logging.ConsoleHandler.level = ALL
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java.util.logging.ConsoleHandler.formatter = org.apache.juli.OneLineFormatter
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java.util.logging.ConsoleHandler.encoding = UTF-8</code></pre></div>
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    <div class="subsection"><h4 id="Documentation_references">Documentation references</h4><div class="text">
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      <p>See the following resources for additional information:</p>
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      <ul>
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        <li>Apache Tomcat Javadoc for the
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          <a href="api/org/apache/juli/package-summary.html"><code>org.apache.juli</code></a>
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          package.
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        </li>
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        <li>Oracle Java 8 Javadoc for the
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          <a href="https://docs.oracle.com/javase/8/docs/api/java/util/logging/package-summary.html"><code>java.util.logging</code></a>
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          package.
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        </li>
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      </ul>
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    </div></div>
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    <div class="subsection"><h4 id="Considerations_for_production_usage">Considerations for production usage</h4><div class="text">
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      <p>You may want to take note of the following:</p>
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      <ul>
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        <li>Consider removing <code>ConsoleHandler</code> from configuration. By
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        default (thanks to the <code>.handlers</code> setting) logging goes both
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        to a <code>AsyncFileHandler</code> and to a <code>ConsoleHandler</code>. The
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        output of the latter one is usually captured into a file, such as
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        <code>catalina.out</code>. Thus you end up with two copies of the same
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        messages.</li>
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        <li>Consider removing <code>AsyncFileHandler</code>s for the applications
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        that you do not use. E.g., the one for <code>host-manager</code>.</li>
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        <li>Consider configuring an
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        <a href="config/valve.html#Access_Logging">Access log</a>.</li>
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      </ul>
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    </div></div>
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  </div><h3 id="Using_Log4j">Using Log4j</h3><div class="text">
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    <p>The Log4j project provides <a href="https://logging.apache.org/log4j/2.x/jakarta.html#replace-tomcat">instructions for using Log4J for Tomcat's internal logging</a>.</p>
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