<?xml version="1.0" encoding="UTF-8"?>
<!--
Licensed to the Apache Software Foundation (ASF) under one or more
contributor license agreements. See the NOTICE file distributed with
this work for additional information regarding copyright ownership.
The ASF licenses this file to You under the Apache License, Version 2.0
(the "License"); you may not use this file except in compliance with
the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
-->
<!DOCTYPE document [
<!ENTITY project SYSTEM "project.xml">
]>
<document url="graal.html">
&project;
<properties>
<title>Ahead of Time compilation support</title>
</properties>
<body>
<section name="Table of Contents">
<toc/>
</section>
<section name="Introduction">
<p>
Tomcat supports using the GraalVM/Mandrel Native Image tool to produce
a native binary including the container. This documentation page
describes the build process of such an image.
</p>
</section>
<section name="Setup">
<p>
The native image tool is much easier to use with single JARs, as a result
the process will use the Maven shade plugin JAR packaging (fat JAR). The
idea is to produce a single JAR that contains all necessary classes from
Tomcat, the webapps and all additional dependencies. Although Tomcat has
received compatibility fixes to support native images, any library
may not be compatible and may require replacement code (the GraalVM
documentation has more details about this).
</p>
<p>
Download and install GraalVM or Mandrel.
</p>
<p>
If using GraalVM, the first step is then to add the Native Image tool.
<source>export JAVA_HOME=/absolute...path...to/graalvm-ce-javaX-x.y.z
cd $JAVA_HOME/bin
./gu install native-image</source>
Mandrel already includes the Native Image tool ready to use, so this
step can be skipped. Only JAVA_HOME must be set to the folder which
contains the bin folder with the JVM binaries, such as:
<source>export JAVA_HOME=/absolute...path...to/mandrel-javaXX-platform-x.x.x.x/mandrelJDK</source>
</p>
<p>
Download the Tomcat Stuffed module from
https://github.com/apache/tomcat/tree/main/modules/stuffed and place
all the files in a folder <code>stuffed</code> in this documentation.
<source>export TOMCAT_STUFFED=/absolute...path...to/stuffed</source>
The build process now requires both Ant and Maven.
</p>
</section>
<section name="Packaging and Building">
<p>
Inside the tomcat-stuffed folder, the directory structure is the same as for
regular Tomcat. The main configuration files are placed in the conf folder,
and if using the default server.xml the webapps are placed in the webapps
folder.
</p>
<p>
The first step is to build the fat Tomcat JAR with all dependencies.
Any JSP in the webapp must all be precompiled and packaged.
<source>cd $TOMCAT_STUFFED
mvn package
ant -Dwebapp.name=somewebapp -f webapp-jspc.ant.xml</source>
Dependencies for the webapp should now be added to the main pom.xml,
following with building the complete fat JAR.
<source>mvn package</source>
</p>
<p>
As it is best to avoid using reflection whenever possible with Ahead of
Time compilation, it can be a good idea to generate and compile Tomcat
Embedded code out of the main server.xml configuration as well as the
context.xml files used to configure the contexts.
<source>$JAVA_HOME/bin/java\
-Dcatalina.base=. -Djava.util.logging.config.file=conf/logging.properties\
-jar target/tomcat-stuffed-1.0.jar --catalina -generateCode src/main/java
mvn package</source>
The rest of the process described here will assume this step was done and
the <code>--catalina -useGeneratedCode</code> arguments are added to the
command lines. If this was not the case, they should be removed.
</p>
</section>
<section name="Native image configuration">
<p>
Native images do not support any form of dynamic classloading or
reflection unless it is defined explicitly in descriptors. Generating
them uses a tracing agent from the GraalVM, and needs additional manual
configuration in some cases.
</p>
<p>
Run the GraalVM substrate VM using the trace agent:
<source>$JAVA_HOME/bin/java\
-agentlib:native-image-agent=config-output-dir=$TOMCAT_STUFFED/target/\
-Dorg.graalvm.nativeimage.imagecode=agent\
-Dcatalina.base=. -Djava.util.logging.config.file=conf/logging.properties\
-jar target/tomcat-stuffed-1.0.jar --catalina -useGeneratedCode</source>
</p>
<p>
Now all paths from the webapp that lead to dynamic classloading
(ex: Servlet access, websockets, etc) need to be accessed using a script
that will exercise the webapp. Servlets may be loaded on startup
instead of needing an actual access. Listeners may also be used to load
additional classes on startup.
</p>
<p>
The descriptors have now been generated in the agent output directory.
At this point, further configuration must be made to add items that are
not traced, including: base interfaces, resource bundles, BeanInfo based
reflection, etc. Please refer to the Graal documentation for more
information on this process.
</p>
<p>
Even though all classes that are used have to be complied AOT into the
native image, webapps must still be left unchanged, and continue including
all needed classes and JARs in the <code>WEB-INF</code> folder. Although
these classes will not actually be run or loaded, access to them is
required.
</p>
</section>
<section name="Building the native image">
<p>
If everything has been done properly, the native image can now be built
using the native-image tool.
<source>$JAVA_HOME/bin/native-image --no-server\
--allow-incomplete-classpath --enable-https\
--initialize-at-build-time=org.eclipse.jdt,org.apache.el.parser.SimpleNode,jakarta.servlet.jsp.JspFactory,org.apache.jasper.servlet.JasperInitializer,org.apache.jasper.runtime.JspFactoryImpl\
-H:+JNI -H:+ReportUnsupportedElementsAtRuntime\
-H:+ReportExceptionStackTraces -H:EnableURLProtocols=http,https,jar,jrt\
-H:ConfigurationFileDirectories=$TOMCAT_STUFFED/target/\
-H:ReflectionConfigurationFiles=$TOMCAT_STUFFED/tomcat-reflection.json\
-H:ResourceConfigurationFiles=$TOMCAT_STUFFED/tomcat-resource.json\
-H:JNIConfigurationFiles=$TOMCAT_STUFFED/tomcat-jni.json\
-jar $TOMCAT_STUFFED/target/tomcat-stuffed-1.0.jar</source>
The additional <code>--static</code> parameter enables static linking of
glibc, zlib and libstd++ in the generated binary.
</p>
<p>
Running the native image is then:
<source>./tomcat-stuffed-1.0 -Dcatalina.base=. -Djava.util.logging.config.file=conf/logging.properties --catalina -useGeneratedCode</source>
</p>
</section>
<section name="Compatibility">
<p>
Servlets, JSPs, EL, websockets, the Tomcat container, tomcat-native, HTTP/2
are all supported out of the box in a native image.
</p>
<p>
At the time of writing this documentation, JULI is not supported as the
log manager configuration property is not supported by Graal, in addition
to some static initializer problems, and the regular java.util.logging
loggers and implementation should be used instead.
</p>
<p>
If using the default server.xml file, some Server listeners have
to be removed from the configuration as they are not compatible with native
images, such as a JMX listener (JMX is unsupported) and leak prevention
listeners (use of internal code that does not exist in Graal).
</p>
<p>
Missing items for better Tomcat functionality:
<ul>
<li>java.util.logging LogManager: Configuration through a system property
is not implemented, so standard java.util.logging must be used instead
of JULI</li>
<li>Static linking configuration: tomcat-native cannot be statically
linked</li>
</ul>
</p>
</section>
</body>
</document>
¤ Dauer der Verarbeitung: 0.1 Sekunden
(vorverarbeitet)
¤
|
Haftungshinweis
Die Informationen auf dieser Webseite wurden
nach bestem Wissen sorgfältig zusammengestellt. Es wird jedoch weder Vollständigkeit, noch Richtigkeit,
noch Qualität der bereit gestellten Informationen zugesichert.
Bemerkung:
Die farbliche Syntaxdarstellung ist noch experimentell.
|
