How would I give the GWT-compiler more memory when using GWT-Maven?

Question

We have a Maven build that runs the GWT plugin (gwt-maven). Unfortently it is running out of memory.

Do I need to give Maven itself more heap or do I need to give GWT more heap? Any idea how to specify this for a pom.xml file?

Answer 1

I assume extraJvmArgs option should be configured.

Answer 2

Add extraJvmArgs tag under configuration tag for gwt-maven-plugin.

Example -

        <!-- GWT Maven Plugin -->
        <plugin>
            <groupId>org.codehaus.mojo</groupId>
            <artifactId>gwt-maven-plugin</artifactId>
            <dependencies>
                <dependency>
                    <groupId>com.google.gwt</groupId>
                    <artifactId>gwt-user</artifactId>
                    <version>${gwtVersion}</version>
                </dependency>
                <dependency>
                    <groupId>com.google.gwt</groupId>
                    <artifactId>gwt-dev</artifactId>
                    <version>${gwtVersion}</version>
                </dependency>
                <dependency>
                    <groupId>com.google.gwt</groupId>
                    <artifactId>gwt-servlet</artifactId>
                    <version>${gwtVersion}</version>
                </dependency>
            </dependencies>
            <!-- JS is only needed in the package phase, this speeds up testing -->
            <executions>
                <execution>
                    <phase>prepare-package</phase>
                    <goals>
                        <goal>compile</goal>
                    </goals>
                </execution>
            </executions>
            <!-- Plugin configuration. There are many available options, see gwt-maven-plugin 
                documentation at codehaus.org -->
            <configuration>
                <runTarget>app.html</runTarget>
                <!-- Turning This on after understanding soyc and when deferredjs count is 48.cache.js -->
                <!-- https://developers.google.com/web-toolkit/articles/fragment_merging -->
                <fragmentCount>25</fragmentCount>
                -->
                <!-- Ask GWT to create the Story of Your Compile (SOYC) (gwt:compile) -->
                <!-- Turn This on for generating soyc. This does not work if closure compiler is turned on.-->
                <!-- Start Generating SOYC -->
                <compileReport>true</compileReport>
                <compilerMetrics>true</compilerMetrics>
                <soycDetailed>true</soycDetailed>
                <!-- End Generating SOYC -->
                <disableCastChecking>true</disableCastChecking>
                <disableClassMetadata>true</disableClassMetadata>
                <enableClosureCompiler>true</enableClosureCompiler>
                <optimizationLevel>9</optimizationLevel>
                <style>${gwt.style}</style>
                <module>${gwtModule}</module>
                <encoding>${project.build.sourceEncoding}</encoding>
                <strict>true</strict>
                <logLevel>INFO</logLevel>
                <copyWebapp>true</copyWebapp>
                <hostedWebapp>
                    ${project.build.directory}/${project.artifactId}
                </hostedWebapp>
                <extraJvmArgs>-Xmx896M -Xms896m -XX:PermSize=64m -XX:MaxPermSize=128m</extraJvmArgs>
                <!-- <extraJvmArgs>-Xmx896M -Xms896m -XX:PermSize=64m -XX:MaxPermSize=128m -XX:+UseConcMarkSweepGC -server</extraJvmArgs> -->
            </configuration>
        </plugin>

Answer 3

I had this error with a large GWT project. The error that you will probably see when running out of memory is:

[ERROR] OutOfMemoryError: Increase heap size of lower gwt.jjs.maxThreads
java.lang.OutOfMemoryError: Java heap space

The extraJvmArgs option needs to be set in conjunction with the MAVEN_OPTS environment variable (this is a possible explanation). I also set the Java -Dgwt.compiler.localWorkers=x option to reduce the number of concurrent compilation threads (I set x to 1, but you can play with it to find something that works).

For an example of the settings you should use with the extraJvmArgs option, see this post.

Note that you may need to add the extraJvmArgs option to the plugin element configuration directly - see https://stackoverflow.com/a/5822929/157605.