How can I configure the heap size when starting a Spring Boot application with embedded Tomcat?

Question

I am trying to deploy a Spring Boot powered web app to production. The app is built with Spring Boot 1.0.1 and has the default Tomcat 7 embedded as application server. I want to allocate larger memory to the app when start the app with java -jar myapp.jar command line.

Should I use JVM parameter such as -Xms -Xmx or use environment variable such as JAVA_OPTS? I have tried to look for the answer in documentation or google it, but I did not get an answer. Can anyone give some hints?

Answer 1

If starting the application with the spring-boot plugin:

mvn spring-boot:run -Drun.jvmArguments="-Xmx512m" -Drun.profiles=dev

Otherwise if running java -jar:

java -Xmx512m -Dspring.profiles.active=dev -jar app.jar

Answer 2

Since this is specifically a Spring Boot question, I'd argue that a more useful answer than @DaveSyer's is this:

You can drop a .conf file in the same directory as your WAR file that is effectively a shell script.

For example,

$ ls
myapp.conf
myapp.war
$ cat myapp.conf
export JAVA_OPTS="-Xmx1024m -Xms256m"

Any configuration you do there will be run before the Spring Boot embedded Tomcat starts up. Personally, I version control a .conf.example file in my application itself and then drop a copy of it on each server I deploy to.

Of course, anything you set in that .conf file is overridable with command-line operations.

Answer 3

Just use whatever normal mechanism you would to set up the JVM. Documentation is available on the command line:

$ java -X
...
-Xms<size>        Set initial Java heap size
-Xmx<size>        Set maximum Java heap size
...

Answer 4

For Spring Boot 2, you have to specify the heap size in the pom.xml file as below:

<plugin>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-maven-plugin</artifactId>
    <configuration>
        <jvmArguments>-Xmx64m</jvmArguments>
    </configuration>
</plugin>

Answer 5

For Spring Boot 1, the Maven argument to specify in the plugin configuration is jvmArguments, and the user property is run.jvmArguments:

mvn spring-boot:run -Drun.jvmArguments="-Xms2048m -Xmx4096m"

For Spring Boot 2, the Maven argument to specify in the plugin configuration is also jvmArguments, but the user property is now spring-boot.run.jvmArguments:

mvn spring-boot:run -Dspring-boot.run.jvmArguments="-Xms2048m -Xmx4096m"

So if you use the plugin configuration way, both for Spring Boot 1 and 2 you can do that:

<plugin>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-maven-plugin</artifactId>
    <configuration>
        <jvmArguments>
            -Xms4048m
            -Xmx8096m
        </jvmArguments>
    </configuration>
</plugin>