Going native with spring GraalVM native image support

The Why

To improve application loading times and reduce memory footprint, we can use GraalVM to generate self-contained JARs that do not require the presence of a JVM on the target environment.

These JARs are particularly valuable when targeting dockerized environments.

Prerequisites

It will be necessary to have a JVM compatible with native compilation. At the time of writing this article, we will use the following version (cmd java -version):

openjdk version "20.0.1" 2023-04-18
OpenJDK Runtime Environment Liberica-NIK-23.0.0-1 (build 20.0.1+10)
OpenJDK 64-Bit Server VM Liberica-NIK-23.0.0-1 (build 20.0.1+10, mixed mode, sharing)

You can easily switch between different JVM versions and update them as needed using a very handy tool, SDKMAN!. After following the installation procedure (https://sdkman.io/install):

# Will install the Liberica Native Image Kit JDK 20
sdk install java 23.r20-nik

# Will set this version as default on future terminal and session opening for this user
sdk default java 23.r20-nik

# Will use this version in the current terminal
sdk use java 23.r20-nik

# To confirm the version
java -version

Build Gradle

In the build.gradle.kts file in the plugins part we need to add this line:

id("org.graalvm.buildtools.native") version "0.9.27"

In the terminal, running this command in the root of the project will launch the native compilation:

gradle nativeCompile

It can take a while but in the end:

BUILD SUCCESSFUL in 3m 20s
9 actionable tasks: 1 executed, 8 up-to-date

Note the message that display where is stored our native image:

Produced artifacts:
 /myWorkspace/my-project/build/native/nativeCompile/my-app (executable)

If everything goes right we can launch our app with this command in the terminal:

/myWorkspace/my-project/build/native/nativeCompile/my-app

It will display something like that :

2023-10-20T10:52:48.995+02:00  INFO 82280 --- [           main] com.company.myapp.MtSftpApplicationKt   : Starting AOT-processed MtSftpApplicationKt using Java 20.0.1 with PID 82280 (/myWorkspace/my-project/build/native/nativeCompile/my-app started by myUser in /myWorkspace/my-project)
2023-10-20T10:52:48.995+02:00  INFO 82280 --- [           main] com.company.myapp.MtSftpApplicationKt   : No active profile set, falling back to 1 default profile: "default"
2023-10-20T10:52:49.009+02:00  INFO 82280 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)
2023-10-20T10:52:49.010+02:00  INFO 82280 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2023-10-20T10:52:49.010+02:00  INFO 82280 --- [           main] o.apache.catalina.core.StandardEngine    : Starting Servlet engine: [Apache Tomcat/10.1.13]
2023-10-20T10:52:49.016+02:00  INFO 82280 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2023-10-20T10:52:49.016+02:00  INFO 82280 --- [           main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 20 ms
2023-10-20T10:52:49.034+02:00  INFO 82280 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2023-10-20T10:52:49.034+02:00  INFO 82280 --- [           main] com.company.myapp.MtSftpApplicationKt   : Started MtSftpApplicationKt in 0.05 seconds (process running for 0.053)

Note the startup time:

Started MtSftpApplicationKt in 0.05 seconds (process running for 0.053)

A previous run on the same rig without native:

Started MtSftpApplicationKt in 1.652 seconds (process running for 2.021)

On the memory side :

Native 93 MB
Classic 172 MB

It's quite an improvement.

	Native	Classic	Gain
Startup	50ms	1652ms	97%
Memory	93MB	172MB	46%

These metrics are taken immediately after the service starts.