How to Supercharge Spring Boot 3.2 Startup with CRaC Checkpointing

Introduction

Spring 6.1 and Spring Boot 3.2 fully support CRaC (Coordinated Restore at Checkpoint), an OpenJDK project that can snapshot a running JVM—including the application state—to disk and later restore it almost instantly.

Prerequisites

A CRaC‑compatible JVM (e.g., Azul Zulu 21.0.1+ CRaC)

The org.crac JAR dependency

A writable directory for checkpoint files

Installation

Install Azul Zulu 21.0.1+ CRaC from Azul . On Linux, grant the necessary permissions for CRIU:

sudo chown root:root $JAVA_HOME/lib/criu
sudo chmod u+s $JAVA_HOME/lib/criu

Add the CRaC dependency to your project:

<dependency>
  <groupId>org.crac</groupId>
  <artifactId>crac</artifactId>
  <version>1.4.0</version>
</dependency>

Baseline Test

Running the Spring Boot Petclinic demo on JDK 17 vs. JDK 21 reduces startup time by about 500 ms. Launch the application with: java -jar spring-petclinic-3.2.0.jar The baseline startup takes roughly 4 seconds.

Automatic Checkpoint

Enable automatic checkpointing by setting the JVM system property -Dspring.context.checkpoint=onRefresh. The checkpoint is created after the LifecycleProcessor.onRefresh phase, before the ContextRefreshedEvent is published.

java -Dspring.context.checkpoint=onRefresh -XX:CRaCCheckpointTo=./tmp_checkpoint -jar spring-petclinic-3.2.0.jar

After the application exits, the checkpoint files reside in ./tmp_checkpoint. Restore the application with: java -XX:CRaCRestoreFrom=./tmp_checkpoint Restored startup time improves by an order of magnitude.

Manual Checkpoint

For even faster restarts, create a checkpoint manually after the application is fully warmed up:

java -XX:CRaCCheckpointTo=./tmp_checkpoint -jar spring-petclinic-3.2.0.jar

In a second shell, trigger the checkpoint: jcmd spring-petclinic-3.2.0.jar JDK.checkpoint Verify the checkpoint files in ./tmp_checkpoint, then restore with the same -XX:CRaCRestoreFrom command. Manual checkpoints include both framework and application code, yielding the fastest startup.

Special Notes

Spring Boot 3.2 requires no code changes to use CRaC; the framework handles resource shutdown before the checkpoint and reopens them after restore. For other frameworks, implement the CRaC Resource interface and manage resources in beforeCheckpoint() and afterRestore().

Conclusion

Using CRaC with Spring Boot 3.2 can reduce startup time by an order of magnitude without modifying application code, offering a simpler alternative to GraalVM Native Image while still benefiting from JVM‑level optimizations.