Using CRaC with SpringBoot 3.2: A Practical Guide and Performance Evaluation

Spring 6.1 and SpringBoot 3.2 fully support CRaC, an OpenJDK project that can snapshot a running JVM (including the application state) to disk and later restore it in milliseconds, dramatically speeding up application startup.

Prerequisites for using CRaC with SpringBoot 3.2 are a CRaC‑enabled JVM (e.g., Azul Zulu 21.0.1 + CRaC), the org.crac library, and a writable folder for storing checkpoints. On Linux you may need to adjust permissions for the CRIU binaries:

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

Add the org.crac dependency to your build: implementation 'org.crac:crac:1.4.0' or, for Maven:

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

Create a folder (e.g., /tmp_checkpoint) in the project directory to hold checkpoint files.

Running without CRaC : after cloning the Spring‑Petclinic repository, build it with ./gradlew clean build and start the jar with java -jar spring-petclinic-3.2.0.jar. Switching from JDK 17 to JDK 21 already reduces startup time by about 500 ms.

Automatic checkpoint : start the application with the JVM flag -Dspring.context.checkpoint=onRefresh and specify the checkpoint directory:

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

The framework creates a checkpoint during the onRefresh phase; restoring it later with java -XX:CRaCRestoreFrom=./tmp_checkpoint cuts the startup time by an order of magnitude without any code changes.

Manual checkpoint : start the app with -XX:CRaCCheckpointTo=./tmp_checkpoint, let it fully start, then in a second shell trigger a checkpoint: jcmd spring-petclinic-3.2.0.jar JDK.checkpoint After the checkpoint is created, restore the application using the same -XX:CRaCRestoreFrom flag, achieving a startup time of roughly 75 ms—two orders of magnitude faster than a cold start.

Because Spring 6.1/Boot 3.2 handle resource shutdown and restoration automatically, no code modifications are required for the automatic checkpoint path; manual checkpoints may need additional resource‑handling code.

Overall, CRaC can dramatically reduce SpringBoot startup latency: the automatic checkpoint provides a ten‑fold improvement, while a manually triggered checkpoint can bring startup down to tens of milliseconds.