breun/crac-demo

CRaC Demo

This is a demo for using CRaC to checkpoint and restore a containerized Spring Boot application on an Apple Silicon device.

How this project was set up

1. Create a new Spring Boot 3.2.3 WebMVC project.
2. Add org.crac:crac dependency.
3. Add a simple REST controller.

Build image

Build application:

./mvnw clean verify

Build application image:

docker build --file Dockerfile-checkpoint-image --tag crac-demo:checkpoint .

Create checkpoint

Create a fresh directory for the CRaC checkpoint files:

mkdir -p crac-files

Start container for checkpoint:

docker run \
    --cap-add=CHECKPOINT_RESTORE \
    --cap-add=SYS_PTRACE \
    --rm \
    --name crac-demo-checkpoint \
    --publish 8080:8080 \
    --volume $PWD/crac-files:/crac-files \
    crac-demo:checkpoint \
    java -XX:CRaCCheckpointTo=/crac-files -jar /app/crac-demo.jar

Optionally interact with the application at http://localhost:8080/hello to warm it up.

Trigger a checkpoint:

docker exec crac-demo-checkpoint jcmd /app/crac-demo.jar JDK.checkpoint

The application and its container will be stopped, and you should see the checkpoint files in crac-files.

Create a restore image:

docker build --file Dockerfile-restore-image --tag crac-demo:restore .

You can remove the local crac-files now:

rm -rf crac-files

You can also remove the image that we used to create the restore image now:

docker rmi crac-demo:checkpoint

Restore from checkpoint

Start a new container that restores the application from the checkpoint:

docker run \
    --cap-add=SYS_RESOURCE \
    --rm \
    --name crac-demo \
    --publish 8080:8080 \
    crac-demo:restore \
    java -XX:CRaCRestoreFrom=/crac-files

This should start up really quickly and http://localhost:8080/hello should work again. 🚀