Exploring Spring Boot with CraC

Table of Contents

• Setup the environment
  • Installing a JDK with support for CRaC:
  • install the JDK with CRaC support via SDKMAN
• Grant permissions to run CRIU
• Build the application
• Start and initialize the MySQL database+
• Start the application without any CRaC
• Start the application and create a checkpoint manually after application startup
• Create the manual checkpoint
• Restore the application from the manually created checkpoint

Setup the environment

Installing a JDK with support for CRaC:

Download and install the JDK with CRaC support

1. Download the JDK with CRaC support from Azul Zulu website:

   • Azul Zulu 22.0.1 + CRaC X64

   • Azul Zulu 22.0.1 + CRaC AARCH64

2. Unpack the tar.gz file and copy the JDK in a folder

   sudo tar zxvf zulu22.30.13-ca-crac-jdk22.0.1-linux_x64.tar.gz

3. Move to the folder where the JDK installation will be located

   mv zulu22.30.13-ca-crac-jdk22.0.1-linux_x64 zulu-22.jdk
   mv zulu-22.jdk /usr/lib/jvm

4. Set the $JAVA_HOME environment variable to the JDK with CRaC support e.g.

   export JAVA_HOME=/usr/lib/jvm/zulu-22.jdk

install the JDK with CRaC support via SDKMAN

• Install a JDK with CRaC support via SDKMAN:

  sdk install java 22.0.1.crac-zulu

Grant permissions to run CRIU

1. Make sure you have the permissions to run CRIU:

   sudo chown root:root $JAVA_HOME/lib/criu

   sudo chmod u+s $JAVA_HOME/lib/criu

Build the application

1. Open the project folder and run:

   ./mvnw verify

2. Now you should find the spring-with-crac-0.0.1-SNAPSHOT.jar jar at target/ directory

3. Create a folder named tmp_manual_checkpoint in the project folder (besides the src folder)

Start and initialize the MySQL database+

sh create-manual-checkpoint.sh <target/spring-with-crac-0.0.1-SNAPSHOT.jar or PID>

1. Start the MySQL database using Docker Compose

   docker compose up -d

Start the application without any CRaC

1. Start the application normally

   ./mvnw spring-boot:run

Note	A checkpoint can also be compressed (only in Azul Zulu) on the hard drive by executing: export CRAC_CRIU_OPTS=--compress

There is a shell script for starting up the app with CRaC support:

• start-manual-crac.sh

So you simply have to un-comment it in this shell script. Be aware that the compression at checkpoint and decompression at restoring will take longer. Meaning to say the restore will be slower when using a compressed checkpoint (on my machine used here it takes around 150ms to de-compress the checkpoint)

Start the application and create a checkpoint manually after application startup

1. Make sure the folder tmp_manual_checkpoint exists

2. Remove all files from the folder tmp_manual_checkpoint with:

   rm -f ./tmp_manual_checkpoint/*.*

3. Start the application

   sh start-manual-crac.sh

Create the manual checkpoint

There are two ways of creating the checkpoint manually, calling the application jar or the pid

1. Calling the application jar

   jcmd target/spring-with-crac-0.0.1-SNAPSHOT.jar JDK.checkpoint

   or executing the create-manual-checkpoint.sh script with the PID (can be found in the output in the 1st shell window)

   sh create-manual-checkpoint.sh target/spring-with-crac-0.0.1-SNAPSHOT.jar

   OR

   sh create-manual-checkpoint.sh <PID>

2. Check if the checkpoint files have been stored in ./tmp_manual_checkpoint

Restore the application from the manually created checkpoint

1. Restore the application from the stored checkpoint by executing

   sh restore-manual-crac.sh