CRaCing Java Snapshots

What if you could launch a fully warmed-up Java application in milliseconds? Discover how CRaC snapshots make it possible.

#1about 1 minute

The problem of slow Java application startup times

Slow application startups can hinder development and deployment, especially when fast rollbacks are needed.

#2about 3 minutes

Introducing CRIU for process snapshotting in Linux

Checkpoint/Restore In Userspace (CRIU) is a Linux utility that can snapshot a running process's memory to disk for later restoration.

#3about 2 minutes

Understanding the limitations of generic CRIU with complex apps

Generic CRIU can fail to correctly restore complex applications like htop or a JVM because it lacks application-specific state awareness.

#4about 3 minutes

Introducing CRaC as a JVM-specific solution for fast startups

Coordinated Restore at Checkpoint (CRaC) is a Linux-only, JVM-aware technology built on CRIU that enables near-instant application startup.

#5about 4 minutes

Creating a basic CRaC snapshot using Docker

To create a CRaC snapshot in Docker, you need a CRaC-enabled JDK and specific container capabilities like cap_sys_ptrace and cap_checkpoint_restore.

#6about 3 minutes

Using JCMD to trigger a checkpoint and restore an image

The jcmd utility triggers the checkpoint on a running Java process, and the resulting container state is committed to a new image for fast restoration.

#7about 3 minutes

Applying CRaC to a real-world Spring Boot application

Spring Boot 3.2 and later have built-in support for CRaC, allowing you to snapshot and restore complex applications like Spring PetClinic.

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Handling custom resources and open connections for CRaC

For resources like network connections that CRaC doesn't manage, implement the Resource interface with beforeCheckpoint and afterRestore methods to handle state correctly.

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Summary of the CRaC workflow and key takeaways

The workflow involves building a JAR, running it with checkpoint flags, triggering the snapshot with jcmd, committing the image, and managing custom resources.