Call for Discussion: New Project: CRaC

Vladimir Kozlov vladimir.kozlov at
Tue Jul 27 17:07:56 UTC 2021

The HotSpot group will participate in sponsoring this project.

Vladimir Kozlov

On 7/18/21 7:48 AM, Anton Kozlov wrote:
> Hi,
> It's been a while since we presented Coordinated Restore at Checkpoint for the
> first time [0].  We are still committed to the idea and researching this topic.
> Java applications can avoid the long start-up and warm-up by saving the state
> of the Java runtime (snapshot, checkpoint).  The saved state is then used to
> start instances fast (restored).  But after the state was saved, the execution
> environment could change.  Also, if multiple instances are started from the
> saved state simultaneously, they should obtain some uniqueness, and their
> executions should diverge at some point.
> We believe that the practical way to solve these problems is to make Java
> applications aware of when the state is saved and restored.  Then an
> application will be able to handle environmental changes.  The application will
> also be able to obtain uniqueness from the environment.
> The CRaC project aims to research Java API for coordination between application
> and runtime to save and restore the state.  Runtime should support multiple
> ways to save the state: virtual machine snapshot, container snapshot, CRIU
> project on Linux, etc.  We hope to come with an API that is general enough for
> any underlying mechanism.  We also plan to explore safety checks in the API and
> runtime, which prevent saving the state if it may not be restored or work
> correctly after the restore.
> I propose myself as a Project Lead of the CRaC Project.  If you're interested
> or want to be the committer, please drop me a message.
> A fork of JDK [1] would be a starting point of this project.
> Thanks,
> Anton
> [0]
> [1]

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