Micronaut CRaC

Adds support for CRaC (Coordinated Restore at Checkpoint) to the Micronaut Framework.

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1 Introduction

This Micronaut module adds support for CRaC (Coordinated Restore at Checkpoint) within the framework.

2 Release History

For this project, you can find a list of releases (with release notes) here:

https://github.com/micronaut-projects/micronaut-crac/releases

3 Installation

Add the following the dependency to your build:

implementation("io.micronaut.crac:micronaut-crac")

<dependency>
    <groupId>io.micronaut.crac</groupId>
    <artifactId>micronaut-crac</artifactId>
</dependency>

4 Resources

To provide CRaC resources, create beans of type OrderedResource.

Micronaut CRaC registers resources for you into the CRaC Context. You just focus on providing implementations for OrderedResource::beforeCheckpoint and OrderedResource::afterRestore in your resources.

Micronaut CRaC registers resources in order. You can control the order by overriding OrderedResource::getOrder.

5 Refresh scope

Prior to a checkpoint being taken, a RefreshEvent will be published to invalidate all beans in the @Refreshable scope.

This behaviour can be disabled by setting the crac.refresh-beans property to false in the application config.

6 Events

To notify external components when the default Resource handlers execute, there are two events; BeforeCheckpointEvent and AfterRestoreEvent. These events contain the java.time.Instant that the action completed, the length of time it took to execute the action in nanoseconds, and the Resource that was acted upon.

Please see the Micronaut Framework guide for information on how to listen for these events.

7 Context Provider

GlobalCracContextProvider, Micronaut CRaC’s default implementation of CracContextProvider, returns the global context. You can provide a replacement for CracContextProvider and provide your custom Context.

8 Docker Support

Support for building CRaC-enabled Docker images is provided by the Micronaut Gradle or Maven plugin. Either one is capable of generating a docker image containing a CRaC enabled JDK and a pre-warmed, checkpointed application.

9 Repository

You can find the source code of this project in this repository:

https://github.com/micronaut-projects/micronaut-crac

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