Implementation:Ray project Ray UnreconstructableException

Knowledge Sources	Ray
Domains	Distributed_Computing, Java_API
Last Updated	2026-02-13 16:00 GMT

Overview

Exception class indicating that a Ray object is lost and cannot be reconstructed, provided by the Ray Java API.

Description

UnreconstructableException extends RayException and is thrown when an object has been lost (either evicted from the object store or explicitly deleted) and cannot be reconstructed by re-running its creating task. This exception only applies to actor objects: if an actor's current state is after the object's creating task, the actor cannot re-run the task to reconstruct the object. The exception stores the ObjectId of the lost object.

Usage

This exception is thrown by the Ray runtime when attempting to retrieve a lost object. Catch it in application code to handle cases where actor state prevents task replay, and the object must be recomputed through other means.

Code Reference

Source Location

• Repository: Ray
• File: java/api/src/main/java/io/ray/api/exception/UnreconstructableException.java

Signature

public class UnreconstructableException extends RayException {
    public ObjectId objectId;
    public UnreconstructableException(ObjectId objectId);
    public UnreconstructableException(String message);
    public UnreconstructableException(String message, Throwable cause);
}

Import

import io.ray.api.exception.UnreconstructableException;

I/O Contract

Inputs

Name	Type	Required	Description
objectId	ObjectId	Yes	Identifier of the lost object that cannot be reconstructed
message	String	No	Custom error message (alternative constructor)
cause	Throwable	No	The underlying cause of the exception

Outputs

Name	Type	Description
exception	UnreconstructableException	Exception instance identifying the lost object

Usage Examples

ObjectRef<byte[]> dataRef = actor.task(MyActor::generateData).remote();

try {
    byte[] data = dataRef.get();
} catch (UnreconstructableException e) {
    System.err.println("Object " + e.objectId + " is lost and cannot be reconstructed.");
    // Recompute the data through alternative means
    dataRef = actor.task(MyActor::generateData).remote();
}

Related Pages

• Environment:Ray_project_Ray_Java_Build_Environment