Implementation:Ray project Ray MessagePackSerializer Encode

Knowledge Sources	Ray MessagePack
Domains	Serialization, Cross_Language_Interop
Last Updated	2026-02-13 17:00 GMT

Overview

Concrete tool for encoding Java objects into MessagePack binary format for cross-language transport provided by the Ray Java runtime.

Description

MessagePackSerializer.encode() converts a Java object to a byte array using MessagePack format. The first 9 bytes are reserved for a length header. The method returns a Pair<byte[], Boolean> where the boolean indicates cross-language compatibility. Supported types produce standard MessagePack values (isCrossLanguage=true). Unsupported types fall back to FST serialization with extension type 101 (isCrossLanguage=false).

Usage

Used internally by the Ray runtime during task argument serialization. Not typically called directly.

Code Reference

Source Location

• Repository: ray-project/ray
• File: java/runtime/src/main/java/io/ray/runtime/serializer/MessagePackSerializer.java (L248-278)

Signature

public static Pair<byte[], Boolean> encode(Object obj)

Import

import io.ray.runtime.serializer.MessagePackSerializer;

I/O Contract

Inputs

Name	Type	Required	Description
obj	Object	Yes	The Java object to serialize. Supported cross-language types: Boolean, Byte, Short, Integer, Long, BigInteger, Float, Double, String, byte[], arrays, null.

Outputs

Name	Type	Description
result	Pair<byte[], Boolean>	Serialized bytes and isCrossLanguage flag

Usage Examples

Automatic Serialization During Cross-Language Calls

import io.ray.api.Ray;
import io.ray.api.function.PyFunction;

// Arguments are automatically serialized via MessagePack
// String, int, and other primitives are cross-language compatible
ObjectRef<Integer> result = Ray.task(
    PyFunction.of("math_module", "add", Integer.class),
    3,  // auto-serialized via MessagePack
    4   // auto-serialized via MessagePack
).remote();

Related Pages

Implements Principle

• Principle:Ray_project_Ray_Cross_Language_Serialization

Requires Environment

• Environment:Ray_project_Ray_Java_Build_Environment