arrow-message

arrow-message makes it possible to create a Message struct in Rust or Python and convert it into a single arrow::array::ArrayData without any copy. It's also possible to get back to the initial struct without any copy as well.

The resulting arrow::array::ArrayData can then be sent safely over the network, a mpsc channel or to a Python script thanks to the pyo3 crate and the pyarrow feature.

The project aims to be used in context where we want to send a single payload containing multiple large fields. Like a struct representing an image or a video frame. This is ideal for Robotics and AI applications.

Example

use arrow::array::*;
use arrow_message::prelude::*;

#[derive(Debug, ArrowMessage)]
enum Encoding {
    RGB8,
    RGBA8,
    BGR8,
    BGRA8,
}

#[derive(Debug, ArrowMessage)]
struct Metadata {
    name: Option<String>,
    width: u32,
    height: u32,
    encoding: Encoding,
}

#[derive(Debug, ArrowMessage)]
struct Image {
    data: UInt8Array,
    metadata: Option<Metadata>,
}

fn main() -> Result<()> {
    use miette::IntoDiagnostic;

    let image = Image {
        data: UInt8Array::from(vec![1, 2, 3]),
        metadata: Some(Metadata {
            name: Some("example".to_string()),
            width: 12,
            height: 12,
            encoding: Encoding::RGB8,
        }),
    };

    println!("{:?}", image);

    let arrow = ArrayData::try_from(image).into_diagnostic()?;
    let image = Image::try_from(arrow).into_diagnostic()?;

    println!("{:?}", image);

    Ok(())
}

You can see an expanded version without the Derive macro here, and a more complex example here.

A python version here

from pyarrow_message import ArrowMessage
from dataclasses import dataclass
from typing import Optional
from enum import Enum

import numpy as np


class Encoding(ArrowMessage, Enum):
    RGB8 = "RGB8"
    RGBA8 = "RGBA8"
    BGR8 = "BGR8"
    BGRA8 = "BGRA8"


@dataclass
class Metadata(ArrowMessage):
    name: Optional[str]
    width: np.uint32
    height: np.uint32
    encoding: Optional[Encoding]


@dataclass
class Image(ArrowMessage):
    data: np.ndarray
    metadata: Optional[Metadata]


def main():
    image = Image(
        data=np.array([1, 2, 3], dtype=np.uint8),
        metadata=Metadata(
            width=np.uint32(12),
            height=np.uint32(12),
            name="example",
            encoding=Encoding.RGB8,
        ),
    )

    print(image)
    arrow = image.to_arrow()
    image2 = Image.from_arrow(arrow)

    print(image2)


if __name__ == "__main__":
    main()

Just run examples

We use a justfile to run examples:

just example-derive-enum # rust enum_derive.rs example
just example-derive-inherit # python enum_inherit.py example

Features

• Fields supported

  • Primitive types
  • Optional Primitive Rust types
  • Arrow Arrays for Rust, Numpy Arrays for Python
  • Optional Arrow Arrays for Rust, Numpy Arrays for Python
  • Rust structs that implement ArrowMessage, Python dataclasses that inherit from ArrowMessage for Python
  • Rust simple enums that implement ArrowMessage for Rust, Python simple enums that inherit from ArrowMessage for Python
  • Optional structs/classes that implement/inherit ArrowMessage
  • Optional enums that implement/inherit ArrowMessage
  • Enums with variant that implements/inherit ArrowMessage? I don't think it's possible, as an ArrowMessage should know it's exact datatype layout at compile time (only Option that are represented as NullArray when on runtime the value is None)

• Operations supported

  • Into/From ArrayData
  • ArrayData Flattening

What's Next?

• Think about Vec/List support. is it possible and is it relevant?.
• Improved error handling and validation: too much panic! in arrow that we must catch.
• Make to python API fully Rust with PyO3 (may be hard because we use a lot of python runtime tricks)
• Enhanced documentation and examples
• Integration with other libraries and frameworks