Achieving true zero-copy with Iceoryx (Shared Memory)

Hi everyone, I've been trying to use this library with CycloneDDS and Iceoryx. I built both libraries from source and can verify everything works from examples & benchmarks.

However, I'm struggling to achieve true zero-copy for large messages (raw images; ~5 MiB/image, 24 Hz). This is my sample IDL:

module TestMessage {
    struct CameraImage {
        unsigned long width;
        unsigned long height;
        sequence<octet> image_data;
    };
};

Given a numpy array, I can use arr.to_bytes() to publish the message. However, it takes ~350 ms to do so:

msg_instance = CameraImage_type(
     width=arr.shape[1],
     height=arr.shape[0],
     image_data=arr.to_bytes()
)
self.writer.write(msg_instance)

Using np.ascontiguousarray() and memoryview, I can get it down to ~0.1 ms:

contiguous_arr = np.ascontiguousarray(image_np)
c_buffer = memoryview(contiguous_arr.data)

msg_instance = CameraImage_type(
    width=contiguous_arr.shape[1],
    height=contiguous_arr.shape[0],
    image_data=c_buffer
)
self.writer.write(msg_instance)

BUT it quickly fails (~30 calls) with this error:

Failed to encode member image_data, value is <memory at 0x72118cf35990>

I was guessing that Python garbage collection is not in tune with CycloneDDS & Iceoryx. So I tried keeping explicit references to the last 1000 references to both contiguous_arr and c_buffer in a collection.deque() - without success.

Is there another way of making this work?

Best
Fabian

Start at the CameraImage_type construction and writer.write(msg_instance) path, reproducing the memoryview case with the provided IDL and the failure after about 30 calls. Done means large image messages publish reliably without the encoding error, with the zero-copy behavior documented or bounded by the implementation.