[Question] About the usage of shared memory in docker

Hi,

I'm trying to setup environment and other thins to be able to transfer messages using shared memory. First of all, here is my Image class:

Image class

@dataclass
class MainCameraImage(IdlStruct):
    img: array[uint8, 4147200]
    shape: array[uint64, 3]

    @classmethod
    def from_numpy(cls, img):
        assert len(img.shape) == 3
        seq_img = img.tobytes()
        return MainCameraImage(seq_img, tuple(img.shape))


    def to_numpy(self):
        shape = self.shape
        return np.frombuffer(self.img, dtype=np.uint8).reshape(shape)

Note that image array has a fixed size. Then I implement publisher and subscriber:

Publisher

import cv2
import time
import numpy as np

import fire

from cyclonedds.core import Listener, Qos, Policy
from cyclonedds.util import duration
from cyclonedds.internal import dds_infinity
from cyclonedds.domain import DomainParticipant
from cyclonedds.topic import Topic
from cyclonedds.pub import DataWriter


from dds_data_structures import MainCameraImage, Image, CameraState,DeviceState


def stream(dev=0, resize_to=None, output_topic_names=['camera_images', 'camera_images_vis', 'camera_images_clr'],
            data_type='MainCameraImage', cap_gstreamer=True):
    data_type = MainCameraImage
    participant = DomainParticipant(0)

    writers = []

    # unknown, disabled, enabled, error
    qos = Qos(
        # livelines: automatic
        # deadline: dds_infinity
        # reliability: reliable
        # durability: volatile
        # history: keep last
        Policy.Liveliness.Automatic(lease_duration=duration(seconds=10)),
        Policy.Deadline(deadline=dds_infinity),
        Policy.Reliability.Reliable(max_blocking_time=duration(seconds=1)),
        Policy.Durability.Volatile,
        Policy.History.KeepLast(1)
    )

    for topic_name in output_topic_names:
        topic_out = Topic(participant, topic_name, data_type)
        writers.append(DataWriter(participant, topic_out, qos))

    frame = np.random.randint(0, 256, (1280, 1080, 3), dtype=np.uint8)
    print(frame.shape, frame.dtype)

    while True:
        time_start = time.time()
        ret, frame = 1, frame
        if not ret:
            print('Error: Unable to read frame')
            
            break
        if resize_to is not None:
            frame = cv2.resize(frame, resize_to[::-1])
        for writer in writers:
            writer.write(data_type.from_numpy(frame))
        
        loop_time = time.time() - time_start
        print(f'Streaming Camera with topic {output_topic_names[0]}, {loop_time=}', end='\r')


if __name__ == '__main__':
    fire.Fire(stream)

Subscriber

import cv2
import time
import numpy as np

import fire

from cyclonedds.core import Listener, Qos, Policy
from cyclonedds.util import duration
from cyclonedds.internal import dds_infinity
from cyclonedds.domain import DomainParticipant
from cyclonedds.topic import Topic
from cyclonedds.sub import DataReader


from dds_data_structures import MainCameraImage


def receive(topic_name='camera_images'):
    data_type = MainCameraImage
    participant = DomainParticipant(0)

    qos = Qos(
        # livelines: automatic
        # deadline: dds_infinity
        # reliability: reliable
        # durability: volatile
        # history: keep last
        Policy.Liveliness.Automatic(lease_duration=duration(seconds=10)),
        Policy.Deadline(deadline=dds_infinity),
        Policy.Reliability.Reliable(max_blocking_time=duration(seconds=1)),
        Policy.Durability.Volatile,
        Policy.History.KeepLast(1)
    )

    topic_in = Topic(participant, topic_name, data_type)
    reader = DataReader(participant, topic_in, qos)

    while True:
        time_start = time.time()
        img = reader.read()
        if len(img) == 0:
            continue
        img = img[0].to_numpy()
        loop_time = time.time() - time_start
        print(f'Received img {img.shape=}, {loop_time=}', end='\r')


if __name__ == '__main__':
    fire.Fire(receive)

I've checked the requirements to the QoS for both publisher and subscriber here (as far as I can see they should be identical).

Next step I'm running iceoryx roudi in one docker container with --net=host --ipc=host -v /dev:/dev -v /tmp:/tmp. I also set the environment variable CYCLONEDDS_URI to the config file. I'm using default config file:

CYclonedds uri config


<?xml version="1.0" encoding="UTF-8" ?>
<CycloneDDS xmlns="https://cdds.io/config" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="https://cdds.io/config https://raw.githubusercontent.com/eclipse-cyclonedds/cyclonedds/master/etc/cyclonedds.xsd">
    <Domain Id="any">
        <General>
            <Interfaces>
                <NetworkInterface autodetermine="true" priority="default" multicast="default" />
            </Interfaces>
            <AllowMulticast>default</AllowMulticast>
        </General>
        <SharedMemory>
            <Enable>true</Enable>
            <LogLevel>info</LogLevel>
        </SharedMemory>
    </Domain>
</CycloneDDS>

Finally I run above scripts in the docker containers with the same net and ipc options. They work fine and subscriber receives messages from publisher. What I'm trying to understand:

How to make sure that messages are being sent via shared memory?
ipcs -m shows only firefox and vs code processes (I've checked pids via `ps -p ). Should my subscriber and publisher be there if everything works as expected?

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