ros2dds plugin Zenoh publications not delivered to remote_api WebSocket subscribers (v1.9.0)

[robertvandervoort]

Summary

When zenoh-plugin-ros2dds and zenoh-plugin-remote-api are loaded in the same zenohd v1.9.0 router, DDS-originated publications bridged into the Zenoh key-space by the ros2dds plugin never reach subscribers declared via the remote_api WebSocket interface. The reverse direction (WS → Zenoh → ros2dds → DDS) works correctly.

Environment

Component	Version
zenohd	1.9.0 (rustc 1.93.0)
zenoh-plugin-ros2dds	bundled .so from eclipse/zenoh:1.9.0 image
zenoh-plugin-remote-api	bundled .so from same image
@eclipse-zenoh/zenoh-ts	1.9.0 (npm)
ROS 2 distro	Jazzy
RMW	rmw_cyclonedds_cpp
Platform	NVIDIA Jetson AGX Thor, Linux 6.8 aarch64
Deployment	Docker Compose (zenohd, audio/ROS2 node, web/Node.js containers)

zenohd configuration (zenohd.json5)

{
  mode: "router",
  listen: { endpoints: ["tcp/0.0.0.0:7447"] },
  scouting: { multicast: { enabled: false }, gossip: { enabled: false } },
  plugins: {
    ros2dds: {
      __path__: "/libzenoh_plugin_ros2dds.so",
      domain: 0,
      namespace: "/",
      allow: {
        publishers:      ["/chip/.*"],
        subscribers:     ["/chip/.*"],
        service_servers: ["/chip/.*"],
        service_clients: ["/chip/.*"],
        action_servers:  ["/chip/.*"],
        action_clients:  ["/chip/.*"],
      },
    },
    remote_api: {
      __path__: "/libzenoh_plugin_remote_api.so",
      websocket_port: "0.0.0.0:10000",
    },
  },
}

What works

Path	Direction	Status
WS client A publishes → WS client A subscriber	same-session	works
WS client B publishes → WS client A subscriber	cross-session	works
WS client publishes chip/audio/config → ros2dds Route Subscriber → ROS2 node receives	Zenoh → DDS	works

What does NOT work

Path	Direction	Status
ROS2 node publishes /chip/audio/utterance → ros2dds Route Publisher → Zenoh key chip/audio/utterance → remote_api WS subscriber	DDS → Zenoh → WS	broken — handler never fires

This applies to all topics bridged by ros2dds, not just one. A wildcard subscriber on chip/audio/** receives zero DDS-bridged samples while receiving self-published and cross-session WS-published samples correctly.

zenohd logs confirm routes are created

INFO zenoh_plugin_ros2dds: Node /audio_node declares Publisher /chip/audio/utterance: std_msgs/msg/String - Allowed
INFO zenoh_plugin_ros2dds::routes_mgr: Route Publisher (ROS:/chip/audio/utterance -> Zenoh:chip/audio/utterance) created

The ROS2 node is actively publishing (confirmed via application logs showing wake-word fires and utterance storage), but zero samples reach any WS subscriber.

Minimal reproduction script (zenoh-ts, runs inside the web container)

import { Config, Session } from '@eclipse-zenoh/zenoh-ts';

// Session A: subscriber
const sessionA = await Session.open(new Config('ws/zenohd:10000'));
let fromDDS = 0, fromWS = 0;

await sessionA.declareSubscriber('chip/audio/**', {
  handler: (sample) => {
    fromDDS++; // should increment when ROS2 node publishes
    console.log('GOT SAMPLE, payload size:', sample.payload().toBytes().length);
  }
});

// Session B: publish via WS (simulates non-DDS traffic)
const sessionB = await Session.open(new Config('ws/zenohd:10000'));
const pub = await sessionB.declarePublisher('chip/audio/utterance');
await pub.put(new TextEncoder().encode('{"test":"from_ws"}'));
fromWS++; // will be received by Session A

await new Promise(r => setTimeout(r, 15000));
// During this 15s window, the ROS2 node published multiple messages on
// /chip/audio/utterance (confirmed in its logs).

console.log('From WS:', fromWS, 'From DDS bridge:', fromDDS);
// Output: From WS: 1  From DDS bridge: 0
// Expected: From DDS bridge: >0

Result: fromDDS stays 0 despite active ROS2 publishers. fromWS correctly increments from the cross-session WS publish.

Hypothesis

The ros2dds plugin's internal Zenoh publisher (created for each Route Publisher) either:

1. Does not propagate its publications through the router to remote_api plugin subscribers, or
2. The remote_api plugin's subscription declarations don't register as "matching" with the ros2dds plugin's publishers, so the plugin never forwards DDS data into the Zenoh key-space

The asymmetry (Zenoh→DDS works but DDS→Zenoh→WS doesn't) suggests the issue is in how the ros2dds plugin's publications interact with the router's forwarding to the remote_api plugin, rather than a DDS discovery or QoS problem.

Workaround

Direct HTTP POST from the ROS2 container to the WebSocket client's HTTP backend, bypassing the Zenoh data plane for this message type.

Cross-reference

The remote_api plugin lives in eclipse-zenoh/zenoh-ts. The bug may originate there rather than in ros2dds — filing here since the ros2dds plugin is the publication source.