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uxrce_dds: support multi-instance uORB topics (#26305)

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uxrce_dds: improve DDS to uORB multi-instance routing and docs

* Route single DDS topic to multiple uORB instances via message field
* Document route_field → instance mapping
* Allow subscriptions_demux without route_field
* Rename subscriptions_demux → subscriptions_multi
* Update docs (ROS 2 wording, version tip, minor fixes)
This commit is contained in:
Marco Hauswirth
2026-03-03 15:57:24 +01:00
committed by GitHub
parent 43aa8de22b
commit 7f5de5d141
5 changed files with 104 additions and 37 deletions
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22
Tools/msg/generate_msg_docs.py
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@@ -833,11 +833,9 @@ def generate_dds_yaml_doc(allMessageFiles, output_file = 'dds_topics.md'):
for message in data["subscriptions"]:
all_message_types.add(message['type'].split("::")[-1])
all_topics.add(message['topic'].split('/')[-1])
if data["subscriptions_multi"]: # There is none now
dds_markdown += "None\n"
for message in data["subscriptions_multi"]:
all_message_types.add(message['type'].split("::")[-1])
all_topics.add(message['topic'].split('/')[-1])
for message in (data.get("subscriptions_multi") or []):
all_message_types.add(message['type'].split("::")[-1])
all_topics.add(message['topic'].split('/')[-1])
for message in allMessageFiles:
all_messages_in_source.add(message.split('/')[-1].split('.')[0])
messagesNotExported = all_messages_in_source - all_message_types
@@ -874,13 +872,17 @@ Topic | Type| Rate Limit
dds_markdown += "\n## Subscriptions Multi\n\n"
if not data["subscriptions_multi"]: # There is none now
subscriptions_multi = data.get("subscriptions_multi") or []
if not subscriptions_multi:
dds_markdown += "None\n"
else:
print("Warning - we now have subscription_multi data - check format")
dds_markdown += "Topic | Type\n--- | ---\n"
for message in data["subscriptions_multi"]:
dds_markdown += f"{message['topic']} | {message['type']}\n"
dds_markdown += "Topic | Type | Route Field | Max Instances\n--- | --- | --- | ---\n"
for message in subscriptions_multi:
type = message['type']
px4Type = type.split("::")[-1]
route_field = f"`{message['route_field']}`" if 'route_field' in message else "-"
max_instances = message.get('max_instances', '-')
dds_markdown += f"{message['topic']} | [{type}](../msg_docs/{px4Type}.md) | {route_field} | {max_instances}\n"
if messagesNotExported:
# Print the topics that are not exported to DDS

39
docs/en/middleware/uxrce_dds.md
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@@ -522,10 +522,10 @@ subscriptions:
subscriptions_multi:
- topic: /fmu/in/vehicle_optical_flow_vel
type: px4_msgs::msg::VehicleOpticalFlowVel
...
- topic: /fmu/in/aux_global_position
type: px4_msgs::msg::AuxGlobalPosition
route_field: id # OPTIONAL: field used to demux into instances
max_instances: 4 # Required when route_field is set
```
@@ -546,27 +546,38 @@ Each (`topic`,`type`) pairs defines:
If provided, this option changes the ROS 2 topic name of the advertised uORB topic appending the instance number: `fmu/out/[uorb topic name][instance]` (plus eventual namespace and message version).
In the example above the final topic name would be `/fmu/out/vehicle_imu1`.
`subscriptions` and `subscriptions_multi` allow us to choose the uORB topic instance that ROS 2 topics are routed to: either a shared instance that may also be getting updates from internal PX4 uORB publishers, or a separate instance that is reserved for ROS2 publications, respectively.
`subscriptions` and `subscriptions_multi` allow us to choose the uORB topic instance that ROS 2 topics are routed to: either a shared instance that may also be getting updates from internal PX4 uORB publishers, or a separate instance that is reserved for ROS 2 publications, respectively.
Without this mechanism all ROS 2 messages would be routed to the _same_ uORB topic instance (because ROS 2 does not have the concept of [multiple topic instances](../middleware/uorb.md#multi-instance)), and it would not be possible for PX4 subscribers to differentiate between streams from ROS 2 or PX4 publishers.
Add a topic to the `subscriptions` section to:
- Create a unidirectional route going from the ROS2 topic to the _default_ instance (instance 0) of the associated uORB topic.
For example, it creates a ROS2 subscriber of `/fmu/in/vehicle_odometry` and a uORB publisher of `vehicle_odometry`.
- If other (internal) PX4 modules are already publishing on the same uORB topic instance as the ROS2 publisher, the instance's subscribers will receive all streams of messages.
The uORB subscriber will not be able to determine if an incoming message was published by PX4 or by ROS2.
- This is the desired behavior when the ROS2 publisher is expected to be the sole publisher on the topic instance (for example, replacing an internal publisher to the topic during offboard control), or when the source of multiple publishing streams does not matter.
- Create a unidirectional route going from the ROS 2 topic to the _default_ instance (instance 0) of the associated uORB topic.
For example, it creates a ROS 2 subscriber of `/fmu/in/vehicle_odometry` and a uORB publisher of `vehicle_odometry`.
- If other (internal) PX4 modules are already publishing on the same uORB topic instance as the ROS 2 publisher, the instance's subscribers will receive all streams of messages.
The uORB subscriber will not be able to determine if an incoming message was published by PX4 or by ROS 2.
- This is the desired behavior when the ROS 2 publisher is expected to be the sole publisher on the topic instance (for example, replacing an internal publisher to the topic during offboard control), or when the source of multiple publishing streams does not matter.
Add a topic to the `subscriptions_multi` section to:
- Create a unidirectional route going from the ROS2 topic to a _new_ instance of the associated uORB topic.
For example, if `vehicle_odometry` has already `2` instances, it creates a ROS2 subscriber of `/fmu/in/vehicle_odometry` and a uORB publisher on instance `3` of `vehicle_odometry`.
- Create a unidirectional route going from the ROS 2 topic to a _new_ instance of the associated uORB topic.
For example, if `vehicle_odometry` has already `2` instances, it creates a ROS 2 subscriber of `/fmu/in/vehicle_odometry` and a uORB publisher on instance `3` of `vehicle_odometry`.
- This ensures that no other internal PX4 module will publish on the same instance used by uXRCE-DDS.
The subscribers will be able to subscribe to the desired instance and distinguish between publishers.
- Note, however, that this guarantees separation between PX4 and ROS2 publishers, not among multiple ROS2 publishers.
In that scenario, their messages will still be routed to the same instance.
- Without `route_field`, this guarantees separation between PX4 and ROS 2 publishers, but not among multiple ROS 2 publishers. In that scenario, their messages will still be routed to the same instance.
- This is the desired behavior, for example, when you want PX4 to log the readings of two equal sensors; they will both publish on the same topic, but one will use instance 0 and the other will use instance 1.
<Badge type="tip" text="main (planned for: PX4 v1.18)" /> Optionally, add `route_field` and `max_instances` to demultiplex a single ROS 2 topic into multiple uORB instances based on a message field value:
- Each unique value of `route_field` is dynamically assigned to a separate uORB instance on first arrival, up to `max_instances`.
For example, a single `/fmu/in/aux_global_position` ROS 2 topic can be demultiplexed to up to 4 separate uORB instances of `aux_global_position`, with each unique `id` value mapped to its own instance.
- This allows multiple ROS 2 publishers to share a single DDS topic while PX4 subscribers can distinguish between them by subscribing to different uORB instances.
- `route_field` must be a field present in the message definition. `max_instances` is required when `route_field` is set and limits how many distinct sources can be demultiplexed simultaneously.
::: warning
The `subscriptions_multi` feature with `route_field` is currently only implemented in the uXRCE-DDS client.
The Zenoh bridge module does not yet support demux routing — topics listed under `subscriptions_multi` in `dds_topics.yaml` will be ignored by the Zenoh bridge.
:::
You can arbitrarily change the configuration.
For example, you could use different default namespaces or use a custom package to store the message definitions.

56
src/modules/uxrce_dds_client/dds_topics.h.em
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@@ -163,7 +163,20 @@ struct RcvTopicsPubs {
@[ end for]@
@[ for sub in subscriptions_multi]@
@[ if sub.get('route_field')]@
uORB::PublicationMulti<@(sub['simple_base_type'])_s> @(sub['topic_simple'])_pubs[@(sub['max_instances'])] {
@[ for idx in range(sub['max_instances'])]@
{ORB_ID(@(sub['topic_simple']))}@('' if idx == sub['max_instances']-1 else ',')
@[ end for]@
};
// Maps route_field values (arbitrary, not bounded to [0, max_instances)) to uORB instance indices
struct {
uint32_t assigned_ids[@(sub['max_instances'])] {};
uint8_t num_assigned {0};
} @(sub['topic_simple'])_demux;
@[ else]@
uORB::PublicationMulti<@(sub['simple_base_type'])_s> @(sub['topic_simple'])_pub{ORB_ID(@(sub['topic_simple']))};
@[ end if]@
@[ end for]@
uint32_t num_payload_received{};
@@ -179,7 +192,7 @@ static void on_topic_update(uxrSession *session, uxrObjectId object_id, uint16_t
pubs->num_payload_received += length;
switch (object_id.id) {
@[ for idx, sub in enumerate(subscriptions + subscriptions_multi)]@
@[ for idx, sub in enumerate(subscriptions)]@
case @(idx)+ (65535U / 32U) + 1: {
@(sub['simple_base_type'])_s data;
@@ -190,6 +203,38 @@ static void on_topic_update(uxrSession *session, uxrObjectId object_id, uint16_t
}
break;
@[ end for]@
@[ for idx, sub in enumerate(subscriptions_multi)]@
case @(idx + len(subscriptions))+ (65535U / 32U) + 1: {
@(sub['simple_base_type'])_s data;
if (ucdr_deserialize_@(sub['simple_base_type'])(*ub, data, time_offset_us)) {
//print_message(ORB_ID(@(sub['simple_base_type'])), data);
@[ if sub.get('route_field')]@
int instance = -1;
for (uint8_t i = 0; i < pubs->@(sub['topic_simple'])_demux.num_assigned; i++) {
if (pubs->@(sub['topic_simple'])_demux.assigned_ids[i] == data.@(sub['route_field'])) {
instance = i;
break;
}
}
if (instance < 0 && pubs->@(sub['topic_simple'])_demux.num_assigned < @(sub['max_instances'])) {
instance = pubs->@(sub['topic_simple'])_demux.num_assigned++;
pubs->@(sub['topic_simple'])_demux.assigned_ids[instance] = data.@(sub['route_field']);
}
if (instance >= 0) {
pubs->@(sub['topic_simple'])_pubs[instance].publish(data);
}
@[ else]@
pubs->@(sub['topic_simple'])_pub.publish(data);
@[ end if]@
}
}
break;
@[ end for]@
default:
@@ -200,13 +245,20 @@ static void on_topic_update(uxrSession *session, uxrObjectId object_id, uint16_t
bool RcvTopicsPubs::init(uxrSession *session, uxrStreamId reliable_out_stream_id, uxrStreamId reliable_in_stream_id, uxrStreamId best_effort_in_stream_id, uxrObjectId participant_id, const char *client_namespace)
{
@[ for idx, sub in enumerate(subscriptions + subscriptions_multi)]@
@[ for idx, sub in enumerate(subscriptions)]@
{
uint16_t queue_depth = orb_get_queue_size(ORB_ID(@(sub['simple_base_type']))) * 2; // use a bit larger queue size than internal
uint32_t message_version = get_message_version<@(sub['simple_base_type'])_s>();
create_data_reader(session, reliable_out_stream_id, best_effort_in_stream_id, participant_id, @(idx), client_namespace, "@(sub['topic'])", message_version, "@(sub['dds_type'])", queue_depth);
}
@[ end for]@
@[ for idx, sub in enumerate(subscriptions_multi)]@
{
uint16_t queue_depth = orb_get_queue_size(ORB_ID(@(sub['topic_simple']))) * @(sub.get('max_instances', 2)); // scale queue for multiple sources
uint32_t message_version = get_message_version<@(sub['simple_base_type'])_s>();
create_data_reader(session, reliable_out_stream_id, best_effort_in_stream_id, participant_id, @(idx + len(subscriptions)), client_namespace, "@(sub['topic'])", message_version, "@(sub['dds_type'])", queue_depth);
}
@[ end for]@
uxr_set_topic_callback(session, on_topic_update, this);

15
src/modules/uxrce_dds_client/dds_topics.yaml
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@@ -133,8 +133,8 @@ subscriptions:
- topic: /fmu/in/config_control_setpoints
type: px4_msgs::msg::VehicleControlMode
- topic: /fmu/in/distance_sensor
type: px4_msgs::msg::DistanceSensor
# - topic: /fmu/in/distance_sensor
# type: px4_msgs::msg::DistanceSensor
- topic: /fmu/in/manual_control_input
type: px4_msgs::msg::ManualControlSetpoint
@@ -190,9 +190,6 @@ subscriptions:
- topic: /fmu/in/actuator_servos
type: px4_msgs::msg::ActuatorServos
- topic: /fmu/in/aux_global_position
type: px4_msgs::msg::AuxGlobalPosition
- topic: /fmu/in/fixed_wing_longitudinal_setpoint
type: px4_msgs::msg::FixedWingLongitudinalSetpoint
@@ -226,5 +223,11 @@ subscriptions:
- topic: /fmu/in/landing_gear
type: px4_msgs::msg::LandingGear
# Create uORB::PublicationMulti
# Subscriptions multiplexed to uORB multi-instances (optionally demultiplexed based on a message field)
subscriptions_multi:
- topic: /fmu/in/aux_global_position
type: px4_msgs::msg::AuxGlobalPosition
route_field: id
max_instances: 4
- topic: /fmu/in/distance_sensor
type: px4_msgs::msg::DistanceSensor

9
src/modules/uxrce_dds_client/generate_dds_topics.py
View File

@@ -130,12 +130,11 @@ if subs_not_empty:
merged_em_globals['subscriptions'] = msg_map['subscriptions'] if subs_not_empty else []
subs_multi_not_empty = msg_map['subscriptions_multi'] is not None
if subs_multi_not_empty:
for sm in msg_map['subscriptions_multi']:
process_message_type(sm)
subs_multi = msg_map.get('subscriptions_multi') or []
for sd in subs_multi:
process_message_type(sd)
merged_em_globals['subscriptions_multi'] = msg_map['subscriptions_multi'] if subs_multi_not_empty else []
merged_em_globals['subscriptions_multi'] = subs_multi
merged_em_globals['type_includes'] = sorted(set(all_type_includes))