Add parameter for minimum subscription QoS depth

README.md

@@ -78,6 +78,7 @@ Parameters are provided to configure the behavior of the bridge. These parameter
  * __use_compression__: Use websocket compression (permessage-deflate). Suited for connections with smaller bandwith, at the cost of additional CPU load.
  * (ROS 1) __max_update_ms__: The maximum number of milliseconds to wait in between polling `roscore` for new topics, services, or parameters. Defaults to `5000`.
  * (ROS 2) __num_threads__: The number of threads to use for the ROS node executor. This controls the number of subscriptions that can be processed in parallel. 0 means one thread per CPU core. Defaults to `0`.
+ * (ROS 2) __min_qos_depth__: Minimum depth used for the QoS profile of subscriptions. Defaults to `1`. This is to set a lower limit for a subscriber's QoS depth which is computed by summing up depths of all publishers. See also [#208](https://github.com/foxglove/ros-foxglove-bridge/issues/208).
  * (ROS 2) __max_qos_depth__: Maximum depth used for the QoS profile of subscriptions. Defaults to `10`.
  * (ROS 2) __capabilities__: List of supported [server capabilities](https://github.com/foxglove/ws-protocol/blob/main/docs/spec.md). Defaults to `[clientPublish,parameters,parametersSubscribe,services,connectionGraph]`.
 

ros2_foxglove_bridge/include/foxglove_bridge/param_utils.hpp

@@ -14,6 +14,7 @@ constexpr char PARAM_SEND_BUFFER_LIMIT[] = "send_buffer_limit";
 constexpr char PARAM_USETLS[] = "tls";
 constexpr char PARAM_CERTFILE[] = "certfile";
 constexpr char PARAM_KEYFILE[] = "keyfile";
+constexpr char PARAM_MIN_QOS_DEPTH[] = "min_qos_depth";
 constexpr char PARAM_MAX_QOS_DEPTH[] = "max_qos_depth";
 constexpr char PARAM_TOPIC_WHITELIST[] = "topic_whitelist";
 constexpr char PARAM_SERVICE_WHITELIST[] = "service_whitelist";
@@ -25,6 +26,7 @@ constexpr char PARAM_CLIENT_TOPIC_WHITELIST[] = "client_topic_whitelist";
 constexpr int64_t DEFAULT_PORT = 8765;
 constexpr char DEFAULT_ADDRESS[] = "0.0.0.0";
 constexpr int64_t DEFAULT_SEND_BUFFER_LIMIT = 10000000;
+constexpr int64_t DEFAULT_MIN_QOS_DEPTH = 1;
 constexpr int64_t DEFAULT_MAX_QOS_DEPTH = 10;
 
 void declareParameters(rclcpp::Node* node);

ros2_foxglove_bridge/launch/foxglove_bridge_launch.xml

@@ -8,6 +8,7 @@
   <arg name="param_whitelist"           default="['.*']" />
   <arg name="service_whitelist"         default="['.*']" />
   <arg name="client_topic_whitelist"    default="['.*']" />
+  <arg name="min_qos_depth"             default="1" />
   <arg name="max_qos_depth"             default="10" />
   <arg name="num_threads"               default="0" />
   <arg name="send_buffer_limit"         default="10000000" />
@@ -24,6 +25,7 @@
     <param name="service_whitelist"       value="$(var service_whitelist)" />
     <param name="param_whitelist"         value="$(var param_whitelist)" />
     <param name="client_topic_whitelist"  value="$(var client_topic_whitelist)" />
+    <param name="min_qos_depth"           value="$(var min_qos_depth)" />
     <param name="max_qos_depth"           value="$(var max_qos_depth)" />
     <param name="num_threads"             value="$(var num_threads)" />
     <param name="send_buffer_limit"       value="$(var send_buffer_limit)" />

ros2_foxglove_bridge/src/param_utils.cpp

@@ -60,6 +60,18 @@ void declareParameters(rclcpp::Node* node) {
   keyfileDescription.read_only = true;
   node->declare_parameter(PARAM_KEYFILE, "", keyfileDescription);
 
+  auto minQosDepthDescription = rcl_interfaces::msg::ParameterDescriptor{};
+  minQosDepthDescription.name = PARAM_MIN_QOS_DEPTH;
+  minQosDepthDescription.type = rcl_interfaces::msg::ParameterType::PARAMETER_INTEGER;
+  minQosDepthDescription.description = "Minimum depth used for the QoS profile of subscriptions.";
+  minQosDepthDescription.read_only = true;
+  minQosDepthDescription.additional_constraints = "Must be a non-negative integer";
+  minQosDepthDescription.integer_range.resize(1);
+  minQosDepthDescription.integer_range[0].from_value = 0;
+  minQosDepthDescription.integer_range[0].to_value = INT32_MAX;
+  minQosDepthDescription.integer_range[0].step = 1;
+  node->declare_parameter(PARAM_MIN_QOS_DEPTH, DEFAULT_MIN_QOS_DEPTH, minQosDepthDescription);
+
   auto maxQosDepthDescription = rcl_interfaces::msg::ParameterDescriptor{};
   maxQosDepthDescription.name = PARAM_MAX_QOS_DEPTH;
   maxQosDepthDescription.type = rcl_interfaces::msg::ParameterType::PARAMETER_INTEGER;

ros2_foxglove_bridge/src/ros2_foxglove_bridge.cpp

@@ -52,6 +52,7 @@ class FoxgloveBridge : public rclcpp::Node {
     const auto useTLS = this->get_parameter(PARAM_USETLS).as_bool();
     const auto certfile = this->get_parameter(PARAM_CERTFILE).as_string();
     const auto keyfile = this->get_parameter(PARAM_KEYFILE).as_string();
+    _minQosDepth = static_cast<size_t>(this->get_parameter(PARAM_MIN_QOS_DEPTH).as_int());
     _maxQosDepth = static_cast<size_t>(this->get_parameter(PARAM_MAX_QOS_DEPTH).as_int());
     const auto topicWhiteList = this->get_parameter(PARAM_TOPIC_WHITELIST).as_string_array();
     _topicWhitelistPatterns = parseRegexStrings(this, topicWhiteList);
@@ -441,6 +442,7 @@ class FoxgloveBridge : public rclcpp::Node {
   std::mutex _clientAdvertisementsMutex;
   std::mutex _servicesMutex;
   std::unique_ptr<std::thread> _rosgraphPollThread;
+  size_t _minQosDepth = DEFAULT_MIN_QOS_DEPTH;
   size_t _maxQosDepth = DEFAULT_MAX_QOS_DEPTH;
   std::shared_ptr<rclcpp::Subscription<rosgraph_msgs::msg::Clock>> _clockSubscription;
   bool _useSimTime = false;
@@ -556,7 +558,7 @@ class FoxgloveBridge : public rclcpp::Node {
       depth = std::min(_maxQosDepth, depth + qos.depth());
     }
 
-    rclcpp::QoS qos{rclcpp::KeepLast(std::max(depth, 1lu))};
+    rclcpp::QoS qos{rclcpp::KeepLast(std::max(depth, _minQosDepth))};
 
     // If all endpoints are reliable, ask for reliable
     if (reliabilityReliableEndpointsCount == publisherInfo.size()) {