Expose the assert_liveliness API for Publishers and Nodes

Signed-off-by: Emerson Knapp <eknapp@amazon.com>

rclpy/rclpy/node.py

@@ -835,3 +835,13 @@ def count_subscribers(self, topic_name: str) -> int:
         :return: the number of subscribers on the topic.
         """
         return self._count_publishers_or_subscribers(topic_name, _rclpy.rclpy_count_subscribers)
+
+    def assert_liveliness(self) -> None:
+        """
+        Manually assert that this Node is alive.
+
+        If the QoS Liveliness policy is set to RMW_QOS_POLICY_LIVELINESS_MANUAL_BY_NODE, the
+        application must call this at least as often as ``QoSProfile.liveliness_lease_duration``.
+        """
+        _rclpy.rclpy_assert_liveliness(self.node_handle)
+

rclpy/rclpy/publisher.py

@@ -67,3 +67,12 @@ def handle(self):
 
     def destroy(self):
         self.handle.destroy()
+
+    def assert_liveliness(self) -> None:
+        """
+        Manually assert that this Publisher is alive.
+
+        If the QoS Liveliness policy is set to RMW_QOS_POLICY_LIVELINESS_MANUAL_BY_TOPIC, the
+        application must call this at least as often as ``QoSProfile.liveliness_lease_duration``.
+        """
+        _rclpy.rclpy_assert_liveliness(self.publisher_handle)

rclpy/src/rclpy/_rclpy.c

@@ -3604,6 +3604,53 @@ rclpy_get_rmw_qos_profile(PyObject * Py_UNUSED(self), PyObject * args)
   return pyqos_profile;
 }
 
+/// Manually assert that an entity is alive.
+/**
+  * When using RMW_QOS_POLICY_MANUAL_BY_*, the application must call this function at least as
+  * often as the qos policy liveliness_lease_duration.
+  * The passed entity can be a Publisher or a Node.
+  *
+  * Raises RuntimeError on failure to assert liveliness
+  * Raises TypeError if passed object is not a valid Publisher or Node
+  *
+  * \param[in] pyentity A capsule containing an rcl_node_t or rcl_publisher_t
+  * \return None
+  */
+static PyObject *
+rclpy_assert_liveliness(PyObject * Py_UNUSED(self), PyObject * args)
+{
+  PyObject * pyentity;
+
+  if (!PyArg_ParseTuple(args, "O", &pyentity)) {
+    return NULL;
+  }
+
+  if (PyCapsule_IsValid(pyentity, "rcl_node_t")) {
+    rcl_node_t * node = (rcl_node_t *)PyCapsule_GetPointer(pyentity, "rcl_node_t");
+    if (RCL_RET_OK != rcl_node_assert_liveliness(node)) {
+      PyErr_Format(PyExc_RuntimeError,
+        "Failed assert liveliness on the Node: %s", rcl_get_error_string().str);
+      rcl_reset_error();
+      return NULL;
+    }
+  } else if (PyCapsule_IsValid(pyentity, "rcl_publisher_t")) {
+    rcl_publisher_t * publisher = (rcl_publisher_t *)PyCapsule_GetPointer(
+      pyentity, "rcl_publisher_t");
+    if (RCL_RET_OK != rcl_publisher_assert_liveliness(publisher)) {
+      PyErr_Format(PyExc_RuntimeError,
+        "Failed to assert liveliness on the Publisher: %s", rcl_get_error_string().str);
+      rcl_reset_error();
+      return NULL;
+    }
+  } else {
+    PyErr_Format(PyExc_TypeError,
+      "Passed capsule is not a valid Node or Publisher.");
+    return NULL;
+  }
+
+  Py_RETURN_NONE;
+}
+
 /// Destructor for a time point
 void
 _rclpy_destroy_time_point(PyObject * pycapsule)
@@ -4784,6 +4831,10 @@ static PyMethodDef rclpy_methods[] = {
     "rclpy_get_rmw_qos_profile", rclpy_get_rmw_qos_profile, METH_VARARGS,
     "Get QOS profile."
   },
+  {
+    "rclpy_assert_liveliness", rclpy_assert_liveliness, METH_VARARGS,
+    "Assert the liveliness of an entity."
+  },
 
   {
     "rclpy_create_time_point", rclpy_create_time_point, METH_VARARGS,