Implement callback support of async_send_request for service generic client

rclcpp/include/rclcpp/generic_client.hpp

@@ -19,6 +19,7 @@
 #include <memory>
 #include <future>
 #include <string>
+#include <tuple>
 #include <vector>
 #include <utility>
 
@@ -46,6 +47,8 @@ class GenericClient : public ClientBase
   using Future = std::future<SharedResponse>;
   using SharedFuture = std::shared_future<SharedResponse>;
 
+  using CallbackType = std::function<void (SharedFuture)>;
+
   RCLCPP_SMART_PTR_DEFINITIONS(GenericClient)
 
   /// A convenient GenericClient::Future and request id pair.
@@ -76,6 +79,20 @@ class GenericClient : public ClientBase
     ~FutureAndRequestId() = default;
   };
 
+  /// A convenient GenericClient::SharedFuture and request id pair.
+  /**
+   * Public members:
+   * - future: a std::shared_future<SharedResponse>.
+   * - request_id: the request id associated with the future.
+   *
+   * All the other methods are equivalent to the ones std::shared_future provides.
+   */
+  struct SharedFutureAndRequestId
+    : detail::FutureAndRequestId<std::shared_future<SharedResponse>>
+  {
+    using detail::FutureAndRequestId<std::shared_future<SharedResponse>>::FutureAndRequestId;
+  };
+
   GenericClient(
     rclcpp::node_interfaces::NodeBaseInterface * node_base,
     rclcpp::node_interfaces::NodeGraphInterface::SharedPtr node_graph,
@@ -106,16 +123,16 @@ class GenericClient : public ClientBase
    * If the future never completes,
    * e.g. the call to Executor::spin_until_future_complete() times out,
    * GenericClient::remove_pending_request() must be called to clean the client internal state.
-   * Not doing so will make the `Client` instance to use more memory each time a response is not
-   * received from the service server.
+   * Not doing so will make the `GenericClient` instance to use more memory each time a response is
+   * not received from the service server.
    *
    * ```cpp
-   * auto future = client->async_send_request(my_request);
+   * auto future = generic_client->async_send_request(my_request);
    * if (
    *   rclcpp::FutureReturnCode::TIMEOUT ==
    *   executor->spin_until_future_complete(future, timeout))
    * {
-   *   client->remove_pending_request(future);
+   *   generic_client->remove_pending_request(future);
    *   // handle timeout
    * } else {
    *   handle_response(future.get());
@@ -129,6 +146,45 @@ class GenericClient : public ClientBase
   FutureAndRequestId
   async_send_request(const Request request);
 
+  /// Send a request to the service server and schedule a callback in the executor.
+  /**
+   * Similar to the previous overload, but a callback will automatically be called when a response
+   * is received.
+   *
+   * If the callback is never called, because we never got a reply for the service server,
+   * remove_pending_request() has to be called with the returned request id or
+   * prune_pending_requests().
+   * Not doing so will make the `GenericClient` instance use more memory each time a response is not
+   * received from the service server.
+   * In this case, it's convenient to setup a timer to cleanup the pending requests.
+   *
+   * \param[in] request request to be send.
+   * \param[in] cb callback that will be called when we get a response for this request.
+   * \return the request id representing the request just sent.
+   */
+  template<
+    typename CallbackT,
+    typename std::enable_if<
+      rclcpp::function_traits::same_arguments<
+        CallbackT,
+        CallbackType
+      >::value
+    >::type * = nullptr
+  >
+  SharedFutureAndRequestId
+  async_send_request(const Request request, CallbackT && cb)
+  {
+    Promise promise;
+    auto shared_future = promise.get_future().share();
+    auto req_id = async_send_request_impl(
+      request,
+      std::make_tuple(
+        CallbackType{std::forward<CallbackT>(cb)},
+        shared_future,
+        std::move(promise)));
+    return SharedFutureAndRequestId{std::move(shared_future), req_id};
+  }
+
   /// Clean all pending requests older than a time_point.
   /**
    * \param[in] time_point Requests that were sent before this point are going to be removed.
@@ -149,15 +205,52 @@ class GenericClient : public ClientBase
       pruned_requests);
   }
 
+  /// Clean all pending requests.
+  /**
+   * \return number of pending requests that were removed.
+   */
   RCLCPP_PUBLIC
   size_t
   prune_pending_requests();
 
+  /// Cleanup a pending request.
+  /**
+   * This notifies the client that we have waited long enough for a response from the server
+   * to come, we have given up and we are not waiting for a response anymore.
+   *
+   * Not calling this will make the client start using more memory for each request
+   * that never got a reply from the server.
+   *
+   * \param[in] request_id request id returned by async_send_request().
+   * \return true when a pending request was removed, false if not (e.g. a response was received).
+   */
   RCLCPP_PUBLIC
   bool
   remove_pending_request(
     int64_t request_id);
 
+  /// Cleanup a pending request.
+  /**
+   * Convenient overload, same as:
+   *
+   * `GenericClient::remove_pending_request(this, future.request_id)`.
+   */
+  RCLCPP_PUBLIC
+  bool
+  remove_pending_request(
+    const FutureAndRequestId & future);
+
+  /// Cleanup a pending request.
+  /**
+   * Convenient overload, same as:
+   *
+   * `GenericClient::remove_pending_request(this, future.request_id)`.
+   */
+  RCLCPP_PUBLIC
+  bool
+  remove_pending_request(
+    const SharedFutureAndRequestId & future);
+
   /// Take the next response for this client.
   /**
    * \sa ClientBase::take_type_erased_response().
@@ -179,8 +272,10 @@ class GenericClient : public ClientBase
   }
 
 protected:
+  using CallbackTypeValueVariant = std::tuple<CallbackType, SharedFuture, Promise>;
   using CallbackInfoVariant = std::variant<
-    std::promise<SharedResponse>>;  // Use variant for extension
+    std::promise<SharedResponse>,
+    CallbackTypeValueVariant>;  // Use variant for extension
 
   int64_t
   async_send_request_impl(

rclcpp/src/rclcpp/generic_client.cpp

@@ -100,6 +100,13 @@ GenericClient::handle_response(
   if (std::holds_alternative<Promise>(value)) {
     auto & promise = std::get<Promise>(value);
     promise.set_value(std::move(response));
+  } else if (std::holds_alternative<CallbackTypeValueVariant>(value)) {
+    auto & inner = std::get<CallbackTypeValueVariant>(value);
+    const auto & callback = std::get<CallbackType>(inner);
+    auto & promise = std::get<Promise>(inner);
+    auto & future = std::get<SharedFuture>(inner);
+    promise.set_value(std::move(response));
+    callback(std::move(future));
   }
 }
 
@@ -119,6 +126,18 @@ GenericClient::remove_pending_request(int64_t request_id)
   return pending_requests_.erase(request_id) != 0u;
 }
 
+bool
+GenericClient::remove_pending_request(const FutureAndRequestId & future)
+{
+  return this->remove_pending_request(future.request_id);
+}
+
+bool
+GenericClient::remove_pending_request(const SharedFutureAndRequestId & future)
+{
+  return this->remove_pending_request(future.request_id);
+}
+
 std::optional<GenericClient::CallbackInfoVariant>
 GenericClient::get_and_erase_pending_request(int64_t request_number)
 {

rclcpp/test/rclcpp/test_generic_client.cpp

@@ -14,6 +14,8 @@
 
 #include <gtest/gtest.h>
 
+#include <chrono>
+#include <cstdint>
 #include <string>
 #include <memory>
 #include <utility>
@@ -28,6 +30,7 @@
 #include "../mocking_utils/patch.hpp"
 
 #include "test_msgs/srv/empty.hpp"
+#include "test_msgs/srv/basic_types.hpp"
 
 using namespace std::chrono_literals;
 
@@ -228,3 +231,69 @@ TEST_F(TestGenericClientSub, construction_and_destruction) {
     }, rclcpp::exceptions::InvalidServiceNameError);
   }
 }
+
+TEST_F(TestGenericClientSub, async_send_request_with_request) {
+  const std::string service_name = "test_service";
+  int64_t expected_change = 1111;
+
+  auto client = node->create_generic_client(service_name, "test_msgs/srv/BasicTypes");
+
+  auto callback = [&expected_change](
+    const test_msgs::srv::BasicTypes::Request::SharedPtr request,
+    test_msgs::srv::BasicTypes::Response::SharedPtr response) {
+      response->int64_value = request->int64_value + expected_change;
+    };
+
+  auto service =
+    node->create_service<test_msgs::srv::BasicTypes>(service_name, std::move(callback));
+
+  ASSERT_TRUE(client->wait_for_service(std::chrono::seconds(5)));
+  ASSERT_TRUE(client->service_is_ready());
+
+  test_msgs::srv::BasicTypes::Request request;
+  request.int64_value = 12345678;
+
+  auto future = client->async_send_request(static_cast<void *>(&request));
+  rclcpp::spin_until_future_complete(
+    node->get_node_base_interface(), future, std::chrono::seconds(5));
+  ASSERT_TRUE(future.valid());
+  auto get_untyped_response = future.get();
+  auto typed_response =
+    static_cast<test_msgs::srv::BasicTypes::Response *>(get_untyped_response.get());
+  EXPECT_EQ(typed_response->int64_value, (request.int64_value + expected_change));
+}
+
+TEST_F(TestGenericClientSub, async_send_request_with_request_and_callback) {
+  const std::string service_name = "test_service";
+  int64_t expected_change = 2222;
+
+  auto client = node->create_generic_client(service_name, "test_msgs/srv/BasicTypes");
+
+  auto server_callback = [&expected_change](
+    const test_msgs::srv::BasicTypes::Request::SharedPtr request,
+    test_msgs::srv::BasicTypes::Response::SharedPtr response) {
+      response->int64_value = request->int64_value + expected_change;
+    };
+
+  auto service =
+    node->create_service<test_msgs::srv::BasicTypes>(service_name, std::move(server_callback));
+
+  ASSERT_TRUE(client->wait_for_service(std::chrono::seconds(5)));
+  ASSERT_TRUE(client->service_is_ready());
+
+  test_msgs::srv::BasicTypes::Request request;
+  request.int64_value = 12345678;
+
+  auto client_callback = [&request, &expected_change](
+    rclcpp::GenericClient::SharedFuture future) {
+      auto untyped_response = future.get();
+      auto typed_response =
+        static_cast<test_msgs::srv::BasicTypes::Response *>(untyped_response.get());
+      EXPECT_EQ(typed_response->int64_value, (request.int64_value + expected_change));
+    };
+
+  auto future =
+    client->async_send_request(static_cast<void *>(&request), client_callback);
+  rclcpp::spin_until_future_complete(
+    node->get_node_base_interface(), future, std::chrono::seconds(5));
+}