Services

Agnocast supports ROS 2-style services with zero-copy request and response handling via shared memory.

Warning

Agnocast service/client is not officially supported yet. The API may introduce breaking changes without a major version increment. Use at your own risk.

Migrating a Service Server

Before (rclcpp)

```cpp

include "rclcpp/rclcpp.hpp"

include "my_package/srv/my_service.hpp"

using ServiceT = my_package::srv::MyService; using RequestT = ServiceT::Request; using ResponseT = ServiceT::Response;

class MyServer : public rclcpp::Node { rclcpp::Service::SharedPtr service_;

public: MyServer() : Node("my_server") { service_ = create_service( "my_service", this { response->result = process(request->data); RCLCPP_INFO(get_logger(), "Processed request"); }); } }; ```

After (Agnocast Stage 1)

```cpp

include "agnocast/agnocast.hpp" // (1)

include "my_package/srv/my_service.hpp"

using ServiceT = my_package::srv::MyService; using RequestT = agnocast::Service::RequestT; // (2) using ResponseT = agnocast::Service::ResponseT; // (2)

class MyServer : public rclcpp::Node { agnocast::Service::SharedPtr service_; // (3)

public: MyServer() : Node("my_server") { service_ = agnocast::create_service( // (4) this, "my_service", this { response->result = process(request->data); RCLCPP_INFO(get_logger(), "Processed request"); }); } }; ```

Key changes:

1. Include changes to agnocast/agnocast.hpp
2. Type aliases change to agnocast::Service<ServiceT>::RequestT / ResponseT
3. rclcpp::Service → agnocast::Service
4. Use free function agnocast::create_service(this, ...) instead of this->create_service(...)
5. Callback takes agnocast::ipc_shared_ptr references instead of std::shared_ptr

After (Agnocast Stage 2)

```cpp

include "agnocast/agnocast.hpp"

include "my_package/srv/my_service.hpp"

using ServiceT = my_package::srv::MyService; using RequestT = agnocast::Service::RequestT; using ResponseT = agnocast::Service::ResponseT;

class MyServer : public agnocast::Node // (1) { agnocast::Service::SharedPtr service_;

public: MyServer() : Node("my_server") { service_ = this->create_service( // (2) "my_service", this { response->result = process(request->data); RCLCPP_INFO(get_logger(), "Processed request"); }); } }; ```

Additional changes from Stage 1:

1. Base class changes to agnocast::Node
2. Service creation uses member function instead of free function

Migrating a Service Client

Before (rclcpp)

```cpp auto client = node->create_client("my_service");

while (!client->wait_for_service(1s)) { RCLCPP_INFO(node->get_logger(), "Waiting for service..."); }

auto request = std::make_shared(); request->data = 42; client->async_send_request( request, { auto response = future.get(); // process response }); ```

After (Agnocast Stage 1)

```cpp auto client = agnocast::create_client( // (1) node.get(), "my_service");

while (!client->wait_for_service(1s)) { RCLCPP_INFO(node->get_logger(), "Waiting for service..."); }

auto request = client->borrow_loaned_request(); // (2) request->data = 42; client->async_send_request( std::move(request), // (3) { // (4) auto response = future.get(); // process response }); ```

Key changes:

1. Use free function agnocast::create_client(node.get(), ...)
2. Allocate request via borrow_loaned_request() (shared memory) instead of std::make_shared
3. Pass request with std::move (zero-copy handoff)
4. Future type changes to agnocast::Client<ServiceT>::SharedFuture

After (Agnocast Stage 2)

cpp auto client = node->create_client<ServiceT>("my_service"); // (1) // Same usage pattern as Stage 1

Additional change from Stage 1:

1. Client creation uses member function instead of free function