Differentiate between ROS Services and ROS Action.

Question

Accepted Answer

# Solution: ROS Services vs ROS Actions

Both ROS Services and Actions provide communication between ROS nodes, but they are designed for different kinds of tasks.

| Feature | ROS Service | ROS Action |
|---|---|---|
| Communication | Request-response | Goal-feedback-result |
| Task type | Short operations | Long-running operations |
| Feedback | Normally no continuous feedback | Provides continuous feedback |
| Cancellation | Not designed for cancellation | Goal can be cancelled/preempted |
| Result | Returned after request | Final result returned separately |
| Example | Reset a sensor | Navigate to a destination |

## ROS Service

A service is synchronous request-response communication.

```text
Client → Request → Service Server
Client ← Response ← Service Server
```

Examples include resetting a controller, requesting a calculation or changing a configuration parameter.

## ROS Action

An action is intended for operations that may take significant time.

```text
Client → Goal → Action Server
Client ← Feedback ← Action Server
Client ← Result ← Action Server
        ↑
      Cancel
```

For example, autonomous navigation may take several seconds or minutes. The client can receive distance/progress feedback and cancel the goal if necessary.

## Conclusion

Use a **Service for short request-response operations** and an **Action for long-running, feedback-producing and cancellable tasks**.

Solution: ROS Services vs ROS Actions

ROS Service

ROS Action

Conclusion

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