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Merge pull request #30 from rosin-project/rxros_spin
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Issue #15: rxros::spin() function uses unnecessary many threads
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@wasowski
wasowski authored Nov 10, 2019
2 parents a515c08 + 55327bd commit d08174c
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116 changes: 38 additions & 78 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -20,40 +20,36 @@ RxROS aspires to the slogan ‘concurrency made easy’.
* [Acknowledgements](#acknowledgements)
* [Example packages](#example-packages)
* [RxROS API](#rxros-api)
* [Initial setup](#initial-setup)
* [Syntax](#syntax)
* [Creating a RxROS Node](#creating-a-rxros-node)
* [Example](#example)
* [Spinning](#spinning)
* [Syntax](#syntax-1)
* [Example](#example-1)
* [Parameters](#parameters)
* [Syntax](#syntax-2)
* [Syntax](#syntax-1)
* [Example](#example-2)
* [Logging](#logging)
* [Syntax](#syntax-3)
* [Syntax](#syntax-2)
* [Example](#example-3)
* [Observables](#observables)
* [Observable from a Topic](#observable-from-a-topic)
* [Syntax](#syntax-4)
* [Syntax](#syntax-3)
* [Example](#example-4)
* [Observable from a transform listener](#observable-from-a-transform-listener)
* [Syntax](#syntax-5)
* [Syntax](#syntax-4)
* [Observable from a Linux device](#observable-from-a-linux-device)
* [Syntax](#syntax-6)
* [Syntax](#syntax-5)
* [Example](#example-5)
* [Observable from a Yaml file](#observable-from-a-yaml-file)
* [Syntax](#syntax-7)
* [Syntax](#syntax-6)
* [Example](#example-6)
* [Operators](#operators)
* [Publish to Topic](#publish-to-topic)
* [Syntax:](#syntax-8)
* [Syntax:](#syntax-7)
* [Example:](#example-7)
* [Send Transform](#send-transform)
* [Syntax:](#syntax-9)
* [Syntax:](#syntax-8)
* [Call Service](#call-service)
* [Syntax:](#syntax-10)
* [Syntax:](#syntax-9)
* [Sample with Frequency](#sample-with-frequency)
* [Syntax:](#syntax-11)
* [Syntax:](#syntax-10)
* [Example:](#example-8)
* [Example 1: A Keyboard Publisher](#example-1-a-keyboard-publisher)
* [Example 2: A Velocity Publisher](#example-2-a-velocity-publisher)
Expand Down Expand Up @@ -146,61 +142,25 @@ Refer to the `README` in that repository for additional setup and installation i

## RxROS API

Now, lets look at the language in more details.
Now, lets look at the RxROS API in more details.
RxROS provides simple access to ROS via a set of functions.
These functions provide more precisely an extension to RxCpp that
gives simple access to ROS.<br>

### Initial setup
These functions provide more precisely an extension to RxCpp in form of observables and operations that give simple access to ROS.<br>

The most fundamental RxROS program is the initialization of a ROS node.
This is done simply by calling the rxros::init function. The rxros::init function takes three arguments:
The number of command line arguments the node or program was called with (argc), the actual arguments (argv)
and the name of the node. argc and argv are inherited directly from the main function and all three arguments
are used to initialize a ROS node. Failure to initialize a node with rxros::init will cause all interaction
with ROS to fail.
### Creating a RxROS node

#### Syntax

```cpp
rxros::init(argc, argv, "Name_of_ROS_node");
```
Creating a RxROS node has some commonalities with creating a normal ROS node, as shown in the example below.
A RxROS node starts by calling `ros::init` to initialize the node and ends with a call to `ros::spin` to block the main thread and listen for topic updates.
Failure to include theses statements will either cause a RxROS node to exit immediately or behave in a unpredictable manner.
However, any variant of ros::init and ros::spin may be used to create a RxROS node.

#### Example

```cpp
#include <rxros/rxros.h>
int main(int argc, char** argv) {
rxros::init(argc, argv, "velocity_publisher"); // Name of this node.
ros::init(argc, argv, "node_name");
// ...
}
```

### Spinning

The other fundamental function of RxROS is rxros::spin. The function blocks the main thread until it is shutdown or terminated.
This means that the rxros::spin function always should be placed at the very bottom of the main function.
The other purpose of the rxros::spin function is to dispatch messages from ROS topics to the appropriate RxROS observables.
Failure to omit the rxros::spin function will cause the program to terminate immediately and observables based on ROS topics
will not emit any events.

The Example below shows a minimal RxROS program that creates a ROS node named “my_node”.
The program will due to rxros:spin() continue to run until it is either shutdown or terminated.

#### Syntax

```cpp
void rxros::spin();
```

#### Example

```cpp
#include <rxros/rxros.h>
int main(int argc, char** argv) {
rxros::init(argc, argv, "my_node"); // Name of this node.
// ...
rxros::spin(); // block the main thread until it is terminated.
ros::spin()
}
```
Expand Down Expand Up @@ -228,13 +188,13 @@ auto rxros::parameter::get(const std::string& name, const std::string& defaultVa
```cpp
#include <rxros/rxros.h>
int main(int argc, char** argv) {
rxros::init(argc, argv, "velocity_publisher"); // Name of this node.
ros::init(argc, argv, "velocity_publisher"); // Name of this node.
//...
const auto frequency = rxros::parameter::get("/velocity_publisher/frequency", 10.0); // hz
const auto minVelLinear = rxros::parameter::get("/velocity_publisher/min_vel_linear", 0.04); // m/s
const auto maxVelLinear = rxros::parameter::get("/velocity_publisher/max_vel_linear", 0.10); // m/s
//...
rxros::spin();
ros::spin()();
}
```
Expand Down Expand Up @@ -262,15 +222,15 @@ rxros::logging& rxros::logging().fatal();
```cpp
#include <rxros/rxros.h>
int main(int argc, char** argv) {
rxros::init(argc, argv, "velocity_publisher"); // Name of this node.
ros::init(argc, argv, "velocity_publisher"); // Name of this node.
//...
rxros::logging().debug() << "frequency: " << frequency;
rxros::logging().info() << "min_vel_linear: " << minVelLinear << " m/s";
rxros::logging().warn() << "max_vel_linear: " << maxVelLinear << " m/s";
rxros::logging().error() << "min_vel_angular: " << minVelAngular << " rad/s";
rxros::logging().fatal() << "max_vel_angular: " << maxVelAngular << " rad/s";
//...
rxros::spin();
ros::spin()();
}
```
Expand Down Expand Up @@ -307,15 +267,15 @@ auto rxros::observable::from_topic<topic_type>(const std::string& topic, const u

```cpp
int main(int argc, char** argv) {
rxros::init(argc, argv, "velocity_publisher"); // Name of this node.
ros::init(argc, argv, "velocity_publisher"); // Name of this node.
//...
auto joy_obsrv = rxros::observable::from_topic<teleop_msgs::Joystick>("/joystick")
| map([](teleop_msgs::Joystick joy) { return joy.event; });
auto key_obsrv = rxros::observable::from_topic<teleop_msgs::Keyboard>("/keyboard")
| map([](teleop_msgs::Keyboard key) { return key.event; });
auto teleop_obsrv = joyObsrv.merge(keyObsrv);
//...
rxros::spin();
ros::spin()();
}
```
Expand Down Expand Up @@ -357,13 +317,13 @@ auto rxros::observable::from_device<device_type>(const std::string& device_name)

```cpp
int main(int argc, char** argv) {
rxros::init(argc, argv, "joystick_publisher"); // Name of this node.
ros::init(argc, argv, "joystick_publisher"); // Name of this node.
//...
rxros::observable::from_device<joystick_event>("/dev/input/js0")
| map(joystickEvent2JoystickMsg)
| publish_to_topic<teleop_msgs::Joystick>("/joystick");
//...
rxros::spin();
ros::spin()();
}
```
Expand Down Expand Up @@ -415,15 +375,15 @@ auto rxros::observable::from_yaml(const std::string& namespace);
```cpp
#include <rxros/rxros.h>
int main(int argc, char** argv) {
rxros::init(argc, argv, "brickpi3"); // Name of this node.
ros::init(argc, argv, "brickpi3"); // Name of this node.
//...
rxros::observable::from_yaml("/brickpi3/brickpi3_robot").subscribe(
[=](auto config) { // on_next event
DeviceConfig device(config);
if (device.getType() == "motor") {
rxros::logging().debug() << device.getType() << ", " << device.getName() << ", " << device.getPort() << ", " << device.getFrequency();
//...
rxros::spin();
ros::spin()();
}
```

Expand Down Expand Up @@ -491,13 +451,13 @@ auto rxros::operators::publish_to_topic<topic_type>(const std::string &topic, co

```cpp
int main(int argc, char** argv) {
rxros::init(argc, argv, "joystick_publisher"); // Name of this node.
ros::init(argc, argv, "joystick_publisher"); // Name of this node.
//...
rxros::observable::from_device<joystick_event>("/dev/input/js0")
| map(joystickEvent2JoystickMsg)
| publish_to_topic<teleop_msgs::Joystick>("/joystick");
//...
rxros::spin();
ros::spin()();
}
```
Expand Down Expand Up @@ -559,12 +519,12 @@ auto rxros::operation::sample_with_frequency(const double frequency, Coordinatio
```cpp
int main(int argc, char** argv) {
rxros::init(argc, argv, "joystick_publisher"); // Name of this node.
ros::init(argc, argv, "joystick_publisher"); // Name of this node.
//...
| sample_with_frequency(frequencyInHz)
| publish_to_topic<geometry_msgs::Twist>("/cmd_vel");
//...
rxros::spin();
ros::spin()();
}
```

Expand All @@ -583,7 +543,7 @@ using namespace rxros::operators;

int main(int argc, char** argv)
{
rxros::init(argc, argv, "keyboard_publisher"); // Name of this Node.
ros::init(argc, argv, "keyboard_publisher"); // Name of this Node.

const auto keyboardDevice = rxros::parameter::get("/keyboard_publisher/device", "/dev/input/event1");
rxros::logging().info() << "Keyboard device: " << keyboardDevice;
Expand Down Expand Up @@ -613,7 +573,7 @@ int main(int argc, char** argv)
| publish_to_topic<teleop_msgs::Keyboard>("/keyboard");

rxros::logging().info() << "Spinning keyboard_publisher...";
rxros::spin();
ros::spin()();
}

```
Expand All @@ -634,7 +594,7 @@ on the /cmd_vel topic. For more information see [rxros_examples](https://github.
int main(int argc, char** argv) {
rxros::init(argc, argv, "velocity_publisher"); // Name of this node.
ros::init(argc, argv, "velocity_publisher"); // Name of this node.
const auto frequencyInHz = rxros::Parameter::get("/velocity_publisher/frequency", 10.0); // hz
const auto minVelLinear = rxros::Parameter::get("/velocity_publisher/min_vel_linear", 0.04); // m/s
Expand Down Expand Up @@ -693,6 +653,6 @@ int main(int argc, char** argv) {
| publish_to_topic<geometry_msgs::Twist>("/cmd_vel"); // publish the Twist messages to the topic "/cmd_vel"
rxros::Logging().info() << "Spinning velocity_publisher ...";
rxros::spin();
ros::spin()();
}
```
16 changes: 1 addition & 15 deletions rxros/include/rxros/rxros.h
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Expand Up @@ -44,20 +44,6 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

namespace rxros
{
static void init(int argc, char** argv, const std::string& name) {
ros::init(argc, argv, name);
}

static void spin() {
ros::MultiThreadedSpinner spinner(0); // Use a spinner for each available CPU core
spinner.spin();
}

static bool ok() {
return ros::ok();
}


class node: public ros::NodeHandle
{
private:
Expand Down Expand Up @@ -225,7 +211,7 @@ namespace rxros
FD_SET(fd, &readfds);
T event{};
bool errReported = false;
while (rxros::ok()) {
while (ros::ok()) {
int rc = select(fd + 1, &readfds, nullptr, nullptr, nullptr); // wait for input on keyboard device
if (rc == -1 && errno == EINTR) { // select was interrupted. This is not an error but we exit the loop
subscriber.on_completed();
Expand Down
2 changes: 1 addition & 1 deletion rxros_tf/include/rxros_tf/rxros_tf.h
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Expand Up @@ -47,7 +47,7 @@ namespace rxros
tf::TransformListener transform_listener;
ros::Rate rate(frequencyInHz);
bool errReported = false;
while (rxros::ok()) {
while (ros::ok()) {
try {
tf::StampedTransform transform;
transform_listener.lookupTransform(parent_frameId, child_frameId, ros::Time(0), transform);
Expand Down

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