iceoryx-rs

Safe Rust bindings for Eclipse iceoryx.

1. About
2. Examples
   • How to start RouDi
   • Run the simple publisher and subscriber example
3. How to write a simple application
4. Limitations

About

Eclipse iceoryx is a true zero-copy, inter-process communication framework with the goal to boost autonomous driving with their demand on high data throughput and low latency. With its bandwidth and speed, iceoryx also fits well into other domains where low latency and transmitting large data structures is a concern. If you would like to know more about Eclipse iceoryx you can take a look at the Getting started section on iceoryx.io or the README.md of the main project.

The Rust bindings are a work in progress and currently support only the pub-sub messaging pattern. Upcoming releases will close the gap and the goal is to have the Rust bindings as a first class citizen in the iceoryx ecosystem.

This project started with the goal to create an awesome looking introspection TUI in Rust and led to iceray. Check it out.

Examples

Before you can run the example you have to build them first with

cargo build --all --examples

In order to run an iceoryx application, the RouDi daemon needs to run.

How to start RouDi

RouDi is the central daemon which takes care of resource management and connects the services when they register. After the registration phase it is not involved in the communication anymore.

You can find more information about RouDi here and if you are more of a visual person, just scroll up a little bit on that page to view an amazing animation.

In case you have iceoryx installed on your system, you can use the iox-roudi binary from that installation. If that's not the case, you can run RouDi with the following command from the root of your crate.

find target -type f -wholename "*/iceoryx-install/bin/iox-roudi" -exec {} \;

Run the simple publisher and subscriber example

The publisher_simple and subscriber_simple examples are demonstrating a typical inter-process communication use case.

A good introductory example to demonstrate the inter-process communication are publisher_simple and subscriber_simple.

You can run the publisher and subscriber by executing the following commands in separate terminals

cargo run --example publisher_simple
cargo run --example subscriber_simple

You should see the messages sent by the publisher like

Sending: 0
Sending: 1
Sending: 2
Sending: 3
Sending: 4

and how they are received by the subscriber

Receiving: 0
Receiving: 1
Receiving: 2
Receiving: 3
Receiving: 4

You might also witness this output

[Warning]: IPC channel still there, doing an unlink of [app_name]

Don't worry about this. This is due to aborting a previous run with Ctrl+C. To prevent this output one has to register a signal handler and gracefully shut down the application. The RouDi daemon will automatically clean up the shared resources of an abnormally terminated application. An application cleans its own leftover on restart up as well, hence the output.

If RouDi is not running you get this output.

[Warning]: RouDi not found - waiting ...

After a waiting period, the application will shut down.

How to write a simple application

This is a brief API guide how to write a simple application.

We start with cargo new.

cargo new --bin hypnotoad

In the Cargo.toml manifest file we create two binaries and add the iceoryx-rs dependency.

[[bin]]
name = "publisher"
path = "src/publisher.rs"

[[bin]]
name = "subscriber"
path = "src/subscriber.rs"

[dependencies]
iceoryx-rs = "0.1"

Now lets define the data we want to transmit and store them in src/topic.rs.

use iceoryx_rs::marker::ShmSend;

#[repr(C)]
#[derive(Default)]
pub struct Counter {
    pub counter: u32,
}

unsafe impl ShmSend for Counter {}

The ShmSend marker trait is used for types that can be transferred via shared memory and is similar to the Send marker trait which is used for types that can be transferred across thread boundaries.

The types which implement ShmSend must satisfy the following constraints:

• no heap is used
• the data structure is entirely contained in the shared memory - no pointers to process local memory, no references to process local constructs, no dynamic allocators
• the data structure has to be relocatable and therefore must not internally use pointers/references
• the type must not implement Drop; drop will not be called when the memory is released since the memory might be located in a shm segment without write access to the subscriber In general, types that could implement the Copy trait fulfill these requirements.

The data type has also the #[repr(C)] attribute to be able to communicate with C and C++ applications and implements the Default trait. If the Default trait is not implemented, an unsafe API must be used to loan samples.

Next is the src/publisher.rs file.

use iceoryx_rs::PublisherBuilder;
use iceoryx_rs::Runtime;

use std::error::Error;
use std::thread;
use std::time::Duration;

mod topic;
use topic::Counter;

fn main() -> Result<(), Box<dyn Error>> {
    Runtime::init("publisher");

    let publisher = PublisherBuilder::<Counter>::new("all", "glory", "hypnotoad").create()?;

    let mut counter = 0u32;
    loop {
        let mut sample = publisher.loan()?;
        sample.counter = counter;
        publisher.publish(sample);

        println!("Send praise hypnotoad: {}", counter);
        counter += 1;

        thread::sleep(Duration::from_millis(1000));
    }
}

The first thing to do is the initialization of the iceoryx Runtime. This does the registration at the central RouDi daemon and takes the application name as parameter.

Then the Publisher is created with the PublisherBuilder by specifying a service, event and instance ID. These can be arbitrary strings and are used to match publisher and subscriber.

The publisher code is completed with a loop where once a second a sample is loaned and published.

Finally we create the src/subsriber.rs file.

use iceoryx_rs::Runtime;
use iceoryx_rs::SubscriberBuilder;

use std::error::Error;
use std::thread;
use std::time::Duration;

mod topic;
use topic::Counter;

fn main() -> Result<(), Box<dyn Error>> {
    Runtime::init("subscriber");

    let (subscriber, sample_receive_token) =
        SubscriberBuilder::<Counter>::new("all", "glory", "hypnotoad")
            .queue_capacity(5)
            .create()?;

    let sample_receiver = subscriber.get_sample_receiver(sample_receive_token);

    loop {
        if let Some(sample) = sample_receiver.take() {
            println!("Receiving praise hypnotoad: {}", sample.counter);
        } else {
            thread::sleep(Duration::from_millis(100));
        }
    }
}

Similar to the publisher application, the first thing to do is initializing the Runtime.

The SubscriberBuilder is used to create a Subscriber and a SampleReceiveToken by specifying the same three service, event and instance ID strings as with the publisher.

Before entering the loop, a SampleReceiver is obtained. In the loop we take samples until the receiver queue is empty and print the data we received. In case there is no data, the thread is suspended for one second and we try to take new samples.

We are done. Lets run our code.

1. Start RouDi with find target -type f -wholename "*/iceoryx-install/bin/iox-roudi" -exec {} \;
2. Start the publisher with cargo run publisher
3. Start the subscriber with cargo run subscriber

Please have a look at the examples in the repository. It contains additional examples to show how uninitialized samples can be loaned and how the wait_for_samples method of the SampleReceiver can be used to get notified on new samples.

Limitations

Currently, only a subset of Eclipse iceoryx v2.0 is supported and some features are missing.

Supported:

• pub-sub messaging pattern
• accessing introspection topics like memory usage and available publisher and subscriber
  • have a look at iceray

Missing:

• user defined header for pub-sub data
• request-response messaging pattern
• Listener and WaitSet
• lookup of available services aka ServiceDiscovery