singleprocess

Single process

Introduction

This example demonstrates how iceoryx can be used in a single process for inter-thread communication. This is for instance helpful if you would like to establish a simple communication API in a 3D engine with a multitude of threads that are interacting without starting RouDi every time separately.

Run singleprocess

The first lines until RouDi is ready for clients are coming from the RouDi startup in which the shared memory management segment and user data segment are created.

Afterward, the publisher and subscriber thread are started and are beginning to transmit and receive data.

Code Walkthrough

Creating a Single Process RouDi, Publisher and Subscriber

1. We start by setting the log level to info since we do not want to see all the debug messages.

iox::log::Logger::init(iox::log::LogLevel::Info);

2. To start RouDi we have to create a configuration for him. We are choosing the default config but set the sharesAddressSpaceWithApplications to tell RouDi to not terminate all registered processes when RouDi goes out of scope. If we would not set it, our application would self terminate in the destructor of roudi. Additionally, RouDi needs some other components like a memory management unit which handles how the memory is created in which the transmission data is stored. The IceOryxRouDiComponents class is handling them for us.

iox::IceoryxConfig config = iox::IceoryxConfig().setDefaults();
config.sharesAddressSpaceWithApplications = true;
iox::roudi::IceOryxRouDiComponents roudiComponents(config);

3. We are starting RouDi by providing the required components and config.

iox::roudi::RouDi roudi(roudiComponents.rouDiMemoryManager, roudiComponents.portManager, config);

4. Here comes a key difference to an inter-process application. If you would like to communicate within one process, you have to use PoshRuntimeSingleProcess. You can create only one runtime at a time!

iox::runtime::PoshRuntimeSingleProcess runtime("singleProcessDemo");

5. Now that everything is up and running, we can start the publisher and subscriber thread and wait until the user terminates the application.

std::thread publisherThread(publisher), subscriberThread(subscriber);

iox::waitForTerminationRequest();

publisherThread.join();
subscriberThread.join();

std::cout << "Finished" << std::endl;

Implementation of Publisher and Subscriber

Since there are no differences to the inter-process ports you can take a look at the icedelivery example for a detailed documentation. We only provide here a short overview.

Publisher

We create a typed publisher with the following service description (Service = Single, Instance = Process, Event = Demo) and a historyCapacity of 10.

iox::popo::PublisherOptions publisherOptions;
publisherOptions.historyCapacity = 10U;
iox::popo::Publisher<TransmissionData_t> publisher({"Single", "Process", "Demo"}, publisherOptions);

After that, we are sending numbers in ascending order with a 100ms interval in a while loop.

uint64_t counter{0};
constexpr const char GREEN_RIGHT_ARROW[] = "\033[32m->\033[m ";
while (!iox::hasTerminationRequested())
{
    publisher.loan().and_then([&](auto& sample) {
        sample->counter = counter++;
        consoleOutput("Sending   ", GREEN_RIGHT_ARROW, sample->counter);
        sample.publish();
    });

    std::this_thread::sleep_for(CYCLE_TIME);
}

Subscriber

We create a subscriber port with the same service description, a queueCapacity of 10 and request to get the last 5 samples when we connect (historyRequest).

iox::popo::SubscriberOptions options;
options.queueCapacity = 10U;
options.historyRequest = 5U;
iox::popo::Subscriber<TransmissionData_t> subscriber({"Single", "Process", "Demo"}, options);

Now we can receive the data in a while loop when our SubscribeState is SUBSCRIBED until someone terminates the application.

constexpr const char ORANGE_LEFT_ARROW[] = "\033[33m<-\033[m ";
while (!iox::hasTerminationRequested())
{
    if (iox::SubscribeState::SUBSCRIBED == subscriber.getSubscriptionState())
    {
        bool hasMoreSamples{true};

        do
        {
            subscriber.take()
                .and_then([&](auto& sample) { consoleOutput("Receiving ", ORANGE_LEFT_ARROW, sample->counter); })
                .or_else([&](auto& result) {
                    hasMoreSamples = false;
                    if (result != iox::popo::ChunkReceiveResult::NO_CHUNK_AVAILABLE)
                    {
                        std::cout << "Error receiving chunk." << std::endl;
                    }
                });
        } while (hasMoreSamples);
    }

    std::this_thread::sleep_for(CYCLE_TIME);
}

[Check out singleprocess on GitHub :fontawesome-brands-github:](https://github.com/eclipse-iceoryx/iceoryx/tree/main/iceoryx_examples/singleprocess){ .md-button }