domains

Domains

Let's assume you want to create multiple iceoryx2 groups of processes where the processes inside a group can communicate and interact with each other. However, the groups themselves should remain isolated, meaning a process from one group cannot interact with a process from another group.

In other words, we aim to create different iceoryx2 domains on a local machine that are strictly separated.

This strict separation can be achieved by using the iceoryx2 configuration. Within the configuration, a wide range of parameters can be adjusted, such as the directory used for files containing static service information (a detailed description of the service) or static node information (a detailed description of a node). Additionally, the prefix of all files, which is by default iox2_, can be modified.

In this example, we use the prefix to separate the iceoryx2 groups. For all examples, the user can set the iceoryx2 domain using -d $DOMAIN_NAME$. The domain name must be a valid file name. The example will only operate within this domain and cannot interact with any services in other domains with different names.

The domains_discovery binary illustrates this by listing all services available in a given domain. Similarly, the domains_publisher will send data only to subscribers within the same domain. Subscribers in other domains will not receive any data.

Implementation

Caution

Every payload you transmit with iceoryx2 must be compatible with shared memory. Specifically, it must:

• be self contained, no heap, no pointers to external sources
• have a uniform memory representation, ensuring that shared structs have the same data layout
  • therefore, only ctypes and ctypes.Structure can be transferred
• not use pointers to manage their internal structure

Any other python data type, except ctypes or ctypes.Structures, like will cause undefined behavior and may result in segmentation faults. Take a look at the publish subscribe example to see how ctypes can be transferred.

To achieve this, we create a copy of the global configuration, modify the setting config.global.prefix using the user-provided CLI argument, and then set up the example accordingly.

How to Build

Before proceeding, a virtual environment with all dependencies needs to be created. You can find the detailed instructions in the Python Examples Readme.

poetry --project iceoryx2-ffi/python install

Then, the iceoryx2 python bindings can be built and installed into the virtual environment:

poetry --project iceoryx2-ffi/python run maturin develop --manifest-path iceoryx2-ffi/python/Cargo.toml --target-dir target/ff/python

How to Run

You can experiment with this setup by creating multiple publishers and subscribers with different service names by using the second argument. Only publisher-subscriber pairs within the same domain will be able to communicate, and the discovery tool will only detect services from within the same domain.

Terminal 1: Subscriber in domain "fuu" subscribing to service "bar"

poetry --project iceoryx2-ffi/python run python examples/python/domains/subscriber.py fuu bar

Terminal 2: Publisher in domain "fuu" publishing on service "bar"

poetry --project iceoryx2-ffi/python run python examples/python/domains/publisher.py fuu bar

Terminal 3: List all services of domain "fuu"

poetry --project iceoryx2-ffi/python run python examples/python/domains/discovery.py fuu