blackboard_event_based_communication

Blackboard with Notification on Value Update

Caution

Every payload you transmit with iceoryx2 must implement [ZeroCopySend] to be compatible with shared memory. Usually, you can use the derive-macro #[derive(ZeroCopySend)] for most types. If you implement it manually you must ensure that the payload type:

• is self contained, no heap, no pointers to external sources
• has a uniform memory representation -> #[repr(C)]
• does not use pointers to manage their internal structure
• and its members don't implement Drop explicitly
• has a 'static lifetime

Data types like String or Vec will cause undefined behavior and may result in segmentation faults. We provide alternative data types that are compatible with shared memory. See the complex data type example for guidance on how to use them.

This example demonstrates how to combine the blackboard with the event messaging pattern so that values can be read when updated instead of using a polling loop. Besides the blackboard service, an additional event service is created. This is used to create a notifier that sends a notification whenever a value is updated, using the entry id, and a listener that waits for notifications with a certain entry id and reads the updated value.

How to Run

To observe the blackboard messaging pattern with notifications on value update in action, open two separate terminals and execute the following commands:

Terminal 1

cargo run --example blackboard_event_based_creator

Terminal 2

cargo run --example blackboard_event_based_opener