API Workshop #6 (Rust) [2025-05-20]

[darkwisebear]

Participants

@darkwisebear
@MarkSchmitt

Agenda

1. Discuss workshop agenda
2. Review package structure of applications
3. Continue on API (methods?)

Minutes

On 1.

• We will start at Mon, 2nd at 10 at FIZ
• Methodology: We will assume that there is an entity (== generator) that is able to generate Rust code for all data and interface declarations. Based on this we will then use macros to generate the glue needed to integrate the API into the low level communication framework.
• In-person Workshop Added workshop goal and updated agenda and times accordingly

On 2.

Decision: We instantiate using generated code. Rationale: Putting the duty of instantiation to the generic code leads to all sorts of trouble (e.g. cyclic dependency between generic and generated code, need for HKT(?)). For the agreed package structure see the puml inside the source (link to come).

On 3.

• ConsumerBuilder/Subscriber does not require an explicit subscribe call? For SOME/IP this might be required since otherwise we'd need to subscribe to ALL events OR lazily subscribe in case receive* is called.
• Subscriber contains three ways to receive: polling, async and blocking. Keeping it like this makes the implementation for Lola cumbersome and/or inefficient: Since each of these three ways requires a different callback setup (notifying, using a Rust Waker, or no callback) we would need to dynamically switch between these methods, switching the callback handler when the user uses different ways.
  This could be solved by providing a default implementation for the blocking calls that block on the future returned by receive. Other implementations could still override this by overriding the default implementation.
  Another option is splitting the trait into a sync and an async part or a blocking, async and polling part. In this case, each "mode" could be perfectly tailored towards its specific needs.
• Constrain lifetimes of returned data of event receive methods so that they cannot outlive the subscribed event.

[darkwisebear]

Code from today's session: eclipse-score/inc_mw_com#7 (includes code from the previous sessions).