Created Procedural Macros For Pub Sub

[zedgell]

Added a Procedural Macro for pubsub client and updated publisher and subscriber example to demo the macro.

[NickLarsenNZ]

Really nice!

[NickLarsenNZ]

@zedgell you'll need to amend the commits with the DCO signoff.
I also recommend rebasing to squash/fixup or rename commits (looking at those "add feature" commits -- see my auto-comment below which I'd written for my internal repos so apologies if the wording is a bit off).

---

To reduce the noise in the target branch, it is a good idea to do an interactive rebase locally to tidy up the branch.

To do so,

git fetch
git rebase -i origin/main

You should see something similar to:

pick b3896031 enable the flux capacitor
pick 979393bd fix typo from previous commit

In your editor, change the first word on each commit from pick to whatever operation you desire.

An example is fixing up a typo from the parent commit:

pick b3896031 enable the flux capacitor
f 979393bd fix typo from previous commit

For the example above, you can also amend the staged typo fix into the last commit instead of creating a new commit with git commit --amend --no-message.

Save, then git push --force-with-lease.

You can also move commits around, but if their changes are near each other, you might just have to step through some conflict resolution (which can seem intimidating at first, but if you keep an eye on which commit the rebase is up to, it should be easier resolve).

[zedgell]

@NickLarsenNZ Should be good now. Let me know if any other changes are needed

[NickLarsenNZ]

Had more of a look over the code, and noted a couple of things.

Oops, I hit Approve instead of Comment

[NickLarsenNZ]

We might want to use fully qualified names to avoid name collision.

[NickLarsenNZ]

It looks like this would only work for a single topic.

The ListTopicSubscriptionsResponse::topic method is a bit misleading. See #81 (comment) to see how to add multiple topics.

[NickLarsenNZ]

Oh, my bad, I see each use of the macro creates an AppCallback implementation.

As far as I could see, this doesn't work with tonic (see my other comment here: #81 (comment)).

So I think we need to have a single implementation generated, but I don't know how that can work in this case.

Could something like this work?

struct MyService {}

#[dapr] // with this creating the single AppCallback implementation
impl MyService {

  // The pubsub_name and topic would be stored, and the method would then be used in the   `on_topic_event` trait implementation (eg: using match).
  // perhaps the function signature should have a parameter for pubsub name and topic (eg a Context struct)
  #[subscribe(pubsub_name = "pubsub", topic = "A")]
  async fn handle_message(&self, order: Order) {
    println!("{:#?}", order)
  }

}

I changed a couple of things in the macro usage (based on the python-sdk):

• topic -> subscribe
• pub_sub_name - > pubsub_name

Keen to hear your thoughts?

[zedgell]

@NickLarsenNZ I will take a look over them.

[NickLarsenNZ]

Hi @zedgell, did you manage to get any further?

[zedgell]

@NickLarsenNZ I added a potential fix for the multiple events. I wanted them to be able to define multiple handlers for each event but not have to create a new struct for each one. I looked at the way you suggested but that poses a challenge of trying to find that method and hoping they dont have one with a similar name. What I did was Created a central AppCallbackService that users can import. It contains a vec of handlers that stores the struct that contains the handler function. I have updated the example and also below is some example code.

#[derive(Serialize, Deserialize, Debug)]
struct Order {
    pub order_number: i32,
    pub order_details: String,
}

#[topic(pub_sub_name = "pubsub", topic = "A")]
async fn handle_a_event(order: Order) {
    println!("Topic A - {:#?}", order)
}

#[topic(pub_sub_name = "pubsub", topic = "B")]
async fn handle_b_event(order: Order) {
    println!("Topic B - {:#?}", order)
}

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let addr = "127.0.0.1:50051".parse().unwrap();

    let mut callback_service = AppCallbackService::new();

    callback_service.add_handler(HandleAEvent::default().get_handler());

    callback_service.add_handler(HandleBEvent::default().get_handler());

    println!("AppCallback server listening on: {}", addr);

    // Create a gRPC server with the callback_service.
    Server::builder()
        .add_service(AppCallbackServer::new(callback_service))
        .serve(addr)
        .await?;

    Ok(())
}

[zedgell]

@NickLarsenNZ did you get a chance to review the above?

[mikeee]

@zedgell Hi Zachary, this looks amazing and will reduce the amount of boilerplate code that needs to be written! Would you be able to move this to the macros folder (and fix conflicts)? This PR has been usurped by the actors PR #99

[zedgell]

@mikeee Should be good now. Excuse all the extra commits. May have reverted a little to far the first time when I forgot to sign off lol.

[mikeee]

No dramas, thank you for picking this up so quickly after it being open for a long time!
The formatted has picked up a few small diffs. Could you please take a look at those?

[zedgell]

@mikeee looks like it ran fine now. Let me know if you see any other potential problems.

[mikeee]

lgtm, will pick up the failing pubsub validation in another issue/pr.