[zombinet] initial implementation of zombienet backchannel

[pepoviola]

Hi @drahnr / @Lldenaurois,
This is the initial implementation of the backchannel for zombienet, targeting #4272.

The general idea is that there is a server side running in zombienet environment that has an http and a ws listeners,

• The http interface accept post request to store new items that should be available for use by the test-runner.
• The ws interface broadcasted those new items to all connected malus actors.

Notes:

• The two env vars are defaulted to the ones we need to use in our CI, since we can resolve backchannel to the correct endpoint.
• The connect fn create the ws connection and return the receiver part in the inner field.
• I only tested locally (with a small client that I create), so we need to complete the integration to the malus crate in order to test the complete flow locally or in the CI.
• I'm not sure if the use of the scale encode if correct because in the zombienet side is stored as string.
• A simple test mocking the zombienet server should be implemented after complete the integration.

Thanks!

[drahnr]

See inline comments

[pepoviola]

Hi @drahnr, I updated the implementation follow the pattern from our last talk. Now you have an init fn that connect you to the ws server on zombienet side and then two fn

• subscribe : give you a receiver to get the new item from the ws
• send : Send new items to the ws.

Let me know if you want to change/refactor something.

---

Examples of usage could be:

• receive part

    let backchannel = ZombienetBackchannel::init().await.expect("Error connecting ws");

    let mut rx = backchannel.subscribe();
    while let Ok(backchannel_item) = rx.recv().await {
        println!("{:?}", backchannel_item);
    }

• send

     let backchannel = ZombienetBackchannel::init().await.expect("Error connecting ws");
     backchannel.send(<key>, <value>)

---

Ping @Lldenaurois, let me know if you want to chat about test cases 0002/0003 for malus integration.

Thanks!!

[drahnr]

LGTM besides the lack of documentation :)

[pepoviola]

Thanks for the feedback @drahnr, I added some docs to those methods :)
Thx!

[drahnr]

Could you merge master, so we can merge this :)

[pepoviola]

Hi @drahnr, merged :) but now the smoke test is failing for the same reason of #4519 (comment) (the collator version).
Thanks!

[drahnr]

Please merge master again

[pepoviola]

Please merge master again

Done 👍, thanks!

[pepoviola]

Hi @drahnr, thanks for the feedback. I already made those changes 👍
Thanks!