Event subscription (TS sdk)

[stella3d]

Add event subscription & general websocket functionality to TS SDK.

Basic use

Event filter type mirrors the Rust SuiEventFilter

This shows subscribing to all DevnetNFT events.

const provider = JsonRpcProvider('http://localhost:9000');
const filter = {All: [{EventType:  "MoveEvent"}, {Package: "0x2"}, {Module: "devnet_nft"}]};

// subscribing to an event returns a SubscriptionId
const devNftSub = await provider.subscribeEvent(filter, (event: SuiEventEnvelope) => {
    console.log(event);
    // handle subscription notification message here
});

// later, to unsubscribe 
const subFoundAndRemoved = await provider.unsubscribeEvent(devNftSub);

Testing

Easiest way to test the functionality is:

1. start a local Sui network, run genesis & start, then start sui node

cargo build --release
cd /target/release
sui genesis 
sui start
sui-node

2. to subscribe to DevNetNFT events as shown above in Basic Use, and log the results.

Socket Messages

As an example, here's the sequence of messages that results from:

• socket connect
• subscribe to devnetNFT events
• receive 2 notifications for the subscription (lower half shows the detailed notification message)
• unsubscribe from our subscription

Connection Maintanence

We delay connecting until a websocket is needed, to avoid spamming the node with connections.

If the connection gets closed with active subscriptions and we reconnect, we re-subscribe those subscriptions.

We will likely need to add some rpc method for doing keep-alive / heartbeat requests in the future, so we can ensure connections stay open longer.

[stella3d]

@666lcz i know accessing the underlying .on('message') seems weird but i spent quite a bit more time than i would like on it, including reading all of the code of several other projects (which is where i got the idea to cast and access the underlying event emitter)
Solana's, for example, uses a different notion of notifications - they subscribe to named events.

We could use this approach if we have named events, and i could do like:

this.wsClient.on(
    'eventNotify',
    this.onSocketMesage.bind(this),
);

The rpc-websockets library does not appear to expose the underlying on('message') callback.

need a fresh review

[666lcz]

What is the desired behavior if filter == {All: []}, will it get subscribed all the events in the Network? cc @longbowlu