Nebulas RPC subscribe interface issue

[qywang2012]

Nebulas subscribe interface using the long connection, RPC using gRPC connection, the long connection by a stream can work well. However, in the HTTP request, using the keep-alive can request but don't return data.

gRPC usage

	addr := fmt.Sprintf("127.0.0.1:%d", uint32(8684))
	conn, err := rpc.Dial(addr)
	if err != nil {
		log.Fatal(err)
	}
	defer conn.Close()

	ac := rpcpb.NewApiServiceClient(conn)

	stream, err := ac.Subscribe(context.Background(), &rpcpb.SubscribeRequest{})

	if err != nil {
		log.Fatalf("could not subscribe: %v", err)
	}
	for {
		reply, err := stream.Recv()
		if err == io.EOF {
			break
		}
		if err != nil {
			log.Printf("failed to recv: %v", err)
		}
		log.Println("recv notification: ", reply.Topic, reply.Data)
	}

http usage

curl and the JS implementation of the RPC don't seem to return the data properly because the data is encoded in chunks.

const http = require("http")

callback = function(response) {
  response.on("data", function(chunk) {
    console.log(chunk.toString("utf8"))
  })
}

var req = http.request(
  {
    host: "localhost",
    port: 8685,
    path: "/v1/user/subscribe",
    method: "POST",
    headers: { "Content-Type": "application/json" },
  },
  callback
)
req.on("error", function(e) {
  console.log("problem with request: " + e.message)
})
req.write('{"topics":["chain.executeTxSuccess"]}')
req.end()

Anybody has a better way to handle the Subscribe via http?

issue

The event emitter is a non-blocking design, evnent data will be lost when the channle is full when there are many subscribed events. Since the RPC stream is sent serially, the message is not delivered in time. We need a non-blocking pipeline for event collection. Can anyone alse take this job, using kafka, redis, etc as the adapter?

The events in event trie May not response in Subscribe, This may be a bug in event emitter.

[fbzhong]

Hi Larry,

How's this issue? Any updates?

[1c7]

Any update?
Why close this issue?

[1c7]

Goal: Reliably listen to event (emit by specific Smart Contract)

For Example: NRC20 token,

Following code come from official doc

    transfer: function (to, value) {
        value = new BigNumber(value);

        var from = Blockchain.transaction.from;
        var balance = this.balances.get(from) || new BigNumber(0);

        if (balance.lt(value)) {
            throw new Error("transfer failed.");
        }

        this.balances.set(from, balance.sub(value));
        var toBalance = this.balances.get(to) || new BigNumber(0);
        this.balances.set(to, toBalance.add(value));

        this.transferEvent(true, from, to, value); // <--------------How do I listen to this?
    },

Example: user transfer NAS to a Nebulas wallet address that we provide(n1...something)

We need to know that when that happen.
and give user our NRC20 token.

it's like a webhook.
I don't want to long polling. like in Web development just keep sending Ajax

[1c7]

Do I have to run a local node myself? and do this?

[1c7]

Doc: https://github.com/nebulasio/wiki/blob/master/rpc.md#subscribe

[1c7]

Seem like I can't subscribe to specific one Smart Contract?
subscribe seem like return all event?