ZeroMQ retransmitting pub-sub model - node.js

Question

I'm trying to use the ZeroMQ javascript bindings to implement a re-transmitting pub-sub backbone.
Something to the effect of:
inbound modules announce themselves to the backbone, the backbone subscribes to them and re-transmits on its own publisher socket
outbound modules subscribe to backbone
I'm running into an issue with the pub sockets required to be used from a single thread though.
My current code, was something like this:
async function listen(name: string, sub: zmq.Subscriber, pub: zmq.Publisher) {
let id = 0;
for await (const [topic, msg] of sub) {
console.log(`BACKBONE | ${name} | received a message id: ${++id} related to: ${topic.toString()} containing message: ${msg.toString()}`);
await pub.send([topic, msg]);
}
}
Which gets instantiated for each of the inbound modules, but then of course they clash on pub.send.

Answer 1

I wrote a queue to serialize the socket access, which resolved the problem.
import * as zmq from "zeromq"
export class PublisherQueue {
private queue: Buffer[][] = []
constructor(private publisher: zmq.Publisher) { }
private static toBuffer(value: Buffer | string): Buffer {
if (value instanceof Buffer) {
return value as Buffer;
} else {
return Buffer.from(value as string);
}
}
send(topic: Buffer | string, msg: Buffer | string) {
this.queue.push([PublisherQueue.toBuffer(topic), PublisherQueue.toBuffer(msg)]);
}
async run() {
while (true) {
if (this.queue.length > 0) {
let msg = this.queue.shift();
if (msg !== undefined) {
await this.publisher.send(msg);
}
} else {
await new Promise(resolve => setTimeout(resolve, 50));
}
}
}
}