Port Peer

A RPC-like facility for making inter-thread function calls.

Introduction

Port Peer provides a simple and intuitive interface that makes inter-thread function calls easy. Please see the Usage or Examples for instructions on how to use Port Peer in your application.

Features

• Bi-directional inter-thread function calls.
• Port Peer will marshal the return value or Error from the other thread back to the caller.
• The other thread may be the main thread or a worker thread.
• Registered functions (i.e., peer.register) persist until deregistered (i.e., peer.deregister) .
• Late binding registrants will be called with previously awaited invocations.

Table of contents

• Installation
• Concepts
• Usage
• Examples
• API
• Versioning
• Notes
• Support

Installation

npm install port-peer --save

Concepts

Peer

An instance of a Peer facilitates bi-directional communication between threads. The Peer can be used in order to register a function in one thread and call it from another thread. Calls may be made from the main thread to a worker thread, and conversely from a worker thread to the main thread.

Late binding registrants will be called with previously awaited invocations; thus preventing a race condition. This means that you may await a call to a function that has not yet been registered. Once the function is registered in the other thread it will be called and its return value or Error will be marshalled back to the caller.

Please see the Examples for variations on the Peer's usage.

Usage

How to create a Peer instance

Import the Peer class and relevant dependencies.

import { Worker, parentPort } from "node:worker_threads";
import { fileURLToPath } from "node:url";
import { Peer } from "port-peer";

You can create a new Peer by passing a MessagePort or Worker instance to the Peer constructor.

In the main thread,

const worker = new Worker(fileURLToPath(import.meta.url));
const peer = new Peer(worker);

or, in a worker thread,

const peer = new Peer(parentPort);

How to use a Peer instance

You can register a function in the main thread or in a worker thread using the peer.register method.

peer.register("hello_world", (value: string): string => `Hello, ${value} world!`);

You can call a function registered in another thread (i.e., the main thread or a worker thread) using the peer.call method:

const greeting = await peer.call<string>("hello_world", "happy");
console.log(greeting); // Hello, happy world!

Examples

A simple example ^</Node.js>

Please see the simple example for a working implementation.

A comprehensive example ^{</TypeScript>}

Please see the comprehensive example for a working implementation.

API

The Peer class

new Peer(port)

• port <threads.MessagePort> or <threads.Worker> The message port.

public peer.call<T>(name, ...args)

• name <string> The name of the registered function.
• ...args <Array<unknown>> Arguments to be passed to the registered function.

Returns: <Promise<T>>

Errors:

• If the registered function in the other thread throws an Error, the Error will be marshalled back from the other thread to this thread and the Promise will reject with the Error as its failure reason.
• If a worker thread throws an unhandled exception while a call is awaited, the Error will be marshalled back from the other thread to this thread and the Promise will reject with the unhandled exception as its failure reason.
• If a worker exits while a call is awaited, the Error will be marshalled back from the other thread to this thread and the Promise will reject with the exit code as its failure reason.

public peer.register(name, fn)

• name <string> The name of the registered function.
• fn <(...args: Array<any>) => any> The registered function.

Returns: <void>

public peer.deregister(name)

• name <string> The name of the registered function.

Returns: <void>

Versioning

The Port Peer package adheres to semantic versioning. Breaking changes to the public API will result in a turn of the major. Minor and patch changes will always be backward compatible.

Excerpted from Semantic Versioning 2.0.0:

Given a version number MAJOR.MINOR.PATCH, increment the:

1. MAJOR version when you make incompatible API changes
2. MINOR version when you add functionality in a backward compatible manner
3. PATCH version when you make backward compatible bug fixes

Additional labels for pre-release and build metadata are available as extensions to the MAJOR.MINOR.PATCH format.

Notes

Support for broadcastChannels

Port Peer supports one to one communication over a MessagePort. BroadcastChannels are not presently supported.

Support for other communication channels

Port Peer is strictly focused on efficient communication over MessagePorts. Port Peer will not support communication over other communication channels e.g., Sockets, IPC, etc.

Support

If you have a feature request or run into any issues, feel free to submit an issue. You’re also welcome to reach out directly to one of the authors.

• Adam Patterson