Async Cancellables / AsyncSimpleRpc

Asynchronous remote function calls with cancellation support via socket.io

Table of contents

• Prerequisites
• Table of contents
• Installation
• API
  • Remote resource
  • Creating server
  • Creating client
  • Calling remote methods
  • Releasing remote resources
  • Misc client methods and properties
  • Misc server methods and properties
  • Events
  • Client error markers
• Authors
• License

Prerequisites

This project requires NodeJS (version 18 or later) and NPM.

Installation

To install and set up the library, run:

$ npm install @async-cancellables/async-simple-rpc

Example

The following example downloads a list of files having no more than 2 concurrent downloads

import { Server } from 'socket.io';
import Client from 'socket.io-client';
import { createServer } from 'http';
import { AsyncRpcServer, AsyncRpcClient } from '@async-cancellables/async-simple-rpc';
import { AsyncLock, AsyncLockTicket } from '@async-cancellables/async-lock';
import AsyncCooldownQueue from '@async-cancellables/async-cooldown-queue';
import CT from '@async-cancellables/ct';

const namespace = '/__asyncSimpleRpc';
const url = `http://127.0.0.1:8080${namespace}`;

const asyncLock = new AsyncLock(2);
const asyncCooldownQueue = new AsyncCooldownQueue(1000);

const methods = {
    add: (a, b) => a + b,
    lock: async (ct, slotCount) => asyncLock.wait(slotCount, ct),
    wait: async (ct) => asyncCooldownQueue.wait(ct),
};

const httpServer = createServer();
httpServer.listen(8080);

const socketServer = new Server(httpServer);
const asyncRpcServer = AsyncRpcServer.socketio(socketServer.of(namespace), methods, { resourceClasses: [AsyncLockTicket, 'release'] });
const asyncRpcClient = AsyncRpcClient.socketio(Client(url));

let sum = await asyncRpcClient.add(CT.manual(), 1, 2); // 3
let ticket = await asyncRpcClient.lock(CT.manual(), 1); // acquire remote lock, returns AsyncRpcRemoteResource
await ticket.waitRelease(); // wait for remote lock release
await asyncRpcClient.wait(CT.manual()); // wait for cooldown

API

Remote resource

Remote resource is a class that represents remote resource and provides methods to release it. Example of such resource is AsyncLockTicket which represents lock ticket. To release slots occupied by the ticket you should call release() method of the ticket, so other waiters can acquire these slots.

Creating server

AsyncRpcServer requires socket.io server instance and methods to be exposed, also you may specify resource classes list and their release method names. AsyncRpcServer.socketio(socketServer, methods, options) method creates AsyncRpcServer instance and exposes methods to socket.io server instance: - socketServer socket.io server instance - methods is an object with methods to be exposed - options is an object with options: - resourceClasses is a mixed array of resource classes and their release method names or a respective Map

Methods can be regular or async functions. If it is an async function, it the first parameter should receive a CancellationToken instance.

const asyncRpcServer = AsyncRpcServer.socketio(
    socketServer, 
    {
        add: (a, b) => a + b,
        wait: async (ct, time) => CT.sleep(time, ct),
    }, 
    { 
        resourceClasses: [AsyncLockTicket, 'release'] 
    }
);

Creating client

AsyncRpcClient requires socket.io client instance and a list of methods to be exposed.

AsyncRpcClient.socketio(socketClient, methods, options) method creates AsyncRpcClient instance and exposes methods to socket.io client instance: - socketClient socket.io client instance - methods is an array with method names to be exposed - options is an object with options: - requestTimeout is a timeout for request to be confirmed by the server in milliseconds, default is no timeout

Calling remote methods

AsyncRpcClient exposes methods that were specified in the constructor and the first argument should be a CancellationToken instance or null regardless of whether the server method is async or not.

let sum = await asyncRpcClient.add(null, 1, 2); // `ct` argument is null, wait for the result indefinitely
sum = await asyncRpcClient.add(CT.timeout(100), 1, 2); // call will be cancelled after 100ms if the result is not received
await asyncRpcClient.wait(CT.manual(), 1000); // wait for 1 second

Releasing remote resources

Remote resources are released by calling release() method of the resource instance. If the resource is not released, it will be released automatically when the connection is closed.

let remoteResource = await asyncRpcClient.lock(null, 1); // acquire remote lock, returns AsyncRpcRemoteResource
remoteResource.release(); // request for a release and return immediately
await remoteResource.waitRelease(CT.manual()); // wait for remote lock release

Misc client methods and properties

• waitConnected(ct = null) wait for the connection to be established
• waitDisconnected(ct = null) wait for the connection to be closed
• connected returns true if the connection is currently established
• connect() establish connection
• disconnect() close connection

Misc server methods and properties

• destroy() stop accepting new connections

Events

• open - emitted when the connection is established
• close - emitted when the connection is closed

Client error markers

Used as markers for cancellation errors thrown by the client (error.marker);

import { AsyncRpcClientMarkers } from '@async-cancellables/async-simple-rpc';

• AsyncRpcClientMarkers.RequestTimeout - request timeout (if requestTimeout option is specified)
• AsyncRpcClientMarkers.ConnectionClosed - connection closed during request or was closed before request was made

Authors

• vuwuv - Initial work - vuwuv

License

[MIT License] © vuwuv