thread_pools v2.5.5

Thread pool with Auto-configuration for worker_threads, provides both thread and pool function, has thread-safe storage

Usage

Use --experimental-worker flag while running the code.

const Pool = require("thread_pools");

let ezpool = new Pool();
let pool = new Pool({
  threads: 2,
  importGlobal: `const os = require('os');`,
  waitMs: 1000,
});

for (let i = 0; i < 10; i++) {
  pool.threadPool((index) => console.log(os.cpus().length + index), i);
}

pool
  .threadSingle(() => {
    process.env.returnType = "String";
  })
  .then(() => console.log(process.env.returnType));

pool.threadSingleStoppable(() => {}).cancel();

features

1. Auto configured

2. Lazy initialize threads in thread pool

3. can use console.log inside thread function

4. has thread-safe storage, can pass javascript Object

Notice

• better initialize Pool only once and Store it in a global variable

• some libraries are unable to support worker_threads, like bcrypt

• process.env is thread unsafe, use with caution.

• thread-safe storage is very expensive

• func cannot use any pre-declared variable, need to pass in as a parameter

let variable = 10;
pool.threadSingle(() => console.log(variable)); // not gonna work, out of scope
pool.threadSingle((v) => console.log(v), variable); // 10

API

Pool(options)

{
    threads = if No. of cpu < 3, then 2, else (cpu No. * 2 - 2)
    importGlobal : import / require statement for every threads
    waitMs: Main Thread Pool Checker, wait certain time until pools freed up
}

async threadSingle(func, ...param)

func : toStringable / cloneable function, param : parameters of func

single thread runner, very expensive, auto closed.

async threadSingleStoppable(func, ...param)

return {cancel:Function, result:Promise} also auto closed after finish

async threadPool(func, ...param)

func : toStringable / cloneable function, param : parameters of func

use already initialized threads, expensive at the beginning but much faster than threadSingle for larger task

async threadPoolStoppable(func, ...param)

return Promise<{cancel:Function,uid:Number, result:Promise}>

threadPoolStoppable().catch() will not catch the error, use

threadPoolStoppable().then(data=>data.result.catch()) instead

every time you call it, it will generate a unique uid, can use it to call _threadPoolStop

when thread returned a result, it will not be cancelled / terminated, but you can still call it;

async _threadPoolStop(uid = 0)

if(uid > 0) cancel corresponding thread, has no effect on already finished thread

if(uid == 0) delete all threads in thread pool

if(uid < 0) no effect

Inner API

usage

const assist = require("thread_pools").assist;

assist is a keyword, so you have to use this one.

inner api is the function you can use within func

i.e.

threadSingle(() => assist.sleep(2)).then(() => {}); // wait 2 seconds

async assist.sleep(seconds)

resolve after certain seconds

assist.serialize(object)

use eval('('+object+')') to deserialize

async assist.lock()

try to manually acquire the main lock, will wait until the lock is lifted

async assist.unlock()

better call assist.lock() beforehand, other threads may have access to the shared data

async assist.waitComplete(callback)

wait for the return of the event queue (wait until main thread worker's event queue's callback)

async assist.autoLocker(callback)

acquire the lock, call assist.waitComplete, and finally release the lock after callback finshed

async assist.storage(callback = (store = {}) => {})

thread-safe & synced storage, can communicate between different threads, can be used by both single and pool, any change on the store will reflecte on the original pool.storage

pool.storage.p = 0;
pool.threadSingle(() => assist.storage((item) => item.p++)).then(() => console.log(pool.storage));

storage will aquire lock first, then copy main thread storage, wait until user callback finish, update main thread storage, remove lock, and return updated value