A semaphore library for node/browsers.

Entry point is ESM.

API

import make_semaphore from '@trex-arms/semaphore'

const delay_1s = () => new Promise(resolve => setTimeout(resolve, 1000))

const semaphore = make_semaphore(2)

const do_stuff = async() => {
	const unlock = await semaphore.lock()
	console.log(`Totally doing work!`)
	await delay_1s()
	unlock()
}

do_stuff() // will start work right away
do_stuff() // will start work right away
do_stuff() // won't start until after one of the other workers finishes

semaphore = make_semaphore(limit)

limit is how many locks are allowed at once.

Returns a semaphore object with two properties:

unlock_function_promise = semaphore.lock()

Returns a promise that resolves as soon as a lock is free. It resolves to an unlock function. Calling that function will release the lock.

locks_free = semaphore.headroom()

Returns the number of unclaimed locks that are currently free.