epic-locks

A project meant to contain multiple different type of mutex locks.

Usage

Import each lock directly from its own module. The package intentionally has no barrel entry point, so you only pull in the lock you actually use:

import Mutex from "epic-locks/build/mutex.js"
import ReadersWriterLock from "epic-locks/build/readers-writer-lock.js"

Mutex

Runs async jobs one at a time (sequentially) — exclusive access, in call order.

import Mutex from "epic-locks/build/mutex.js"
const mutex = new Mutex()

const result = await mutex.sync(async () => {
  return await doSomethingExclusive()
})

ReadersWriterLock

1. Multiple readers
2. Single writer
3. Prioritises reads
4. Processes queued jobs at the end of the event queue to let the original callers finish work before the lock processes the next queued item
5. Queues reads while writing

Initialize

import ReadersWriterLock from "epic-locks/build/readers-writer-lock.js"
const lock = new ReadersWriterLock()

Reading

lock.read(() => {
  console.log("Reading!")
})

Writing

lock.write(() => {
  console.log("Writing!")
})

Advanced

import ReadersWriterLock from "epic-locks/build/readers-writer-lock.js"
const lock = new ReadersWriterLock()
const promises = []
const result = []

promises.push(
  lock.read(async () => {
    await awaitTimeout(50)
    result.push(3)
  })
)
promises.push(
  lock.write(async () => {
    await awaitTimeout(10)

    lock.read(async () => {
      result.push(5)
    })

    result.push(4)
  })
)
promises.push(
  lock.read(async () => {
    await awaitTimeout(40)
    result.push(2)
  })
)
promises.push(
  lock.write(async () => {
    await awaitTimeout(20)
    result.push(6)
  })
)
promises.push(
  lock.read(async () => {
    await awaitTimeout(30)
    result.push(1)
  })
)

await Promise.all(promises)

expect(result).toEqual([1, 2, 3, 4, 5, 6])