mortice

Isomorphic read/write lock that works in single processes, node clusters and web workers

About

• Reads occur concurrently
• Writes occur one at a time
• No reads occur while a write operation is in progress
• Locks can be created with different names
• Reads/writes can time out

Usage

import mortice from 'mortice'
import delay from 'delay'

// the lock name & options objects are both optional
const mutex = mortice('my-lock', {

  // how long before write locks time out (default: 24 hours)
  timeout: 30000,

   // control how many read operations are executed concurrently (default: Infinity)
  concurrency: 5,

  // by default the the lock will be held on the main thread, set this to true if the
  // a lock should reside on each worker (default: false)
  singleProcess: false
})

Promise.all([
  (async () => {
    const release = await mutex.readLock()

    try {
      console.info('read 1')
    } finally {
      release()
    }
  })(),
  (async () => {
    const release = await mutex.readLock()

    try {
      console.info('read 2')
    } finally {
      release()
    }
  })(),
  (async () => {
    const release = await mutex.writeLock()

    try {
      await delay(1000)

      console.info('write 1')
    } finally {
      release()
    }
  })(),
  (async () => {
    const release = await mutex.readLock()

    try {
      console.info('read 3')
    } finally {
      release()
    }
  })()
])

read 1
read 2
<small pause>
write 1
read 3

Browser

Because there's no global way to evesdrop on messages sent by Web Workers, please pass all created Web Workers to the observable-webworkers module:

// main.js
import mortice from 'mortice'
import observe from 'observable-webworkers'

// create our lock on the main thread, it will be held here
const mutex = mortice()

const worker = new Worker('worker.js')

observe(worker)

// worker.js
import mortice from 'mortice'
import delay from 'delay'

const mutex = mortice()

let release = await mutex.readLock()
// read something
release()

release = await mutex.writeLock()
// write something
release()

Install

$ npm i mortice

Browser <script> tag

Loading this module through a script tag will make it's exports available as Mortice in the global namespace.

<script src="https://unpkg.com/mortice/dist/index.min.js"></script>

API Docs

• https://achingbrain.github.io/mortice

License

Licensed under either of

• Apache 2.0, (LICENSE-APACHE / http://www.apache.org/licenses/LICENSE-2.0)
• MIT (LICENSE-MIT / http://opensource.org/licenses/MIT)

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.