p-lock

Simple promise lock.

_If I should maintain this repo, please ⭐️_

_DM me on Twitter if you have questions or suggestions._

---

About

This package provides a simple promise lock, which is useful for preventing race conditions between multiple promises.

Installation

``sh
yarn add p-lock
`

`sh
npm install p-lock
`

`sh
pnpm install p-lock
`

Overview

First, we get a lock function:

`ts
import { getLock } from "p-lock";

const lock = getLock();
`

Calling the lock function returns a promise that resolves when the lock is acquired.

The promise resolves with a release function, which must be called to release the lock:

`ts
lock("example-key").then((release) => {
// Now I have the lock for "example-key"
// do something...
release();
});
`

Full Example

In this example, we have two promises writing to the same file. However, we want to ensure that the first one finishes before the second one starts.

`ts
import { writeFile } from "fs";
import { getLock } from "p-lock";

const lock = getLock();

lock("file").then((release) => {
setTimeout(() => {
writeFile("test.txt", "hello", () => {
release();
});
}, 1000);
});

lock("file").then((release) => {
writeFile("test.txt", "world", () => {
release();
});
});

// Contents of test.txt will be "world"
`

$3

In some cases, we may want to replace an existing promise waiting for a lock, rather than waiting for it to finish.

The replace option allows us to do this:

`ts
import { writeFile } from "fs";
import { getLock } from "p-lock";

const lock = getLock({ replace: true });

let writeCounter = 0;

lock("file").then((release) => {
setTimeout(() => {
writeCounter += 1;
writeFile("test.txt", update #${writeCounter}, () => {
release();
});
}, 1000);
});

lock("file").then((release) => {
writeCounter += 1;
writeFile("test.txt", update #${writeCounter}, () => {
release();
});
}).catch(() => {
// This promise will reject, since the next one replaces.
});

lock("file").then((release) => {
writeCounter += 1;
writeFile("test.txt", update #${writeCounter}, () => {
release();
});
});

// Contents of test.txt will be "update #2"
``

Dev Dependencies

- autorepo: Autorepo abstracts away your dev dependencies, providing a single command to run all of your scripts.

License

MIT - _MIT License_