locked-sync v1.0.0

Usage

npm install --save locked-sync

Synchronize and serialize a piece of code.

Why do you need this in javascript or Node.js. Consider the following code

redis.get('key', function(err, value) {
  redis.set('key', value + 1);
});

If two users run concurrency, the execution order may like this

user1: var val = redis.get('key');  => 1
user2: var val = redis.get('key');  => 1
user1: redis.set('key', val + 1) => 2
user2: redis.set('key', val + 1) => 2

So, you can use locked-sync to avoid it.

const lockedSync = require('locked-sync');
const sync = lockedSync();

function getAndSet() {
  sync().then(end => {
    redis.get('key', (val, err) => {
      redis.set('key', val + 1);
      end();
    });
  });
}

getAndSet(); getAndSet(); getAndSet(); getAndSet(); // almost same time to get and set

const lockedSync = require('locked-sync');
const sync = lockedSync();

async function getAndSet() {
  const end = await sync();
  try {
    const val = await redis.get('key');
    await redis.set('key', val + 1);
  } finally {
    end(); // Always put it in finally block.
  }
}

getAndSet(); getAndSet(); getAndSet(); getAndSet();