Question 413622 in Javascript Question posted in
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Can javascript have race condition?

For the following code in javascript I want to know if there are concurrent api requests to increment count is there any possibility of a race condition considering the fact that javascript is single threaded.

  app.post('/increment', async (req, res) => {
    await someAsyncFunction(); // Asynchronous operation
    count++; // Increment operation
    res.send('Count incremented');
  });

From what I understand there shouldn’t be any as once the execution resumes after await someAsyncFunction() count++ being synchronous should be executed in one stretch for a request before the execution resumes the increment for other requests. Let me know if I am wrong to understand this.

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2

Answers


  1. 0

    you can use a Mutex/Lock
    Here’s an example using the async-mutex library to prevent concurrent increments:

    const { Mutex } = require('async-mutex');
const mutex = new Mutex();

app.post('/increment', async (req, res) => {
  await someAsyncFunction(); // Asynchronous operation

  // Lock access to count to prevent race condition
  const release = await mutex.acquire();
  try {
    count++;
  } finally {
    release(); // Ensure mutex is released
  }
  
  res.send('Count incremented');
});

    This guarantees that only one request can increment count at a time, effectively preventing race conditions.

    Also, if you don’t want to use this package, you can write it yourself as follows

    let isLocked = false;

function acquireLock() {
  return new Promise((resolve) => {
    const tryAcquire = () => {
      if (!isLocked) {
        isLocked = true;
        resolve();
      } else {
        setTimeout(tryAcquire, 10); // If it is locked, it will retry every 10 milliseconds
      }
    };
    tryAcquire();
  });
}

function releaseLock() {
  isLocked = false;
}

app.post('/increment', async (req, res) => {
  await someAsyncFunction(); // Asynchronous operation

  await acquireLock(); // Lock access to count to prevent race condition
  try {
    count++;
  } finally {
    releaseLock(); // Ensure lock is released
  }

  res.send('Count incremented');
});
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  2. 0

    Yes, JavaScript can experience race conditions, especially in environments where asynchronous code execution is involved, such as with promises, callbacks, or web APIs like setTimeout, fetch, or event listeners.

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