Serial queue in node.js/Javascript?-CodePudding

In my node.js codebase I have three function I want to prevent to run in parallel. So I want to have a way to run those functions serially at any given time.

On other platforms I am used to setup a serial queue and then dispatch code onto the queue knowing that the execution of dispatched work is going to be serialized.

I am not sure how to do this in Node.js or Javascript. What reliable option do I have in either to serialize the execution of functions?

CodePudding user response：

You can use async functions for that. Check inline comments for more details:

// Timeout function for example purpose
const timeout = ms => new Promise(resolve => setTimeout(resolve, ms));

// Your ASYNC functions
const fn1 = async () => {
  // Simulate some work by waiting for timeout
  await timeout(1000);
  console.log(`Function 1 completed`);
}
const fn2 = async () => {
  // Simulate some work by waiting for timeout
  await timeout(2000);
  console.log(`Function 2 completed`);
}
const fn3 = async () => {
  // Simulate some work by waiting for timeout
  await timeout(500);
  console.log(`Function 3 completed`);
}

// Now run them in sequence. You can create
// separate function for this
const runInSeq = async fns => {
  // For each function in provided array
  // run it, wait till complete, run next
  for(const fn of fns) await fn();
}

// Now you can pass all your async functions
// to your runner as an array and it will
// run them in seq
runInSeq([fn1, fn2, fn3]);

And this is one of options how you can create queue

// Timeout function for example purpose
const timeout = ms => new Promise(resolve => setTimeout(resolve, ms));

// Your ASYNC functions
const fn1 = async () => {
  // Simulate some work by waiting for timeout
  await timeout(1000);
  console.log(`Function 1 completed`);
}
const fn2 = async () => {
  // Simulate some work by waiting for timeout
  await timeout(2000);
  console.log(`Function 2 completed`);
}
const fn3 = async () => {
  // Simulate some work by waiting for timeout
  await timeout(500);
  console.log(`Function 3 completed`);
}

// To run functions in queue you can create some array
// in which you will push additional functions and
// iterate it with some control logic
//
// Create queue array
const fnQueue = [];
// Also create some while loop indicator
let runningWhile = false;
// Queue function
const runInQueue = async fn => {
  // Push new function to queue array
  fnQueue.push(fn);
  // If while loop not running, run it
  if(!runningWhile) {
    // Set while loop indicator to true
    runningWhile = true;
    // Run while loop
    while(fnQueue.length > 0) {
      // Shift array and run function
      const fn = fnQueue.shift();
      await fn();
    }
    // After while loop, set indicator to false
    runningWhile = false;
  }
}

// Add functions to queue with some delays
(async () => {
  runInQueue(fn1);
  await timeout(1100);
  runInQueue(fn2);
  await timeout(500);
  runInQueue(fn3);
})();