async queue
async queue
using a sync queue to throttle requests
xxxxxxxxxx// Including the async moduleconst async = require('async');// Creating an array for all elements executionconst tasks = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];// Initializing the queueconst queue = async.queue((task, executed) => { console.log("Currently Busy Processing Task " + task); setTimeout(()=>{ // Number of tasks remaining and to be processed const tasksRemaining = queue.length(); executed(null, {task, tasksRemaining}); }, 1000);}, 1); // concurrency value = 1// Queue is idle initially as no elements are there...console.log(`Queue Started ? ${queue.started}`)// Adding each task from the tasks listtasks.forEach((task)=>{ // Adding the task 5 to the head for priority execution if(task == 5){ queue.unshift(task, (error, {task, tasksRemaining})=>{ if(error){ console.log(`An error occurred while processing task ${task}`); }else { console.log(`Finished processing task ${task}. ${tasksRemaining} tasks remaining`); } }) // Adding all the tasks at tail to be executed except task 5 } else { queue.push(task, (error, {task, tasksRemaining})=>{ if(error){ console.log(`An error occurred while processing task ${task}`); }else { console.log(`Finished processing task ${task}. ${tasksRemaining} tasks remaining`); } }) }});// Executes the callback when the queue is done processing all the tasksqueue.drain(() => { console.log('All items are succesfully processed !');})// Checking if the queue is started after adding tasksconsole.log(`Queue Started ? ${queue.started}`)/*console.log(queue.length());// Executes when the queue is done processing all the itemsqueue.drain(() => { console.log('Successfully processed all items');})// Pauses the execution of the queuequeue.pause()// Resumes the execution of the queuequeue.resume()// Forces the queue into idle mode// and removes the drain callbackqueue.kill()// Returns whether the queue is idle or notqueue.idle()Queue Started ? FalseQueue Started ? TrueCurrently Busy Processing Task 5Finished processing task 5. 9 tasks remainingCurrently Busy Processing Task 1Finished processing task 1. 8 tasks remainingCurrently Busy Processing Task 2Finished processing task 2. 7 tasks remainingCurrently Busy Processing Task 3Finished processing task 3. 6 tasks remainingCurrently Busy Processing Task 4Finished processing task 4. 5 tasks remainingCurrently Busy Processing Task 6Finished processing task 6. 4 tasks remainingCurrently Busy Processing Task 7Finished processing task 7. 3 tasks remainingCurrently Busy Processing Task 8Finished processing task 8. 2 tasks remainingCurrently Busy Processing Task 9Finished processing task 9. 1 tasks remainingCurrently Busy Processing Task 10Finished processing task 10. 0 tasks remainingAll items are succesfully processed !*/Source: www.tutorialspoint.com
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xxxxxxxxxxfunction createQueue(tasks, maxNumOfWorkers = 4) { var numOfWorkers = 0; var taskIndex = 0; return new Promise(done => { const handleResult = index => result => { tasks[index] = result; numOfWorkers--; getNextTask(); }; const getNextTask = () => { if (numOfWorkers < maxNumOfWorkers && taskIndex < tasks.length) { tasks[taskIndex]().then(handleResult(taskIndex)).catch(handleResult(taskIndex)); taskIndex++; numOfWorkers++; getNextTask(); } else if (numOfWorkers === 0 && taskIndex === tasks.length) { done(tasks); } }; getNextTask(); });}Source: krasimirtsonev.com
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