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Node.js Design Patterns

Parallel Execution: The Pattern

Explore the parallel execution pattern in Node.js to efficiently run multiple asynchronous tasks simultaneously. Understand how to avoid race conditions typical in parallel operations, and learn techniques to control concurrency safely in a single-threaded environment. This lesson helps you implement reliable parallel processing in your applications for improved performance and resource management.

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The pattern

Finally, we can extract our nice little pattern for the parallel execution flow. Let’s represent a generic version of the pattern with the following code:

Node.js
function makeSampleTask (name) {
  return (cb) => {
    console.log(`${name} started`)
    setTimeout(() => {
      console.log(`${name} completed`)
      cb()
    }, Math.random() * 2000)
  }
}
const tasks = [
  makeSampleTask('Task 1'),
  makeSampleTask('Task 2'),
  makeSampleTask('Task 3'),
  makeSampleTask('Task 4')
]
let completed = 0
tasks.forEach(task => {
  task(() => {
    if (++completed === tasks.length) {
      finish()
    }
  })
})
function finish () {
  // all the tasks completed
  console.log('All tasks executed!')
}

With small modifications, we can adapt the pattern to accumulate the results of each task into a collection, to filter or map the elements of an array, or to invoke the finish() callback as soon as one or a given number of tasks are completed (this last situation in ...