ASync TAsk LIMiter

(Parallel manager for asynchronous tasks with a limit on the number of concurrently executing tasks)

import astalim from "astalim"

// Number of concurrently running tasks
const limit: number = 5

// Create task executor
const tasks = astalim.taskPool(limit)

// Add tasks in a loop
for (const path of <paths>) {
  await tasks.addTask(async () => {
    ...
    <Some work with the current path>
    ...
  })
}

// Get processing result
const results = await tasks.waitResult()

1. Creating the Executor

const tasks = astalim.taskPool(limit: number)

At most limit tasks will be running concurrently.

2. Adding Tasks

for (const path of <paths>) {
  await tasks.addTask(async () => {
    ...
    <Some work with the current path>
    ...
  })
}

The addTask method accepts either a Promise or a function that returns a Promise. Once the limit is reached, the next task will not start until space in the pool is freed and it's added to the pool.

🔴 IMPORTANT: Regardless of what happens inside a task, the main execution flow will not be interrupted. All thrown exceptions (errors) will silently be recorded in the result’s shared error array.

3. Getting the Result

const results = await tasks.waitResult()

Waits for all tasks to fully complete and returns the results. The results object contains two arrays:

• successful: results of successfully completed tasks,
• failed: array of errors, where each object includes:
  • error: the error description,
  • index: index of the task (in the order they were added).

⚠️ The waitResult() call resets the internal state, so you can reuse addTask() afterward without creating a new tasks instance.

import astalim from "astalim"

// Task executor with a pool of 3 tasks
const tasks = astalim.taskPool(3)

// Generator for pseudo-random events
function* randGen() {
  let i = 0
  while (i++ < 10) yield Math.random()
}

// Task handling
for (const rand of randGen()) {
  await tasks.addTask(async () => {
    // Successful task execution, return data
    if (rand > .5) return rand
    // Failed execution, trigger error
    else JSON.parse("") // OR else throw `Error: ${rand}`
  })
}

// Get result
const results = await tasks.waitResult()

console.log("results:", results)

Expected Output:

results: {
  successful: [
    0.5774501276332757,
    0.8140335738582891,
    0.9180485044161926,
    0.9421955524500936,
    0.8163302889107125,
    0.8032588867553216,
    0.783284406112269
  ],
  failed: [
    {
      error: SyntaxError: Unexpected end of JSON input
          at JSON.parse (<anonymous>)
          ...
      index: 1
    },
    {
      error: SyntaxError: Unexpected end of JSON input
          at JSON.parse (<anonymous>)
          ...
      index: 2
    },
    {
      error: SyntaxError: Unexpected end of JSON input
          at JSON.parse (<anonymous>)
          ...
      index: 4
    }
  ]
}