FuturableTask.createLimiter()

Create a limiter that restricts concurrent task execution.

Syntax

FuturableTask.createLimiter(
  concurrency: number,
  events?: LimiterEvents
): FuturableTaskLimiter

Parameters

concurrency

Maximum number of concurrent tasks.

events (optional)

Event hooks for monitoring:

• onActive(task) - Task starts
• onCompleted(result) - Task completes
• onError(error) - Task fails
• onIdle() - All tasks finished

Return Value

A limiter function with properties:

• activeCount - Currently running tasks
• pendingCount - Tasks waiting to run
• concurrency - Max concurrent tasks

Examples

const limiter = FuturableTask.createLimiter(3);

const tasks = urls.map(url =>
  limiter(FuturableTask.fetch(url))
);

await FuturableTask.parallel(tasks).run();
// Only 3 requests run at once

With Events

const limiter = FuturableTask.createLimiter(5, {
  onActive: () => console.log(`Active: ${limiter.activeCount}/5`),
  onCompleted: (result) => console.log('Done:', result),
  onIdle: () => console.log('All finished')
});

API Rate Limiting

const apiLimiter = FuturableTask.createLimiter(10);

const fetchUsers = (ids: number[]) => {
  const tasks = ids.map(id =>
    apiLimiter(
      FuturableTask.fetch(`/api/users/${id}`)
        .map(res => res.json())
    )
  );
  return FuturableTask.parallel(tasks);
};

See Also

• parallel()
• Concurrency Guide