Bulkhead

Limit concurrent function executions to prevent resource exhaustion

Function Signature

function createBulkhead<T extends AnyFn>(
  fn: T,
  options: BulkheadOptions
): T

Wraps a function with bulkhead pattern to limit concurrent executions. Prevents resource exhaustion by queueing excess calls.

Options

maxConcurrent · number · required

Maximum number of concurrent function executions allowed.

maxQueue · number

Maximum number of calls to queue when at max concurrency. If not set, the queue is unbounded.

onReject · () => void

Callback invoked when a call is rejected because the queue is full.

Return Type

Returns the wrapped function with concurrency limiting.

Types

interface BulkheadOptions {
  maxConcurrent: number
  maxQueue?: number
  onReject?: () => void
}

Example

import { createBulkhead } from 'cruel'

const limitedFetch = createBulkhead(
  async (url: string) => {
    const response = await fetch(url)
    return response.json()
  },
  {
    maxConcurrent: 5,
    maxQueue: 10,
    onReject: () => {
      console.warn('Too many requests queued')
    }
  }
)

// Only 5 requests will run concurrently, rest will queue
const promises = urls.map(url => limitedFetch(url))
const results = await Promise.all(promises)