butter-spread

Execute chunked blocking operations in a way that won't cause event loop starvation.

Note that you should also consider using worker threads; piscina is a fantastic library for that. Thread management, however, comes with an overhead of its own, and is not recommended for operations that execute within 10-20 msecs. Also be mindful of the "rule of a thumb" for determining how many threads you should be running on your server, which in simplified form is cpus * 1.5 threads, rounded down.

If you have to run your app in an environment that only has a single core, your processing typically completes fast (but can sometimes spike), or you are searching for a simpler solution, look no further than this library!

Node.js task queue consideration

Each following chunk of work is added to the end of the event loop task queue after previous one is finished.

This potentially increases latency of processing a single batch operation while improving throughput - all new work that was received after first chunk started processing will be completed before second chunk will be processed.

If there are multiple butter-spread-managed operations running at the same time, processing time will be divided equally among them.

This behaviour can be controlled via executeSynchronouslyThresholdInMsecs option, which will keep processing chunks synchronously and immediately within the given timeframe.

Common usage

import { chunk, executeSyncChunksSequentially, defaultLogger } from 'butter-spread'

const chunks = chunk(someInputArray, 100)

const results = await executeSyncChunksSequentially(chunks, (chunk) => { return someProcessingLogic(chunk) }, {
    id: 'Some blocking operation', // this is used for logging purposes if threshold is exceeded
    logger: defaultLogger, // logger for "threshold exceeded" warnings. `console.warn` is used by default
    warningThresholdInMsecs: 30, // warning will be logged if any single iteration (which blocks the loop) will take longer than that
    executeSynchronouslyThresholdInMsecs: 15 // if total execution of all chunks in this iteration took less than this amount of time, next chunk will be processed immediately synchronously and not deferred
})