batch-process

In the real world, most async operations against large data sets need to be batched and throttled.

The batchProcess function provides a simple, configurable utility for batching and throttling async operations.

batchProcess logs the progress of batch operations to console or to an injected logging dependency.

Installation

npm i @karmaniverous/batch-process
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Usage

import { batchProcess } from '@karmaniverous/batch-process';

type Item = Record<string, unknown>; // Your data type.

// Say you have a function processBatch that processes a batch of items, for
// example writing them to a database. Maybe not every item is processed
// successfully, so the function returns a count of processed items and an
// array of unprocessed ones.
interface AsyncResult {
  processed: number;
  unprocessed: Item[];
}

const processBatch = async (items: Item[]): AsyncResult =>
  doSomethingAsync(items);

// Let's write a function that extracts any unprocessed items from an
// AsyncResult.
const unprocessedItemExtractor = ({ unprocessed }: AsyncResult) => unprocessed;

// Here's a bunch of items to process.
const items: Item[] = [
  ... // Your items here.
];

// Now you can asynchronously process a bunch of items in throttled sets of
// parallel batches!

// batchProcess will...
// - break items into batches of no more than `batchSize` items, and
// - process up to `throttle` batches in parallel, and
// - write a debug log message for each batch attempted, and
// - wait `delayIncrement` ms with exponential backoff to retry failed batches, and
// - throw an exception after `maxRetries` failed retries, and
// - return an array of AsyncResults generated during batch processing.
const results = await batchProcess(items, {
  processBatch,
  unprocessedItemExtractor,
  // see other options below
});
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batchProcess Options

The options parameter has the following properties:

Default Batchable options are:

Option	Type	Default	Description
batchHandler	(items: Item[]) => Promise<Output>	required	Async function to process an individual batch.
batchSize	number	25	The number of items to process in each batch.
delayIncrement	number	100	The number of milliseconds to wait before retrying a failed batch, with 2x exponential backoff.
logger	Pick<Console, 'debug'>	console	Injected logger object. Must support debug method.
maxRetries	number	5	The number of times to retry a failed batch before throwing an exception.
throttle	number	10	The number of batches to process in parallel.
unprocessedItemExtractor	(output: Output) => Item[] ⏐ undefined	undefined	Function to extract unprocessed items from an individual batch output. If undefined no retries will be attempted.

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