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Important: This documentation is about an older version. It's relevant only to the release noted, many of the features and functions have been updated or replaced. Please view the current version.

Documentationbreadcrumb arrow Grafana k6breadcrumb arrow JavaScript APIbreadcrumb arrow k6/experimentalbreadcrumb arrow streamsbreadcrumb arrow ReadableStreambreadcrumb arrow CountQueuingStrategy
Open source

CountQueuingStrategy

The CountQueuingStrategy interface of the Streams API represents a built-in queuing strategy that counts the number of chunks in the queue.

Properties

NameTypeDescription
highWaterMarknumberThe maximum number of chunks that the queue can contain.

Example

JavaScript 
import { CountQueuingStrategy, ReadableStream } from 'k6/experimental/streams';
import { setTimeout } from 'k6/timers';

export default async function () {
  // Define a number stream that emits numbers from 1 to 10 every second
  const stream = numbersStream();

  // We use the getReader method to create a reader and lock the stream to it
  const reader = stream.getReader();

  while (true) {
    const { done, value } = await reader.read();
    if (done) break;
    console.log(`received number ${value} from stream`);
  }
}

function numbersStream() {
  let currentNumber = 0;

  // Using the CountQueuingStrategy to limit the number of chunks in the queue to 5
  const queuingStrategy = new CountQueuingStrategy({ highWaterMark: 5 });

  return new ReadableStream(
    {
      start(controller) {
        const fn = () => {
          if (currentNumber < 10) {
            controller.enqueue(++currentNumber);
            setTimeout(fn, 1000);
            return;
          }

          controller.close();
        };
        setTimeout(fn, 1000);
      },
    },
    queuingStrategy
  );
}