iterable-backoff

Backoff generators usable as simple iterables

Install

Installation of the npm package:

> yarn add iterable-backoff

# Or

> npm install --save iterable-backoff

Usage

import { fibonacci } from "iterable-backoff";

async function fetch(url) {
  for (const delay of fibonacci()
    .toMs()
    .take(5)) {
    try {
      return await got(url); // or any promise-returning HTTP lib
    } catch (error) {
      console.warn(error);
      await Bluebird.delay(delay); // or any promise-returning timer
    }
  }

  throw new Error("too many tries");
}

Generators

linear(slope = 1, intersect = 1)

Linear function

power(power = 2)

Power sequence

fibonacci()

Fibonacci sequence

exponential(base = 2)

Exponential sequence

Methods

addNoise(factor = 0.1)

Add a noise to the sequence, proportional to the value (default is 10%).

Particularly useful when the backoff is used to wait access for a shared resource and you don't want multiple consumer retrying at the same time.

for (const delay of power().addNoise()) {
  // ...
}

clamp(min, max)

Clamps the value within inclusive min and max bounds.

for (const delay of exponential().clamp(null, 10)) {
  // ...
}

map(fn)

Applies a custom function to each value of the sequence.

Clamps the value within inclusive min and max bounds.

for (const delay of fibonacci().map(x => x / 2)) {
  // ...
}

take(n)

Limits the sequence to at most n values.

You usually want to use this if you do not want to keep retrying for ever.

for (const delay of power().take(10)) {
  // ...
}

toMs()

Converts the sequence's values to milliseconds (from seconds).

for (const delay of exponential(3)
  .take(10)
  .toMs()) {
  // ...
}

Development

# Install dependencies
> npm ci

# Run the tests
> npm test

# Continuously compile
> npm run dev

# Continuously run the tests
> npm run dev-test

# Build for production (automatically called by npm install)
> npm run build

Contributions

Contributions are very welcomed, either on the documentation or on the code.

You may:

• report any issue you've encountered;
• fork and create a pull request.

License

ISC © Julien Fontanet