Circuit Breaker

A zero-dependency Node.js circuit breaker that executes asynchronous functions and monitors their execution status. When things start failing, circuit breaker plays dead and fails fast.

Usage

import CircuitBreaker from "circuit-breaker";

(async () => {
  const breaker = new CircuitBreaker(AsyncAction, {
    timeout: 100,
    maxFailures: 3,
    resetTimeout: 3000,
    debug: true,
  });

  // Initially, breaker must be in the CLOSE state
  await breaker.fire(...args);

  // Reject the promise $maxFailures times to OPEN the breaker
  for (let i = 1; i <= breaker.options.maxFailures; i++)
    await breaker.fire(...args).catch(() => {});

  // Breaker must be in the OPEN state for the next $resetTimeout milliseconds
  breaker.fire(...args).catch(() => {});

  // Wait for $resetTimeout milliseconds
  await sleep(breaker.options.resetTimeout);

  // Resolve the promise 1 time to CLOSE the breaker
  await breaker.fire(...args);

  // Breaker must be in the CLOSE state
  for (let i = 1; i <= breaker.options.maxFailures - 1; i++)
    breaker.fire(...args).catch(() => {});

  // Resolve the promise 1 time to CLOSE the breaker
  await breaker
    .fire(...args, (breaker.options.timeout as number) + 1)
    .catch(() => {});
})();

Readme sample can be found in the example.

Configuration Options

| Property | Type | Explanation | Default Value | | -------------- | --------------------- | -------------------------------------------------------------------------------------------------------------------------------------------- | -------------------- | | timeout | Number | Boolean | The time in milliseconds that action should be allowed to execute before timing out. Timeout can be disabled by setting this to false. | 10000 (10 seconds) | | maxFailures | Number | The number of times the circuit can fail before opening. | 10 | | resetTimeout | Number | The time in milliseconds to wait before setting the breaker to halfOpen state, and trying the action again. | 10000 (10 seconds) | | debug | Boolean | Enable/disable debug logging. | false |

How is it tracks the circuit breaker status?

The Status class, Tracks execution status for a given circuit breaker. It listen for all events on the circuit breaker and track them in a rolling statistical window. The window consists of an array of Objects like this:

[
  { failures: 0, successes: 0, rejects: 0, fires: 0, timeouts: 0 },
  { failures: 0, successes: 0, rejects: 0, fires: 0, timeouts: 0 },
  { failures: 0, successes: 0, rejects: 0, fires: 0, timeouts: 0 },
];

Each representing the counts for a circuit breaker events.

Local Development

Clone the repository, and navigate into it.

Install development dependencies:

yarn

Make your changes, then run tests:

yarn test

License

MIT License