JKancel / ts-breakers

Circuit Breakers for Typescript

ts-breakers

This package aims to provide a simple, basic and efficient Circuit Breaker implementation.

The CircuitBreaker pattern is a stateful pattern, as it associates a state to function calls in order to decide if it should fail fast, give a try to the function execution, or execute it normally.

Usage

Some usage examples are available as tests in CircuitBreaker.test.ts file.

The most basic example is to create a CircuitBreaker instance (for holding the state) then associate it to your subject to failure function by wrapping it.

One example worth thousands words:

const sum = (a: number, b: number): number => a + b;
const cb = new CircuitBreaker('mycb', 5, 2000);
const wrapped = cb.wrapFunction(sum);
const result = wrapped(2, 3);
expect(result).toBe(5);

You may also want to be notified on state changes for logging or collecting metric:

const sum = (a: number, b: number): number => a + b;
const cb = new CircuitBreaker('mycb', 5, 2000);
cb.addObserver((previousState: CircuitBreakerState, currentState: CircuitBreakerState) => {
    console.log(`${previousState} => ${currentState}`);
});

const wrapped = cb.wrapFunction(sum);
const result = wrapped(2, 3);
expect(result).toBe(5);

Testing

Tests are run:

• locally by using npm test which runs jest test suite on the local branch
• within the CI which runs jest tests suite on every pushed branch and collects the test report within CircleCI UI

Publishing a new version

Use the standard npm version x.y.z to update the package version, tag the main branch and push the tags to the GitHub repository.

The CircleCI pipeline will run the tests and publish the new package to npm.