const CircuitBreaker = require('opossum');
 
function asyncFunctionThatCouldFail (x, y) {
  return new Promise((resolve, reject) => {
    // Do something, maybe on the network or a disk
  });
}
 
const options = {
  timeout: 3000, // If our function takes longer than 3 seconds, trigger a failure
  errorThresholdPercentage: 50, // When 50% of requests fail, trip the circuit
  resetTimeout: 30000 // After 30 seconds, try again.
};
const breaker = new CircuitBreaker(asyncFunctionThatCouldFail, options);

// if asyncFunctionThatCouldFail starts to fail, firing the breaker
// will trigger our fallback function
breaker.fallback(() => 'Sorry, out of service right now');
 
breaker.fire(params)
  .then(console.log)
  .catch(console.error);

const circuit = new CircuitBreaker(() => axios.get(route), circuitBreakerOptions);
 
circuit.fallback(() => ({ body: `${route} unavailable right now. Try later.` }));
 
circuit.on('success',
  (result) => console.log(`SUCCESS: ${JSON.stringify(result)}`));
 
circuit.on('timeout',
  () => console.log(`TIMEOUT: ${route} is taking too long to respond.`));
 
circuit.on('reject',
  () => console.log(`REJECTED: The breaker for ${route} is open. Failing fast.`));
 
circuit.on('open',
  () => console.log(`OPEN: The breaker for ${route} just opened.`));
 
circuit.on('halfOpen',
  () => console.log(`HALF_OPEN: The breaker for ${route} is half open.`));
 
circuit.on('close',
  () => console.log(`CLOSE: The breaker for ${route} has closed. Service OK.`));
 
circuit.on('fallback',
  (data) => console.log(`FALLBACK: ${JSON.stringify(data)}`));