circuit-breaker-aopromise v0.2.2

circuit-breaker-aopromise

Circuit-breaker aspect for aopromise aspect oriented programming toolkit to manage. It circuit-breaker-js as the underlying implementation, extending with timeout and fallback feature.

Quick start

You can use the aspect simply applying it to the wrapped method. You may pass configuration options to the aspect according to the documentation of circuit-breaker-js.

var aop = require('aopromise');
aop.register('circuitbreaker', require('circuit-breaker-aopromise').Aspect);

// some remote service call
var remoteService = {};
remoteService.getData = aop()
	.circuitbreaker({
		timeoutDuration: 3000,
		errorThreshold: 25, // it opens the circuit if 25% of the requests fail in the last bucket
		volumeThreshold: 5 // error threshold will only apply if the requests count reaches this in a bucket
	}) // you may specify options
	.fn(function (params) {
		// some remote call to other webservice or DB
		return Promise.resolve([]);
	});

remoteService.getData({id: 123})
	.then(function (result) {
		// process
	})
	.catch(function (err) {
		console.log(err);
		// called if circuit is open
	});

Fallback

If the circuit is open, circuit-breaker will fast-fail, meaning it will return a rejected promise without calling the wrapped method. You may pass a fallback method for open circuit if applicable.

var prices; // price cache

// remote price api
remoteService.getPrices = aop()
	.circuitbreaker(
	    {}, 
	    function(){ return prices; } // cachedPrices will return local cache. It is still better than nothing
	 ) 
	.fn(function (params) {
		// remote call to download prices
	});

remoteService.getPrices()
    .then(function(result){
        prices = result; // caching prices
        // some other task
    });
    

Default options

You may want to set default options for every aspect added. You can do that by registering the aspect with the withDefaults converter.

var aop = require('aopromise');
var CircuitBreakerAspect = require('circuit-breaker-aopromise').Aspect;
aop.register(
    'circuitbreaker', 
    CircuitBreakerAspect
        .withDefaults({
        timeoutDuration: 3000,
        errorThreshold: 25,
        volumeThreshold: 5
    });
);

var remoteService = {};
remoteService.getData = aop()
	.circuitbreaker() // Options above are applied
	.fn(function (params) {
		// ...
	});