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https://github.com/debitoor/circuit-breaker-request

Make http requests with retries, and a circuit-breaker group per node process. Scales back the load on micro-services when the micro-service has problems
https://github.com/debitoor/circuit-breaker-request

Last synced: 12 days ago
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Make http requests with retries, and a circuit-breaker group per node process. Scales back the load on micro-services when the micro-service has problems

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README 

        
# circuit-breaker-request



A wrapper around [request-retry-stream](https://github.com/debitoor/request-retry-stream#readme), that itself wraps

 [request](https://github.com/request/request#readme).



 cuircuit-breaker-request Implements a circuit breaker using the

 [levee](https://github.com/krakenjs/levee#readme) module.



 For more information about circuit breaking read the

 [akka docs on the circuit breaker pattern](http://doc.akka.io/docs/akka/snapshot/common/circuitbreaker.html)



	npm install circuit-breaker-request



## Usage - Basic with callbacks



```js



var cbr = require('circuit-breaker-request');



cbr.get('https://google.com', function(err, resp){

	// handle err and resp. Any response that does not have http status code 2XX is an error here

});

```



## Usage - Simple stream in express middleware with pump (piping streams)



```js

var cbr = require('circuit-breaker-request');

var pump = require('pump');



function(req, res, next){

    pump(cbr.get('http://google.com', {timeout: 5000}), res, next);

}

```



## Usage - Options and defaults

```javascript



// NOTE: all options are OPTIONAL.

// Defaults, displayed in parenthesis, will be used for anything you don't specify



var cbr = require('circuit-breaker-request').defaults({

	timeout: 25000, //total timeout for request including any time spend on retries (25000)

	maxFailures: 5, //Max consecutive errors, before closing circuit breaker (5)

	resetTimeout: 30000, //Amount of time circuit breaker will be closed on consecutive errors (30000)

	getGroupId: function getGroupId(url) {

    	var u = urlParser.parse(url);

        return u.protocol + u.host;

    }, //A function that returns the circuit-breaker group to use, given an URL. (default displayed)

	requestTimeout: 8333, //Timeout for each individual http request, (Math.floor(timeout/attempts))

	attempts: 3, //Number of attempts at HTTP request, retrying recoverable errors (3)

	delay: 500 //Delay between HTTP request retries, will back off to 500, 1000, 1500 (500)

});



cbr.get({url: 'https://google.com'}, function(err, resp){

	// handle err and resp. Any response that does not have http status code 2XX is an error here

});



cbr.get({url: 'https://debitoor.com'}, function(err, resp){

	// handle err and resp. Any response that does not have http status code 2XX is an error here

});



// ... more HTTP requests with cbr



//cbr request with special options, can also be used when defaults are not used.

cbr.get({timeout: 10000, requestTimeout: 10000, attempts: 5, url: 'https://debitoor.com'}, function(err, resp){

	// handle err and resp. Any response that does not have http status code 2XX is an error here

});

```



## Grouping



Circuit breaking is done per group of urls. By default the urls are grouped by protocol and host.

Here is an example of this grouping:



### Group 1

	https://debitoor.com/test

	https://debitoor.com

	https://debitoor.com/test?a=true



### Group 2

	https://developers.debitoor.com/api

	https://developers.debitoor.com

	https://developers.debitoor.com/api?b=false



### Group 3

	https://google.com/api

	https://google.com

	https://plus.google.com/api?b=false



Each group has it's own circuit breaker. So if errors start happening in group 1, it will not close down group 2 or 3.



You can create a different grouping by passing a function in the `getGroupId` parameter. The default getGroupId function

is:



```js

var urlParser = require('url');



function getGroupId(url) {

    var u = urlParser.parse(url);

    return u.protocol + u.host;

}

```



So anything with a URL on the same protocol and host will be in the same circuit-breaker. This means if there are 5

consecutive errors returned for URLs with the same protocol and host, the circuit-breaker will pause requests to that

protocol and host for a while, but anything on a different host and/or protocol will still be let through.



## License



[MIT](http://opensource.org/licenses/MIT)