simplified-hystrixjs/README.md

Netflix's Hystrix latency and fault tolerance library, for Node.js

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# simplified-hystrixjs

A simplified hystrixjs library for Nodejs based on [opossum](https://www.npmjs.com/package/opossum)

### Install
```
$ npm i simplified-hystrixjs -S
```

### Usage
```Javascript
const { createHystrixCommands, createHystrixStream, getPrometheusStream } = require('simplified-hystrixjs');

function hello(name) {
  return new Promise(function(resolve, reject) {
    setTimeout(function () {
      resolve(`Hello, ${name}`)
    }, 1000);
  });
}

const serviceCommand = createHystrixCommands(hello, { name : 'HelloService'});

app.get('/hello', async (req, res) => {
  try {
    const response = await serviceCommand.hello(req.query.name);
    res.send(response)
  } catch (e) {
    console.log(e);
  }
});
```

### Methods

**createCommands(fn, service);**

**fn** - can be of type object, Array of functions or a function.

**service** - service object with the following properties

* *statisticalWindowNumberOfBuckets* - number of buckets within the statistical window
* *statisticalWindowLength* - length of the window to keep track of execution counts metrics (success, failure)
* *errorThreshold* - error percentage threshold to trip the circuit
* *timeout* for request
* *cbRequestVolume* - minimum number of requests in a rolling window
* *cbsleep* - how long the circuit breaker should stay opened.
* *name* - service name
* *isFailure* - emitted when the breaker action fails, called with the error
* *modifyError* - modifies the error message by adding circuit name. false by default.


### Monitoring

Expose a monitoring endpoint for hystrix stream.

```Javascript
createHystrixStream(app, /*[endpoint]*/); // default /manage/hystrix.stream
```

Prometheus stream.

```Javascript
getPrometheusStream()
```

### Hystrix Dashboard

![monitorer](images/hystrix-dash.gif)

to run the dashboard, download [standalone-hystrix-dashboard](https://bintray.com/kennedyoliveira/maven/standalone-hystrix-dashboard)
̨
and run
```java
$ java -jar standalone-hystrix-dashboard-{VERSION}-all.jar
```
Access the dashboard in  your browser: http://localhost:7979/hystrix-dashboard

### Contributing

We gladly welcome pull requests and code contributions, take care to maintain the existing coding style.