feat: Add an example on how to use the Hystrix Metrics

examples/hystrix/README.md

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+# Hystrix Example
+
+This example shows how to access the Hystrix Metrics and create an SSE stream that can be plugged into the Hystrix Dashboard.
+
+Similiar to the jQuery example, a simple service is exposed at the route `http://localhost:3000`. As the service receives requests, it gets slower and slower. Once it takes more than 1 second to respond, the service just returns a `423 (Locked)` error.  There is also a SSE stream available at `http://localhost:3000/hystrix.stream`
+
+To see the Hystrix Metrics in action, you will need to run the Hystrix Dashboard.  There are instructions on how to do that here: https://github.com/Netflix/Hystrix/tree/master/hystrix-dashboard
+
+Once the dashboard is running, navigate to `http://localhost:7979/hystrix-dashboard` (this assumes you are running it from the git repo), and add our servers hystrix stream.
+
+Now make a few requests to `http://localhost:3000` and you should see movement on the dashboard
+
+
+Install the dependecies
+
+```sh
+$ npm install
+```
+
+Start the server.
+
+```sh
+$ npm start
+```

examples/hystrix/app.js

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+const express = require('express');
+const bodyParser = require('body-parser');
+
+const app = express();
+
+const circuitBreaker = require('../../');
+
+app.use(bodyParser.json());
+app.use(bodyParser.urlencoded({ extended: false }));
+
+const baseline = process.env.CB_BASELINE || 20;
+let delay = baseline;
+
+function flakeFunction () {
+  return new Promise((resolve, reject) => {
+    if (delay > 1000) {
+      return reject('Flakey Service is Flakey');
+    }
+
+    setTimeout(() => {
+      console.log('replying with flakey response after delay of ', delay);
+      resolve(`Sending flakey service. Current Delay at ${delay}`);
+      delay = delay * 2;
+    }, delay);
+  });
+}
+
+setInterval(() => {
+  if (delay !== baseline) {
+    delay = baseline;
+    console.log('resetting flakey service delay', delay);
+  }
+}, 20000);
+
+// circuit breaker
+const circuitBreakerOptions = {
+  maxFailures: 5,
+  timeout: 5000,
+  resetTimeout: 10000,
+  name: 'customName',
+  group: 'customGroupName'
+};
+
+function fallback () {
+  return 'Service Fallback';
+}
+
+const circuit = circuitBreaker(flakeFunction, circuitBreakerOptions);
+circuit.fallback(fallback);
+
+const hystrixStats = circuit.hystrixStats;
+
+// setup our SSE endpoint
+app.use('/hystrix.stream', (request, response) => {
+  response.writeHead(200, {'Content-Type': 'text/event-stream', 'Cache-Control': 'no-cache', 'Connection': 'keep-alive'});
+  response.write('retry: 10000\n');
+  response.write('event: connecttime\n');
+
+  hystrixStats.getHystrixStream().pipe(response);
+});
+
+app.use('/', (request, response) => {
+  circuit.fire().then((result) => {
+    response.send(result);
+  }).catch((err) => {
+    response.send(err);
+  });
+});
+
+module.exports = app;

examples/hystrix/bin/www

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+#!/usr/bin/env node
+
+/**
+ * Module dependencies.
+ */
+
+var app = require('../app');
+var debug = require('debug')('hystrix:server');
+var http = require('http');
+
+/**
+ * Get port from environment and store in Express.
+ */
+
+var port = normalizePort(process.env.PORT || '3000');
+app.set('port', port);
+
+/**
+ * Create HTTP server.
+ */
+
+var server = http.createServer(app);
+
+/**
+ * Listen on provided port, on all network interfaces.
+ */
+
+server.listen(port);
+server.on('error', onError);
+server.on('listening', onListening);
+
+/**
+ * Normalize a port into a number, string, or false.
+ */
+
+function normalizePort(val) {
+  var port = parseInt(val, 10);
+
+  if (isNaN(port)) {
+    // named pipe
+    return val;
+  }
+
+  if (port >= 0) {
+    // port number
+    return port;
+  }
+
+  return false;
+}
+
+/**
+ * Event listener for HTTP server "error" event.
+ */
+
+function onError(error) {
+  if (error.syscall !== 'listen') {
+    throw error;
+  }
+
+  var bind = typeof port === 'string'
+    ? 'Pipe ' + port
+    : 'Port ' + port;
+
+  // handle specific listen errors with friendly messages
+  switch (error.code) {
+    case 'EACCES':
+      console.error(bind + ' requires elevated privileges');
+      process.exit(1);
+      break;
+    case 'EADDRINUSE':
+      console.error(bind + ' is already in use');
+      process.exit(1);
+      break;
+    default:
+      throw error;
+  }
+}
+
+/**
+ * Event listener for HTTP server "listening" event.
+ */
+
+function onListening() {
+  var addr = server.address();
+  var bind = typeof addr === 'string'
+    ? 'pipe ' + addr
+    : 'port ' + addr.port;
+  debug('Listening on ' + bind);
+}

examples/hystrix/package.json

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+{
+  "name": "hystrix-example",
+  "version": "0.0.0",
+  "private": true,
+  "scripts": {
+    "start": "node ./bin/www"
+  },
+  "dependencies": {
+    "body-parser": "~1.16.0",
+    "debug": "~2.6.0",
+    "express": "~4.14.1"
+  }
+}