feat: allow multiple circuits to aggregate stats (#140)

If a user creates multiple circuits in the same process, they should aggregate
their stats in the Hystrix stream.

Fixes: #125
Ref: #124

Now that we are piping all event data for all circuits through a single 
`TransformStream`, a LOT of events are being listened for. I've bumped
the limit to 100.

examples/hystrix/README.md

@@ -4,9 +4,13 @@ This example shows how to access the Hystrix Metrics and create an SSE stream th
 
 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
+To see the Hystrix Metrics in action, you will need to run the Hystrix Dashboard. There is a standalone Hystrix Dashboard that you can run for the purposes of this example at https://github.com/kennedyoliveira/standalone-hystrix-dashboard. The easiest way is to just download the fat jar and run it in its own terminal window.
 
-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.
+```sh
+java -jar standalone-hystrix-dashboard-1.5.6-all.jar
+```
+
+Once the dashboard is running, navigate to `http://localhost:7979/hystrix-dashboard`, and add the hystrix stream at `http://localhost:3000/hystrix.stream`.
 
 Now make a few requests to `http://localhost:3000` and you should see movement on the dashboard
 

examples/hystrix/app.js

@@ -14,7 +14,7 @@ let delay = baseline;
 function flakeFunction () {
   return new Promise((resolve, reject) => {
     if (delay > 1000) {
-      return reject('Flakey Service is Flakey');
+      return reject(new Error('Flakey Service is Flakey'));
     }
 
     setTimeout(() => {
@@ -48,21 +48,13 @@ function 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('/hystrix.stream', require('./hystrix-stream')(circuitBreaker));
 
 app.use('/', (request, response) => {
-  circuit.fire().then((result) => {
+  circuit.fire().then(result => {
     response.send(result);
-  }).catch((err) => {
+  }).catch(err => {
     response.send(err);
   });
 });

examples/hystrix/hystrix-stream.js

@@ -0,0 +1,15 @@
+
+function hystrixStream (circuitBreaker) {
+  return (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');
+
+    circuitBreaker.stats.pipe(response);
+  };
+}
+
+module.exports = hystrixStream;