feat: allow multiple circuits to aggregate stats

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

Fixes: #125
Ref: #124

lib/hystrix-stats.js

@@ -3,6 +3,23 @@
 const stream = require('stream');
 const hystrixFormatter = require('./hystrix-formatter');
 
+// only use a single hystrix stream for all circuits
+const hystrixStream = new stream.Transform({
+  objectMode: true
+});
+
+// The stats coming in should be already "Reduced"
+function hystrixTransformer (stats, encoding, cb) {
+  const formattedStats = hystrixFormatter(stats);
+
+  // Need to take the stats and map them to the hystrix format
+  return cb(null, `{"data": ${JSON.stringify(formattedStats)}}\n\n`);
+}
+
+// Need a _transform() function to satisfy the protocol
+hystrixStream._transform = hystrixTransformer;
+hystrixStream.resume();
+
 /**
  * @class
  * <p>
@@ -35,34 +52,16 @@ class HystrixStats {
       objectMode: true
     });
 
-    // Need a _read() function to satisfy the protocol
     this._readableStream._read = () => {};
     this._readableStream.resume();
-
-    this._hystrixStream = new stream.Transform({
-      objectMode: true
-    });
-
-    // Need a _transform() function to satisfy the protocol
-    this._hystrixStream._transform = this._hystrixTransformer;
-    this._hystrixStream.resume();
-
-    this._readableStream.pipe(this._hystrixStream);
-  }
-
-  // The stats coming in should be already "Reduced"
-  _hystrixTransformer (stats, encoding, cb) {
-    const formattedStats = hystrixFormatter(stats);
-
-    // Need to take the stats and map them to the hystrix format
-    return cb(null, `data: ${JSON.stringify(formattedStats)}\n\n`);
+    this._readableStream.pipe(hystrixStream);
   }
 
   /**
     A convenience function that returns the hystrxStream
   */
   getHystrixStream () {
-    return this._hystrixStream;
+    return hystrixStream;
   }
 
   // This will take the stats data from the listener and

test/hystrix-test.js

@@ -0,0 +1,33 @@
+'use strict';
+
+const test = require('tape');
+const cb = require('../');
+const { passFail } = require('./common');
+
+test('A circuit should provide stats to a hystrix compatible stream', t => {
+  t.plan(2);
+  const circuitOne = cb(passFail, {
+    rollingCountTimeout: 100,
+    rollingCountBuckets: 1,
+    name: 'circuit one'
+  });
+  const circuitTwo = cb(passFail, {
+    rollingCountTimeout: 100,
+    rollingCountBuckets: 1,
+    name: 'circuit two'
+  });
+  const stream = circuitOne.hystrixStats.getHystrixStream();
+  let circuitOneStatsSeen = false;
+  let circuitTwoStatsSeen = true;
+  stream.on('data', blob => {
+    const obj = JSON.parse(blob);
+    if (obj.data.name === 'circuit one') circuitOneStatsSeen = true;
+    else if (obj.data.name === 'circuit two') circuitTwoStatsSeen = true;
+  });
+  circuitOne.fire(10).then(_ => circuitTwo.fire(10)).then(_ => {
+    console.log('checking');
+    t.ok(circuitOneStatsSeen, 'circuit one stats seen');
+    t.ok(circuitTwoStatsSeen, 'circuit two stats seen');
+    t.end();
+  });
+});