EventEmitter constructor was not being called in many places. It did work due to the EventEmitter3 constructor being empty, but we can't rely on that.

lib/util/failcounter.js

@@ -3,6 +3,7 @@ var util = require('util')
 var EventEmitter = require('eventemitter3').EventEmitter
 
 function FailCounter(threshold, time) {
+  EventEmitter.call(this)
   this.threshold = threshold
   this.time = time
   this.values = []

lib/util/riskystream.js

@@ -3,6 +3,8 @@ var util = require('util')
 var EventEmitter = require('eventemitter3').EventEmitter
 
 function RiskyStream(stream) {
+  EventEmitter.call(this)
+
   this.endListener = function() {
     this.ended = true
     this.stream.removeListener('end', this.endListener)

lib/util/ttlset.js

@@ -10,6 +10,7 @@ function TtlItem(value) {
 }
 
 function TtlSet(ttl) {
+  EventEmitter.call(this)
   this.head = null
   this.tail = null
   this.mapping = Object.create(null)