fix(metrics): discard negative transport delay values

Author: gergelyke

lib/agent/metrics/incomingEdge/index.js

@@ -30,6 +30,12 @@ IncomingEdgeMetrics.prototype._getEdge = function (protocol, serviceKey) {
 }
 
 IncomingEdgeMetrics.prototype.report = function (data) {
+  // the transportDelay can be negative in some edge-cases:
+  // * system clocks are out of sync
+  // * ran locally with clock issues
+  if (data.transportDelay < 0) {
+    return
+  }
   var serviceKey = data.serviceKey === undefined
     ? 'root' : data.serviceKey
   var edge = this._getEdge(data.protocol, serviceKey)

lib/agent/metrics/incomingEdge/index.spec.js

@@ -3,6 +3,31 @@ var expect = require('chai').expect
 var EdgeMetrics = require('./')
 
 describe('The IncomingEdgeMetrics module', function () {
+  it('discards negative transportDelays', function () {
+    var ISOString = 'date-string'
+    var collectorApi = {
+      sendIncomingEdgeMetrics: this.sandbox.spy()
+    }
+
+    var edgeMetrics = EdgeMetrics.create({
+      collectorApi: collectorApi,
+      config: {
+        collectInterval: 1
+      }
+    })
+
+    this.sandbox.stub(Date.prototype, 'toISOString', function () {
+      return ISOString
+    })
+
+    edgeMetrics.report({
+      serviceKey: 3,
+      protocol: 'http',
+      transportDelay: -10
+    })
+    expect(edgeMetrics.metrics).to.eql({})
+  })
+
   it('sends metrics', function () {
     var ISOString = 'date-string'
     var collectorApi = {