fix(instrumenation/httpServer): status code getter

Author: Peter Marton

lib/instrumentations/trace-instrumentation-http/server.js

@@ -123,7 +123,7 @@ function httpServer (listener, agent) {
           alreadyEnded = true
           writeHeadAlreadyCalled = true
           var ssTime = microtime.now()
-          var statusCode = response.statusCode || arguments[0]
+          var statusCode = arguments[0] || response.statusCode
           var skipCollecting = isStatusCodeIgnored(ignoreStatusCodes, statusCode)
           var status = statusCode >= 400 ? 'bad' : 'ok'
           var ss = collector.serverSend({
@@ -157,7 +157,7 @@ function httpServer (listener, agent) {
             debug.warn('httpServer', '[Warning] failed to create SS, cannot intrument headers')
           }
           agent.rpmMetrics.addResponseTime(ssTime - srTime)
-          agent.rpmMetrics.addStatusCode(response.statusCode)
+          agent.rpmMetrics.addStatusCode(statusCode)
         } else {
           debug.warn('httpServer', 'writeHead called multiple times, wrongly reported status codes may occur')
         }

lib/instrumentations/trace-instrumentation-http/server.spec.js

@@ -263,6 +263,34 @@ describe('The http.Server.prototype wrapper module', function () {
     })
   })
 
+  it('calls agent.tracer.collector.serverSend with expected payload: status code in writeHead', function () {
+    this.sandbox.stub(microtime, 'now').returns(5)
+    var s = server(original, agent)
+
+    var request = {
+      headers: {
+        host: 'host',
+        'x-span-id': 'comm-id',
+        'x-request-id': 'tr-id',
+        'x-parent': '1'
+      },
+      url: '/',
+      method: 'GET'
+    }
+    response.statusCode = 401
+
+    s(request, response)
+
+    response.writeHead(200)
+
+    expect(agent.tracer.collector.serverSend.args[0][0]).to.eql({
+      data: { statusCode: 200 },
+      protocol: 'http',
+      status: 'ok',
+      severity: agent.tracer.collector.defaultSeverity
+    })
+  })
+
   it('calls agent.tracer.collector.serverSend with expected briefcase', function () {
     this.sandbox.stub(microtime, 'now').returns(5)
     var s = server(original, agent)