feat(http): adopt traceparent as context parent

Author: Stephen Belanger

lib/instrumentation/http-shared.js

@@ -16,7 +16,8 @@ exports.instrumentRequest = function (agent, moduleName) {
           // don't leak previous transaction
           agent._instrumentation.currentTransaction = null
         } else {
-          var trans = agent.startTransaction()
+          var traceparent = req.headers['elastic-apm-traceparent']
+          var trans = agent.startTransaction(null, null, traceparent)
           trans.type = 'request'
           trans.req = req
           trans.res = res

lib/instrumentation/index.js

@@ -128,8 +128,8 @@ Instrumentation.prototype.addEndedSpan = function (span) {
   }
 }
 
-Instrumentation.prototype.startTransaction = function (name, type) {
-  return new Transaction(this._agent, name, type)
+Instrumentation.prototype.startTransaction = function (name, type, header) {
+  return new Transaction(this._agent, name, type, header)
 }
 
 Instrumentation.prototype.endTransaction = function (result) {

lib/instrumentation/transaction.js

@@ -12,7 +12,7 @@ var Timer = require('./timer')
 
 module.exports = Transaction
 
-function Transaction (agent, name, type) {
+function Transaction (agent, name, type, traceparent) {
   Object.defineProperty(this, 'name', {
     configurable: true,
     enumerable: true,
@@ -67,7 +67,10 @@ function Transaction (agent, name, type) {
   // Random sampling
   this.sampled = Math.random() <= agent._conf.transactionSampleRate
 
-  this.context = TraceContext.create(this.sampled)
+  this.context = traceparent
+    ? TraceContext.fromString(traceparent).child()
+    : TraceContext.create(this.sampled)
+
   this._defaultName = name || ''
   this._customName = ''
   this._user = null

test/instrumentation/modules/http/basic.js

@@ -8,6 +8,7 @@ var test = require('tape')
 
 var assert = require('./_assert')
 var mockClient = require('../../../_mock_http_client')
+var TraceContext = require('../../../../lib/instrumentation/context')
 
 test('http.createServer', function (t) {
   t.test('direct callback', function (t) {
@@ -17,7 +18,7 @@ test('http.createServer', function (t) {
       t.end()
     })
 
-    var server = http.createServer(onRequest)
+    var server = http.createServer(onRequest(t))
     sendRequest(server)
   })
 
@@ -29,7 +30,7 @@ test('http.createServer', function (t) {
     })
 
     var server = http.createServer()
-    server.addListener('request', onRequest)
+    server.addListener('request', onRequest(t))
     sendRequest(server)
   })
 
@@ -41,7 +42,7 @@ test('http.createServer', function (t) {
     })
 
     var server = http.createServer()
-    server.on('request', onRequest)
+    server.on('request', onRequest(t))
     sendRequest(server)
   })
 })
@@ -54,7 +55,7 @@ test('new http.Server', function (t) {
       t.end()
     })
 
-    var server = new http.Server(onRequest)
+    var server = new http.Server(onRequest(t))
     sendRequest(server)
   })
 
@@ -66,7 +67,7 @@ test('new http.Server', function (t) {
     })
 
     var server = new http.Server()
-    server.addListener('request', onRequest)
+    server.addListener('request', onRequest(t))
     sendRequest(server)
   })
 
@@ -78,18 +79,27 @@ test('new http.Server', function (t) {
     })
 
     var server = new http.Server()
-    server.on('request', onRequest)
+    server.on('request', onRequest(t))
     sendRequest(server)
   })
 })
 
 function sendRequest (server, timeout) {
   server.listen(function () {
     var port = server.address().port
-    var req = http.get('http://localhost:' + port, function (res) {
+    var req = http.request({
+      hostname: 'localhost',
+      port: port,
+      path: '/',
+      method: 'GET',
+      headers: {
+        'Elastic-APM-traceparent': TraceContext.create().toString()
+      }
+    }, function (res) {
       if (timeout) throw new Error('should not get to here')
       res.resume()
     })
+    req.end()
 
     if (timeout) {
       process.nextTick(function () {
@@ -99,8 +109,17 @@ function sendRequest (server, timeout) {
   })
 }
 
-function onRequest (req, res) {
-  res.end()
+function onRequest (t) {
+  return function onRequestHandler (req, res) {
+    var traceparent = req.headers['elastic-apm-traceparent']
+    var parent = TraceContext.fromString(traceparent).toJSON()
+    var context = agent.currentTransaction.context.toJSON()
+    t.equal(parent.traceId, context.traceId, 'context trace id matches parent trace id')
+    t.notEqual(parent.id, context.id, 'context id does not match parent id')
+    t.equal(parent.flags, context.flags, 'context flags matches parent flags')
+    t.equal(parent.id, context.parentId, 'context is a child of traceparent')
+    res.end()
+  }
 }
 
 function resetAgent (cb) {