fix: drop 'transaction.sync' field, it was never used by apm-server

Also add a test for span.sync=false for ES and HTTP spans from
@elastic/elasticsearch instrumentation for #1996.

Move the span.sync test from async-hooks.test.js over to span.test.js
because its impl no longer deps on lib/instrumentation/async-hooks.js.

Fixes: #2292

lib/instrumentation/generic-span.js

@@ -23,7 +23,6 @@ function GenericSpan (agent, ...args) {
 
   this.timestamp = this._timer.start
   this.ended = false
-  this.sync = true
 
   this.outcome = constants.OUTCOME_UNKNOWN
 

lib/instrumentation/span.js

@@ -35,6 +35,7 @@ function Span (transaction, name, ...args) {
   this._message = null
   this._stackObj = null
   this._capturedStackTrace = null
+  this.sync = true
   this._startXid = executionAsyncId()
 
   this.transaction = transaction

lib/instrumentation/transaction.js

@@ -1,6 +1,5 @@
 'use strict'
 
-const { executionAsyncId } = require('async_hooks')
 var util = require('util')
 
 var ObjectIdentityMap = require('object-identity-map')
@@ -36,7 +35,6 @@ function Transaction (agent, name, ...args) {
   this._contextLost = false // TODO: Send this up to the server some how
   this._abortTime = 0
   this._breakdownTimings = new ObjectIdentityMap()
-  this._startXid = executionAsyncId()
 
   this.outcome = constants.OUTCOME_UNKNOWN
 }
@@ -131,7 +129,6 @@ Transaction.prototype.toJSON = function () {
     result: String(this.result),
     sampled: this.sampled,
     context: undefined,
-    sync: this.sync,
     span_count: {
       started: this._builtSpans
     },
@@ -234,9 +231,6 @@ Transaction.prototype.end = function (result, endTime) {
   this._timer.end(endTime)
   this._captureBreakdown(this)
   this.ended = true
-  if (executionAsyncId() !== this._startXid) {
-    this.sync = false
-  }
 
   var trans = this._agent._instrumentation.currentTransaction
 

test/instrumentation/async-hooks.test.js

@@ -121,30 +121,6 @@ test('post-defined, post-resolved promise', function (t) {
   })
 })
 
-test('sync.sync', function (t) {
-  var trans = agent.startTransaction()
-  t.strictEqual(trans.sync, true)
-
-  var span1 = agent.startSpan('span1')
-  t.strictEqual(span1.sync, true)
-
-  // This span will be *ended* synchronously. It should stay `span.sync=true`.
-  var span2 = agent.startSpan('span2')
-  t.strictEqual(span2.sync, true, 'span2.sync=true immediately after creation')
-  span2.end()
-  t.strictEqual(span2.sync, true, 'span2.sync=true immediately after end')
-
-  setImmediate(() => {
-    span1.end()
-    t.strictEqual(span1.sync, false)
-    trans.end()
-    t.strictEqual(trans.sync, false)
-    t.strictEqual(span2.sync, true,
-      'span2.sync=true later after having ended sync')
-    t.end()
-  })
-})
-
 function twice (fn) {
   setImmediate(fn)
   setImmediate(fn)

test/instrumentation/modules/@elastic/elasticsearch.test.js

@@ -586,12 +586,14 @@ function checkDataAndEnd (t, method, path, dbStatement) {
     t.strictEqual(esSpan.type, 'db')
     t.strictEqual(esSpan.subtype, 'elasticsearch')
     t.strictEqual(esSpan.action, 'request')
+    t.strictEqual(esSpan.sync, false, 'span.sync=false')
 
     const httpSpan = findObjInArray(data.spans, 'subtype', 'http')
     t.ok(httpSpan, 'have an http span')
     t.strictEqual(httpSpan.type, 'external')
     t.strictEqual(httpSpan.subtype, 'http')
     t.strictEqual(httpSpan.action, method)
+    t.strictEqual(httpSpan.sync, false, 'span.sync=false')
 
     t.equal(httpSpan.name, method + ' ' + host, 'http span should have expected name')
     t.equal(esSpan.name, 'Elasticsearch: ' + method + ' ' + path, 'elasticsearch span should have expected name')

test/instrumentation/span.test.js

@@ -161,13 +161,24 @@ test('#addLabels', function (t) {
   t.end()
 })
 
-test('sync/async tracking', function (t) {
-  var trans = new Transaction(agent)
-  var span = new Span(trans)
-  t.strictEqual(span.sync, true)
+test('span.sync', function (t) {
+  var trans = agent.startTransaction()
+
+  var span1 = agent.startSpan('span1')
+  t.strictEqual(span1.sync, true)
+
+  // This span will be *ended* synchronously. It should stay `span.sync=true`.
+  var span2 = agent.startSpan('span2')
+  t.strictEqual(span2.sync, true, 'span2.sync=true immediately after creation')
+  span2.end()
+  t.strictEqual(span2.sync, true, 'span2.sync=true immediately after end')
+
   setImmediate(() => {
-    span.end()
-    t.strictEqual(span.sync, false)
+    span1.end()
+    t.strictEqual(span1.sync, false, 'span1.sync=false immediately after end')
+    trans.end()
+    t.strictEqual(span2.sync, true,
+      'span2.sync=true later after having ended sync')
     t.end()
   })
 })

test/instrumentation/transaction.test.js

@@ -291,16 +291,6 @@ test('parallel transactions', function (t) {
   }, 25)
 })
 
-test('sync/async tracking', function (t) {
-  var trans = new Transaction(agent)
-  t.strictEqual(trans.sync, true)
-  setImmediate(() => {
-    trans.end()
-    t.strictEqual(trans.sync, false)
-    t.end()
-  })
-})
-
 test('#_encode() - un-ended', function (t) {
   var trans = new Transaction(agent)
   t.strictEqual(trans._encode(), null, 'cannot encode un-ended transaction')