remove spurious ARs from dns, converting to 4-event system

Author: bengl

packages/datadog-instrumentations/src/dns.js

@@ -48,7 +48,8 @@ function patchResolveShorthands (prototype) {
 
 function wrap (prefix, fn, expectedArgs, rrtype) {
   const startCh = channel(prefix + ':start')
-  const finishCh = channel(prefix + ':finish')
+  const asyncEndCh = channel(prefix + ':async_end')
+  const endCh = channel(prefix + ':end')
   const errorCh = channel(prefix + ':error')
 
   const wrapped = function () {
@@ -67,28 +68,31 @@ function wrap (prefix, fn, expectedArgs, rrtype) {
       startArgs.push(rrtype)
     }
 
-    const asyncResource = new AsyncResource('bound-anonymous-fn')
-    return asyncResource.runInAsyncScope(() => {
-      startCh.publish(startArgs)
+    const context = { args: startArgs }
+    startCh.publish(context)
 
-      arguments[arguments.length - 1] = asyncResource.bind(function (error, result) {
-        if (error) {
-          errorCh.publish(error)
-        }
-        finishCh.publish(result)
-        cb.apply(this, arguments)
-      })
+    arguments[arguments.length - 1] = function (error, result) {
+      if (error) {
+        context.error = error
+        errorCh.publish(context)
+      }
+      context.result = result
+      asyncEndCh.publish(context)
+      cb.apply(this, arguments)
+    }
 
-      try {
-        return fn.apply(this, arguments)
+    try {
+      return fn.apply(this, arguments)
       // TODO deal with promise versions when we support `dns/promises`
-      } catch (error) {
-        error.stack // trigger getting the stack at the original throwing point
-        errorCh.publish(error)
-
-        throw error
-      }
-    })
+    } catch (error) {
+      error.stack // trigger getting the stack at the original throwing point
+      context.error = error
+      errorCh.publish(context)
+
+      throw error
+    } finally {
+      endCh.publish(context)
+    }
   }
 
   return shimmer.wrap(fn, wrapped)

packages/datadog-plugin-dns/src/lookup.js

@@ -6,7 +6,7 @@ class DNSLookupPlugin extends ClientPlugin {
   static get name () { return 'dns' }
   static get operation () { return 'lookup' }
 
-  start ([hostname]) {
+  start ({ args: [hostname] }) {
     this.startSpan('dns.lookup', {
       service: this.config.service,
       resource: hostname,
@@ -19,7 +19,7 @@ class DNSLookupPlugin extends ClientPlugin {
     })
   }
 
-  finish (result) {
+  finish ({ result }) {
     const span = this.activeSpan
 
     if (Array.isArray(result)) {

packages/datadog-plugin-dns/src/lookup_service.js

@@ -6,7 +6,7 @@ class DNSLookupServicePlugin extends ClientPlugin {
   static get name () { return 'dns' }
   static get operation () { return 'lookup_service' }
 
-  start ([address, port]) {
+  start ({ args: [address, port] }) {
     this.startSpan('dns.lookup_service', {
       service: this.config.service,
       resource: `${address}:${port}`,

packages/datadog-plugin-dns/src/resolve.js

@@ -6,7 +6,7 @@ class DNSResolvePlugin extends ClientPlugin {
   static get name () { return 'dns' }
   static get operation () { return 'resolve' }
 
-  start ([hostname, maybeType]) {
+  start ({ args: [hostname, maybeType] }) {
     const rrtype = typeof maybeType === 'string' ? maybeType : 'A'
 
     this.startSpan('dns.resolve', {

packages/datadog-plugin-dns/src/reverse.js

@@ -6,7 +6,7 @@ class DNSReversePlugin extends ClientPlugin {
   static get name () { return 'dns' }
   static get operation () { return 'reverse' }
 
-  start ([ip]) {
+  start ({ args: [ip] }) {
     this.startSpan('dns.reverse', {
       service: this.config.service,
       resource: ip,