From d3d4e10107a594a758baf2cd5e2c1258671e58c5 Mon Sep 17 00:00:00 2001
From: Anatoli Papirovski <anatoli.papirovski@postmates.com>
Date: Sun, 31 Mar 2019 12:41:14 -0700
Subject: [PATCH] async_hooks: improve AsyncResource performance

Accessing symbols is generally quite expensive and so is emitInit,
only do both when actually required.

PR-URL: https://github.com/nodejs/node/pull/27032
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>
---
 lib/async_hooks.js          | 25 ++++++++++++++-----------
 lib/internal/async_hooks.js |  5 +----
 2 files changed, 15 insertions(+), 15 deletions(-)

diff --git a/lib/async_hooks.js b/lib/async_hooks.js
index 88b8fd705a0efa..3a12a241ea5d5f 100644
--- a/lib/async_hooks.js
+++ b/lib/async_hooks.js
@@ -27,6 +27,7 @@ const {
   emitBefore,
   emitAfter,
   emitDestroy,
+  initHooksExist,
 } = internal_async_hooks;
 
 // Get symbols
@@ -146,29 +147,31 @@ class AsyncResource {
       throw new ERR_INVALID_ASYNC_ID('triggerAsyncId', triggerAsyncId);
     }
 
-    this[async_id_symbol] = newAsyncId();
+    const asyncId = newAsyncId();
+    this[async_id_symbol] = asyncId;
     this[trigger_async_id_symbol] = triggerAsyncId;
+
     // This prop name (destroyed) has to be synchronized with C++
-    this[destroyedSymbol] = { destroyed: false };
+    const destroyed = { destroyed: false };
+    this[destroyedSymbol] = destroyed;
 
-    emitInit(
-      this[async_id_symbol], type, this[trigger_async_id_symbol], this
-    );
+    if (initHooksExist()) {
+      emitInit(asyncId, type, triggerAsyncId, this);
+    }
 
     if (!opts.requireManualDestroy) {
-      registerDestroyHook(this, this[async_id_symbol], this[destroyedSymbol]);
+      registerDestroyHook(this, asyncId, destroyed);
     }
   }
 
   runInAsyncScope(fn, thisArg, ...args) {
-    emitBefore(this[async_id_symbol], this[trigger_async_id_symbol]);
-    let ret;
+    const asyncId = this[async_id_symbol];
+    emitBefore(asyncId, this[trigger_async_id_symbol]);
     try {
-      ret = Reflect.apply(fn, thisArg, args);
+      return Reflect.apply(fn, thisArg, args);
     } finally {
-      emitAfter(this[async_id_symbol]);
+      emitAfter(asyncId);
     }
-    return ret;
   }
 
   emitDestroy() {
diff --git a/lib/internal/async_hooks.js b/lib/internal/async_hooks.js
index 676a2bd2c0be44..a1f3c07defe879 100644
--- a/lib/internal/async_hooks.js
+++ b/lib/internal/async_hooks.js
@@ -286,14 +286,11 @@ function defaultTriggerAsyncIdScope(triggerAsyncId, block, ...args) {
   const oldDefaultTriggerAsyncId = async_id_fields[kDefaultTriggerAsyncId];
   async_id_fields[kDefaultTriggerAsyncId] = triggerAsyncId;
 
-  let ret;
   try {
-    ret = Reflect.apply(block, null, args);
+    return Reflect.apply(block, null, args);
   } finally {
     async_id_fields[kDefaultTriggerAsyncId] = oldDefaultTriggerAsyncId;
   }
-
-  return ret;
 }