async_hooks: avoid unneeded AsyncResource creation

Flarna · addaleax · commit 0a4401713ad5 · 2020-09-22T23:48:03.000+02:00
Inspired by the callstack at #34556 (comment) If the wanted store is equal to the active store it's not needed to create an AsyncResource. Refs: #34556 (comment) PR-URL: #34616 Reviewed-By: Anna Henningsen <anna@addaleax.net> Reviewed-By: Stephen Belanger <admin@stephenbelanger.com> Reviewed-By: Vladimir de Turckheim <vlad2t@hotmail.com> Reviewed-By: Andrey Pechkurov <apechkurov@gmail.com>
diff --git a/lib/async_hooks.js b/lib/async_hooks.js
@@ -3,6 +3,7 @@
 const {
   NumberIsSafeInteger,
   ObjectDefineProperties,
+  ObjectIs,
   ReflectApply,
   Symbol,
 } = primordials;
@@ -285,6 +286,10 @@ class AsyncLocalStorage {
   }
 
   run(store, callback, ...args) {
+    // Avoid creation of an AsyncResource if store is already active
+    if (ObjectIs(store, this.getStore())) {
+      return callback(...args);
+    }
     const resource = new AsyncResource('AsyncLocalStorage');
     return resource.runInAsyncScope(() => {
       this.enterWith(store);
diff --git a/test/async-hooks/test-async-local-storage-run-resource.js b/test/async-hooks/test-async-local-storage-run-resource.js
@@ -10,8 +10,21 @@ const asyncLocalStorage = new AsyncLocalStorage();
 
 const outerResource = executionAsyncResource();
 
-asyncLocalStorage.run(new Map(), () => {
-  assert.notStrictEqual(executionAsyncResource(), outerResource);
+const store = new Map();
+asyncLocalStorage.run(store, () => {
+  assert.strictEqual(asyncLocalStorage.getStore(), store);
+  const innerResource = executionAsyncResource();
+  assert.notStrictEqual(innerResource, outerResource);
+  asyncLocalStorage.run(store, () => {
+    assert.strictEqual(asyncLocalStorage.getStore(), store);
+    assert.strictEqual(executionAsyncResource(), innerResource);
+    const otherStore = new Map();
+    asyncLocalStorage.run(otherStore, () => {
+      assert.strictEqual(asyncLocalStorage.getStore(), otherStore);
+      assert.notStrictEqual(executionAsyncResource(), innerResource);
+      assert.notStrictEqual(executionAsyncResource(), outerResource);
+    });
+  });
 });
 
 assert.strictEqual(executionAsyncResource(), outerResource);
