Convert execution async resource to use a stack

Author: Qard

lib/async_hooks.js

@@ -171,7 +171,7 @@ class AsyncResource {
 
   runInAsyncScope(fn, thisArg, ...args) {
     const asyncId = this[async_id_symbol];
-    emitBefore(asyncId, this[trigger_async_id_symbol]);
+    emitBefore(asyncId, this[trigger_async_id_symbol], this);
 
     const ret = thisArg === undefined ?
       fn(...args) :

lib/internal/async_hooks.js

@@ -76,7 +76,8 @@ const active_hooks = {
 const { registerDestroyHook } = async_wrap;
 const { enqueueMicrotask } = internalBinding('task_queue');
 
-const { executionAsyncResource, setExecutionAsyncResource } = async_wrap;
+const { executionAsyncResource, pushExecutionAsyncResource,
+        popExecutionAsyncResource } = async_wrap;
 
 // Each constant tracks how many callbacks there are for any given step of
 // async execution. These are tracked so if the user didn't include callbacks
@@ -360,7 +361,7 @@ function emitBeforeScript(asyncId, triggerAsyncId, resource) {
   validateAsyncId(asyncId, 'asyncId');
   validateAsyncId(triggerAsyncId, 'triggerAsyncId');
 
-  setExecutionAsyncResource(resource);
+  pushExecutionAsyncResource(resource);
   pushAsyncIds(asyncId, triggerAsyncId);
 
   if (async_hook_fields[kBefore] > 0)
@@ -374,8 +375,7 @@ function emitAfterScript(asyncId) {
   if (async_hook_fields[kAfter] > 0)
     emitAfterNative(asyncId);
 
-  setExecutionAsyncResource(null);
-
+  popExecutionAsyncResource();
   popAsyncIds(asyncId);
 }
 
@@ -477,7 +477,8 @@ module.exports = {
   emitAfter: emitAfterScript,
   emitDestroy: emitDestroyScript,
   registerDestroyHook,
-  setExecutionAsyncResource,
+  pushExecutionAsyncResource,
+  popExecutionAsyncResource,
   nativeHooks: {
     init: emitInitNative,
     before: emitBeforeNative,

lib/internal/timers.js

@@ -97,7 +97,8 @@ const {
   emitBefore,
   emitAfter,
   emitDestroy,
-  setExecutionAsyncResource
+  popExecutionAsyncResource,
+  pushExecutionAsyncResource,
 } = require('internal/async_hooks');
 
 // Symbols for storing async id state.
@@ -539,7 +540,7 @@ function getTimerCallbacks(runNextTicks) {
         else
           timer._onTimeout(...args);
       } finally {
-        setExecutionAsyncResource(null);
+        popExecutionAsyncResource();
         if (timer._repeat && timer._idleTimeout !== -1) {
           timer._idleTimeout = timer._repeat;
           if (start === undefined)
@@ -555,6 +556,7 @@ function getTimerCallbacks(runNextTicks) {
           }
           timer._destroyed = true;
         }
+        pushExecutionAsyncResource(timer);
       }
 
       emitAfter(asyncId);

src/async_wrap.cc

@@ -148,7 +148,7 @@ void AsyncWrap::EmitTraceEventBefore() {
 void AsyncWrap::EmitBefore(Environment* env, double async_id,
     v8::Local<v8::Object> resource) {
   v8::Local<v8::Context> context = env->isolate()->GetCurrentContext();
-  env->async_hooks()->set_execution_async_resource(resource);
+  env->async_hooks()->push_execution_async_resource(resource);
 
   Emit(env, async_id, AsyncHooks::kBefore,
        env->async_hooks_before_function());
@@ -180,7 +180,7 @@ void AsyncWrap::EmitAfter(Environment* env, double async_id) {
   Emit(env, async_id, AsyncHooks::kAfter,
        env->async_hooks_after_function());
 
-  env->async_hooks()->clear_execution_async_resource();
+  env->async_hooks()->pop_execution_async_resource();
 }
 
 class PromiseWrap : public AsyncWrap {
@@ -266,10 +266,14 @@ static void PromiseHook(PromiseHookType type, Local<Promise> promise,
 
       // needed for async functions :/
       // the top level will not emit before and after
-      env->async_hooks()->set_execution_async_resource(wrap->object());
+      env->async_hooks()->push_execution_async_resource(wrap->object());
     }
   }
 
+  if (type == PromiseHookType::kResolve && !parent->IsPromise()) {
+    env->async_hooks()->pop_execution_async_resource();
+  }
+
   if (wrap == nullptr) return;
 
   if (type == PromiseHookType::kBefore) {
@@ -402,11 +406,19 @@ static void GetExecutionAsyncResource(const FunctionCallbackInfo<Value>& args) {
   args.GetReturnValue().Set(env->async_hooks()->get_execution_async_resource());
 }
 
-static void SetExecutionAsyncResource(const FunctionCallbackInfo<Value>& args) {
+static void PushExecutionAsyncResource(
+  const FunctionCallbackInfo<Value>& args) {
+  Isolate* isolate = args.GetIsolate();
+  Environment* env = Environment::GetCurrent(args);
+  v8::Local<v8::Context> context = isolate->GetCurrentContext();
+  env->async_hooks()->push_execution_async_resource(args[0]);
+}
+
+static void PopExecutionAsyncResource(const FunctionCallbackInfo<Value>& args) {
   Isolate* isolate = args.GetIsolate();
   Environment* env = Environment::GetCurrent(args);
   v8::Local<v8::Context> context = isolate->GetCurrentContext();
-  env->async_hooks()->set_execution_async_resource(args[0]);
+  env->async_hooks()->pop_execution_async_resource();
 }
 
 void AsyncWrap::GetAsyncId(const FunctionCallbackInfo<Value>& args) {
@@ -497,10 +509,12 @@ void AsyncWrap::Initialize(Local<Object> target,
   env->SetMethod(target, "disablePromiseHook", DisablePromiseHook);
   env->SetMethod(target, "registerDestroyHook", RegisterDestroyHook);
   env->SetMethod(target, "executionAsyncResource", GetExecutionAsyncResource);
-  env->SetMethod(target, "setExecutionAsyncResource",
-                 SetExecutionAsyncResource);
+  env->SetMethod(target, "pushExecutionAsyncResource",
+                 PushExecutionAsyncResource);
+  env->SetMethod(target, "popExecutionAsyncResource",
+                 PopExecutionAsyncResource);
 
-  env->async_hooks()->clear_execution_async_resource();
+  env->async_hooks()->push_execution_async_resource(v8::Object::New(isolate));
 
   PropertyAttribute ReadOnlyDontDelete =
       static_cast<PropertyAttribute>(ReadOnly | DontDelete);

src/env-inl.h

@@ -67,8 +67,7 @@ inline MultiIsolatePlatform* IsolateData::platform() const {
 inline AsyncHooks::AsyncHooks()
     : async_ids_stack_(env()->isolate(), 16 * 2),
       fields_(env()->isolate(), kFieldsCount),
-      async_id_fields_(env()->isolate(), kUidFieldsCount),
-      execution_async_resource_(env()->isolate(), v8::Null(env()->isolate())) {
+      async_id_fields_(env()->isolate(), kUidFieldsCount) {
   v8::HandleScope handle_scope(env()->isolate());
 
   // Always perform async_hooks checks, not just when async_hooks is enabled.
@@ -207,17 +206,23 @@ inline AsyncHooks::DefaultTriggerAsyncIdScope ::~DefaultTriggerAsyncIdScope() {
     old_default_trigger_async_id_;
 }
 
-inline void AsyncHooks::set_execution_async_resource(
+inline void AsyncHooks::push_execution_async_resource(
   v8::Local<v8::Value> execution_async_resource) {
-  execution_async_resource_.Reset(env()->isolate(), execution_async_resource);
+  execution_async_resources_.push(v8::Global<v8::Value>(
+    env()->isolate(), execution_async_resource));
 }
 
-inline v8::Local<v8::Value> AsyncHooks::get_execution_async_resource() {
-  return execution_async_resource_.Get(env()->isolate());
+inline void AsyncHooks::pop_execution_async_resource() {
+  if (execution_async_resources_.size()) {
+    execution_async_resources_.pop();
+  }
 }
 
-inline void AsyncHooks::clear_execution_async_resource() {
-  execution_async_resource_.Reset();
+inline v8::Local<v8::Value> AsyncHooks::get_execution_async_resource() {
+  if (!execution_async_resources_.size()) {
+    return v8::Null(env()->isolate());
+  }
+  return execution_async_resources_.top().Get(env()->isolate());
 }
 
 Environment* Environment::ForAsyncHooks(AsyncHooks* hooks) {

src/env.h

@@ -45,6 +45,7 @@
 #include <cstdint>
 #include <functional>
 #include <list>
+#include <stack>
 #include <unordered_map>
 #include <unordered_set>
 #include <vector>
@@ -684,10 +685,10 @@ class AsyncHooks : public MemoryRetainer {
   inline bool pop_async_id(double async_id);
   inline void clear_async_id_stack();  // Used in fatal exceptions.
 
-  inline void set_execution_async_resource(
+  inline void push_execution_async_resource(
     v8::Local<v8::Value> execution_async_resource_);
+  inline void pop_execution_async_resource();
   inline v8::Local<v8::Value> get_execution_async_resource();
-  inline void clear_execution_async_resource();
 
   AsyncHooks(const AsyncHooks&) = delete;
   AsyncHooks& operator=(const AsyncHooks&) = delete;
@@ -732,7 +733,7 @@ class AsyncHooks : public MemoryRetainer {
 
   void grow_async_ids_stack();
 
-  v8::Persistent<v8::Value> execution_async_resource_;
+  std::stack<v8::Global<v8::Value>> execution_async_resources_;
 };
 
 class ImmediateInfo : public MemoryRetainer {