async_hooks: clean up usage in internal code

Instead of exposing internals of async_hooks & async_wrap throughout
the code base, create necessary helper methods within the internal
async_hooks that allows easy usage by Node.js internals. This stops
every single internal user of async_hooks from importing a ton of
functions, constants and internal Aliased Buffers from C++ async_wrap.

Adds functions initHooksExist, afterHooksExist, and destroyHooksExist
to determine whether the related emit methods need to be triggered.

Adds clearDefaultTriggerAsyncId and clearAsyncIdStack on the JS side
as an alternative to always calling C++.

Moves async_id_symbol and trigger_async_id_symbol to internal
async_hooks as they are never used in C++.

Renames newUid to newAsyncId for added clarity of its purpose.

Adjusts usage throughout the codebase, as well as in a couple of tests.

PR-URL: #18720
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ali Ijaz Sheikh <ofrobots@google.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

lib/_http_agent.js

@@ -25,7 +25,7 @@ const net = require('net');
 const util = require('util');
 const EventEmitter = require('events');
 const debug = util.debuglog('http');
-const { async_id_symbol } = process.binding('async_wrap');
+const { async_id_symbol } = require('internal/async_hooks').symbols;
 const { nextTick } = require('internal/process/next_tick');
 
 // New Agent code.

lib/_http_outgoing.js

@@ -31,7 +31,7 @@ const common = require('_http_common');
 const checkIsHttpToken = common._checkIsHttpToken;
 const checkInvalidHeaderChar = common._checkInvalidHeaderChar;
 const { outHeadersKey } = require('internal/http');
-const { async_id_symbol } = process.binding('async_wrap');
+const { async_id_symbol } = require('internal/async_hooks').symbols;
 const { nextTick } = require('internal/process/next_tick');
 const errors = require('internal/errors');
 

lib/async_hooks.js

@@ -9,34 +9,31 @@ const internal_async_hooks = require('internal/async_hooks');
 // resource gets gced.
 const { registerDestroyHook } = async_wrap;
 const {
+  executionAsyncId,
+  triggerAsyncId,
   // Private API
   getHookArrays,
   enableHooks,
   disableHooks,
   // Internal Embedder API
-  newUid,
+  newAsyncId,
   getDefaultTriggerAsyncId,
   emitInit,
   emitBefore,
   emitAfter,
   emitDestroy,
 } = internal_async_hooks;
 
-// Get fields
-const { async_id_fields } = async_wrap;
-
 // Get symbols
 const {
+  async_id_symbol, trigger_async_id_symbol,
   init_symbol, before_symbol, after_symbol, destroy_symbol,
   promise_resolve_symbol
 } = internal_async_hooks.symbols;
 
-const { async_id_symbol, trigger_async_id_symbol } = async_wrap;
-
 // Get constants
 const {
   kInit, kBefore, kAfter, kDestroy, kTotals, kPromiseResolve,
-  kExecutionAsyncId, kTriggerAsyncId
 } = async_wrap.constants;
 
 // Listener API //
@@ -125,16 +122,6 @@ function createHook(fns) {
 }
 
 
-function executionAsyncId() {
-  return async_id_fields[kExecutionAsyncId];
-}
-
-
-function triggerAsyncId() {
-  return async_id_fields[kTriggerAsyncId];
-}
-
-
 // Embedder API //
 
 const destroyedSymbol = Symbol('destroyed');
@@ -170,7 +157,7 @@ class AsyncResource {
                                   triggerAsyncId);
     }
 
-    this[async_id_symbol] = newUid();
+    this[async_id_symbol] = newAsyncId();
     this[trigger_async_id_symbol] = triggerAsyncId;
     // this prop name (destroyed) has to be synchronized with C++
     this[destroyedSymbol] = { destroyed: false };

lib/dgram.js

@@ -28,9 +28,11 @@ const dns = require('dns');
 const util = require('util');
 const { isUint8Array } = require('internal/util/types');
 const EventEmitter = require('events');
-const { defaultTriggerAsyncIdScope } = require('internal/async_hooks');
+const {
+  defaultTriggerAsyncIdScope,
+  symbols: { async_id_symbol }
+} = require('internal/async_hooks');
 const { UV_UDP_REUSEADDR } = process.binding('constants').os;
-const { async_id_symbol } = process.binding('async_wrap');
 const { nextTick } = require('internal/process/next_tick');
 
 const { UDP, SendWrap } = process.binding('udp_wrap');

lib/internal/async_hooks.js

@@ -27,7 +27,7 @@ const async_wrap = process.binding('async_wrap');
  * It has a fixed size, so if that is exceeded, calls to the native
  * side are used instead in pushAsyncIds() and popAsyncIds().
  */
-const { async_id_symbol, async_hook_fields, async_id_fields } = async_wrap;
+const { async_hook_fields, async_id_fields } = async_wrap;
 // Store the pair executionAsyncId and triggerAsyncId in a std::stack on
 // Environment::AsyncHooks::async_ids_stack_ tracks the resource responsible for
 // the current execution stack. This is unwound as each resource exits. In the
@@ -71,6 +71,8 @@ const { kInit, kBefore, kAfter, kDestroy, kPromiseResolve,
         kDefaultTriggerAsyncId, kStackLength } = async_wrap.constants;
 
 // Used in AsyncHook and AsyncResource.
+const async_id_symbol = Symbol('asyncId');
+const trigger_async_id_symbol = Symbol('triggerAsyncId');
 const init_symbol = Symbol('init');
 const before_symbol = Symbol('before');
 const after_symbol = Symbol('after');
@@ -245,7 +247,7 @@ function disableHooks() {
 // Increment the internal id counter and return the value. Important that the
 // counter increment first. Since it's done the same way in
 // Environment::new_async_uid()
-function newUid() {
+function newAsyncId() {
   return ++async_id_fields[kAsyncIdCounter];
 }
 
@@ -254,7 +256,7 @@ function getOrSetAsyncId(object) {
     return object[async_id_symbol];
   }
 
-  return object[async_id_symbol] = newUid();
+  return object[async_id_symbol] = newAsyncId();
 }
 
 
@@ -270,6 +272,11 @@ function getDefaultTriggerAsyncId() {
 }
 
 
+function clearDefaultTriggerAsyncId() {
+  async_id_fields[kDefaultTriggerAsyncId] = -1;
+}
+
+
 function defaultTriggerAsyncIdScope(triggerAsyncId, block, ...args) {
   // CHECK(Number.isSafeInteger(triggerAsyncId))
   // CHECK(triggerAsyncId > 0)
@@ -287,6 +294,19 @@ function defaultTriggerAsyncIdScope(triggerAsyncId, block, ...args) {
 }
 
 
+function initHooksExist() {
+  return async_hook_fields[kInit] > 0;
+}
+
+function afterHooksExist() {
+  return async_hook_fields[kAfter] > 0;
+}
+
+function destroyHooksExist() {
+  return async_hook_fields[kDestroy] > 0;
+}
+
+
 function emitInitScript(asyncId, type, triggerAsyncId, resource) {
   validateAsyncId(asyncId, 'asyncId');
   if (triggerAsyncId !== null)
@@ -345,6 +365,20 @@ function emitDestroyScript(asyncId) {
 }
 
 
+// Keep in sync with Environment::AsyncHooks::clear_async_id_stack
+// in src/env-inl.h.
+function clearAsyncIdStack() {
+  async_id_fields[kExecutionAsyncId] = 0;
+  async_id_fields[kTriggerAsyncId] = 0;
+  async_hook_fields[kStackLength] = 0;
+}
+
+
+function hasAsyncIdStack() {
+  return async_hook_fields[kStackLength] > 0;
+}
+
+
 // This is the equivalent of the native push_async_ids() call.
 function pushAsyncIds(asyncId, triggerAsyncId) {
   const offset = async_hook_fields[kStackLength];
@@ -377,20 +411,38 @@ function popAsyncIds(asyncId) {
 }
 
 
+function executionAsyncId() {
+  return async_id_fields[kExecutionAsyncId];
+}
+
+function triggerAsyncId() {
+  return async_id_fields[kTriggerAsyncId];
+}
+
+
 module.exports = {
+  executionAsyncId,
+  triggerAsyncId,
   // Private API
   getHookArrays,
   symbols: {
+    async_id_symbol, trigger_async_id_symbol,
     init_symbol, before_symbol, after_symbol, destroy_symbol,
     promise_resolve_symbol
   },
   enableHooks,
   disableHooks,
+  clearDefaultTriggerAsyncId,
+  clearAsyncIdStack,
+  hasAsyncIdStack,
   // Internal Embedder API
-  newUid,
+  newAsyncId,
   getOrSetAsyncId,
   getDefaultTriggerAsyncId,
   defaultTriggerAsyncIdScope,
+  initHooksExist,
+  afterHooksExist,
+  destroyHooksExist,
   emitInit: emitInitScript,
   emitBefore: emitBeforeScript,
   emitAfter: emitAfterScript,

lib/internal/bootstrap_node.js

@@ -431,18 +431,19 @@
   function noop() {}
 
   function setupProcessFatal() {
-    const async_wrap = process.binding('async_wrap');
-    // Arrays containing hook flags and ids for async_hook calls.
-    const { async_hook_fields, async_id_fields } = async_wrap;
-    // Internal functions needed to manipulate the stack.
-    const { clearAsyncIdStack } = async_wrap;
-    const { kAfter, kExecutionAsyncId,
-            kDefaultTriggerAsyncId, kStackLength } = async_wrap.constants;
+    const {
+      executionAsyncId,
+      clearDefaultTriggerAsyncId,
+      clearAsyncIdStack,
+      hasAsyncIdStack,
+      afterHooksExist,
+      emitAfter
+    } = NativeModule.require('internal/async_hooks');
 
     process._fatalException = function(er) {
-      // It's possible that kDefaultTriggerAsyncId was set for a constructor
+      // It's possible that defaultTriggerAsyncId was set for a constructor
       // call that threw and was never cleared. So clear it now.
-      async_id_fields[kDefaultTriggerAsyncId] = -1;
+      clearDefaultTriggerAsyncId();
 
       if (exceptionHandlerState.captureFn !== null) {
         exceptionHandlerState.captureFn(er);
@@ -465,11 +466,10 @@
       NativeModule.require('timers').setImmediate(noop);
 
       // Emit the after() hooks now that the exception has been handled.
-      if (async_hook_fields[kAfter] > 0) {
-        const { emitAfter } = NativeModule.require('internal/async_hooks');
+      if (afterHooksExist()) {
         do {
-          emitAfter(async_id_fields[kExecutionAsyncId]);
-        } while (async_hook_fields[kStackLength] > 0);
+          emitAfter(executionAsyncId());
+        } while (hasAsyncIdStack());
       // Or completely empty the id stack.
       } else {
         clearAsyncIdStack();

lib/internal/http2/core.js

@@ -4,7 +4,7 @@
 
 require('internal/util').assertCrypto();
 
-const { async_id_symbol } = process.binding('async_wrap');
+const { async_id_symbol } = require('internal/async_hooks').symbols;
 const http = require('http');
 const binding = process.binding('http2');
 const assert = require('assert');

lib/internal/process/next_tick.js

@@ -5,19 +5,20 @@ exports.setup = setupNextTick;
 exports.nextTick = null;
 
 function setupNextTick() {
-  const async_wrap = process.binding('async_wrap');
-  const async_hooks = require('internal/async_hooks');
+  const {
+    getDefaultTriggerAsyncId,
+    newAsyncId,
+    initHooksExist,
+    destroyHooksExist,
+    emitInit,
+    emitBefore,
+    emitAfter,
+    emitDestroy,
+    symbols: { async_id_symbol, trigger_async_id_symbol }
+  } = require('internal/async_hooks');
   const promises = require('internal/process/promises');
   const errors = require('internal/errors');
   const { emitPromiseRejectionWarnings } = promises;
-  const getDefaultTriggerAsyncId = async_hooks.getDefaultTriggerAsyncId;
-  // Two arrays that share state between C++ and JS.
-  const { async_hook_fields, async_id_fields } = async_wrap;
-  // Used to change the state of the async id stack.
-  const { emitInit, emitBefore, emitAfter, emitDestroy } = async_hooks;
-  // Grab the constants necessary for working with internal arrays.
-  const { kInit, kDestroy, kAsyncIdCounter } = async_wrap.constants;
-  const { async_id_symbol, trigger_async_id_symbol } = async_wrap;
 
   // tickInfo is used so that the C++ code in src/node.cc can
   // have easy access to our nextTick state, and avoid unnecessary
@@ -104,7 +105,7 @@ function setupNextTick() {
         // that nextTick() doesn't allow the event loop to proceed, but if
         // any async hooks are enabled during the callback's execution then
         // this tock's after hook will be called, but not its destroy hook.
-        if (async_hook_fields[kDestroy] > 0)
+        if (destroyHooksExist())
           emitDestroy(asyncId);
 
         const callback = tock.callback;
@@ -128,11 +129,11 @@ function setupNextTick() {
       this.callback = callback;
       this.args = args;
 
-      const asyncId = ++async_id_fields[kAsyncIdCounter];
+      const asyncId = newAsyncId();
       this[async_id_symbol] = asyncId;
       this[trigger_async_id_symbol] = triggerAsyncId;
 
-      if (async_hook_fields[kInit] > 0) {
+      if (initHooksExist()) {
         emitInit(asyncId,
                  'TickObject',
                  triggerAsyncId,

lib/internal/timers.js

@@ -1,15 +1,11 @@
 'use strict';
 
-const async_wrap = process.binding('async_wrap');
-// Two arrays that share state between C++ and JS.
-const { async_hook_fields, async_id_fields } = async_wrap;
 const {
   getDefaultTriggerAsyncId,
-  // The needed emit*() functions.
+  newAsyncId,
+  initHooksExist,
   emitInit
 } = require('internal/async_hooks');
-// Grab the constants necessary for working with internal arrays.
-const { kInit, kAsyncIdCounter } = async_wrap.constants;
 // Symbols for storing async id state.
 const async_id_symbol = Symbol('asyncId');
 const trigger_async_id_symbol = Symbol('triggerId');
@@ -70,9 +66,9 @@ function Timeout(callback, after, args, isRepeat, isUnrefed) {
 
   this[unrefedSymbol] = isUnrefed;
 
-  this[async_id_symbol] = ++async_id_fields[kAsyncIdCounter];
+  this[async_id_symbol] = newAsyncId();
   this[trigger_async_id_symbol] = getDefaultTriggerAsyncId();
-  if (async_hook_fields[kInit] > 0) {
+  if (initHooksExist()) {
     emitInit(this[async_id_symbol],
              'Timeout',
              this[trigger_async_id_symbol],

lib/net.js

@@ -47,8 +47,11 @@ const { Pipe, constants: PipeConstants } = process.binding('pipe_wrap');
 const { TCPConnectWrap } = process.binding('tcp_wrap');
 const { PipeConnectWrap } = process.binding('pipe_wrap');
 const { ShutdownWrap, WriteWrap } = process.binding('stream_wrap');
-const { async_id_symbol } = process.binding('async_wrap');
-const { newUid, defaultTriggerAsyncIdScope } = require('internal/async_hooks');
+const {
+  newAsyncId,
+  defaultTriggerAsyncIdScope,
+  symbols: { async_id_symbol }
+} = require('internal/async_hooks');
 const { nextTick } = require('internal/process/next_tick');
 const errors = require('internal/errors');
 const dns = require('dns');
@@ -91,7 +94,7 @@ function createHandle(fd, is_server) {
 
 function getNewAsyncId(handle) {
   return (!handle || typeof handle.getAsyncId !== 'function') ?
-    newUid() : handle.getAsyncId();
+    newAsyncId() : handle.getAsyncId();
 }