lib: implement async_hooks API in core

Implement async_hooks support in the following:

* fatalException handler
* process.nextTick
* Timers
* net/dgram/http

PR-URL: https://github.com/nodejs/node/pull/12892
Ref: https://github.com/nodejs/node/pull/11883
Ref: https://github.com/nodejs/node/pull/8531
Reviewed-By: Andreas Madsen <amwebdk@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Sam Roberts <vieuxtech@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>

10 files changed, 343 insertions, 39 deletions

diff --git a/lib/_http_agent.js b/lib/_http_agent.js
index 88f4df402a..d791a961c7 100644
--- a/lib/_http_agent.js
+++ b/lib/_http_agent.js
@@ -25,6 +25,8 @@ 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').async_id_symbol;
+const nextTick = require('internal/process/next_tick').nextTick;
 
 // New Agent code.
 
@@ -93,6 +95,7 @@ function Agent(options) {
           self.freeSockets[name] = freeSockets;
           socket.setKeepAlive(true, self.keepAliveMsecs);
           socket.unref();
+          socket[async_id_symbol] = -1;
           socket._httpMessage = null;
           self.removeSocket(socket, options);
           freeSockets.push(socket);
@@ -163,6 +166,8 @@ Agent.prototype.addRequest = function addRequest(req, options, port/*legacy*/,
   if (freeLen) {
     // we have a free socket, so use that.
     var socket = this.freeSockets[name].shift();
+    // Assign the handle a new asyncId and run any init() hooks.
+    socket._handle.asyncReset();
     debug('have free socket');
 
     // don't leak
@@ -177,7 +182,7 @@ Agent.prototype.addRequest = function addRequest(req, options, port/*legacy*/,
     // If we are under maxSockets create a new one.
     this.createSocket(req, options, function(err, newSocket) {
       if (err) {
-        process.nextTick(function() {
+        nextTick(newSocket._handle.getAsyncId(), function() {
           req.emit('error', err);
         });
         return;
@@ -290,7 +295,7 @@ Agent.prototype.removeSocket = function removeSocket(s, options) {
     // If we have pending requests and a socket gets closed make a new one
     this.createSocket(req, options, function(err, newSocket) {
       if (err) {
-        process.nextTick(function() {
+        nextTick(newSocket._handle.getAsyncId(), function() {
           req.emit('error', err);
         });
         return;
diff --git a/lib/_http_client.js b/lib/_http_client.js
index e1f064e832..a238a4f14c 100644
--- a/lib/_http_client.js
+++ b/lib/_http_client.js
@@ -36,6 +36,7 @@ const Agent = require('_http_agent');
 const Buffer = require('buffer').Buffer;
 const urlToOptions = require('internal/url').urlToOptions;
 const outHeadersKey = require('internal/http').outHeadersKey;
+const nextTick = require('internal/process/next_tick').nextTick;
 
 // The actual list of disallowed characters in regexp form is more like:
 //    /[^A-Za-z0-9\-._~!$&'()*+,;=/:@]/
@@ -587,9 +588,12 @@ function responseKeepAlive(res, req) {
     socket.removeListener('close', socketCloseListener);
     socket.removeListener('error', socketErrorListener);
     socket.once('error', freeSocketErrorListener);
+    // There are cases where _handle === null. Avoid those. Passing null to
+    // nextTick() will call initTriggerId() to retrieve the id.
+    const asyncId = socket._handle ? socket._handle.getAsyncId() : null;
     // Mark this socket as available, AFTER user-added end
     // handlers have a chance to run.
-    process.nextTick(emitFreeNT, socket);
+    nextTick(asyncId, emitFreeNT, socket);
   }
 }
 
diff --git a/lib/_http_common.js b/lib/_http_common.js
index b33e38e08d..59eaec5811 100644
--- a/lib/_http_common.js
+++ b/lib/_http_common.js
@@ -28,6 +28,7 @@ const HTTPParser = binding.HTTPParser;
 const FreeList = require('internal/freelist');
 const ondrain = require('internal/http').ondrain;
 const incoming = require('_http_incoming');
+const emitDestroy = require('async_hooks').emitDestroy;
 const IncomingMessage = incoming.IncomingMessage;
 const readStart = incoming.readStart;
 const readStop = incoming.readStop;
@@ -211,8 +212,13 @@ function freeParser(parser, req, socket) {
     parser.incoming = null;
     parser.outgoing = null;
     parser[kOnExecute] = null;
-    if (parsers.free(parser) === false)
+    if (parsers.free(parser) === false) {
       parser.close();
+    } else {
+      // Since the Parser destructor isn't going to run the destroy() callbacks
+      // it needs to be triggered manually.
+      emitDestroy(parser.getAsyncId());
+    }
   }
   if (req) {
     req.parser = null;
diff --git a/lib/_http_outgoing.js b/lib/_http_outgoing.js
index 4ff84aea7d..9b492df85a 100644
--- a/lib/_http_outgoing.js
+++ b/lib/_http_outgoing.js
@@ -31,6 +31,8 @@ const common = require('_http_common');
 const checkIsHttpToken = common._checkIsHttpToken;
 const checkInvalidHeaderChar = common._checkInvalidHeaderChar;
 const outHeadersKey = require('internal/http').outHeadersKey;
+const async_id_symbol = process.binding('async_wrap').async_id_symbol;
+const nextTick = require('internal/process/next_tick').nextTick;
 
 const CRLF = common.CRLF;
 const debug = common.debug;
@@ -264,8 +266,9 @@ function _writeRaw(data, encoding, callback) {
     if (this.output.length) {
       this._flushOutput(conn);
     } else if (!data.length) {
-      if (typeof callback === 'function')
-        process.nextTick(callback);
+      if (typeof callback === 'function') {
+        nextTick(this.socket[async_id_symbol], callback);
+      }
       return true;
     }
     // Directly write to socket.
@@ -623,7 +626,10 @@ const crlf_buf = Buffer.from('\r\n');
 OutgoingMessage.prototype.write = function write(chunk, encoding, callback) {
   if (this.finished) {
     var err = new Error('write after end');
-    process.nextTick(writeAfterEndNT.bind(this), err, callback);
+    nextTick(this.socket[async_id_symbol],
+             writeAfterEndNT.bind(this),
+             err,
+             callback);
 
     return true;
   }
diff --git a/lib/async_hooks.js b/lib/async_hooks.js
index 736b189097..867b5eb52d 100644
--- a/lib/async_hooks.js
+++ b/lib/async_hooks.js
@@ -32,7 +32,7 @@ var processing_hook = false;
 // Use to temporarily store and updated active_hooks_array if the user enables
 // or disables a hook while hooks are being processed.
 var tmp_active_hooks_array = null;
-// Keep track of the field counds held in tmp_active_hooks_array.
+// Keep track of the field counts held in tmp_active_hooks_array.
 var tmp_async_hook_fields = null;
 
 // Each constant tracks how many callbacks there are for any given step of
@@ -41,9 +41,9 @@ var tmp_async_hook_fields = null;
 const { kInit, kBefore, kAfter, kDestroy, kCurrentAsyncId, kCurrentTriggerId,
     kAsyncUidCntr, kInitTriggerId } = async_wrap.constants;
 
+const { async_id_symbol, trigger_id_symbol } = async_wrap;
+
 // Used in AsyncHook and AsyncEvent.
-const async_id_symbol = Symbol('_asyncId');
-const trigger_id_symbol = Symbol('_triggerId');
 const init_symbol = Symbol('init');
 const before_symbol = Symbol('before');
 const after_symbol = Symbol('after');
diff --git a/lib/dgram.js b/lib/dgram.js
index f2da1da1cc..4d9f7eb29f 100644
--- a/lib/dgram.js
+++ b/lib/dgram.js
@@ -25,7 +25,10 @@ const assert = require('assert');
 const Buffer = require('buffer').Buffer;
 const util = require('util');
 const EventEmitter = require('events');
+const setInitTriggerId = require('async_hooks').setInitTriggerId;
 const UV_UDP_REUSEADDR = process.binding('constants').os.UV_UDP_REUSEADDR;
+const async_id_symbol = process.binding('async_wrap').async_id_symbol;
+const nextTick = require('internal/process/next_tick').nextTick;
 
 const UDP = process.binding('udp_wrap').UDP;
 const SendWrap = process.binding('udp_wrap').SendWrap;
@@ -111,6 +114,7 @@ function Socket(type, listener) {
   this._handle = handle;
   this._receiving = false;
   this._bindState = BIND_STATE_UNBOUND;
+  this[async_id_symbol] = this._handle.getAsyncId();
   this.type = type;
   this.fd = null; // compatibility hack
 
@@ -432,6 +436,10 @@ function doSend(ex, self, ip, list, address, port, callback) {
     req.callback = callback;
     req.oncomplete = afterSend;
   }
+  // node::SendWrap isn't instantiated and attached to the JS instance of
+  // SendWrap above until send() is called. So don't set the init trigger id
+  // until now.
+  setInitTriggerId(self[async_id_symbol]);
   var err = self._handle.send(req,
                               list,
                               list.length,
@@ -441,7 +449,7 @@ function doSend(ex, self, ip, list, address, port, callback) {
   if (err && callback) {
     // don't emit as error, dgram_legacy.js compatibility
     const ex = exceptionWithHostPort(err, 'send', address, port);
-    process.nextTick(callback, ex);
+    nextTick(self[async_id_symbol], callback, ex);
   }
 }
 
@@ -468,7 +476,7 @@ Socket.prototype.close = function(callback) {
   this._stopReceiving();
   this._handle.close();
   this._handle = null;
-  process.nextTick(socketCloseNT, this);
+  nextTick(this[async_id_symbol], socketCloseNT, this);
 
   return this;
 };
diff --git a/lib/internal/bootstrap_node.js b/lib/internal/bootstrap_node.js
index 67a7c10919..b93b817aba 100644
--- a/lib/internal/bootstrap_node.js
+++ b/lib/internal/bootstrap_node.js
@@ -292,10 +292,20 @@
   }
 
   function setupProcessFatal() {
+    const async_wrap = process.binding('async_wrap');
+    // Arrays containing hook flags and ids for async_hook calls.
+    const { async_hook_fields, async_uid_fields } = async_wrap;
+    // Internal functions needed to manipulate the stack.
+    const { clearIdStack, popAsyncIds } = async_wrap;
+    const { kAfter, kCurrentAsyncId, kInitTriggerId } = async_wrap.constants;
 
     process._fatalException = function(er) {
       var caught;
 
+      // It's possible that kInitTriggerId was set for a constructor call that
+      // threw and was never cleared. So clear it now.
+      async_uid_fields[kInitTriggerId] = 0;
+
       if (process.domain && process.domain._errorHandler)
         caught = process.domain._errorHandler(er);
 
@@ -314,9 +324,21 @@
           // nothing to be done about it at this point.
         }
 
-      // if we handled an error, then make sure any ticks get processed
       } else {
+        // If we handled an error, then make sure any ticks get processed
         NativeModule.require('timers').setImmediate(process._tickCallback);
+
+        // Emit the after() hooks now that the exception has been handled.
+        if (async_hook_fields[kAfter] > 0) {
+          do {
+            NativeModule.require('async_hooks').emitAfter(
+                async_uid_fields[kCurrentAsyncId]);
+          // popAsyncIds() returns true if there are more ids on the stack.
+          } while (popAsyncIds(async_uid_fields[kCurrentAsyncId]));
+        // Or completely empty the id stack.
+        } else {
+          clearIdStack();
+        }
       }
 
       return caught;
diff --git a/lib/internal/process/next_tick.js b/lib/internal/process/next_tick.js
index c834ffc2e3..0ba26ce033 100644
--- a/lib/internal/process/next_tick.js
+++ b/lib/internal/process/next_tick.js
@@ -7,11 +7,26 @@
 const kMaxCallbacksPerLoop = 1e4;
 
 exports.setup = setupNextTick;
+// Will be overwritten when setupNextTick() is called.
+exports.nextTick = null;
 
 function setupNextTick() {
+  const async_wrap = process.binding('async_wrap');
+  const async_hooks = require('async_hooks');
   const promises = require('internal/process/promises');
   const errors = require('internal/errors');
   const emitPendingUnhandledRejections = promises.setup(scheduleMicrotasks);
+  const initTriggerId = async_hooks.initTriggerId;
+  // Two arrays that share state between C++ and JS.
+  const { async_hook_fields, async_uid_fields } = async_wrap;
+  // Used to change the state of the async id stack.
+  const { pushAsyncIds, popAsyncIds } = async_wrap;
+  // The needed emit*() functions.
+  const { emitInit, emitBefore, emitAfter, emitDestroy } = async_hooks;
+  // Grab the constants necessary for working with internal arrays.
+  const { kInit, kBefore, kAfter, kDestroy, kAsyncUidCntr, kInitTriggerId } =
+      async_wrap.constants;
+  const { async_id_symbol, trigger_id_symbol } = async_wrap;
   var nextTickQueue = [];
   var microtasksScheduled = false;
 
@@ -27,6 +42,9 @@ function setupNextTick() {
   process._tickCallback = _tickCallback;
   process._tickDomainCallback = _tickDomainCallback;
 
+  // Set the nextTick() function for internal usage.
+  exports.nextTick = internalNextTick;
+
   // This tickInfo thing is used so that the C++ code in src/node.cc
   // can have easy access to our nextTick state, and avoid unnecessary
   // calls into JS land.
@@ -51,10 +69,13 @@ function setupNextTick() {
     if (microtasksScheduled)
       return;
 
-    nextTickQueue.push({
-      callback: runMicrotasksCallback,
-      domain: null
-    });
+    const tickObject =
+        new TickObject(runMicrotasksCallback, undefined, null);
+    // For the moment all microtasks come from the void until the PromiseHook
+    // API is implemented.
+    tickObject[async_id_symbol] = 0;
+    tickObject[trigger_id_symbol] = 0;
+    nextTickQueue.push(tickObject);
 
     tickInfo[kLength]++;
     microtasksScheduled = true;
@@ -89,20 +110,58 @@ function setupNextTick() {
     }
   }
 
+  // TODO(trevnorris): Using std::stack of Environment::AsyncHooks::ids_stack_
+  // is much slower here than was the Float64Array stack used in a previous
+  // implementation. Problem is the Float64Array stack was a bit brittle.
+  // Investigate how to harden that implementation and possibly reintroduce it.
+  function nextTickEmitBefore(asyncId, triggerId) {
+    if (async_hook_fields[kBefore] > 0)
+      emitBefore(asyncId, triggerId);
+    else
+      pushAsyncIds(asyncId, triggerId);
+  }
+
+  function nextTickEmitAfter(asyncId) {
+    if (async_hook_fields[kAfter] > 0)
+      emitAfter(asyncId);
+    else
+      popAsyncIds(asyncId);
+  }
+
   // Run callbacks that have no domain.
   // Using domains will cause this to be overridden.
   function _tickCallback() {
-    var callback, args, tock;
-
     do {
       while (tickInfo[kIndex] < tickInfo[kLength]) {
-        tock = nextTickQueue[tickInfo[kIndex]++];
-        callback = tock.callback;
-        args = tock.args;
+        const tock = nextTickQueue[tickInfo[kIndex]++];
+        const callback = tock.callback;
+        const args = tock.args;
+
+        // CHECK(Number.isSafeInteger(tock[async_id_symbol]))
+        // CHECK(tock[async_id_symbol] > 0)
+        // CHECK(Number.isSafeInteger(tock[trigger_id_symbol]))
+        // CHECK(tock[trigger_id_symbol] > 0)
+
+        nextTickEmitBefore(tock[async_id_symbol], tock[trigger_id_symbol]);
+        // emitDestroy() places the async_id_symbol into an asynchronous queue
+        // that calls the destroy callback in the future. It's called before
+        // calling tock.callback so destroy will be called even if the callback
+        // throws an exception that is handles by 'uncaughtException' or a
+        // domain.
+        // TODO(trevnorris): This is a bit of a hack. It relies on the fact
+        // 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)
+          emitDestroy(tock[async_id_symbol]);
+
         // Using separate callback execution functions allows direct
         // callback invocation with small numbers of arguments to avoid the
         // performance hit associated with using `fn.apply()`
         _combinedTickCallback(args, callback);
+
+        nextTickEmitAfter(tock[async_id_symbol]);
+
         if (kMaxCallbacksPerLoop < tickInfo[kIndex])
           tickDone();
       }
@@ -113,20 +172,33 @@ function setupNextTick() {
   }
 
   function _tickDomainCallback() {
-    var callback, domain, args, tock;
-
     do {
       while (tickInfo[kIndex] < tickInfo[kLength]) {
-        tock = nextTickQueue[tickInfo[kIndex]++];
-        callback = tock.callback;
-        domain = tock.domain;
-        args = tock.args;
+        const tock = nextTickQueue[tickInfo[kIndex]++];
+        const callback = tock.callback;
+        const domain = tock.domain;
+        const args = tock.args;
         if (domain)
           domain.enter();
+
+        // CHECK(Number.isSafeInteger(tock[async_id_symbol]))
+        // CHECK(tock[async_id_symbol] > 0)
+        // CHECK(Number.isSafeInteger(tock[trigger_id_symbol]))
+        // CHECK(tock[trigger_id_symbol] > 0)
+
+        nextTickEmitBefore(tock[async_id_symbol], tock[trigger_id_symbol]);
+        // TODO(trevnorris): See comment in _tickCallback() as to why this
+        // isn't a good solution.
+        if (async_hook_fields[kDestroy] > 0)
+          emitDestroy(tock[async_id_symbol]);
+
         // Using separate callback execution functions allows direct
         // callback invocation with small numbers of arguments to avoid the
         // performance hit associated with using `fn.apply()`
         _combinedTickCallback(args, callback);
+
+        nextTickEmitAfter(tock[async_id_symbol]);
+
         if (kMaxCallbacksPerLoop < tickInfo[kIndex])
           tickDone();
         if (domain)
@@ -138,6 +210,25 @@ function setupNextTick() {
     } while (tickInfo[kLength] !== 0);
   }
 
+  function TickObject(callback, args, domain) {
+    this.callback = callback;
+    this.domain = domain;
+    this.args = args;
+    this[async_id_symbol] = -1;
+    this[trigger_id_symbol] = -1;
+  }
+
+  function setupInit(tickObject, triggerId) {
+    tickObject[async_id_symbol] = ++async_uid_fields[kAsyncUidCntr];
+    tickObject[trigger_id_symbol] = triggerId || initTriggerId();
+    if (async_hook_fields[kInit] > 0) {
+      emitInit(tickObject[async_id_symbol],
+               'TickObject',
+               tickObject[trigger_id_symbol],
+               tickObject);
+    }
+  }
+
   function nextTick(callback) {
     if (typeof callback !== 'function')
       throw new errors.TypeError('ERR_INVALID_CALLBACK');
@@ -152,11 +243,33 @@ function setupNextTick() {
         args[i - 1] = arguments[i];
     }
 
-    nextTickQueue.push({
-      callback,
-      domain: process.domain || null,
-      args
-    });
+    var obj = new TickObject(callback, args, process.domain || null);
+    setupInit(obj, null);
+    nextTickQueue.push(obj);
+    tickInfo[kLength]++;
+  }
+
+  function internalNextTick(triggerId, callback) {
+    if (typeof callback !== 'function')
+      throw new TypeError('callback is not a function');
+    // CHECK(Number.isSafeInteger(triggerId) || triggerId === null)
+    // CHECK(triggerId > 0 || triggerId === null)
+
+    if (process._exiting)
+      return;
+
+    var args;
+    if (arguments.length > 2) {
+      args = new Array(arguments.length - 2);
+      for (var i = 2; i < arguments.length; i++)
+        args[i - 2] = arguments[i];
+    }
+
+    var obj = new TickObject(callback, args, process.domain || null);
+    setupInit(obj, triggerId);
+    // The call to initTriggerId() was skipped, so clear kInitTriggerId.
+    async_uid_fields[kInitTriggerId] = 0;
+    nextTickQueue.push(obj);
     tickInfo[kLength]++;
   }
 }
diff --git a/lib/net.js b/lib/net.js
index 2da278a32d..2431820783 100644
--- a/lib/net.js
+++ b/lib/net.js
@@ -39,6 +39,9 @@ const TCPConnectWrap = process.binding('tcp_wrap').TCPConnectWrap;
 const PipeConnectWrap = process.binding('pipe_wrap').PipeConnectWrap;
 const ShutdownWrap = process.binding('stream_wrap').ShutdownWrap;
 const WriteWrap = process.binding('stream_wrap').WriteWrap;
+const async_id_symbol = process.binding('async_wrap').async_id_symbol;
+const { newUid, setInitTriggerId } = require('async_hooks');
+const nextTick = require('internal/process/next_tick').nextTick;
 
 var cluster;
 var dns;
@@ -57,6 +60,12 @@ function createHandle(fd) {
 }
 
 
+function getNewAsyncId(handle) {
+  return (!handle || typeof handle.getAsyncId !== 'function') ?
+      newUid() : handle.getAsyncId();
+}
+
+
 const debug = util.debuglog('net');
 
 function isPipeName(s) {
@@ -147,6 +156,7 @@ function initSocketHandle(self) {
   if (self._handle) {
     self._handle.owner = self;
     self._handle.onread = onread;
+    self[async_id_symbol] = getNewAsyncId(self._handle);
 
     // If handle doesn't support writev - neither do we
     if (!self._handle.writev)
@@ -162,6 +172,10 @@ function Socket(options) {
   if (!(this instanceof Socket)) return new Socket(options);
 
   this.connecting = false;
+  // Problem with this is that users can supply their own handle, that may not
+  // have _handle.getAsyncId(). In this case an[async_id_symbol] should
+  // probably be supplied by async_hooks.
+  this[async_id_symbol] = -1;
   this._hadError = false;
   this._handle = null;
   this._parent = null;
@@ -176,9 +190,11 @@ function Socket(options) {
 
   if (options.handle) {
     this._handle = options.handle; // private
+    this[async_id_symbol] = getNewAsyncId(this._handle);
   } else if (options.fd !== undefined) {
     this._handle = createHandle(options.fd);
     this._handle.open(options.fd);
+    this[async_id_symbol] = this._handle.getAsyncId();
     // options.fd can be string (since it is user-defined),
     // so changing this to === would be semver-major
     // See: https://github.com/nodejs/node/pull/11513
@@ -264,6 +280,10 @@ function onSocketFinish() {
   var req = new ShutdownWrap();
   req.oncomplete = afterShutdown;
   req.handle = this._handle;
+  // node::ShutdownWrap isn't instantiated and attached to the JS instance of
+  // ShutdownWrap above until shutdown() is called. So don't set the init
+  // trigger id until now.
+  setInitTriggerId(this[async_id_symbol]);
   var err = this._handle.shutdown(req);
 
   if (err)
@@ -329,7 +349,7 @@ function writeAfterFIN(chunk, encoding, cb) {
   // TODO: defer error events consistently everywhere, not just the cb
   this.emit('error', er);
   if (typeof cb === 'function') {
-    process.nextTick(cb, er);
+    nextTick(this[async_id_symbol], cb, er);
   }
 }
 
@@ -887,6 +907,10 @@ function internalConnect(
     req.localAddress = localAddress;
     req.localPort = localPort;
 
+    // node::TCPConnectWrap isn't instantiated and attached to the JS instance
+    // of TCPConnectWrap above until connect() is called. So don't set the init
+    // trigger id until now.
+    setInitTriggerId(self[async_id_symbol]);
     if (addressType === 4)
       err = self._handle.connect(req, address, port);
     else
@@ -896,6 +920,10 @@ function internalConnect(
     const req = new PipeConnectWrap();
     req.address = address;
     req.oncomplete = afterConnect;
+    // node::PipeConnectWrap isn't instantiated and attached to the JS instance
+    // of PipeConnectWrap above until connect() is called. So don't set the
+    // init trigger id until now.
+    setInitTriggerId(self[async_id_symbol]);
     err = self._handle.connect(req, address, afterConnect);
   }
 
@@ -1020,6 +1048,7 @@ function lookupAndConnect(self, options) {
   debug('connect: dns options', dnsopts);
   self._host = host;
   var lookup = options.lookup || dns.lookup;
+  setInitTriggerId(self[async_id_symbol]);
   lookup(host, dnsopts, function emitLookup(err, ip, addressType) {
     self.emit('lookup', err, ip, addressType, host);
 
@@ -1167,6 +1196,7 @@ function Server(options, connectionListener) {
     configurable: true, enumerable: false
   });
 
+  this[async_id_symbol] = -1;
   this._handle = null;
   this._usingSlaves = false;
   this._slaves = [];
@@ -1274,6 +1304,7 @@ function setupListenHandle(address, port, addressType, backlog, fd) {
     this._handle = rval;
   }
 
+  this[async_id_symbol] = getNewAsyncId(this._handle);
   this._handle.onconnection = onconnection;
   this._handle.owner = this;
 
@@ -1286,7 +1317,7 @@ function setupListenHandle(address, port, addressType, backlog, fd) {
     var ex = exceptionWithHostPort(err, 'listen', address, port);
     this._handle.close();
     this._handle = null;
-    process.nextTick(emitErrorNT, this, ex);
+    nextTick(this[async_id_symbol], emitErrorNT, this, ex);
     return;
   }
 
@@ -1297,7 +1328,7 @@ function setupListenHandle(address, port, addressType, backlog, fd) {
   if (this._unref)
     this.unref();
 
-  process.nextTick(emitListeningNT, this);
+  nextTick(this[async_id_symbol], emitListeningNT, this);
 }
 
 Server.prototype._listen2 = setupListenHandle;  // legacy alias
@@ -1398,6 +1429,7 @@ Server.prototype.listen = function() {
   // (handle[, backlog][, cb]) where handle is an object with a handle
   if (options instanceof TCP) {
     this._handle = options;
+    this[async_id_symbol] = this._handle.getAsyncId();
     listenInCluster(this, null, -1, -1, backlogFromArgs);
     return this;
   }
@@ -1521,8 +1553,10 @@ function onconnection(err, clientHandle) {
 
 
 Server.prototype.getConnections = function(cb) {
+  const self = this;
+
   function end(err, connections) {
-    process.nextTick(cb, err, connections);
+    nextTick(self[async_id_symbol], cb, err, connections);
   }
 
   if (!this._usingSlaves) {
@@ -1597,7 +1631,8 @@ Server.prototype._emitCloseIfDrained = function() {
     return;
   }
 
-  process.nextTick(emitCloseNT, this);
+  const asyncId = this._handle ? this[async_id_symbol] : null;
+  nextTick(asyncId, emitCloseNT, this);
 };
 
 
diff --git a/lib/timers.js b/lib/timers.js
index 5d21227b7b..fb9984abf4 100644
--- a/lib/timers.js
+++ b/lib/timers.js
@@ -21,14 +21,29 @@
 
 'use strict';
 
+const async_wrap = process.binding('async_wrap');
 const TimerWrap = process.binding('timer_wrap').Timer;
 const L = require('internal/linkedlist');
 const internalUtil = require('internal/util');
 const { createPromise, promiseResolve } = process.binding('util');
+const async_hooks = require('async_hooks');
 const assert = require('assert');
 const util = require('util');
 const debug = util.debuglog('timer');
 const kOnTimeout = TimerWrap.kOnTimeout | 0;
+const initTriggerId = async_hooks.initTriggerId;
+// Two arrays that share state between C++ and JS.
+const { async_hook_fields, async_uid_fields } = async_wrap;
+// Used to change the state of the async id stack.
+const { pushAsyncIds, popAsyncIds } = async_wrap;
+// The needed emit*() functions.
+const { emitInit, emitBefore, emitAfter, emitDestroy } = async_hooks;
+// Grab the constants necessary for working with internal arrays.
+const { kInit, kBefore, kAfter, kDestroy, kAsyncUidCntr } =
+    async_wrap.constants;
+// Symbols for storing async id state.
+const async_id_symbol = Symbol('asyncId');
+const trigger_id_symbol = Symbol('triggerId');
 
 // Timeout values > TIMEOUT_MAX are set to 1.
 const TIMEOUT_MAX = 2147483647; // 2^31-1
@@ -134,6 +149,22 @@ exports._unrefActive = function(item) {
 };
 
 
+function timerEmitBefore(asyncId, triggerId) {
+  if (async_hook_fields[kBefore] > 0)
+    emitBefore(asyncId, triggerId);
+  else
+    pushAsyncIds(asyncId, triggerId);
+}
+
+
+function timerEmitAfter(asyncId) {
+  if (async_hook_fields[kAfter] > 0)
+    emitAfter(asyncId);
+  else
+    popAsyncIds(asyncId);
+}
+
+
 // The underlying logic for scheduling or re-scheduling a timer.
 //
 // Appends a timer onto the end of an existing timers list, or creates a new
@@ -154,6 +185,14 @@ function insert(item, unrefed) {
     lists[msecs] = list = createTimersList(msecs, unrefed);
   }
 
+  if (!item[async_id_symbol] || item._destroyed) {
+    item._destroyed = false;
+    item[async_id_symbol] = ++async_uid_fields[kAsyncUidCntr];
+    item[trigger_id_symbol] = initTriggerId();
+    if (async_hook_fields[kInit] > 0)
+      emitInit(item[async_id_symbol], 'Timeout', item[trigger_id_symbol], item);
+  }
+
   L.append(list, item);
   assert(!L.isEmpty(list)); // list is not empty
 }
@@ -218,7 +257,14 @@ function listOnTimeout() {
     L.remove(timer);
     assert(timer !== L.peek(list));
 
-    if (!timer._onTimeout) continue;
+    if (!timer._onTimeout) {
+      if (async_hook_fields[kDestroy] > 0 && !timer._destroyed &&
+            typeof timer[async_id_symbol] === 'number') {
+        emitDestroy(timer[async_id_symbol]);
+        timer._destroyed = true;
+      }
+      continue;
+    }
 
     var domain = timer.domain;
     if (domain) {
@@ -268,11 +314,25 @@ function listOnTimeout() {
 // 4.7) what is in this smaller function.
 function tryOnTimeout(timer, list) {
   timer._called = true;
+  const timerAsyncId = (typeof timer[async_id_symbol] === 'number') ?
+      timer[async_id_symbol] : null;
   var threw = true;
+  if (timerAsyncId !== null)
+    timerEmitBefore(timerAsyncId, timer[trigger_id_symbol]);
   try {
     ontimeout(timer);
     threw = false;
   } finally {
+    if (timerAsyncId !== null) {
+      if (!threw)
+        timerEmitAfter(timerAsyncId);
+      if (!timer._repeat && async_hook_fields[kDestroy] > 0 &&
+          !timer._destroyed) {
+        emitDestroy(timerAsyncId);
+        timer._destroyed = true;
+      }
+    }
+
     if (!threw) return;
 
     // Postpone all later list events to next tick. We need to do this
@@ -324,6 +384,15 @@ function reuse(item) {
 
 // Remove a timer. Cancels the timeout and resets the relevant timer properties.
 const unenroll = exports.unenroll = function(item) {
+  // Fewer checks may be possible, but these cover everything.
+  if (async_hook_fields[kDestroy] > 0 &&
+      item &&
+      typeof item[async_id_symbol] === 'number' &&
+      !item._destroyed) {
+    emitDestroy(item[async_id_symbol]);
+    item._destroyed = true;
+  }
+
   var handle = reuse(item);
   if (handle) {
     debug('unenroll: list empty');
@@ -516,6 +585,11 @@ function Timeout(after, callback, args) {
   this._onTimeout = callback;
   this._timerArgs = args;
   this._repeat = null;
+  this._destroyed = false;
+  this[async_id_symbol] = ++async_uid_fields[kAsyncUidCntr];
+  this[trigger_id_symbol] = initTriggerId();
+  if (async_hook_fields[kInit] > 0)
+    emitInit(this[async_id_symbol], 'Timeout', this[trigger_id_symbol], this);
 }
 
 
@@ -570,6 +644,15 @@ Timeout.prototype.ref = function() {
 Timeout.prototype.close = function() {
   this._onTimeout = null;
   if (this._handle) {
+    // Fewer checks may be possible, but these cover everything.
+    if (async_hook_fields[kDestroy] > 0 &&
+        this &&
+        typeof this[async_id_symbol] === 'number' &&
+        !this._destroyed) {
+      emitDestroy(this[async_id_symbol]);
+      this._destroyed = true;
+    }
+
     this._idleTimeout = -1;
     this._handle[kOnTimeout] = null;
     this._handle.close();
@@ -673,11 +756,21 @@ function processImmediate() {
 // 4.7) what is in this smaller function.
 function tryOnImmediate(immediate, oldTail) {
   var threw = true;
+  timerEmitBefore(immediate[async_id_symbol], immediate[trigger_id_symbol]);
   try {
     // make the actual call outside the try/catch to allow it to be optimized
     runCallback(immediate);
     threw = false;
   } finally {
+    // clearImmediate checks _callback === null for kDestroy hooks.
+    immediate._callback = null;
+    if (!threw)
+      timerEmitAfter(immediate[async_id_symbol]);
+    if (async_hook_fields[kDestroy] > 0 && !immediate._destroyed) {
+      emitDestroy(immediate[async_id_symbol]);
+      immediate._destroyed = true;
+    }
+
     if (threw && immediate._idleNext) {
       // Handle any remaining on next tick, assuming we're still alive to do so.
       const curHead = immediateQueue.head;
@@ -726,7 +819,12 @@ function Immediate() {
   this._callback = null;
   this._argv = null;
   this._onImmediate = null;
+  this._destroyed = false;
   this.domain = process.domain;
+  this[async_id_symbol] = ++async_uid_fields[kAsyncUidCntr];
+  this[trigger_id_symbol] = initTriggerId();
+  if (async_hook_fields[kInit] > 0)
+    emitInit(this[async_id_symbol], 'Immediate', this[trigger_id_symbol], this);
 }
 
 function setImmediate(callback, arg1, arg2, arg3) {
@@ -785,6 +883,13 @@ function createImmediate(args, callback) {
 exports.clearImmediate = function(immediate) {
   if (!immediate) return;
 
+  if (async_hook_fields[kDestroy] > 0 &&
+      immediate._callback !== null &&
+      !immediate._destroyed) {
+    emitDestroy(immediate[async_id_symbol]);
+    immediate._destroyed = true;
+  }
+
   immediate._onImmediate = null;
 
   immediateQueue.remove(immediate);