v8: integrate node-heapdump into core

Adds `v8.writeHeapSnapshot(filename)` with impl adapted
from the `node-heapdump` module.

Also, adds a v8.getHeapSnapshot() alternative that returns
a Readable Stream

PR-URL: #26501
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Sam Roberts <vieuxtech@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>

LICENSE

@@ -634,7 +634,7 @@ The externally maintained libraries used by Node.js are:
 
 - OpenSSL, located at deps/openssl, is licensed as follows:
   """
-    Copyright (c) 1998-2018 The OpenSSL Project.  All rights reserved.
+    Copyright (c) 1998-2019 The OpenSSL Project.  All rights reserved.
 
     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
@@ -1445,3 +1445,40 @@ The externally maintained libraries used by Node.js are:
      ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
      THE POSSIBILITY OF SUCH DAMAGE.
   """
+
+- node-heapdump, located at src/heap_utils.cc, is licensed as follows:
+  """
+    ISC License
+
+    Copyright (c) 2012, Ben Noordhuis <info@bnoordhuis.nl>
+
+    Permission to use, copy, modify, and/or distribute this software for any
+    purpose with or without fee is hereby granted, provided that the above
+    copyright notice and this permission notice appear in all copies.
+
+    THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+    WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+    MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+    ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+    WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+    ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+    === src/compat.h src/compat-inl.h ===
+
+    ISC License
+
+    Copyright (c) 2014, StrongLoop Inc.
+
+    Permission to use, copy, modify, and/or distribute this software for any
+    purpose with or without fee is hereby granted, provided that the above
+    copyright notice and this permission notice appear in all copies.
+
+    THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+    WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+    MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+    ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+    WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+    ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+  """

doc/api/v8.md

@@ -87,6 +87,24 @@ The value returned is an array of objects containing the following properties:
 ]
 ```
 
+## v8.getHeapSnapshot()
+<!-- YAML
+added: REPLACEME
+-->
+
+* Returns: {stream.Readable} A Readable Stream containing the V8 heap snapshot
+
+Generates a snapshot of the current V8 heap and returns a Readable
+Stream that may be used to read the JSON serialized representation.
+This JSON stream format is intended to be used with tools such as
+Chrome DevTools. The JSON schema is undocumented and specific to the
+V8 engine, and may change from one version of V8 to the next.
+
+```js
+const stream = v8.getHeapSnapshot();
+stream.pipe(process.stdout);
+```
+
 ## v8.getHeapStatistics()
 <!-- YAML
 added: v1.0.0
@@ -159,6 +177,58 @@ v8.setFlagsFromString('--trace_gc');
 setTimeout(() => { v8.setFlagsFromString('--notrace_gc'); }, 60e3);
 ```
 
+## v8.writeHeapSnapshot([filename])
+<!-- YAML
+added: REPLACEME
+-->
+
+* `filename` {string} The file path where the V8 heap snapshot is to be
+  saved. If not specified, a file name with the pattern
+  `'Heap-${yyyymmdd}-${hhmmss}-${pid}-${thread_id}.heapsnapshot'` will be
+  generated, where `{pid}` will be the PID of the Node.js process,
+  `{thread_id}` will be `0` when `writeHeapSnapshot()` is called from
+  the main Node.js thread or the id of a worker thread.
+* Returns: {string} The filename where the snapshot was saved.
+
+Generates a snapshot of the current V8 heap and writes it to a JSON
+file. This file is intended to be used with tools such as Chrome
+DevTools. The JSON schema is undocumented and specific to the V8
+engine, and may change from one version of V8 to the next.
+
+A heap snapshot is specific to a single V8 isolate. When using
+[Worker Threads][], a heap snapshot generated from the main thread will
+not contain any information about the workers, and vice versa.
+
+```js
+const { writeHeapSnapshot } = require('v8');
+const {
+  Worker,
+  isMainThread,
+  parentPort
+} = require('worker_threads');
+
+if (isMainThread) {
+  const worker = new Worker(__filename);
+
+  worker.once('message', (filename) => {
+    console.log(`worker heapdump: ${filename}`);
+    // Now get a heapdump for the main thread.
+    console.log(`main thread heapdump: ${writeHeapSnapshot()}`);
+  });
+
+  // Tell the worker to create a heapdump.
+  worker.postMessage('heapdump');
+} else {
+  parentPort.once('message', (message) => {
+    if (message === 'heapdump') {
+      // Generate a heapdump for the worker
+      // and return the filename to the parent.
+      parentPort.postMessage(writeHeapSnapshot());
+    }
+  });
+}
+```
+
 ## Serialization API
 
 > Stability: 1 - Experimental
@@ -417,4 +487,5 @@ A subclass of [`Deserializer`][] corresponding to the format written by
 [`vm.Script`]: vm.html#vm_constructor_new_vm_script_code_options
 [HTML structured clone algorithm]: https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API/Structured_clone_algorithm
 [V8]: https://developers.google.com/v8/
+[Worker Threads]: worker_threads.html
 [here]: https://github.com/thlorenz/v8-flags/blob/master/flags-0.11.md

lib/internal/test/heap.js

@@ -4,14 +4,17 @@ process.emitWarning(
   'These APIs are for internal testing only. Do not use them.',
   'internal/test/heap');
 
-const { createHeapDump, buildEmbedderGraph } = internalBinding('heap_utils');
+const {
+  createHeapSnapshot,
+  buildEmbedderGraph
+} = internalBinding('heap_utils');
 const assert = require('internal/assert');
 
 // This is not suitable for production code. It creates a full V8 heap dump,
 // parses it as JSON, and then creates complex objects from it, leading
 // to significantly increased memory usage.
-function createJSHeapDump() {
-  const dump = createHeapDump();
+function createJSHeapSnapshot() {
+  const dump = createHeapSnapshot();
   const meta = dump.snapshot.meta;
 
   const nodes =
@@ -81,6 +84,6 @@ function readHeapInfo(raw, fields, types, strings) {
 }
 
 module.exports = {
-  createJSHeapDump,
+  createJSHeapSnapshot,
   buildEmbedderGraph
 };

lib/v8.js

@@ -20,9 +20,65 @@ const {
   Serializer: _Serializer,
   Deserializer: _Deserializer
 } = internalBinding('serdes');
+const assert = require('internal/assert');
 const { copy } = internalBinding('buffer');
 const { objectToString } = require('internal/util');
 const { FastBuffer } = require('internal/buffer');
+const { toPathIfFileURL } = require('internal/url');
+const { validatePath } = require('internal/fs/utils');
+const { toNamespacedPath } = require('path');
+const {
+  createHeapSnapshotStream,
+  triggerHeapSnapshot
+} = internalBinding('heap_utils');
+const { Readable } = require('stream');
+const { owner_symbol } = require('internal/async_hooks').symbols;
+const {
+  kUpdateTimer,
+  onStreamRead,
+} = require('internal/stream_base_commons');
+const kHandle = Symbol('kHandle');
+
+
+function writeHeapSnapshot(filename) {
+  if (filename !== undefined) {
+    filename = toPathIfFileURL(filename);
+    validatePath(filename);
+    filename = toNamespacedPath(filename);
+  }
+  return triggerHeapSnapshot(filename);
+}
+
+class HeapSnapshotStream extends Readable {
+  constructor(handle) {
+    super({ autoDestroy: true });
+    this[kHandle] = handle;
+    handle[owner_symbol] = this;
+    handle.onread = onStreamRead;
+  }
+
+  _read() {
+    if (this[kHandle])
+      this[kHandle].readStart();
+  }
+
+  _destroy() {
+    // Release the references on the handle so that
+    // it can be garbage collected.
+    this[kHandle][owner_symbol] = undefined;
+    this[kHandle] = undefined;
+  }
+
+  [kUpdateTimer]() {
+    // Does nothing
+  }
+}
+
+function getHeapSnapshot() {
+  const handle = createHeapSnapshotStream();
+  assert(handle);
+  return new HeapSnapshotStream(handle);
+}
 
 // Calling exposed c++ functions directly throws exception as it expected to be
 // called with new operator and caused an assert to fire.
@@ -210,6 +266,7 @@ function deserialize(buffer) {
 
 module.exports = {
   cachedDataVersionTag,
+  getHeapSnapshot,
   getHeapStatistics,
   getHeapSpaceStatistics,
   setFlagsFromString,
@@ -218,5 +275,6 @@ module.exports = {
   DefaultSerializer,
   DefaultDeserializer,
   deserialize,
-  serialize
+  serialize,
+  writeHeapSnapshot
 };

src/async_wrap.h

@@ -41,6 +41,7 @@ namespace node {
   V(FSREQPROMISE)                                                             \
   V(GETADDRINFOREQWRAP)                                                       \
   V(GETNAMEINFOREQWRAP)                                                       \
+  V(HEAPSNAPSHOT)                                                             \
   V(HTTP2SESSION)                                                             \
   V(HTTP2STREAM)                                                              \
   V(HTTP2PING)                                                                \

src/env.h

@@ -383,6 +383,7 @@ constexpr size_t kFsStatsBufferLength = kFsStatsFieldsNumber * 2;
   V(script_data_constructor_function, v8::Function)                            \
   V(secure_context_constructor_template, v8::FunctionTemplate)                 \
   V(shutdown_wrap_template, v8::ObjectTemplate)                                \
+  V(streambaseoutputstream_constructor_template, v8::ObjectTemplate)           \
   V(tcp_constructor_template, v8::FunctionTemplate)                            \
   V(tick_callback_function, v8::Function)                                      \
   V(timers_callback_function, v8::Function)                                    \