v8: add setHeapSnapshotNearHeapLimit

doc/api/v8.md

@@ -356,6 +356,20 @@ if (isMainThread) {
 }
 ```
 
+## `v8.setHeapSnapshotNearHeapLimit(limit)`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+> Stability: 1 - Experimental
+
+* `limit` {integer}
+
+The API is a no-op if `--heapsnapshot-near-heap-limit` is already set from the
+command line or the API is called more than once. `limit` must be a positive
+integer. See [`--heapsnapshot-near-heap-limit`][] for more information.
+
 ## Serialization API
 
 The serialization API provides means of serializing JavaScript values in a way
@@ -1020,6 +1034,7 @@ Returns true if the Node.js instance is run to build a snapshot.
 [HTML structured clone algorithm]: https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API/Structured_clone_algorithm
 [Hook Callbacks]: #hook-callbacks
 [V8]: https://developers.google.com/v8/
+[`--heapsnapshot-near-heap-limit`]: cli.md#--heapsnapshot-near-heap-limitmax_count
 [`AsyncLocalStorage`]: async_context.md#class-asynclocalstorage
 [`Buffer`]: buffer.md
 [`DefaultDeserializer`]: #class-v8defaultdeserializer

lib/v8.js

@@ -33,7 +33,7 @@ const {
 } = primordials;
 
 const { Buffer } = require('buffer');
-const { validateString } = require('internal/validators');
+const { validateString, validateUint32 } = require('internal/validators');
 const {
   Serializer,
   Deserializer
@@ -59,6 +59,7 @@ const {
 } = internalBinding('heap_utils');
 const { HeapSnapshotStream } = require('internal/heap_utils');
 const promiseHooks = require('internal/promise_hooks');
+const { getOptionValue } = require('internal/options');
 
 /**
  * Generates a snapshot of the current V8 heap
@@ -95,6 +96,7 @@ const {
   updateHeapStatisticsBuffer,
   updateHeapSpaceStatisticsBuffer,
   updateHeapCodeStatisticsBuffer,
+  setHeapSnapshotNearHeapLimit: _setHeapSnapshotNearHeapLimit,
 
   // Properties for heap statistics buffer extraction.
   kTotalHeapSizeIndex,
@@ -226,6 +228,18 @@ function getHeapCodeStatistics() {
   };
 }
 
+let heapSnapshotNearHeapLimitCallbackAdded = false;
+function setHeapSnapshotNearHeapLimit(limit) {
+  validateUint32(limit, 'limit', 1);
+  if (heapSnapshotNearHeapLimitCallbackAdded ||
+      getOptionValue('--heapsnapshot-near-heap-limit') > 0
+  ) {
+    return;
+  }
+  heapSnapshotNearHeapLimitCallbackAdded = true;
+  _setHeapSnapshotNearHeapLimit(limit);
+}
+
 /* V8 serialization API */
 
 /* JS methods for the base objects */
@@ -387,5 +401,6 @@ module.exports = {
   serialize,
   writeHeapSnapshot,
   promiseHooks,
-  startupSnapshot
+  startupSnapshot,
+  setHeapSnapshotNearHeapLimit,
 };

src/env-inl.h

@@ -914,6 +914,24 @@ v8::Local<v8::Context> Environment::context() const {
   return PersistentToLocal::Strong(context_);
 }
 
+inline void Environment::set_heap_snapshot_near_heap_limit(uint32_t limit) {
+  heap_snapshot_near_heap_limit_ = limit;
+}
+
+inline void Environment::AddHeapSnapshotNearHeapLimitCallback() {
+  DCHECK(!heapsnapshot_near_heap_limit_callback_added_);
+  heapsnapshot_near_heap_limit_callback_added_ = true;
+  isolate_->AddNearHeapLimitCallback(Environment::NearHeapLimitCallback, this);
+}
+
+inline void Environment::RemoveHeapSnapshotNearHeapLimitCallback(
+    size_t heap_limit) {
+  DCHECK(heapsnapshot_near_heap_limit_callback_added_);
+  heapsnapshot_near_heap_limit_callback_added_ = false;
+  isolate_->RemoveNearHeapLimitCallback(Environment::NearHeapLimitCallback,
+                                        heap_limit);
+}
+
 }  // namespace node
 
 // These two files depend on each other. Including base_object-inl.h after this

src/env.cc

@@ -720,6 +720,9 @@ Environment::Environment(IsolateData* isolate_data,