src: add uv_get_available_memory to report and process

Author: theanarkh

doc/api/process.md

@@ -1127,6 +1127,21 @@ is unknown, `undefined` is returned.
 See [`uv_get_constrained_memory`][uv_get_constrained_memory] for more
 information.
 
+## `process.availableMemory()`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+> Stability: 1 - Experimental
+
+* {number}
+
+Gets the amount of free memory that is still available to the process.
+
+See [`uv_get_available_memory`][uv_get_available_memory] for more
+information.
+
 ## `process.cpuUsage([previousValue])`
 
 <!-- YAML
@@ -4027,6 +4042,7 @@ cases:
 [report documentation]: report.md
 [terminal raw mode]: tty.md#readstreamsetrawmodemode
 [uv_get_constrained_memory]: https://docs.libuv.org/en/v1.x/misc.html#c.uv_get_constrained_memory
+[uv_get_available_memory]: https://docs.libuv.org/en/v1.x/misc.html#c.uv_get_available_memory
 [uv_rusage_t]: https://docs.libuv.org/en/v1.x/misc.html#c.uv_rusage_t
 [wikipedia_major_fault]: https://en.wikipedia.org/wiki/Page_fault#Major
 [wikipedia_minor_fault]: https://en.wikipedia.org/wiki/Page_fault#Minor

lib/internal/bootstrap/node.js

@@ -178,6 +178,7 @@ const rawMethods = internalBinding('process_methods');
   process.resourceUsage = wrapped.resourceUsage;
   process.memoryUsage = wrapped.memoryUsage;
   process.constrainedMemory = rawMethods.constrainedMemory;
+  process.availableMemory = rawMethods.availableMemory;
   process.kill = wrapped.kill;
   process.exit = wrapped.exit;
 

src/node_process_methods.cc

@@ -216,6 +216,11 @@ static void GetConstrainedMemory(const FunctionCallbackInfo<Value>& args) {
   }
 }
 
+static void GetAvailableMemory(const FunctionCallbackInfo<Value>& args) {
+  uint64_t value = uv_get_available_memory();
+  args.GetReturnValue().Set(static_cast<double>(value));
+}
+
 void RawDebug(const FunctionCallbackInfo<Value>& args) {
   CHECK(args.Length() == 1 && args[0]->IsString() &&
         "must be called with a single string");
@@ -633,6 +638,7 @@ static void CreatePerIsolateProperties(IsolateData* isolate_data,
   SetMethod(isolate, target, "umask", Umask);
   SetMethod(isolate, target, "memoryUsage", MemoryUsage);
   SetMethod(isolate, target, "constrainedMemory", GetConstrainedMemory);
+  SetMethod(isolate, target, "availableMemory", GetAvailableMemory);
   SetMethod(isolate, target, "rss", Rss);
   SetMethod(isolate, target, "cpuUsage", CPUUsage);
   SetMethod(isolate, target, "resourceUsage", ResourceUsage);
@@ -674,6 +680,7 @@ void RegisterExternalReferences(ExternalReferenceRegistry* registry) {
   registry->Register(RawDebug);
   registry->Register(MemoryUsage);
   registry->Register(GetConstrainedMemory);
+  registry->Register(GetAvailableMemory);
   registry->Register(Rss);
   registry->Register(CPUUsage);
   registry->Register(ResourceUsage);

src/node_report.cc

@@ -634,17 +634,10 @@ static void PrintResourceUsage(JSONWriter* writer) {
   }
 
   uint64_t constrained_memory = uv_get_constrained_memory();
-  if (constrained_memory) {
-    writer->json_keyvalue("constrained_memory", constrained_memory);
-  }
+  writer->json_keyvalue("constrained_memory", constrained_memory);
 
-  // See GuessMemoryAvailableToTheProcess
-  if (!err && constrained_memory && constrained_memory >= rss) {
-    uint64_t available_memory = constrained_memory - rss;
-    writer->json_keyvalue("available_memory", available_memory);
-  } else {
-    writer->json_keyvalue("available_memory", free_memory);
-  }
+  uint64_t available_memory = uv_get_available_memory();
+  writer->json_keyvalue("available_memory", available_memory);
 
   if (uv_getrusage(&rusage) == 0) {
     double user_cpu =

test/common/report.js

@@ -233,13 +233,12 @@ function _validateContent(report, fields = []) {
 
   // Verify the format of the resourceUsage section.
   const usage = { ...report.resourceUsage };
-  // Delete it, otherwise checkForUnknownFields will throw error
-  delete usage.constrained_memory;
   const resourceUsageFields = ['userCpuSeconds', 'kernelCpuSeconds',
                                'cpuConsumptionPercent', 'userCpuConsumptionPercent',
                                'kernelCpuConsumptionPercent',
                                'maxRss', 'rss', 'free_memory', 'total_memory',
-                               'available_memory', 'pageFaults', 'fsActivity'];
+                               'available_memory', 'pageFaults', 'fsActivity',
+                              'constrained_memory'];
   checkForUnknownFields(usage, resourceUsageFields);
   assert.strictEqual(typeof usage.userCpuSeconds, 'number');
   assert.strictEqual(typeof usage.kernelCpuSeconds, 'number');
@@ -251,10 +250,7 @@ function _validateContent(report, fields = []) {
   assert(typeof usage.free_memory, 'string');
   assert(typeof usage.total_memory, 'string');
   assert(typeof usage.available_memory, 'string');
-  // This field may not exsit
-  if (report.resourceUsage.constrained_memory) {
-    assert(typeof report.resourceUsage.constrained_memory, 'string');
-  }
+  assert(typeof usage.constrained_memory, 'string');
   assert(typeof usage.pageFaults === 'object' && usage.pageFaults !== null);
   checkForUnknownFields(usage.pageFaults, ['IORequired', 'IONotRequired']);
   assert(Number.isSafeInteger(usage.pageFaults.IORequired));

test/parallel/test-process-available-memory.js

@@ -0,0 +1,10 @@
+'use strict';
+require('../common');
+const assert = require('assert');
+const { Worker } = require('worker_threads');
+const availableMemory = process.availableMemory();
+assert(typeof availableMemory, 'number');
+if (!process.env.isWorker) {
+  process.env.isWorker = true;
+  new Worker(__filename);
+}