when tracking threads, use a monotonic clock that ignores system suspension

Using the system time causes each suspension to be detected as an event
loop delay which is not useful. System suspensions may be common when
running in low cost cloud environments where systems are suspended when
not actively serving requests.

Author: matthew-nicholson-anrok

module.cc

@@ -3,6 +3,16 @@
 #include <mutex>
 #include <node.h>
 
+// Platform-specific includes for time functions
+#ifdef _WIN32
+#include <realtimeapiset.h>
+#include <windows.h>
+#elif defined(__APPLE__)
+#include <time.h>
+#elif defined(__linux__)
+#include <time.h>
+#endif
+
 using namespace v8;
 using namespace node;
 using namespace std::chrono;
@@ -243,6 +253,32 @@ void RegisterThread(const FunctionCallbackInfo<Value> &args) {
   }
 }
 
+// Cross-platform monotonic time function. Provides a monotonic clock that only
+// increases and does not tick when the system is suspended.
+steady_clock::time_point GetUnbiasedMonotonicTime() {
+#ifdef _WIN32
+  // Windows: QueryUnbiasedInterruptTimePrecise returns time in 100-nanosecond
+  // units
+  ULONGLONG interrupt_time;
+  QueryUnbiasedInterruptTimePrecise(&interrupt_time);
+  // Convert from 100-nanosecond units to nanoseconds
+  uint64_t time_ns = interrupt_time * 100;
+  return steady_clock::time_point(nanoseconds(time_ns));
+#elif defined(__APPLE__)
+  // macOS: CLOCK_UPTIME_RAW returns time in nanoseconds
+  uint64_t time_ns = clock_gettime_nsec_np(CLOCK_UPTIME_RAW);
+  return steady_clock::time_point(nanoseconds(time_ns));
+#elif defined(__linux__)
+  struct timespec ts;
+  clock_gettime(CLOCK_MONOTONIC, &ts);
+  return steady_clock::time_point(seconds(ts.tv_sec) + nanoseconds(ts.tv_nsec));
+#else
+  // Fallback for other platforms using steady_clock. Note: this will be
+  // monotonic but is not gaurenteed to ignore time spent while suspended.
+  return steady_clock::now();
+#endif
+}
+
 // Function to track a thread and set its state
 void ThreadPoll(const FunctionCallbackInfo<Value> &args) {
   auto isolate = args.GetIsolate();
@@ -275,8 +311,8 @@ void ThreadPoll(const FunctionCallbackInfo<Value> &args) {
       if (disable_last_seen) {
         thread_info.last_seen = milliseconds::zero();
       } else {
-        thread_info.last_seen =
-            duration_cast<milliseconds>(system_clock::now().time_since_epoch());
+        thread_info.last_seen = duration_cast<milliseconds>(
+            GetUnbiasedMonotonicTime().time_since_epoch());
       }
     }
   }
@@ -286,8 +322,8 @@ void ThreadPoll(const FunctionCallbackInfo<Value> &args) {
 void GetThreadsLastSeen(const FunctionCallbackInfo<Value> &args) {
   Isolate *isolate = args.GetIsolate();
   Local<Object> result = Object::New(isolate);
-  milliseconds now =
-      duration_cast<milliseconds>(system_clock::now().time_since_epoch());
+  milliseconds now = duration_cast<milliseconds>(
+      GetUnbiasedMonotonicTime().time_since_epoch());
   {
     std::lock_guard<std::mutex> lock(threads_mutex);
     for (const auto &[thread_isolate, info] : threads) {