Try to restructure RuntimeMetricsWriter for .NET Framework

Author: andrewlock

tracer/src/Datadog.Trace/RuntimeMetrics/RuntimeMetricsWriter.cs

@@ -9,6 +9,7 @@
 using System.Runtime.CompilerServices;
 using System.Runtime.ExceptionServices;
 using System.Threading;
+using System.Threading.Tasks;
 using Datadog.Trace.Logging;
 using Datadog.Trace.Vendors.StatsdClient;
 
@@ -39,8 +40,11 @@ internal class RuntimeMetricsWriter : IDisposable
 
         private readonly TimeSpan _delay;
 
+#if NETFRAMEWORK
+        private readonly Task _pushEventsTask;
+#else
         private readonly Timer _timer;
-
+#endif
         private readonly IRuntimeMetricsListener _listener;
 
         private readonly bool _enableProcessMetrics;
@@ -120,7 +124,11 @@ internal RuntimeMetricsWriter(IDogStatsd statsd, TimeSpan delay, bool inAzureApp
                 Log.Warning(ex, "Unable to initialize runtime listener, some runtime metrics will be missing");
             }
 
+#if NETFRAMEWORK
+            _pushEventsTask = Task.Factory.StartNew(PushEvents, TaskCreationOptions.LongRunning);
+#else
             _timer = new Timer(_ => PushEvents(), null, delay, Timeout.InfiniteTimeSpan);
+#endif
         }
 
         /// <summary>
@@ -137,6 +145,12 @@ public void Dispose()
             }
 
             Log.Debug("Disposing Runtime Metrics timer");
+#if NETFRAMEWORK
+            if (_pushEventsTask.Wait(TimeSpan.FromMilliseconds(5_000)))
+            {
+                Log.Warning("Failed to dispose Runtime Metrics timer after 5 seconds");
+            }
+#else
             // Callbacks can occur after the Dispose() method overload has been called,
             // because the timer queues callbacks for execution by thread pool threads.
             // Using the Dispose(WaitHandle) method overload to waits until all callbacks have completed.
@@ -148,7 +162,7 @@ public void Dispose()
                     Log.Warning("Failed to dispose Runtime Metrics timer after 5 seconds");
                 }
             }
-
+#endif
             Log.Debug("Disposing other resources for Runtime Metrics");
             AppDomain.CurrentDomain.FirstChanceException -= FirstChanceException;
             // We don't dispose runtime metrics on .NET Core because of https://github.com/dotnet/runtime/issues/103480
@@ -256,6 +270,23 @@ internal void PushEvents()
             {
                 var callbackExecutionDuration = DateTime.UtcNow - now;
 
+#if NETFRAMEWORK
+                // Ideally we'd wait for the full time, but we need to make sure we shutdown in a relatively timely fashion
+                const int loopDurationMs = 200;
+                var newDelay = (int)(_delay - callbackExecutionDuration).TotalMilliseconds;
+
+                // Missed it, so just reset
+                if (newDelay <= 0)
+                {
+                    newDelay = (int)_delay.TotalMilliseconds;
+                }
+
+                while (newDelay > 0 && Volatile.Read(ref _disposed) == 0)
+                {
+                    Thread.Sleep(Math.Min(newDelay, loopDurationMs));
+                    newDelay -= loopDurationMs;
+                }
+#else
                 var newDelay = _delay - callbackExecutionDuration;
 
                 if (newDelay < TimeSpan.Zero)
@@ -270,6 +301,7 @@ internal void PushEvents()
                 catch (ObjectDisposedException)
                 {
                 }
+#endif
             }
         }