fix: don't report ANR while the app is in the background

CHANGELOG.md

@@ -6,6 +6,10 @@
 
 - Include build ID in an event release info ([#795](https://github.com/getsentry/sentry-unity/pull/795))
 
+### Fixes
+
+- Don't report Aplication-Not-Responding while the app is in the background ([#796](https://github.com/getsentry/sentry-unity/pull/796))
+
 ## 0.18.0
 
 ### Features

src/Sentry.Unity/Integrations/AnrIntegration.cs

@@ -48,6 +48,7 @@ internal abstract class AnrWatchDog
         protected readonly IDiagnosticLogger? Logger;
         protected readonly SentryMonoBehaviour MonoBehaviour;
         internal event EventHandler<ApplicationNotResponding> OnApplicationNotResponding = delegate { };
+        protected bool Paused { get; private set; } = false;
 
         internal AnrWatchDog(IDiagnosticLogger? logger, SentryMonoBehaviour monoBehaviour, int detectionTimeoutMilliseconds = 5000)
         {
@@ -56,6 +57,9 @@ internal AnrWatchDog(IDiagnosticLogger? logger, SentryMonoBehaviour monoBehaviou
             DetectionTimeoutMs = detectionTimeoutMilliseconds;
             SleepIntervalMs = Math.Max(1, DetectionTimeoutMs / 5);
 
+            MonoBehaviour.ApplicationPausing += () => Paused = true;
+            MonoBehaviour.ApplicationResuming += () => Paused = false;
+
             // Stop when the app is being shut down.
             MonoBehaviour.Application.Quitting += () => Stop();
         }
@@ -64,9 +68,13 @@ internal AnrWatchDog(IDiagnosticLogger? logger, SentryMonoBehaviour monoBehaviou
 
         protected void Report()
         {
-            var message = $"Application not responding for at least {DetectionTimeoutMs} ms.";
-            Logger?.LogInfo("Detected an ANR event: {0}", message);
-            OnApplicationNotResponding?.Invoke(this, new ApplicationNotResponding(message));
+            // Don't report events while in the background.
+            if (!Paused)
+            {
+                var message = $"Application not responding for at least {DetectionTimeoutMs} ms.";
+                Logger?.LogInfo("Detected an ANR event: {0}", message);
+                OnApplicationNotResponding?.Invoke(this, new ApplicationNotResponding(message));
+            }
         }
     }
 
@@ -129,7 +137,11 @@ private void Run()
                     _ticksSinceUiUpdate++;
                     Thread.Sleep(SleepIntervalMs);
 
-                    if (_ticksSinceUiUpdate >= reportThreshold && !_reported)
+                    if (Paused)
+                    {
+                        _ticksSinceUiUpdate = 0;
+                    }
+                    else if (_ticksSinceUiUpdate >= reportThreshold && !_reported)
                     {
                         Report();
                         _reported = true;

src/Sentry.Unity/SentryMonoBehaviour.cs

@@ -64,6 +64,20 @@ internal IApplication Application
             set => _application = value;
         }
 
+        internal void UpdatePauseStatus(bool paused)
+        {
+            if (paused && _isRunning)
+            {
+                _isRunning = false;
+                ApplicationPausing?.Invoke();
+            }
+            else if (!paused && !_isRunning)
+            {
+                _isRunning = true;
+                ApplicationResuming?.Invoke();
+            }
+        }
+
         /// <summary>
         /// To receive Leaving/Resuming events on Android.
         /// <remarks>
@@ -75,20 +89,9 @@ internal IApplication Application
         /// </summary>
         internal void OnApplicationPause(bool pauseStatus)
         {
-            if (Application.Platform != RuntimePlatform.Android)
-            {
-                return;
-            }
-
-            if (pauseStatus && _isRunning)
-            {
-                _isRunning = false;
-                ApplicationPausing?.Invoke();
-            }
-            else if (!pauseStatus && !_isRunning)
+            if (Application.Platform == RuntimePlatform.Android)
             {
-                _isRunning = true;
-                ApplicationResuming?.Invoke();
+                UpdatePauseStatus(pauseStatus);
             }
         }
 
@@ -99,20 +102,9 @@ internal void OnApplicationPause(bool pauseStatus)
         internal void OnApplicationFocus(bool hasFocus)
         {
             // To avoid event duplication on Android since the pause event will be handled via OnApplicationPause
-            if (Application.Platform == RuntimePlatform.Android)
-            {
-                return;
-            }
-
-            if (hasFocus && !_isRunning)
-            {
-                _isRunning = true;
-                ApplicationResuming?.Invoke();
-            }
-            else if (!hasFocus && _isRunning)
+            if (Application.Platform != RuntimePlatform.Android)
             {
-                _isRunning = false;
-                ApplicationPausing?.Invoke();
+                UpdatePauseStatus(!hasFocus);
             }
         }
 

test/Sentry.Unity.Tests/AnrDetectionTests.cs

@@ -99,5 +99,34 @@ public void DoesntReportShortlyStuckUI(bool multiThreaded)
 
             Assert.IsNull(arn);
         }
+
+        [UnityTest]
+        public IEnumerator DoesntReportWhilePaused([ValueSource(nameof(MultiThreadingTestValues))] bool multiThreaded)
+        {
+            ApplicationNotResponding? arn = null;
+            _sut = CreateWatchDog(multiThreaded);
+            _sut.OnApplicationNotResponding += (_, e) => arn = e;
+
+            // mark the app as paused
+            _monoBehaviour.UpdatePauseStatus(true);
+
+            // Thread.Sleep blocks the UI thread
+            Thread.Sleep(Timeout * 2);
+
+            // We need to let the single-threaded watchdog populate `arn` after UI became responsive again.
+            if (!multiThreaded)
+            {
+                var watch = Stopwatch.StartNew();
+                while (watch.ElapsedMilliseconds < Timeout && arn is null)
+                {
+                    yield return null;
+                }
+            }
+
+            // mark as resumed
+            _monoBehaviour.UpdatePauseStatus(false);
+
+            Assert.IsNull(arn);
+        }
     }
 }