Basic watchdog that triggers thread dumps on puck jank

Author: jush

app/src/main/java/com/mapbox/maps/testapp/examples/LocationComponentAnimationActivity.kt

@@ -1,8 +1,11 @@
 package com.mapbox.maps.testapp.examples
 
+import android.animation.Animator
+import android.animation.ValueAnimator
 import android.os.Bundle
 import android.os.Handler
 import android.os.Looper
+import android.util.Log
 import androidx.appcompat.app.AppCompatActivity
 import androidx.interpolator.view.animation.FastOutSlowInInterpolator
 import com.mapbox.geojson.Point
@@ -33,6 +36,28 @@ class LocationComponentAnimationActivity : AppCompatActivity() {
   private inner class FakeLocationProvider : LocationProvider {
 
     private var locationConsumer: LocationConsumer? = null
+    private val listeners =
+      object : ValueAnimator.AnimatorUpdateListener, Animator.AnimatorListener {
+        override fun onAnimationUpdate(animation: ValueAnimator) {
+          Watchdog.reschedule()
+        }
+
+        override fun onAnimationStart(animation: Animator) {
+          Watchdog.reschedule()
+        }
+
+        override fun onAnimationEnd(animation: Animator) {
+          Watchdog.stop()
+          animation.removeListener(this)
+          (animation as ValueAnimator).removeUpdateListener(this)
+        }
+
+        override fun onAnimationCancel(animation: Animator) {
+        }
+
+        override fun onAnimationRepeat(animation: Animator) {
+        }
+      }
 
     private fun emitFakeLocations() {
       // after several first emits we update puck animator options
@@ -73,7 +98,10 @@ class LocationComponentAnimationActivity : AppCompatActivity() {
                   POINT_LNG + delta,
                   POINT_LAT + delta
                 )
-              )
+              ) {
+                addUpdateListener(this@FakeLocationProvider.listeners)
+                addListener(this@FakeLocationProvider.listeners)
+              }
             }
           }
           locationConsumer?.onBearingUpdated(BEARING + delta * 10000.0 * 5)
@@ -88,11 +116,20 @@ class LocationComponentAnimationActivity : AppCompatActivity() {
     override fun registerLocationConsumer(locationConsumer: LocationConsumer) {
       this.locationConsumer = locationConsumer
       emitFakeLocations()
+      Watchdog.enabled = true
+      // Fake a busy main thread after 15s
+      handler.postDelayed({
+        Log.d("TAG", "emitFakeLocations: Blocking main thread")
+        // Simulate main thread busy for few milliseconds
+        Thread.sleep(150)
+        Log.d("TAG", "emitFakeLocations: Finished blocking main thread")
+      }, 15_000L)
     }
 
     override fun unRegisterLocationConsumer(locationConsumer: LocationConsumer) {
       this.locationConsumer = null
       handler.removeCallbacksAndMessages(null)
+      Watchdog.enabled = false
     }
   }
 

app/src/main/java/com/mapbox/maps/testapp/examples/Watchdog.kt

@@ -0,0 +1,93 @@
+package com.mapbox.maps.testapp.examples
+
+import android.os.Handler
+import android.os.HandlerThread
+import android.os.Message
+import android.os.Process
+import android.util.Log
+import com.mapbox.maps.testapp.examples.Watchdog.TIME_TO_FIRST_TRIGGER
+import com.mapbox.maps.testapp.examples.Watchdog.TIME_TO_SUBSEQUENT_TRIGGER
+import com.mapbox.maps.testapp.examples.Watchdog.reschedule
+import com.mapbox.maps.testapp.examples.Watchdog.stop
+
+/**
+ * A simple watchdog that will trigger a [Process.SIGNAL_QUIT] signal if [reschedule] is not called
+ * within [TIME_TO_FIRST_TRIGGER] milliseconds and continues to do so every
+ * [TIME_TO_SUBSEQUENT_TRIGGER] until [reschedule] or [stop] is called.
+ */
+object Watchdog {
+  var enabled = false
+    set(value) {
+      if (field == value) return
+      field = value
+      if (value) {
+        // Start the watchdog thread when enabled to avoid unnecessary overhead
+        watchdogHandlerThread = HandlerThread(TAG).apply { start() }
+        watchdogHandler = Handler(watchdogHandlerThread!!.looper)
+      } else {
+        // Stop the watchdog thread and free properties when disabled to avoid unnecessary overhead
+        stop()
+        watchdogHandlerThread?.quit()
+        watchdogHandler = null
+        watchdogHandlerThread = null
+      }
+    }
+
+  private var watchdogHandlerThread: HandlerThread? = null
+  private var watchdogHandler: Handler? = null
+  private var currentCounter = 0
+
+  private val quitSignalTask: () -> Unit = {
+    Log.w(TAG, "(${currentCounter++}) Task not rescheduled on time. Triggering SIGNAL_QUIT.")
+    // Send a quit signal to the current process to write a thread dump to `/data/anr/`.
+    Process.sendSignal(Process.myPid(), Process.SIGNAL_QUIT)
+    scheduleQuitSignalTask()
+  }
+
+  private fun scheduleQuitSignalTask() {
+    if (currentCounter >= MAX_CONSECUTIVE_TRIGGERS) {
+      Log.w(
+        TAG,
+        "Max consecutive triggers ($currentCounter) reached. Not scheduling another trigger."
+      )
+      return
+    }
+    if (enabled) {
+      watchdogHandler?.let {
+        it.sendMessageDelayed(Message.obtain(it, quitSignalTask), TIME_TO_SUBSEQUENT_TRIGGER)
+      }
+    }
+  }
+
+  fun reschedule() {
+    if (enabled) {
+      stop()
+      watchdogHandler?.let {
+        it.sendMessageDelayed(Message.obtain(it, quitSignalTask), TIME_TO_FIRST_TRIGGER)
+      }
+    }
+  }
+
+  fun stop() {
+    // Cancel all pending tasks
+    watchdogHandler?.removeCallbacksAndMessages(null)
+    currentCounter = 0
+  }
+
+  private const val TAG = "Watchdog"
+
+  /**
+   * The amount of time that need to pass before the watchdog triggers the first time.
+   * That is, if [reschedule] is not called within this time, the watchdog task will trigger.
+   * Unit is milliseconds.
+   */
+  private const val TIME_TO_FIRST_TRIGGER: Long = 50L
+
+  /**
+   * The amount of time that the task will wait before running again.
+   * Unit is milliseconds.
+   */
+  private const val TIME_TO_SUBSEQUENT_TRIGGER: Long = 100L
+
+  private const val MAX_CONSECUTIVE_TRIGGERS = 5
+}