Bug 1910449 - Add explicit call to cancel for MPS (java.util.Timer) i…

…n Glean Android bindings

This adds an explicit call to `Timer.cancel()` for the Metrics Ping Scheduler's  timer when the application enters the background (`handleClientInactive`) in order to prevent the Timer thread from blocking the application from termination (see `java.util.Timer` docs here: https://developer.android.com/reference/java/util/Timer)

This also adds a check to ensure the application is running and in the foreground when the `Timer` fires before rescheduling the next metrics ping `Timer`

glean-core/android/src/main/java/mozilla/telemetry/glean/Dispatchers.kt

@@ -6,7 +6,6 @@ package mozilla.telemetry.glean
 
 import androidx.annotation.VisibleForTesting
 import kotlinx.coroutines.CoroutineScope
-import kotlinx.coroutines.DelicateCoroutinesApi
 import kotlinx.coroutines.Job
 import kotlinx.coroutines.SupervisorJob
 import kotlinx.coroutines.launch

glean-core/android/src/main/java/mozilla/telemetry/glean/Glean.kt

@@ -320,7 +320,7 @@ open class GleanInternalAPI internal constructor() {
         branch: String,
         extra: Map<String, String>? = null,
     ) {
-        var map = extra ?: mapOf()
+        val map = extra ?: mapOf()
         gleanSetExperimentActive(experimentId, branch, map)
     }
 
@@ -448,6 +448,12 @@ open class GleanInternalAPI internal constructor() {
         // Persist data on backgrounding the app
         persistPingLifetimeData()
 
+        // The MetricsPingScheduler makes use of java.util.Timer, which has the
+        // potential to keep the app from terminating. So, we cancel the MPS when
+        // the app transitions to background to try and prevent this.
+        // See https://developer.android.com/reference/java/util/Timer
+        metricsPingScheduler?.cancel()
+
         gleanHandleClientInactive()
     }
 

glean-core/android/src/main/java/mozilla/telemetry/glean/scheduler/MetricsPingScheduler.kt

@@ -4,6 +4,8 @@
 
 package mozilla.telemetry.glean.scheduler
 
+import android.app.ActivityManager
+import android.app.ActivityManager.RunningAppProcessInfo
 import android.content.Context
 import android.content.SharedPreferences
 import android.text.format.DateUtils
@@ -103,7 +105,7 @@ internal class MetricsPingScheduler(
         val millisUntilNextDueTime = getMillisecondsUntilDueTime(sendTheNextCalendarDay, now)
         Log.d(LOG_TAG, "Scheduling the 'metrics' ping in ${millisUntilNextDueTime}ms")
 
-        // Cancel any existing scheduled work. Does not actually ancel a
+        // Cancel any existing scheduled work. Does not actually cancel a
         // currently-running task.
         cancel()
 
@@ -311,8 +313,20 @@ internal class MetricsPingScheduler(
         // Update the collection date: we don't really care if we have data or not, let's
         // always update the sent date.
         updateSentDate(getISOTimeString(now, truncateTo = TimeUnit.DAY))
-        // Reschedule the collection.
-        schedulePingCollection(now, sendTheNextCalendarDay = true, reason = Pings.metricsReasonCodes.reschedule)
+        // The MetricsPingScheduler makes use of java.util.Timer, which has the potential to
+        // keep the app from terminating. We only reschedule if the application is in the
+        // foreground, otherwise we cancel the MPS to try and prevent it from blocking
+        // application termination.
+        // See https://developer.android.com/reference/java/util/Timer
+        if (isAppOnForeground()) {
+            schedulePingCollection(
+                now,
+                sendTheNextCalendarDay = true,
+                reason = Pings.metricsReasonCodes.reschedule,
+            )
+        } else {
+            cancel()
+        }
     }
 
     /**
@@ -363,6 +377,23 @@ internal class MetricsPingScheduler(
      */
     @VisibleForTesting(otherwise = VisibleForTesting.PRIVATE)
     internal fun getCalendarInstance(): Calendar = Calendar.getInstance()
+
+    /**
+     * Utility function used in determining whether or not to reschedule the MPS
+     */
+    private fun isAppOnForeground(): Boolean {
+        val activityManager = applicationContext.getSystemService(Context.ACTIVITY_SERVICE) as ActivityManager
+        val appProcesses = activityManager.runningAppProcesses ?: return false
+        val packageName = applicationContext.packageName
+        for (appProcess in appProcesses) {
+            if (appProcess.importance ==
+                RunningAppProcessInfo.IMPORTANCE_FOREGROUND && appProcess.processName == packageName
+            ) {
+                return true
+            }
+        }
+        return false
+    }
 }
 
 /**